Jeffrey A Brinker, M.D.
- Professor of Medicine
- Joint Appointment in Radiology and Radiological Science
To d o Give three possible causes of partial loss of vision occurring as a result of optic nerve damage at the chiasma or following the separation of the nerve fibres as they proceed to purchase pentoxifylline 400mg on-line arthritis treatment knuckles the visual cortex of the brain generic 400mg pentoxifylline fast delivery arthritis in fingers cure. Loss of vision occurring as a result of damage to cheap pentoxifylline 400mg online arthritis medication for dogs uk the optic pathways is not generally an ophthalmic problem, but patients who complain primarily of a loss of vision are generally seen in the ophthalmic department where the health of the retina may be ascertained and the visual fields recorded for diagnostic purposes. Protective effect on the corneal epithelium and remaining efficiency at the anterior chamber for three different kinds of viscoelastic devices. Caceci on the anatomy and physiology of the eye and development of the eye in invertebrates. The conjunctival glands of Krause and Wolfring, situated in the upper and lower fornices, are responsible for secreting what? What anatomical structures are involved in the conventional drainage route from the eye? Name the two main layers of the retina 22 Basic anatomy and physiology of the eye 14. The fibres from the optic nerve cross over at an area lying just above the pituitary gland. Understanding how light is refracted within the eye is key to understanding the visual needs of our patients, particularly when it comes to obtaining accurate intraocular lens readings and understand ing spectacle prescriptions and associated visual difficulties. Essential learning If you normally work with cataract patients, it is essential that you begin to get a grasp of the following: G the vocabulary common when discussing refraction. G Some of the pitfalls associated with inaccurate measurements prior to cataract surgery, or the insertion of a lens of the incorrect power (see Chapters 5, 6 and 7). Refraction of light by the eye to produce good, unaided vision (by focusing the light on to the retina) is dependent on the power of the cornea, the lens and the length of the eye. All the individual transparent areas of the eye contribute to bending and focusing the light rays on the retina. Snell and Lemp (1998) state that the power of the whole normal (emmetropic) eye is about 58 dioptres (see Dioptre in Appendix 2); the cornea has a refractive power of about 42 dioptres and is responsible for more than two-thirds of this refractive ability. In addition it should be recognised that the tear film, aqueous humour, lens and vitreous all contribute to refraction of the light rays so that they normally come to a focus at the macula. The signifi cance of the lens is that it can change its dioptric power by contraction and relaxation of the ciliary muscle. This is because the lens becomes thicker (more convex) when the ciliary muscle contracts and thinner when it relaxes. Contraction of the ciliary muscle releases the tension on the zonule fibres, allowing the lens to increase its curvature. This process of changing the lens shape is called accommodation, and it allows distant and near objects to be focused on the retina. The amount by which the lens can change in power reduces with age about 8 dioptres at the age of 40 and only 1?2 dioptres at the age of 60 (Snell and Lemp, 1998). Focusing the eye for near vision this involves: Pupil constriction: Smaller pupil diameters result in an increased depth of focus and an improved retinal image. Convergence: this is when the eyes turn slightly inwards towards the nose, and it ensures that the image is projected on to the fovea of each eye, aiding binocular vision and increasing 3-D perception (stereopsis). Accommodation: When we look at objects near to us, diverging light rays reach our corneas so the eye requires more refractive power to focus the light on to the retina (but parallel light rays come from objects in the distance). In order to do this, the ciliary muscles contract, making a smaller ring, and taking the tension off the suspensory ligaments. This means the lens becomes smaller and fatter and moves slightly backwards, to increase refraction. The ciliary muscles are innervated by the autonomic nervous system, and accommodation is controlled automatically by the brain. You can read more about the process of accommodation at the websites of Georgia State University HyperPhysics and Ted Montgomery. Emmetropia (normal sight) the refractive components of the normal eye are able to focus light from a distant object (parallel light) on the retina accurately, so that the person is able to see distant objects clearly without spectacles. When a person is young and has normal accommodation they will also be able to read without spectacles. However, with age even normal sighted people have decreased ability to accommodate (presbyopia) which means that spectacles will be needed for close work. Ammetropia (refractive error) this term indicates a variation in the shape of the eye that interferes with accurate light refraction. Factors affecting the possibility of someone having (or developing) a refractive error include their age, whether their parents were long or short-sighted, their race and the environment they live and work in. For example, people who live and work for days in confined spaces such as underwater diving bells and submarines tend to develop myopia (see below). This may pass off to some extent following a return to a normal environment (Onoo et al. The result is that close objects look clear, while objects further away look blurred. When looking into the distance the person must use the natural power of their lens to see clearly. Because the hypermetropic person already has to use most of their natural focusing power to see in the distance, they are less able to see near objects clearly. As young people they can often use the focusing power of their eyes to overcome the problem of hypermetropia. However, in their late teens and early 20s, the lens begins to become a little harder and they may then require spectacles. If you have hypermetropia, your prescription will have a positive value (for example, +2. It can be because the cornea or lens curves more in one direction than in the other, with resulting distortion when viewing both distant and near objects.
Other causes of a cicatricial entropion are trauma purchase discount pentoxifylline on line symptoms of arthritis in the knee joint, chemical burns buy pentoxifylline online from canada arthritis back pain natural remedies, Stevens Johnson syndrome and ocular cicatricial pemphigoid generic pentoxifylline 400mg with mastercard arthritis pain when sleeping. Treatment: Many plastic operations have been devised for the relief of cicatricial entropion, but only the more simple will be described here. The principles governing the various operations are (i) lengthening of the posterior lid lamina to restore the normal direction of the lashes; and (ii) tarsal rota tion. A local submuscular pre-tarsal injection of 2% ligno caine or a general anaesthetic is indicated, but the former B method does not obviate all pain, especially if the tarsus is cut. A skin incision is made 3 mm from the lash line and a wedge of tarsus approximately is freed by blunt dissection over an area of about 10 mm, 3 mm in height is pared off to a depth of more than three and excess pre-septal skin and orbicularis muscle may be fourths of the tarsus. There is also a skin, is made along the whole length of the lid in the sulcus horizontal lid laxity present in such cases. These conditions subtarsalis, about 2?3 mm above the posterior border of the are found particularly in old people who are therefore liable intermarginal strip. It may be caused by tight bandaging, as be divided by a vertical incision through the free edge of the after a surgical operation, and is favoured by narrowness of lid, including the whole thickness. Spastic entropion thus left attached only by skin, and when cicatrization has is almost invariably restricted to the lower lid (Fig. Lubricants take may be kept everted during the process of healing by means care of surface disorders and antibiotics of conjunctival or of suitably applied sutures. If the condition is due to bandaging, it is In an alternative operation, the incision is made as be often cured by simply removing the bandage. In spastic en fore, but the tarsal plate is pared down to a chiseledge along tropion of the elderly, temporary relief may be obtained after the whole length and mattress sutures passed through the everting the lid, by pulling it out with a strip of adhesive plate and lid margin, emerging through the grey line. If the entropion persists, botulinum toxin may be sutures are tied over a rubber tubing, thus bending the lid margin forwards and upwards. Very extensive scarring may necessitate the replacement of the conjunctiva by a mucous membrane graft and a dis torted tarsal plate by cartilage or chondromucosal grafts. Spastic Entropion this generally occurs in response to ocular irritation such as infammations or trauma, and is due to spasm of the orbicu laris in the presence of degeneration of the palpebral connec tive tissue separating the orbicularis muscle fbres. The infe rior lid aponeurosis normally maintains the orbicularis muscle in such a position that it presses against the lower tarsus and prevents an entropion by contraction of the capsu lar palpebral head of the inferior rectus. Abnormal lid laxity is diagnosed if the in the orbicularis muscle and thus preventing the fbres lid can be drawn away from the globe by more than from sliding in a vertical direction. A horizontal incision is 6?7 mm and does not snap back into position when re made 4 mm below the lid margin through all the lid struc leased. Two double-armed sutures are placed through the a displacement of the canthi by more than 2 mm, laxity of tarsal plate in the inferior lip of the wound, entering from the canthal ligaments is diagnosed. These sutures are inserted under Mild forms of ectropion can be treated with artifcial the skin of the upper lip of the wound to exit just below the tears and protection from drying of the eyes. The skin incision is closed, the clamp released be instructed to wipe their eyes in an upward direction and the deep sutures tied. Congenital Entropion Senile Ectropion this rare condition is due to dysgenesis of the lower lid Involutional ectropion usually develops as a result of laxity retractors or a developmental abnormality of the tarsal of the suspensory system of the lower eyelid, and the plate, causing the lid margin to turn onto the globe. Treat medial and lateral canthal ligaments, allowing the lid to ment should address the cause. This laxity is accompanied by a diagnosis is an epiblepharon where an anomalous skin horizontal lengthening of the lid. Surgical treatment: In mild-to-moderate entropion a horizontal spindle of conjunctiva 7?8 mm long, 4 mm high and at least 5 mm below the punctum is excised and sutured Ectropion to its margins. This allows the puncta to be replaced in their Eversion of the lid margin and eyelashes away from the normal position. It occurs in several forms, but If the ectropion is most pronounced in the mid-section the main types are as follows: of the lower lid, full-thickness lid shortening is recom mended in that area. An inverted house-shaped l Involutional or senile incision of tissue is made and then repaired. If the degree of l Cicatricial ectropion is severe and marked over the lateral half of the l Paralytic lower lid, with little laxity of the lateral canthal ligament, a l Mechanical Kuhnt?Szymanowski procedure as modifed by Bryon 2. A line is drawn 3 mm the functions of the lower eyelid are protection of the eye inferior to the lid margin following the contour of the lower and working of the lacrimal pump. The line is drawn slightly past the lateral canthus in an slow relaxation of the lid structures, especially the canthal upward manner, at which point it is sloped downwards. A ligaments and the orbicularis, which form the suspensory skin fap is prepared and a full thickness lid shortening then system of the lid. In very mild cases, asking the patient to performed at the lateral canthus as previously described. Over time, as the ectropion progresses to the moderate moved and the skin margins sutured with 7-0 silk. Traction stage, it will be found that the puncta are not apposed even sutures are kept at the point of meeting of the lid margin in primary gaze, and progressively the entire lid margin will and are taped to the forehead at the end of the procedure. Finally, in severe cases, the palpe there is laxity of the lateral canthal ligament, cantholysis bral conjunctiva and the fornix are exposed. Weakness of and tarsal excision at its lateral margin permits reattach the capsulopalpebral tissues allows the whole tarsus to fall ment of the tarsal plate to the periosteum. The puncta drain tears from the palpebral sac to the nose; however, as the punctum moves away from its nor mal position against the globe, tears are not drained into the nose, but overfow onto the cheek. Chronic exposure in long standing ectropion can lead to punctal phimosis, and kerati nization of the lid margin and palpebral conjunctiva. A medial ectropion released from any underlying adhesions before the applica can be corrected by a modifed Lazy T operation, in which tion of a skin graft.
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In fact purchase pentoxifylline 400mg online adjuvant arthritis definition, the occurrence of early seizures adds a significant increment of risk for later epilepsy to 400mg pentoxifylline with mastercard arthritis flare up in dogs that associated with the primary condition purchase 400 mg pentoxifylline fast delivery rheumatoid arthritis pain in back of knee. In general, the risk for subsequent unprovoked seizures is greatest in the first 2 years following the acute insult. Approximately 12% of individuals suffering an occlusive cerebrovascular insult resulting in a fixed neurological deficit will experience a seizure at the time of the insult. Unprovoked seizures will occur within the next 5 years in 16% of all individuals with an occlusive vascular insult. This rate seems not to be modified significantly by the occurrence of early seizures. The risk is increased primarily in individuals with lesions associated with cerebral cortical or subcortical deficits. The same risk of seizure and recommendations are applicable for intracerebral or subarachnoid hemorrhage. The length of time an individual is seizure free and off anticonvulsant medication is considered the best predictor of future risk for seizures. Therefore, according to medical guidelines, for the entire waiting period before being considered for certification, the driver should be both. For those individuals who survive severe head injury, the risk for developing unprovoked seizures does not decrease significantly over time. Based upon the risk for unprovoked seizures alone, the driver should not be considered for certification. Individuals who have undergone such procedures, including those who have had surgery for epilepsy, should not be considered eligible for certification. Waiting Period Minimum 1 year seizure free and off anticonvulsant medication following. Page 143 of 260 Decision Maximum certification 1 year Recommend to certify if: the driver with a history of mild or moderate insult has. Completed the minimum waiting period seizure free and off anticonvulsant medication. Recommend not to certify if: the driver has a history of a severe brain insult with or without early seizures. Has not completed the minimum waiting period seizure free and off anticonvulsant medication. Monitoring/Testing You may on a case-by-case basis obtain additional tests and/or consultation to adequately assess driver medical fitness for duty. Acute Seizures Systemic Metabolic Illness Seizures are the normal reaction of a properly functioning nervous system to adverse events. In the presence of systemic metabolic illness, seizures are generally related to the consequences of a general systemic alteration of biochemical homeostasis and are not known to be associated with any inherent tendency to have further seizures. The risk for recurrence of seizures is related to the likelihood of recurrence of the inciting condition. Waiting Period No recommended time frame You should not certify the driver until etiology is confirmed and treatment has been shown to be adequate/effective, safe, and stable. Decision Maximum certification 2 years Page 144 of 260 Recommend to certify if. Recommend not to certify if: As the medical examiner, you believe that the nature and severity of the medical condition of the driver endangers the health and safety of the driver and the public. Monitoring/Testing You may on a case-by-case basis obtain additional tests and/or consultation to adequately assess driver medical fitness for duty. Childhood Febrile Seizures Febrile seizures occur in from 2% to 5% of the children in the United States before 5 years of age and seldom occur after 5 years of age. From a practical standpoint, most individuals who have experienced a febrile seizure in infancy are unaware of the event and the condition would not be readily identified through routine screening. Most of the increased risk for unprovoked seizure is appreciated in the first 10 years of life. Waiting Period No recommended time frame You should not certify the driver until etiology is confirmed and treatment has been shown to be adequate/effective, safe, and stable. Decision Maximum certification 2 years Recommend to certify if: the history of seizures is limited to childhood febrile seizures. Recommend not to certify if: As the medical examiner, you believe that the nature and severity of the medical condition of the driver endangers the health and safety of the driver and the public. Monitoring/Testing You may on a case-by-case basis obtain additional tests and/or consultation to adequately assess driver medical fitness for duty. Therefore, the following drivers cannot be qualified: (1) a driver who has a medical history of epilepsy; (2) a driver who has a current clinical diagnosis of epilepsy; or (3) a driver who is taking antiseizure medication. Recommend not to certify if: the driver is taking anticonvulsant medication because of a medical history of one or more seizures or is at risk for seizures. Monitoring/Testing You may on a case-by-case basis obtain additional tests and/or consultation to adequately assess driver medical fitness for duty. Clearance from a specialist in neurological diseases who understands the Page 146 of 260 functions and demands of commercial driving is a prudent course of action if choosing to certify the driver with an established history of epilepsy. Headaches Chronic or chronic-recurring headache syndromes can potentially interact with other neurological diagnostic categories in two ways. The following types of headaches may interfere with the ability to drive a commercial motor vehicle safely. Consider headache frequency and severity when evaluating a driver whose history includes headaches. In addition to pain, inquire about other symptoms caused by headaches, such as visual disturbances, that may interfere with safe driving. Waiting Period No recommended time frame You should not certify the driver until etiology is confirmed and treatment has been shown to be adequate/effective, safe, and stable.
Physician ownership of ambulatory surgery centers and practice patterns for urological surgery: Evidence from the state of Pennsylvania Health Care Cost Containment Council buy generic pentoxifylline online arthritis in the knee and hip. Reference surgery performed in an ambulatory surgery center versus a based benefit design changes consumers choices and employers hospital: Comparison of perioperative time intervals buy pentoxifylline 400mg overnight delivery arthritis diet chocolate. How should Medicare Medicare has paid for outpatient dialysis services using a prospective payment payments change in 2020? Assessment of payment adequacy Our payment adequacy indicators for outpatient dialysis services are generally positive discount 400 mg pentoxifylline free shipping arthritis cure. Beneficiaries access to care?Measures of the capacity and supply of providers, beneficiaries ability to obtain care, and changes in the volume of services suggest payments are adequate. Between 2012 and 2017, beneficiaries use of home dialysis, which is associated with improved patient satisfaction and quality of life, increased from 9. It is not clear whether this trend will continue since the results for 2017 and 2018 are not yet available. Providers access to capital?Information from investment analysts suggests that access to capital for dialysis providers continues to be strong. The number of facilities, particularly for-profit facilities, continues to increase. During this period, cost per treatment increased by 2 percent, while Medicare payment per treatment increased by 0. Patients may select various protocols for is done either manually (continuous ambulatory each of these two dialysis types. Most dialysis patients travel to a treatment facility to undergo hemodialysis three times per week, although Each dialysis method has advantages and patients can also undergo hemodialysis at home. Because of recent reasons, including quality of life, patients awareness of clinical findings, there is increased interest in more different treatment methods and personal preferences, frequent hemodialysis, administered five or more times and physician training and recommendations. The use per week while the patient sleeps, and short (two to of home dialysis has grown since 2009, a trend that three hours per treatment) daily dialysis administered has continued under the dialysis prospective payment during the day. Some patients switch methods when their the use of every-other-day hemodialysis; reducing the conditions or needs change. Although most patients two-day gap in thrice-weekly hemodialysis could be still undergo in-center dialysis, home dialysis remains linked to improved outcomes. In 2017, Medicare removes wastes and fluid from the body?and those who Part B spending for outpatient dialysis services included have a functioning kidney transplant. Patients receive additional items and services related to their dialysis treatments, including dialysis drugs to treat Characteristics of fee-for-service dialysis conditions such as anemia and bone disease resulting from beneficiaries, 2017 the loss of kidney function. Between 2006 and 2016 (most recent year available), the qualify for Medicare, he or she must be fully or currently adjusted incidence rate decreased by 1 percent per year, insured under the Social Security or Railroad Retirement from 399 per million people to 355 per million people 3 program or be the spouse or dependent child of an eligible (United States Renal Data System 2018). For adult dialysis beneficiaries fee schedule and has made recommendations to support (18 years or older), the base payment rate does not differ primary care, which in turn could support better by type of dialysis. In providers separately for all dialysis drugs and biologics, addition, effective in 2012, outpatient dialysis payments are including biosimilars and generic drugs, that the Food and linked to the quality of care that dialysis facilities provide. Capacity has kept pace with patient demand Growth in the number of dialysis facilities and treatment Are Medicare payments adequate in stations alongside growth in the number of dialysis 2019? During To address whether payments for 2019 are adequate to that period, the number of facilities increased annually cover the costs that efficient providers incur and how much by 5 percent; facilities capacity to provide care?as providers costs should change in the update year (2020), measured by dialysis treatment stations?grew 4 percent we examine several indicators of payment adequacy. Most facilities that were hospital based and nonprofit decreased of our payment adequacy indicators for dialysis services annually (?5 percent and 1 percent, respectively). Between 2012 and 2016, capacity at urban facilities grew 4 percent per year, while capacity at all rural facilities Beneficiaries access to care: Indicators grew about 2 percent per year. Provider location refects the county where the provider is located in one of four categories (urban, micropolitan, rural adjacent to urban, and rural nonadjacent to urban) based on an aggregation of the urban infuence codes. The number of nonannualized Types of facilities that closed and their effect on dialysis treatments per beneficiary remained steady at 115. The agency said that facilities must Between 2016 and 2017, the number of dialysis treatment provide medical justification to be paid for furnishing stations?a measure of providers capacity?increased more than three dialysis treatments per week and that by 3 percent. There was a net increase in the number of the choice of dialysis modalities that require more facilities that were freestanding, for profit, and located in than three treatments per week does not constitute both urban and rural areas. Medicare Payment Advisory Commission 2017, Medicare Payment Advisory Commission 2016b). Dollars per treatment calculated by multiplying drug units reported on claims by 2018 average sales price. Source: 2017 (the most current year for which complete data are declined by 23 percent per year. Under the prior payment method, dialysis drugs the column totals were added manually. Between 2016 and 2017, holding price constant, the use of administered: In other words, the more units of a drug all dialysis drugs declined by nearly 4 percent. Individual units per treatment are rounded; the aggregate percentage change is calculated using unrounded units per treatment. If Medicare payments are larger than announced that between 85 percent and 90 percent of its the marginal costs of treating an additional beneficiary, a facilities will have switched to epoetin beta by the end of provider has a financial incentive to increase its volume of Report to the Congress: Medicare Payment Policy | March 2019 165 Medicare patients. The increased slightly (Centers for Medicare & Medicaid negative cardiovascular outcomes associated with high Services 2018a). Anemia is measured by a blood test to check the level of hemoglobin, the protein In assessing quality, we also examine the multiple factors that carries oxygen in red blood cells. Figure 6-2 than dialysis in terms of patients clinical and quality of shows that the proportion of dialysis beneficiaries with life outcomes and Medicare spending, and demand far higher hemoglobin levels declined, and the proportion with outstrips supply. However, there 80 has been an increasing trend between 2015 and 2017 Hemoglobinlevel at or exceeding12g/dL 16 (Centers for Medicare & Medicaid Services 2018a).
On the left the pupil buy pentoxifylline 400 mg low price arthritis in dogs tylenol, looking as if it were on the surface of the lens cheap pentoxifylline 400 mg otc rheumatoid arthritis kansas city, of both Fig buy pentoxifylline 400mg visa arthritis nsaids. The black space on the right is the anterior appearance over the whole pupillary area suggests a total or chamber. A mature cataract; if it is yellowish-white, with white spots of dim central interval can be distinguished, formed by the calcifcation and the iris is tremulous, a shrunken calcare embryonic nucleus with its Y-sutures. Finally, the pupil may the successive zones of discontinuity the fetal nucleus, be blocked with uveal exudates forming an infammatory the infantile nucleus, the adult nucleus and the cortex. Ocular problems can be identifed by different meth ods of examination, which differ in the positioning of the illuminating light and the angle between the illumination and observation arms. Various permutations and combina tions of these techniques are used, some simultaneously and others sequentially. Specular Refection Specular refection allows the observer to visualize the cor neal endothelium by viewing light refected back from this interface. The illuminating and viewing arms are adjusted so that each forms an angle of about 30 to the central per pendicular, the slit-lamp beam is narrowed to a height of 2 mm and focused onto the central corneal endothelium. This is placed immediately adjacent to the refection of the slit-lamp bulb on the cornea. A golden sheen with darker lines outlining the hexagonal endothelial cells is seen (Fig. This light is totally internally refected through the thickness of the cornea, like a fbre-optic light pipe, and emerges at the opposite limbus. The fundal glow highlights the pre Tonometry is the assessment of the intraocular pressure of the sence of opacities in the media, such as cataracts (Fig. It also highlights the presence of Subjective method: It may be done digitally in the defects in the integrity of the normally opaque iris. The light refected off the iris allows Instruments known as tonometers have been devised for visualization of subtle, transparent corneal irregularities, such measuring the intraocular pressure of the intact eye and are as ghost vessels or keratic precipitates. An assistant the nearest mm Hg for the different weight of the Schiotz may separate the lids while you concentrate on proper placement tonometer. After anesthetic drops use the nest highest weight that will give a reading of 5 or are instilled, the patient will not experience any pain from this more. It is important to have a relaxed patient because squinting and blepharospasm may interfere with the reading. Note: Use the above chart to determine the converted reading Gloves should be worn. The depth and the volume of the Rod indentation are dependent on the intraocular pressure and the distensibility of the ocular walls. Housing the instrument is calibrated so that the equivalent read ings in millimetres of mercury can be read off a chart. The Schiotz tonometer is often inaccurate, largely because of wide individual variations in the rigidity of the corneo scleral coats. However, the tonometer is useful for obtain Adjustment knob ing approximate readings, particularly for comparative A(i) A(ii) measurements, such as between the two eyes or for succes sive measurements on the same eye. To allow for this inac curacy the type of tonometer should always be cited and the reading expressed in this form 220. The readings are not accurate in steep, thick or irregular corneas, high myopia or hyperopia, with the use of miotics, vasodilators or vasoconstrictors, or after any intra ocular surgery, especially vitreoretinal surgery. Instead of measuring the amount of indentation, the appla (From Harold A Stein, Raymond M Stein, Melvin I Freeman. When the cornea is fattened by the application of a plane surface on it, the intraocular pressure is directly proportional to the pressure applied and inversely to the the circular meniscus of fuorescein is seen as two half area fattened. The most popular applanation tonometer was de when the two inner edges of the mires coincide. The mires signed by Goldmann for use with the Haag?Streit slit-lamp should not be too thick or too thin, because of excess or (Fig. In it, a fat circular plexiglass plate 7 mm in scarcity of fuorescein, as the intraocular pressure will then area is applied to the anaesthetized cornea so as to fatten an be over or underestimated, respectively. The ap ingenious duplicating optical device, formed by prisms planation tonometer cannot be used in scarred corneas. This particular area of fattening is A hand-held version is available as the Perkin tonome chosen, as with it a force of 0. The patient is seated at a slit-lamp after anaesthe using the applanation principle is that of Mackay Marg. Indirect Goniolenses l Goldmann single-mirror Mirror inclined at 62 gonioscope A l Zeiss four-mirror All four mirrors inclined at gonioscope 64?; requires holder (Unger); fuid bridge not required 1 2 l Posner four-mirror Modifed Zeiss four-mirror gonioscope gonioprism with attached handle Not aligned. End-point of perfect alignment of mires when recording intraocular diagnostic lens pressure with the Goldmann applanation tonometer. The average of several tracings is taken as the reading of the intraocular pressure. A digital, hand-held version of the same is available as 64, in which the image of the recesses of the angle is re the Tonopen tonometer, which provides a mean and stan fected (Fig. Gonioscopes with one, two or dard deviation of 4?10 acceptable readings, automatically. A base of about 7 mm enables viewing cornea and a photoelectric cell measures refected light of the angle using a tear flm bridge, and also allows depres obtained when a fxed area of cornea is applanated. The sion of the central cornea for indentation gonioscopy time taken for applanation is proportional to the intraocular (Fig. The average intraocular pressure is approximately the centre peripherally, to push away the iris, and allow 15?17 mmHg (applanation).