[转帖]眼科及眼科设备相关背景知识--英文

Ophthalmology A phoropter in use. Slit lamp examination of eyes in an Ophthalmology Clinic Ophthalmology is the branch of medicine which deals with the diseases and surgery of the visual pathways, including the eye, brain, and areas surrounding the eye, such as the lacrimal system and eyelids. The term ophthalmologist is an eye specialist for medical and surgical problems. Since ophthalmologists perform operations on eyes, they considered both a surgical and medical specialty.
The word ophthalmology comes from the Greek roots ophthalmos meaning eye and logos meaning word, thought or discourse; ophthalmology literally means "the science of eyes". As a discipline, it applies to animal eyes also, since the differences from human practice are surprisingly minor and are related mainly to differences in anatomy or prevalence, not differences in disease processes. However, veterinary medicine is regulated separately in many countries and states/provinces resulting in few ophthalmologists treating both humans and animals.
Contents  1 History 1.1 Sushruta 1.2 Pre-Hippocrates 1.3 Alexandrian studies 1.4 Rufus 1.5 After Galen 1.6 Middle Eastern ophthalmology 1.7 Seventeenth and eighteenth century 1.8 Ophthalmic surgery in Great Britain 2 Professional requirements 2.1 Australia and New Zealand 2.2 Canada 2.3 Finland 2.4 Germany 2.5 India 2.6 Pakistan 2.7 United Kingdom and Republic of Ireland 2.8 United States 3 Sub-specialities 4 Ophthalmic surgery 5 Notable ophthalmologists 5.1 Pre-18th century 5.2 18th-19th century 5.3 20th-21st century 6 See also 7 External links 8 References //
 History The eye, including its structure and mechanism, has fascinated scientists and the public in general since ancient times. The majority of all input to the brain comes from vision. Many of the expressions in the English language that mean to understand are equivalent vision terms. "I see", to mean I understand.
Many patients when told that they may have an eye problem will be more concerned about diseases that affect vision than other, more lethal diseases[citation needed]. Being deprived of sight can have a devastating effect on the psyche, as well as economic and social effects, as many blind individuals require significant assistance with activities of daily living and are often unable to continue gainful employment previously held while seeing[citation needed].
The maintenance of ocular health and correction of eye problems that decrease vision contribute greatly to the ability to appreciate the longer lifespan that all of medicine continues to allow. Given the importance of vision to quality of life, many ophthalmologists consider their job to be rewarding, as they are often able to restore or improve a patient's sight. As detailed below, advances in diagnosis and treatment of disease, and improved surgical techniques have extended our abilities to restore vision like never before.

 Sushruta Sushruta wrote Sushruta Samhita in about fifth Century BCE in India. He described about 72 ocular diseases as well as several ophthalmological surgical instruments and techniques. Sushruta has been described as the first Indian cataract surgeon.[1][2] Arab scientists are some of the earliest to have written about and drawn the anatomy of the eye—the earliest known diagram being in Hunain ibn Is-hâq's Book of the Ten Treatises on the Eye. Earlier manuscripts exist which refer to diagrams which are not known to have survived. Current knowledge of the Græco-Roman understanding of the eye is limited, as many manuscripts lacked diagrams. In fact, there are very few Græco-Roman diagrams of the eye still in existence. Thus, it is not clear to which structures the texts refer, and what purpose they were thought to have.

 Pre-Hippocrates The pre-Hippocratics largely based their anatomical conceptions of the eye on speculation, rather than empiricism. They recognized the sclera and transparent cornea running flushly as the outer coating of the eye, with an inner layer with pupil, and a fluid at the centre. It was believed, by Alcamaeon and others, that this fluid was the medium of vision and flowed from the eye to the brain via a tube. Aristotle advanced such ideas with empiricism. He dissected the eyes of animals, and discovering three layers (not two), found that the fluid was of a constant consistency with the lens forming (or congealing) after death, and the surrounding layers were seen to be juxtaposed. He, and his contemporaries, further put forth the existence of three tubes leading from the eye, not one. One tube from each eye met within the skull.

 Alexandrian studies Alexandrian studies extensively contributed to knowledge of the eye. Aëtius tells us that Herophilus dedicated an entire study to the eye which no longer exists. In fact, no manuscripts from the region and time are known to have survived, leading us to rely on Celsius' account—which is seen as a confused account written by a man who did not know the subject matter. From Celsius it is known that the lens had been recognised, and they no longer saw a fluid flowing to the brain through some hollow tube, but likely a continuation of layers of tissue into the brain. Celsius failed to recognise the retina's role, and did not think it was the tissue that continued into the brain.

 Rufus Rufus recognised a more modern eye, with conjunctiva, extending as a fourth epithelial layer over the eye. Rufus was the first to recognise a two chambered eye — with one chamber from cornea to lens (filled with water), the other from lens to retina (filled with an egg-white-like substance). Galen remedied some mistakes including the curvature of the cornea and lens, the nature of the optic nerve, and the existence of a posterior chamber. Though this model was roughly a correct but simplistic modern model of the eye, it contained errors. Yet it was not advanced upon again until after Vesalius. A ciliary body was then discovered and the sclera, retina, choroid and cornea were seen to meet at the same point. The two chambers were seen to hold the same fluid as well as the lens being attached to the choroid. Galen continued the notion of a central canal, though he dissected the optic nerve, and saw it was solid, He mistakenly counted seven optical muscles, one too many. He also knew of the tear ducts.

 After Galen After Galen a period of speculation is again noted by Arab scientists — the lens modified Galen's model to place the lens in the middle of the eye, a notion which lasted until Vesalius reversed the era of speculation. However, Vesalius was not an ophthalmologist and taught that the eye was a more primitive notion than the notion of both Galen and the Arabian scientists — the cornea was not seen as being of greater curvature and the posterior side of the lens wasn't seen to be larger.
Understanding of the eye had been so slow to develop because for a long time the lens was perceived to be the seat of vision, not as part of the pathway for vision. This mistake was corrected when Fabricius and his successors correctly placed the lens and developed the modern notion of the structure of the eye. They removed the idea of Galen's seventh muscle (the retractor bulbi) and reinstated the correct curvatures of the lens and cornea, as well as stating the ciliary body as a connective structure between the lens and the choroid.

 Middle Eastern ophthalmology Main article: Ophthalmology in medieval Islam Of all the branches of Islamic medicine, ophthalmology was considered one of the foremost. Scores of specialized instruments were developed. Innovations such as the “injection syringe”, invented by the Iraqi physician Ammar ibn Ali of Mosul, which was used for the extraction by suction of soft cataracts, were quite common. In cataract surgery, Ammar ibn Ali attempted the earliest extraction of cataracts using suction. He introduced a hollow metallic syringe hypodermic needle through the sclera and successfully extracted the cataracts through suction.[3]
Ibn al-Haytham (Alhazen), the "father of optics", studied the anatomy of the eye extensively. He made important contributions to ophthalmology and eye surgery and posited the first correct explanations of the process of sight and visual perception in his Book of Optics (1021).[4] He was also the first to hint at the retina being involved in the process of image formation.[5]
Ibn al-Nafis, in The Polished Book on Experimental Ophthalmology, discovered that the muscle behind the eyeball does not support the ophthalmic nerve, that they do not get in contact with it, and that the optic nerves transect but do not get in touch with each other. He also discovered many new treatments for glaucoma and the weakness of vision in one eye when the other eye is affected by disease.[6] Salah–ud-din bin Youssef al-Kalal bi Hama (i.e. the eye doctor of Hama) was a Syrian oculist who flourished in Hama in 1296. He wrote for his son a very elaborate treatise of ophthalmology entitled Nur al-Uyun wa Jami al-Funun (light of the eyes and collection of rules).

 Seventeenth and eighteenth century The seventeenth and eighteenth century saw the use of hand-lenses (by Malpighi), microscopes (van Leeuwenhoek), preparations for fixing the eye for study (Ruysch) and later the freezing of the eye (Petit). This allowed for detailed study of the eye and an advanced model. Some mistakes persisted such as: why the pupil changed size (seen to be vessels of the iris filling with blood), the existence of the posterior chamber, and of course the nature of the retina. In 1722 Leeuwenhoek noted the existence of rods and cones though they were not properly discovered until Gottfried Reinhold Treviranus in 1834 by use of a microscope.

 Ophthalmic surgery in Great Britain The first ophthalmic surgeon in Great Britain was John Freke, appointed to the position by the Governors of St Bartholomew's Hospital in 1727, but the establishment of the first dedicated ophthalmic hospital in 1805 — now called Moorfields Eye Hospital in London, England was a transforming event in modern ophthalmology. Clinical developments at Moorfields and the founding of the Institute of Ophthalmology by Sir Stewart Duke-Elder established the site as the largest eye hospital in the world and a nexus for ophthalmic research.

 Professional requirements Ophthalmologists are medical doctors (M.D.) or Doctors of Osteopathic Medicine (D.O.). who have completed a college degree, medical school, and an additional four years of post-graduate training in ophthalmology in many countries. Many ophthalmologists also undergo additional specialized training in one of the many subspecialities. Ophthalmology was the first branch of medicine to offer board certification, now a standard practice among all specialties.

 Australia and New Zealand In Australia and New Zealand, the FRACO/FRANZCO is the equivalent postgraduate specialist qualification. Overseas-trained Ophthalmologists are assessed using the pathway published on the RANZCO website. Those who have completed their formal training in the UK and have the CCST/CCT are usually deemed to be comparable.

 Canada In Canada, an Ophthalmology residency after medical school is undertaken. The residency lasts a minimum of 5 years after the MD degree although subspecialty training is undertaken by about 30% of fellows (FRCSC). There are about 30 vacancies per year for ophthalmology training in all of Canada.

 Finland In Finland, physicians willing to become ophthalmologists must undergo a 5 year specialization which includes practical training and theoretical studies.

 Germany In Germany, physicians willing to become ophthalmologists must undergo a 5 year specialization of practical training.
 
 India In India, after completing MBBS degree, post-graduation in Ophthalmology is required. The degrees are Doctor of Medicine (MD), Master of Surgery (MS), Diploma in Ophthalmic Medicine and Surgery (DOMS) or Diplomate of National Board (DNB). The concurrent training and work experience is in the form of a Junior Residency at a Medical College, Eye Hospital or Institution under the supervision of experienced faculty. Further work experience in form of fellowship, registrar or senior resident refines the skills of these eye surgeons. All India Ophthalmological Society (AIOS) and various state level Ophthalmological Societies (like DOS) hold regular conferences and actively promote continuing medical education. Royal colleges of the united kingdom, mainly Royal college of surgeons of Edinburgh (RCSEd), Royal College of ophthalmologists (RCOphth)[dead link] and Royal college of physicians and Surgeons of Glasgow (RCPSG) are conducting their fellowship and membership examinations since mid 1990s and awarding fellowships and memberships to the successful candidates.

 Pakistan In Pakistan, there is a structured residency program leading into FCPS. Further detail is at https://cpsp.edu.pk/

 United Kingdom and Republic of Ireland In the United Kingdom, there are three colleges that grant postgraduate degrees in ophthalmology. The Royal College of Ophthalmologists grants MRCOphth and FRCOphth (postgraduate exams), the Royal College of Edinburgh grants MRCSEd, the Royal College of Glasgow grants FRCS. In Ireland the Royal College of Ireland grants FRCSI. Work experience as a specialist registrar and one of these degrees is required for specialisation in eye diseases.

 United States In the United States, 4 years of residency training after medical school are required, with the first year being an internship in surgery, internal medicine, pediatrics, or a general transition year. Optional fellowships in advanced topics may be pursued for several years after residency. Most currently practicing ophthalmologists train in medical residency programs accredited by the Accreditation Council for Graduate Medical Education (ACGME) and are board certified by the American Board of Ophthalmology. Some physicians train in osteopathic medical schools may hold a Doctor of Osteopathy ("DO") degree rather than an MD. The same residency and certification requirements for ophthalmology training must be fulfilled by osteopathic physicians. Completing the requirements of continuing medical education is mandatory for continuing licensure and re-certification. Professional bodies like the AAO and ASCRS organize conferences and help members through continuing medical education programs to maintain certification, in addition to political advocacy and peer support.

 Sub-specialities Ophthalmology includes sub-specialities which deal either with certain diseases or diseases of certain parts of the eye. Some of them are:
Anterior segment surgery Cataract — not considered a subspecialty per se, since most general ophthalmologists do surgery for this. Cornea, ocular surface, and external disease Glaucoma Neuro-ophthalmology Ocular oncology Oculoplastics & Orbit surgery Ophthalmic pathology Pediatric ophthalmology/Strabismus (mis-alignment of the eyes) Refractive surgery Medical retina, deals with treatment of retinal problems conservatively. Vitreoretinal Surgery, deals with surgical management of retinal and posterior segment diseases and disorders. Medical retina and vitreoretinal surgery sometimes together called posterior segment subspecialisation. Uveitis/Immunology Veterinary" Formal specialty training programs in veterinary ophthalmology now exist in some countries [1] [2] [3].
 Ophthalmic surgery For a comprehensive list of surgeries performed by ophthalmologists, see eye surgery.
 Notable ophthalmologists This is an incomplete list, which may never be able to satisfy certain standards for completion. You can help by expanding it with sourced additions. See also: :Category:Ophthalmologists
 Pre-18th century Marie Colinet, wife of Wilhelm Fabry, employs a magnet for removing a foreign body from the eye, 1627.
 18th-19th century Sir William Adams (UK) Founder of Exeter's West of England Eye Infirmary. Carl Ferdinand von Arlt (1812-1887), the elder (Austrian) proved that myopia is largely due to an excessive axial length, published influential textbooks on eye disease, and ran annual eye clinics in needy areas long before the concept of volunteer eye camps became popular. His name is still attached to some disease signs, eg, von Arlt's line in trachoma. His son Ferdinand Ritter von Arlt, the younger, was also an ophthalmologist. Jacques Daviel (France) claimed to be the 'father' of modern cataract surgery in that he performed extracapsular extraction instead of needling the cataract or pushing it back into the vitreous. It is said that he carried out the technique on 206 patients in 1752-3, out of which 182 were reported to be successful. These figures are not very credible, given the total lack of both anaesthesia and aseptic technique at that time. Frans Cornelis Donders (1818-1889) (Dutch) published pioneering analyses of ocular biomechanics, intraocular pressure, glaucoma, and physiological optics. Made possible the prescribing of combinations of spherical and cylindrical lenses to treat astigmatism. Albrecht von Graefe (1828-1870) (Germany) Along with Helmholtz and Donders, one of the 'founding fathers' of ophthalmology as a specialty. A brilliant clinician and charismatic teacher who had an international influence on the development of ophthalmology. A pioneer in mapping visual field defects and diagnosis and treatment of glaucoma. Introduced a cataract extraction technique that remained the standard for over 100 years, and many other important surgical techniques such as iridectomy. Rationalised the use of many ophthalmically important drugs, including mydriatics & miotics. The founder of the one of the earliest ophthalmic societies (German Ophthalmological Society, 1857) and one of the earliest ophthalmic journals (Graefe's Archives of Ophthalmology). The most important ophthalmologist of the nineteenth century. Allvar Gullstrand (Sweden), Nobel Prize winner in 1911 for his research on the eye as a light-refracting apparatus. Described the schematic eye a mathematical model of the human eye based on his measurements known as the optical constants of the eye. His measurements are still used today. Hermann von Helmholtz, great German polymath, invented the ophthalmoscope (1851) and published important work on physiological optics, including colour vision (1850s). Hermann Snellen (Netherlands) introduced the Snellen chart to study visual acuity. Sir Arthur Conan Doyle (United Kingdom). English writer, primarily of the Sherlock Holmes stories. Trained in but apparently never practiced Ophthalmology.
 20th-21st century William Horatio Bates (1860-1931) (United States) Creator of the unorthodox Bates Method, credited for being the founder of the Natural Vision Improvement movement. Vladimir Petrovich Filatov (1875-1956) (Ukraine) His contributions to the medical world include the tube flap grafting method, corneal transplantation and preservation of grafts from cadaver eyes and tissue therapy. He founded The Filatov Institute of Eye Diseases & Tissue Therapy, Odessa, one of the leading eye care institutes in the world. Ignacio Barraquer (1884-1965) (Spain) In 1917, invented the first motorized vacuum instrument (erisophake) for intracapsular cataract extraction. Founded of the Barraquer Clinic in 1941 and the Barraquer Institute in 1947 in Barcelona, Spain. Tsutomu Sato (Japan) Pioneer in incisional refractive surgery, including techniques for astigmatism and the invention of radial keratotomy for myopia. Jules Gonin (1870-1935) (Switzerland) "Father of retinal detachment surgery". Sir Harold Ridley (United Kingdom) In 1949, may have been the first to successfully implant an artificial intraocular lens after observing that plastic fragments in the eyes of wartime pilots were well tolerated. He fought for decades against strong reactionary opinions to have the concept accepted as feasible and useful. Charles Schepens (Belgium) "Father of modern retinal surgery". Developer of the Schepens indirect binocular ophthalmoscope whilst at Moorfields Eye Hospital. Founder of the Schepens Eye Research Institute in Boston, Massachusetts. This premier research institute is associated with Harvard Medical School and Massachusetts Eye & Ear Infirmary. Marshall M. Parks "Father of pediatric ophthalmology". José Ignacio Barraquer (1916-1998) (Spain) "Father of modern refractive surgery". In the 1960s, developed lamellar techniques including keratomileusis and keratophakia, as well as the first microkeratome and corneal microlathe. Tadeusz Krwawicz (Poland) In 1961, developed the first cryoprobe for intracapsular cataract extraction. Svyatoslav Fyodorov (Russia) Popularizer of radial keratotomy. Charles Kelman (United States) Developed the ultrasound and mechanized irrigation and aspiration system for phacoemulsification, first allowing cataract extraction through a small incision. Ioannis Pallikaris (Greece) Performed the first laser-assisted intrastromal keratomileusis or LASIK surgery. Fred Hollows (New Zealand/Australia) Pioneered programs in Nepal, Eritrea, and Vietnam, and among Australian aborigines, including the establishment of cheap laboratory production of intraocular lenses in Nepal and Eritrea. Ian Constable (Australia) Founded the Lions Eye Institute in Perth, Western Australia, the largest eye research institute in the southern hemisphere and home to ten ophthalmologists. L. L. Zamenhof (Poland) Creator of the Esperanto language. Bashar al-Assad (Syria) The President of Syria. He did his ophthalmology residency in a hospital in London. Syed Modasser Ali (Bangladesh) An ophthalmic surgeon who used to be the Director-General of Health Services for the government of Bangladesh. He wrote the first book on community ophthalmology (public eye health).
 See also Eye examination Eye care professional History of eye colors Ophthalmology in medieval Islam Optometry Optics Orthoptics Pediatric ophthalmology Prentice position
 External links American Academy of Ophthalmology Association for Research in Vision and Ophthalmology American Society of Cataract & Refractive Surgery European Society of Cataract & Refractive Surgery European Vitreo-Retinal Society Royal College of Ophthalmologists American Board of Eye Surgeons American Board of Ophthalmology International Council of Ophthalmology Indian Journal of Ophthalmology All India Ophthalmological Society Delhi Ophthalmological Society Ophthalmological Society of Bangladesh The David G. Cogan Ophthalmic Pathology Collection Royal College of Surgeons in Edinburgh Canadian Ophthalmological Society Daily Ophthalmology News
 References ^ "Susruta: The Great Surgeon of Yore". Infinityfoundation.com. https://www.infinityfoundation.com/mandala/t_es/t_es_agraw_susruta.htm. Retrieved on 2008-11-04.  ^ "Sushruta: the father of Indian surgery and ophthal...[Doc Ophthalmol. 1997] - PubMed Result". Ncbi.nlm.nih.gov. https://www.ncbi.nlm.nih.gov/pubmed/9476614?dopt=abstractplus. Retrieved on 2008-11-04.  ^ Ibrahim B. Syed PhD, "Islamic Medicine: 1000 years ahead of its times", Journal of the International Society for the History of Islamic Medicine, 2002 (2): 2-9 [7]. ^ Bashar Saad, Hassan Azaizeh, Omar Said (October 2005). "Tradition and Perspectives of Arab Herbal Medicine: A Review", Evidence-based Complementary and Alternative Medicine 2 (4), p. 475-479 [476]. Oxford University Press. ^ N. J. Wade (1998). A Natural History of Vision.. Cambridge, MA: MIT Press..  ^ Mohamad S. M. Takrouri (King Khalid University Hospital Riyadh), Medical aspects of Ala al-Din Abu'l-Hasan Ali Ibn Abi'l-Haram al-Qurashi (Ibn al-Nafis)'s contributions to science

Eye examination

Traditional Snellen chart used for visual acuity testing.

Slit lamp examination of the eyes in an ophthalmology clinic

An eye examination is a battery of tests performed by an ophthalmologist, optometrist, or orthoptist assessing vision and ability to focus on and discern objects, as well as other tests and examinations pertaining to the eyes. All people should have periodic and thorough eye examinations as part of routine primary care, especially since many eye diseases are silent or asymptomatic.

Eye examinations may detect potentially treatable blinding eye diseases, ocular manifestations of systemic disease, or signs of tumours or other anomalies of the brain.

Contents   1 Comprehensive eye examination 1.1 Case history 1.2 Entrance tests 1.3 Refraction 1.4 Functional tests 1.5 Health assessment 1.6 Advanced techniques 1.6.1 Corneal pachymetry 2 Setting 3 Basic examination 3.1 External examination 3.2 Visual acuity 3.3 Pupil function 3.4 Ocular motility 3.5 Visual field (confrontation) testing 3.6 Intraocular pressure 3.7 Ophthalmoscopy 3.8 Slit-lamp 4 School vision screening 5 References 5.1 On-line 5.2 Others 6 See also 6.1 Conditions diagnosed during eye examinations 6.2 Other tests that may be performed during eye examinations 6.3 Miscellaneous 7 External links

 Comprehensive eye examination

 Case history

 Entrance tests

• External examination
• Visual acuity
• Amplitude of accommodation
• Color vision
• Cover test
• Stereopsis
• Near point of convergence
• Extraocular motilities
• Pupils
• Visual field screening
• Interpupillary distance

 Refraction

• Lensometry
• Keratometry
• Retinoscopy
• Refraction

• Monocular
• Binocular balance

• Cycloplegic refraction

 Functional tests

• Accommodative system

• Negative relative accommodation
• Positive relative accommodation

• Vergence system

 Health assessment

• Slit lamp biomicroscopy
• Direct ophthalmoscopy
• Binocular indirect ophthalmoscopy
• Tonometry
• Amsler grid
• Visual field assessment
• Gonioscopy

 Advanced techniques

• Corneal topography
• Corneal pachymetry
• Scheimpflug ocular imaging
• Retinal tomography
• Ocular computed tomography
• Scanning laser polarimetry

 Corneal pachymetry

Corneal pachymetry is a measurement of the thickness of the cornea using ultrasound^[1]

 Setting

Ideally, the eye examination consists of an external examination, followed by specific tests for visual acuity, pupil function, extraocular muscle motility, visual fields, intraocular pressure and ophthalmoscopy through a dilated pupil.

A minimal eye examination consists of tests for visual acuity, pupil function, and extraocular muscle motility, as well as direct ophthalmoscopy through an undilated pupil.

 Basic examination

Determining a prescription for eyeglasses

 External examination

External examination of eyes consists of inspection of the eyelids, surrounding tissues and palpebral fissure. Palpation of the orbital rim may also be desirable, depending on the presenting signs and symptoms. The conjunctiva and sclera can be inspected by having the individual look up, and shining a light while retracting the upper or lower eyelid. The cornea and iris may be similarly inspected.

 Visual acuity

Main article: Visual acuity

Visual acuity is the eye's ability to detect fine details and is the quantitative measure of the eye's ability to see an in-focus image at a certain distance. The standard definition of normal visual acuity (20/20 or 6/6 vision) is the ability to resolve a spatial pattern separated by a visual angle of one minute of arc. The terms 20/20 and 6/6 are derived from standardized sized objects that can be seen by a "person of normal vision" at the specified distance. For example, if one can see at a distance of 20 ft an object that normally can be seen at 20 ft, then one has 20/20 vision. If one can see at 20 ft what a normal person can see at 40 ft, then one has 20/40 vision. Put another way, suppose you have trouble seeing objects at a distance and you can only see out to 20 ft what a person with normal vision can see out to 200 feet, then you have 20/200 vision. The 6/6 terminology is more commonly used in Europe and Australia, and represents the distance in metres.

This is often measured with a Snellen chart.

 Pupil function

Main article: Pupil

An examination of pupilary function includes inspecting the pupils for equal size (1 mm or less of difference may be normal), regular shape, reactivity to light, and direct and consensual accommodation. These steps can be easily remembered with the mnemonic PERRLA (D+C): Pupils Equal and Round; Reactive to Light and Accommodation (Direct and Consensual).

A swinging-flashlight test may also be desirable if neurologic damage is suspected. The swinging-flashlight test is the most useful clinical test available to a general physician for the assessment of optic nerve anomalies. This test detects the afferent pupil defect, also referred to as the Marcus Gunn pupil. In a normal reaction to the swinging-flashlight test, both pupils constrict when one is exposed to light. As the light is being moved from one eye to another, both eyes begin to dilate, but constrict again when light has reached the other eye.

If there is an efferent defect in the left eye, the left pupil will remain dilated regardless of where the light is shining, while the right pupil will respond normally. If there is an afferent defect in the left eye, both pupils will dilate when the light is shining on the left eye, but both will constrict when it is shining on the right eye.

If there is a unilateral small pupil with normal reactivity to light, it is unlikely that a neuropathy is present. However, if accompanied by ptosis of the upper eyelid, this may indicate Horner's syndrome.

If there is a small, irregular pupil that constricts poorly to light, but normally to accommodation, this is an Argyll Robertson pupil.

 Ocular motility

Main article: Extraocular muscles

Ocular motility should always be tested, especially when patients complain of double vision or physicians suspect neurologic disease. First, the doctor should visually assess the eyes for deviations that could result from strabismus, extraocular muscle dysfunction, or palsy of the cranial nerves innervating the extraocular muscles. Saccades are assessed by having the patient move his or her eye quickly to a target at the far right, left, top and bottom. This tests for saccadic dysfunction whereupon poor ability of the eyes to "jump" from one place to another may impinge on reading ability and other skills.

Slow tracking, or "pursuits" are assessed by the 'follow my finger' test, in which the examiner's finger traces an imaginary "double-H", which touches upon the eight fields of gaze. These test the inferior, superior, lateral and medial rectus muscles of the eye, as well as the superior and inferior oblique muscles.

 Visual field (confrontation) testing

Main article: Visual field

Main article: Visual field test

Evaluation of the visual fields should never be omitted from the basic eye examination. Testing the visual fields consists of confrontation field testing in which each eye is tested separately to assess the extent of the peripheral field. To perform the test, the individual occludes one eye while fixated on the examiner's eye with the non-occluded eye. The patient is then asked to count the number of fingers that are briefly flashed in each of the four quadrants. This method is preferred to the wiggly finger test that was historically used because it represents a rapid and efficient way of answering the same question: is the peripheral visual field affected?

Common problems of the visual field include scotoma (area of reduced vision), hemianopia (half of visual field lost), homonymous quadrantanopia (involving both eyes) and bitemporal hemianopia.

 Intraocular pressure

Intraocular pressure (IOP) can be measured by Tonometry devices designed to measure the outflow (and resistance to outflow) of the aqueous humour from the eye. Diaton Tonometry can measure IOP though the Eyelid

 Ophthalmoscopy

Ophthalmoscopic examination may include visually magnified inspection of the internal eye structures and also assessment of the quality of the eye's red reflex.

Ophthalmoscopy allows the one to look directly at the retina and other tissue at the back of the eye. This is best done after the pupil has been dilated with eye drops. A limited view can be obtained through an undilated pupil, in which case best results are obtained with the room darkened and the patient looking towards the far corner.

The appearance of the optic disc and retinal vasculature are the main focus of examination during ophthalmoscopy. Anomalies in the appearance of these internal ocular structures may indicate eye disease or condition.

A red reflex can be seen when looking at a patient's pupil through a direct ophthalmoscope. This part of the examination is done from a distance of about 50 cm and is usually symmetrical between the two eyes. An opacity may indicate a cataract.

 Slit-lamp

Close inspection of the anterior eye structures and ocular adnexa are often done with a slit lamp machine. A small beam of light that can be varied in width, height, incident angle, orientation and colour, is passed over the eye. Often, this light beam is narrowed into a vertical "slit", during slit-lamp examination. The examiner views the illuminated ocular structures, through an optical system that magnifies the image of the eye.

This allows inspection of all the ocular media, from cornea to vitreous, plus magnified view of eyelids, and other external ocular related structures. Fluorescein staining before slit lamp examination may reveal corneal abrasions or herpes simplex infection.

The binocular slit-lamp examination provides stereoscopic magnified view of the eye structures in striking detail, enabling exact anatomical diagnoses to be made for a variety of eye conditions.

Also ophthalmoscopy and gonioscopy examinations can also be performed through the slit lamp when combined with special lenses. These lenses include the Goldmann 3-mirror lens, gonioscopy single-mirror/ Zeiss 4-mirror lens for (ocular) anterior chamber angle structures and +90D lens, +78D lens, +66D lens & Hruby (-56D) lens, the examination of retinal structures is accomplished.

 School vision screening

See pediatric ophthalmology

 References

 On-line

1. ^ EyeMDLink

 Others

• eMedicine article on Neuro-ophthalmic examination

 See also

 Conditions diagnosed during eye examinations

Main article: List of eye diseases and disorders

• Amblyopia
• Diplopia
• Myopia
• Hyperopia
• Presbyopia
• Strabismus

 Other tests that may be performed during eye examinations

• Electrooculography
• Electroretinography
• Ultrasound biomicroscopy

 Miscellaneous

• Binocular vision
• Eyeglass prescription
• Orthoptics
• Stereopsis
• Vergence

 External links

• Eye examination equipment in the market
• Hollands of London Eye test information
• What A Vision Test Involves?
• A simulator for eye movements and pupil function tests

Slit lamp

From Wikipedia, the free encyclopedia

 

 

 

Slit lamp examination of the eyes in an ophthalmology clinic

Cataract in Human Eye- Magnified view seen on examination with a slit lamp

The slit lamp is an instrument consisting of a high-intensity light source that can be focused to shine a thin sheet of light into the eye. It is used in conjunction with a biomicroscope. The lamp facilitates an examination of the anterior segment, or frontal structures and posterior segment, of the human eye, which includes the eyelid, sclera, conjunctiva, iris, natural crystalline lens, and cornea. The binocular slit-lamp examination provides stereoscopic magnified view of the eye structures in detail, enabling anatomical diagnoses to be made for a variety of eye conditions.

While a patient is seated in the examination chair, he rests his chin and forehead on a support to steady the head. Using the biomicroscope, the ophthalmologist or optometrist then proceeds to examine the patient's eye. A fine strip of paper, stained with fluorescein, a fluorescent dye, may be touched to the side of the eye; this stains the tear film on the surface of the eye to aid examination. The dye is naturally rinsed out of the eye by tears.

A subsequent test may involve placing drops in the eye in order to dilate the pupils. The drops take about 15 to 20 minutes to work, after which the examination is repeated, allowing the back of the eye to be examined. Patients will experience some light sensitivity for a few hours after this exam, and the dilating drops may also cause increased pressure in the eye, leading to nausea and pain. Patients who experience these rare but serious symptoms are advised to seek medical attention immediately.

Adults need no special preparation for the test; however children may need some preparation, depending on age, previous experiences, and level of trust.

The slit lamp exam may detect many diseases of the eye, including:

• Cataract
• Conjunctivitis
• Corneal injury
• Fuchs' dystrophy
• Keratoconus (Fleischer ring)
• Macular degeneration
• Presbyopia
• Retinal detachment
• Retinal vessel occlusion
• Retinitis pigmentosa
• Sjögren's syndrome
• Uveitis
• Wilson's disease (Kayser-Fleischer ring)

Retrieved from "https://en.wikipedia.org/wiki/Slit_lamp"

Categories: Ophthalmic equipment

Keratometer

A keratometer, also known as a ophthalmometer, is a diagnostic instrument for measuring the curvature of the anterior surface of the cornea, particularly for assessing the extent and axis of astigmatism. It was invented by the German physiologist Hermann von Helmholtz in 1880, (although an earlier model was developed in 1796 by Jesse Ramsden and Everard Home.

A keratometer uses the relationship between object size (O), image size (I), the distance between the reflective surface and the object (d), and the radius of the reflective surface (R). If three of these variables are known (or fixed), the fourth can be calculated using the formula

R = 2dI/O

There are two distinct variants of determining R; Javal-Schiotz type keratometers have a fixed image size and are typically 'two position', whereas Bausch and Lomb type keratometers have a fixed object size and are usually 'one position'.

Contents   1 Javal-Schiotz Principles 2 Bausch and Lomb principles 3 References 4 External links

 Javal-Schiotz Principles

The Javal-Schiotz keratometer is a two position instrument which uses a fixed image and doubling size and adjustable object size to determine the radius of curvature of the reflective surface. It uses two self illuminated mires (the object), one a red square, the other a green staircase design, which are held on a circumferential track in order to maintain a fixed distance from the eye. The object size is adjusted by maneuvering the mires along this track, changing the distance between them. The reflected image is doubled through a Wollaston prism, which then allows either side of the doubled image to be aligned, and any eye movement to cancel out as both images move with the same magnitude and direction, the relative separation remaining constant. A Wollaston prism uses the polarising property of light in order to split a single image into two separate, visually identical but oppositely polarised images. Once the mires are focused, the only variable remaining is object size, which is calibrated to a measurement of reflective surface radius (and sometimes dioptric power using an estimation of refractive index). This gives the curvature of the meridian along the path of the circumferential arms, the axis of which can be read from a scale around which the arms rotate. The axis can be manipulated to any axis, giving a distinct advantage over a single position keratometer in cases of irregular astigmatism.

In order to get repeatable, accurate measurements, it is important that the instrument stays focused. It uses the Scheiner principle, common in autofocus devices, in which the converging reflected rays coming towards the eyepiece are viewed through (at least) two separate symmetrical apertures. As the rays passing through each aperture will have the same vergence, they should, meet at the same point. By adjust the distance between the object and the reflective surface, the vergence of the rays can be altered until a crisp focus is obtained, correlating to the fixed focal point of the telescopic eyepiece.

 Bausch and Lomb principles

The Bausch and Lomb keratometer is a one position keratometer that gives readings in dioptric form. It differs from the Javal-Schiotz in that object size is fixed, image size is the manipulable variable. The reflected rays are passed through a Scheiner disc with 4 apertures – two of which are used for the focusing of the mires at the fixed telescope focal distance, the other two for dual prism doubling. The instrument is based on the Helmholtz design which has two maneuverable prisms aligned vertically and horizontally. This creates two adjustable images in addition to the original image, one above and one to the left. By adjusting the distance between the eyepiece and the prism, the effective power of these prisms can be altered. As the distance is decreased, the effective prismatic power decreases. This decreases the image size along the respective prism alignment, moving the duplicate image closer to the original. An increase in the eyepiece to prism distance leads to an increase in prismatic shift. As there are two prisms, each aligned perpendicular to the other, the major and minor axis powers can be measured independently without adjusting the orientation of the instrument.

In converting the measurements obtained from the corneal surface into a dioptric value, the B&L keratometer uses the general lens formula (n’-n/R) and assumes an n’ of 1.3375 (compared to the actual corneal refractive index of n’=1.376). This is a fictional value, which includes an allowance for the small, yet significant, negative power of the posterior corneal surface. This allows for a readout in both refractive power (dioptres) and radius of curvature (millimeters).

 References

• Javal L, Schiötz H. Un opthalmomètre pratique. Annales d’oculistique, Paris, 1881, 86: 5-21.

 External links

• Keratometers in the market

Retinoscopy A retinoscope being used in conjunction with a trial frame and trial lenses in order to determine the patient's refractive error Retinoscopy is a technique to obtain an objective measurement of the refractive condition of a patient's eyes. The examiner uses a retinoscope to shine light into the patient's eye and observes the reflection (reflex) off the patient's retina. While moving the streak or spot of light across the pupil the examiner observes the relative movement of the reflex then uses a phoropter or manually places lenses over the eye (using a trial frame and trial lenses) to "neutralize" the reflex.
Retinoscope Static retinoscopy is a type of retinoscopy used in determining a patient's refractive error. It relies on Foucault's principle, which basically states that the examiner should simulate the infinity to obtain the correct refractive power. Hence, a power corresponding to the working distance is subtracted from the gross retinoscopy value to give the patient's refractive condition, the working distance lens being one which has a focal length of the examiner's distance from the patient (e.g. +2.00 dioptre lens for a 50 cm working distance). Myopes display an "against" reflex, which means that the direction of movement of light observed from the retina is a different direction to that in which the light beam is swept. Hyperopes, on the other hand, display a "with" movement, which means that the direction of movement of light observed from the retina is the same as that in which the light beam is swept.
Static retinoscopy is performed when the patient has relaxed accommodative status. This can be obtained by the patient viewing a distance target or by the use of cycloplegic drugs (where, for example, a child's lack of reliable fixation of the target can lead to fluctuations in accommodation and thus the results obtained). Dynamic retinoscopy is performed when the patient has active accommodation from viewing a near target.
Retinoscopy is particularly useful in prescribing corrective lenses for patients who are unable to undergo a subjective refraction that requires a judgement and response from the patient (such as children or those with severe intellectual disabilities or communication problems). In most tests however, it is used as a basis for further refinement by subjective refraction. It is also used to evaluate accommodative ability of the eye and detect latent hyperopia.

 

See also Eye examination Ophthalmoscope Monocular estimate method Red reflex Eye care professional Ophthalmologist Optometrist Orthoptist This eye article is a stub. You can help Wikipedia by expanding it.

Tonometry

A patient in front of a tonometer

Tonometry is the measurement of tension or pressure [1]. A tonometer is an instrument for measuring tension or pressure [2].

In ophthalmology, tonometry is the procedure eye care professionals perform to determine the intraocular pressure (IOP), the fluid pressure inside the eye. It is an important test in the evaluation of patients with glaucoma. Most tonometers are calibrated to measure pressure in mmHg.

Contents   1 Methods 2 Gallery 3 References 4 External links

 Methods

The slit lamp of a Goldmann tonometer

Semicircles seen during Goldmann tonometry through slit lamp

The PASCAL Dynamic Contour Tonometer

‎

Position of the Transpalpebral Diaton Tonometer Tip on the Eyelid with No Contact with Cornea or use of Anesthesia

Hand-held Diaton tonometer with Test and Training Eye case

• Applanation tonometry is the method used by Goldmann and Perkins tonometers. It infers the intraocular pressure from the force required to flatten (applanate) a constant area of the cornea (3.06mm using the Goldmann tonometry) .^[1]

A special disinfected prism is mounted on the tonometer head and then placed against the cornea. The examiner then uses a cobalt blue filter to view two green semi circles. The force applied to the tonometer head is then adjusted using the dial until the inner edges of these green semi-circles meet. Because the probe makes contact with the cornea, a topical anesthetic, such as oxybuprocaine, tetracaine, proparacaine (alcaine) or proxymetacaine is introduced onto the surface of the eye in the form of an eye drops.

• Goldmann tonometry is considered to be the gold standard in tonometry as it is the most widely accepted method of determining approximate intraocular pressure.^[2][3] James D. Brandt, MD,gives a dissenting opinion that, Goldmann tonometry is an inherently imprecise measurement. Goldmann tonometer principle is based on the Imbert-Fick law.

• Dynamic Contour Tonometry

Dynamic contour tonometry (DCT) is a novel method which uses principle of contour matching instead of applanation. This is designed to reduce the influence of biomechanical properties of the cornea on measurement. These include corneal thickness, rigidity, curvature, and elastic properties. It is less influenced by corneal thickness but more influence by corneal curvature than the Goldmann tonometer.^[4]

The PASCAL tonometer is currently the only commercial DCT tonometer available. It uses a miniature pressure sensor embedded within a tonometer tip contour-matched to the shape of the cornea. The tonometer tip rests on the cornea with a constant appositional force of one gram. When the sensor is subjected to a change in pressure, the electrical resistance is altered and the PASCAL's computer calculates a change in pressure in concordance with the change in resistance.

The contour matched tip has a concave surface of radius 10.5 mm, which approximates to the shape of a normal cornea when the pressure on both sides is equal. The probe is placed adjacent to the central cornea (see gallery) and the integrated piezoresistive pressure sensor automatically begins to acquire data, measuring IOP 100 times per second. A complete measurement cycle requires about 8 seconds of contact time. During the measurement cycle, audio feedback is generated, which helps the clinician maintain proper contact with the cornea. The device also measures the variation in pressure that occurs with the cardiac cycle. Literature references: ^[5][6][7]

• Transpalpebral Tonometry

Diaton tonometer (BiCOM, Inc) Transpalpebral tonometry refers to methods of measuring intraocular pressure through the Eyelid. The Diaton tonometer calculates pressure by measuring the response of a free falling rod, the principle is based on Newton's second law, as it rebounds against the tarsal plate of the eyelid. The patient is positioned so that the tip of the device and lid are overlying sclera. ^[8]. Transpalpebral tonometry does not involve contact with the cornea and does not require sterilization of the device or topical anesthetic during routine use. Early data comparing Goldmann, Tonopen and Diaton tonometers have shown good correlation. ^{[9] [10] [11]} The Diaton tonometer was preceded by the TGDc-01 which was discontinued in 2001.

• non-contact tonometry or air-puff tonometry Non-contact tonometry is different from pneumatonometry and was invented by Bernard Grolman of Reichert, Inc (formerly American Optical). It uses a rapid air pulse to applanate the cornea. Corneal applanation is detected via an electro-optical system. Intraocular pressure is estimated by detecting the force of the air jet at the instance of applanation.[3] Historically, Non-contact tonometers were not considered to be an accurate way to measure IOP but instead a fast and simple way to screen for high IOP. However, modern non-contact tonometers have been shown to correlate well with Goldmann tonomtery measurements and are particularly useful for measuring IOP in children and other non-compliant patient groups. non-contact tonometry is accomplished without the instrument contacting the cornea which reduces the potential for disease transmission.

• Electronic indentation tonometry. The Tono-Pen (Reichert, Inc) is a portable electronic, digital pen-like instrument that determines IOP by making contact with the cornea, after use of topical anesthetic eye drops. This is especially useful for very young children, patients unable to reach a slit lamp due to disability, patients who are uncooperative during applanation tonometry, or patients with cornea disease in whom contact tonometer cannot be accurately performed.

• Pneumatonometry A pneumatonometer utilizes a pneumatic sensor (consisting of a piston floating on an air bearing). It is touched to the anesthetized cornea. A precisely regulated flow of filtered air (from an internal air pump) enters the piston. A small (5-mm dia.) fenestrated membrane at the end of the piston reacts to both the force of the air blowing through it and to the force represented by the pressure behind the cornea, against which it is being pressed. The precise balance between these two forces represents the precise intra-ocular pressure (I.O.P.)

• Impression tonometry, also known as indentation tonometry, measures the depth of the impression produced by a small plunger carrying a known weight.^[12] Intraocular pressure is determined by assessing the movement of the plunger to a calibrated scale.^[12]

• Rebound Tonometry

Rebound tonometers ([Icare Tonometer https://www.icaretonometer.com]) determine intraocular pressure by bouncing a small plastic tipped metal probe against the cornea. The device uses an induction coil to magnetise the probe and fire it against the cornea. As the probe bounces against the cornea and back in to the device it creates an induction current from which the intraocular pressure is calculated. The device is simple, cheap and easy to use. It is portable, does not require the use of eye drops and is particularly suitable for children.

• Schiötz tonometry is a type of indentation tonometery, historically was used to determine IOP. This type of tonometry makes use of a plunger to indent the cornea. The IOP is determined by correlation of scale reading using a nomogram, with additional small metal weights added for higher levels of IOP.

• Perkins tonometer is a special type of portable applanation tonometer, which allows measurement of IOP in children, patients unable to cooperate for slit lamp exam, and in anesthetised patients who may be in a supine position.
• MacKay Marg tonometer

• Palpation, also known as digital tonometry, is the method of estimating intraocular pressure by pressing gently against the cornea of a closed eye with your index finger.^[13]

• Ocular Response Analyzer The ocular response analyser (ORA) is a non-contact (air puff ) tonometer that does not require topical anaesthesia and provides additional information on the biomechanical properties of the cornea. It uses an air pulse to deform the cornea in to a slight concavity. The difference between the pressures at which the cornea flattens inward and outward is measured by the machine and termed corneal hysteresis (CH). The machine uses this value to correct for the effects of the cornea on measurement ^[14]

 Gallery

A Goldmann tonometer	PASCAL Dynamic Contour Tonometer	SensorTip of a PASCAL tonometer in contact with patient's cornea	Diaton Tonometry through the Eyelid‎
Position of the Diaton Tonometer Tip on the Eyelid with No Contact with Cornea or use of Anesthesia	Hand-held Diaton tonometer with Test and Training Eye case

 References

1. ^ Goldman H, Schmidt TH.Uber Applanations-tonometrie. Ophthalmologica. 1957; 134: 221-242
2. ^ Amm M, Hedderich J. "[Transpalpebral tonometry with a digital tonometer in healthy eyes and after penetrating keratoplasty.]" Ophthalmologe. 2005 Jan;102(1):70-6. PMID 15322801.
3. ^ Schlote T, Landenberger H. "[Intraocular pressure difference in Goldmann applanation tonometry versus a transpalpebral tonometer TGDc-01'PRA' in glaucoma patients]." Klin Monatsbl Augenheilkd. 2005 Feb;222(2):123-31. PMID 15719316.
4. ^ Francis BA, Hsieh A, Lai MY, Chopra V, Pena F, Azen S, Varma R; Los Angeles Latino Eye Study Group. Effects of corneal thickness, corneal curvature, and intraocular pressure level on Goldmann applanation tonometry and dynamic contour tonometry. Ophthalmology. 2007 Jan;114(1):20-6.
5. ^ Kaufmann C, Bachmann LM, Thiel M, Comparison of Dynamic Contour Tonometry with Goldmann Applanation Tonometry. Invest Ophthalmol and Vis Sci 2004, Vol.45, No.9, 3118-3121. PMID 15326129
6. ^ Kaufmann C, Bachmann LM, Thiel MA, Intraocular Pressure Measurements Using Dynamic Contour Tonometry after Laser In Situ Keratomileusis. Invest Ophthalmol and Vis Sci 2003;44:3790-3794. PMID 12939293
7. ^ Kniestedt C, Nee M, Stamper RL, Dynamic Contour Tonometry. A Comparative Study on Human Cadaver Eyes. Arch Ophthalmol. 2004; 122:1287–1293. PMID 15364707
8. ^ Dr. Shaun Maria Dacosta, Dr. Babu Rajendran, Dr. Janakiraman P. "Comparison of Diaton Tonometry and Non Contact Tonometry in Indian Subjects" AIOC PROCEEDINGS 2008 Dec; 260
9. ^ Dr. Mark A. Latina Dr. Tarek A. Shazly R. Iospa Dr. Emil W. Chynn "Accuracy of Transpalpebral Tonometer Compared to Goldmann Applanation Tonometer in Normal and Glaucomatous Eyes" ARVO PROCEEDINGS 2009 May; 2843/A177
10. ^ Curtis, Theodore H.; MacKenzie, Douglas L.; Noecker, Robert J.; Kahook, Malik Y. "Comparison of the Diaton Transpalpebral Tonometer Versus Tono-Pen Applanation" ASCRS/ASOA 2007 April; P-128
11. ^ Richard S. Davidson, N. Faberowski, R. J. Noecker, Malik Y. Kahook "Comparison of the Diaton Transpalpebral Tonometer Versus Goldmann Applanation" ASCRS/ASOA 2007 April; P-130
12. ^ ^{a b} Cline D; Hofstetter HW; Griffin JR. Dictionary of Visual Science. 4th ed. Butterworth-Heinemann, Boston 1997. ISBN 0-7506-9895-0
13. ^ Troost A, Yun SH, Specht K, Krummenauer F, Schwenn O. "Transpalpebral tonometry: reliability and comparison with Goldmann applanation tonometry and palpation in healthy volunteers." Br J Ophthalmol. 2005 Mar;89(3):280-3. PMID 15722303.
14. ^ Felipe A. Medeiros, MD and Robert N. Weinreb, MD. "[Evaluation of the Influence of Corneal Biomechanical Properties on Intraocular Pressure Measurements Using the Ocular Response Analyzer]." J Glaucoma Volume 15, Number 5, October 2006.

 External links

• Tonometry - WebMD
• Tonometry - The Johns Hopkins Consumer Guide to Medical Tests
• Kirstein, E. "An Update on Methods for Assessing Intraocular Pressure." Retrieved June 7, 2006.
• Tonometry- Transpalpebral Diaton Tonometry
• Rebound Tonometer from Icare Finland
• Trans-Scleral Tonometry
• Tonometers in the market
• Tonometer from Keeler Ltd, UK based Company
• Through Eyelid Tonometer from BiCOM Inc.

Study

Too difficult