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Visual impairment in the working age person
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Visual impairment in the working age person Giuliana Silvestri
Many of the conditions causing visual loss in persons of working age are not exclusive to this age group and have therefore been described elsewhere. Visually impaired persons in this age group may, however, reach a critical stage in their disease process and therefore experience significant changes in visual function with resulting changes in circumstances and/or employment. The conditions described in this chapter are those that cause unexpected visual compromise in the previously normally sighted adult.
3.1 Diabetic retinopathy 3.1.1 Clinical presentation Patients with diabetes mellitus may develop none, some or all of the following retinal changes throughout life: microaneurysms, dot and blot haemorrhages, venous dilatation, venous beading and loops, hard exudate formation, cotton-wool spots, vascular occlusion, vasoproliferation, vitreous haemorrhage and tractional retinal detachment. Although dilatation of the retinal veins is the earliest clinical sign of diabetic retinopathy, this can be difficult to detect on ophthalmoscopy. The earliest easily detectable sign of diabetic retinopathy is the appearance of a few tiny red dots in the retina; histological studies have shown these to be microaneurysms. 56
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Practical advice The earliest clinical changes – microaneurysms – are usually found in the area of retina just temporal to the macula. This is the vascular ‘watershed’ zone.
The temporal macular area represents a watershed zone, where the medial and lateral posterior ciliary arteries meet; this is an area of potential vascular weakness. In health, the retinal capillary walls contain pericyte cells, which are responsible for maintaining tone in the capillary walls. Death of the pericytes is the first histological change in diabetic retinopathy and is responsible for the formation of outpouchings of the capillary walls, known as microaneurysms.1 Once the pericytes are lost, the endothelial cells also lose their tight junctions and leakage of blood and protein into the retina occurs. Microaneurysms and small punctate haemorrhages cause no symptoms as long as the central fovea remains uninvolved. Microaneurysms are particularly obvious on fluorescein angiography and are easily distinguished from punctate haemorrhages owing to differing angiographic features. The retinopathy may remain stable for many years with minor background changes or, alternatively, progression may occur. Macular oedema is the commonest cause of impaired visual acuity in patients with early diabetic maculopathy. Intraretinal oedema, particularly when minor in nature, does not change the retinal transparency and is difficult to recognise by monocular ophthalmoscopy. A stereo view is required to detect clinically significant macular oedema (CSMO). In the clinical setting, use of the simple macular photostress recovery test is helpful in deciding whether CSMO is a possibility.
Practical advice The superfield non-contact Volk lens affords the observer a wideangled stereo view of the posterior pole and peripheral retina, and is useful in the diagnosis of diabetic retinopathy and, in particular, CSMO. The resolution of the lens can be enhanced using a contact lens adaptor.
Deposits of hard yellowish-white material are frequently seen at the periphery of oedematous areas; these represent lipid and/or 57
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protein that has ‘precipitated out’ from the oedematous fluid (hard exudates). Unfortunately, these changes characteristically occur in the posterior pole near the macula and can cause loss of central vision. As the disease progresses, other features become apparent on ophthalmoscopy. Cotton-wool spots, which represent areas of focal ischaemia and further dilatation and beading of the retinal veins, indicate progression of retinopathy. The mechanism whereby this occurs is obscure, but is probably related to hypoxia and venous stasis. Studies indicate that approximately 30% of patients with diabetes progress to either proliferative retinopathy or macular oedema over a 14-year period.2 New vessels arise most frequently on the optic disc or along the course of the major retinal veins. Unfortunately, wherever the vessels grow on the surface of the retina, they become adherent to the vitreous. When the vitreous contracts, it cannot easily separate from the retina and the vitreous pulls on the fragile new vessels, causing rupture of their walls and vitreous haemorrhage. Subsequently tractional retinal detachment may also ensue. A fuller description of the clinical grading of diabetic retinopathy is shown in Table 3.1. Before the availability of laser photocoagulation, 50% of eyes with fully developed proliferative retinopathy progressed to marked reduction of vision and often complete blindness.3 In the past, considerable controversy existed regarding the role of accurate control of diabetes in the prevention of retinopathy, as well as nephropathy and other vascular complications. The recent United Kingdom Prospective Diabetic Study has confirmed that good control of blood sugar levels is important in the prevention of both microvascular and macrovascular complications.4 This study also highlighted the importance of attending to the other ‘bad companions’ of diabetes – hypertension, hypercholesterolaemia and smoking. It is essential that all those involved in managing patients with diabetes have a thorough understanding of its complications and that they are willing to devote considerable time to education of their patients.
Practical advice Patient education is absolutely essential, as it is the patient who must understand and manage their disease from day to day and from hour to hour. In some diabetic units, a diabetic education centre and a diabetic liaison nurse are available to improve diabetic knowledge.
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Table 3.1 Grading of Diabetic Retinopathy Grade of retinopathy
Clinical signs
Features on angiography
Background
Venous dilatation (can be preclinical); microaneurysms; dot haemorrhages; blot haemorrhages; hard exudates
Leakage from microaneurysms; masking due to haemorrhages and exudates
Microaneurysms; hard exudates – diffuse or circinate
Diffuse or focal leakage from microaneurysms; little, if any, capillary fall-out
Oedematous
Retinal thickening – focal or diffuse; microaneurysms; dot and blot haemorrhages
Predominantly intraretinal leakage ± ischaemia
Ischaemic
Microaneurysms; large blot and blotch haemorrhages ± retinal thickening
Widespread areas of capillary fall-out often involving the perifoveal arcade
Pre-proliferative
All features of background retinopathy plus cottonwool spots; widespread intraretinal haemorrhages; venous dilatation, beading and venous loops; intraretinal microvascular abnormalities (IRMAs)
Widespread inner retinal ischaemia; masking from large haemorrhages; IRMAs
Proliferative
New vessels on the disc or elsewhere; fibrous tissue; pre-retinal and vitreous haemorrhage; ‘raspberry’ or abortive neovascular outgrowth
Widespread inner retinal ischaemia; profuse early leakage from new vessels
Maculopathy Exudative
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3.1.2 Prevalence of diabetic retinopathy The prevalence of diabetic retinopathy increases with duration of diabetes. In type 1 (juvenile) diabetes, retinopathy is virtually never present in the first 5 years. However, 27% of those who have had diabetes for 5–10 years and 71% of those who have had diabetes for 10 years or longer will have diabetic retinopathy. After 30 years the incidence rises to 90%, with 30% of these patients having proliferative diabetic retinopathy (PDR).5 Times of added risk are around puberty and during pregnancy. In adult onset diabetes, maculopathy is more common than proliferative retinopathy but may in some cases be associated with neovascularisation. Often in patients with type 2 diabetes, maculopathy can be the presenting feature of the disease. Adult-onset diabetes can remain undiagnosed for many years, with severe damage to the retinal capillaries resulting in subsequent irreversible visual loss.
Practical advice Visual acuity may appear good even in the presence of PDR or extensively treated non-proliferative retinopathy.
3.1.3 Laser photocoagulation and surgery for diabetic retinopathy Laser photocoagulation of the diabetic retina utilises an argon or krypton laser to coagulate ischaemic retina, rendering the ischaemic retina non-viable and thereby removing the stimulus for neovascularisation. Recent randomised controlled studies have shown that laser photocoagulation is effective in preserving vision and slowing the rate of visual decline in diabetic patients with pre-retinal and papillary neovascularisation and early maculopathy.5–7 Advanced retinal neovascularisation and macular oedema respond less favourably to photocoagulation; thus, it is imperative to detect disease in its early stages by meticulous screening and careful observation of diabetic patients. Persistent dense vitreous haemorrhage, fibrovascular membranes and traction detachments, which threaten macular function, may be treated by vitrectomy. This technique may dramatically improve visual function by irrigating blood from the vitreous cavity using an intraocular infusion and suction system, fitted with a cutting head. Fibrovascular 60
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membranes may also be carefully dissected from the retinal surface.7
3.1.4 The management of diabetic retinopathy The management of diabetic retinopathy has been the subject of many excellent randomised controlled trials, with the result that many management questions have been answered conclusively. Some questions that are of paramount importance to both the patient and the surgeon are discussed below.
Q.1 Does laser photocoagulation have any impact on the progression of retinopathy? Yes. Laser photocoagulation has been shown to reduce blindness in diabetic retinopathy by 50%.
Q.2 When should laser be applied in proliferative retinopathy? The Early Treatment Diabetic Retinopathy Study (ETDRS) has shown that panretinal laser photocoagulation (PRP) (Fig. 3.1 [Plates 5 & 6]) should be applied when ‘high risk’ criteria are present. High-risk criteria are as follows and indicate the need for prompt and aggressive PRP: • NVD (new vessels on the disc) covering more than onequarter to one-third of the disc area • NVD covering less than one-quarter to one-third of the disc area in the presence of pre-retinal or vitreous haemorrhage • NVE (new vessels elsewhere) with pre-retinal or vitreous haemorrhage.
Q.3 Is laser treatment equally helpful for all types of maculopathy? No. Unfortunately laser therapy is not helpful in all types of maculopathy. Exudative maculopathy responds best, in particular for patients who have circinate patterns of hard exudates. Oedematous maculopathy responds, at best, with stabilisation of vision in 30% of patients. No treatment has 61
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been found to be of help in ischaemic maculopathy; in fact, laser photocoagulation can sometimes exacerbate the situation. The outcome for patients with mixed maculopathies depends on the degree of each of the above components. Patients are often disappointed if they are told that they are unsuitable for laser treatment, or that it would not be of benefit. These patients usually have an ischaemic type of maculopathy.
Q.4 Should laser treatment be applied in pre-proliferative retinopathy? No, although it would appear sensible to pre-empt complications. The reason that laser treatment is not automatically indicated in all patients who develop to preproliferative retinopathy is that only 50% will progress to fullblown PDR. In addition, PRP is not without side-effects.
Q.5 Are there any side-effects to laser photocoagulation? Yes. The potential side-effects of laser treatment, whether permanent or transient, are many (Table 3.2). In practice, the most common side-effects of PRP are night blindness and loss of the peripheral field. These side-effects are, however, well tolerated by patients and are often accepted as a necessary pay-off against the preservation of what can often be excellent central acuity. Patients who have had successful PRP often maintain 6/6 [LogMAR 0.0] vision 20–30 years later. What is often most annoying for patients is the photophobia associated with scatter PRP. This is thought to be due to internal scattering and reflection of light from the laser scars.
In providing low vision support for those with visual impairment resulting from diabetes, the key is versatility. As aspects of the underlying condition change (lens hydration, macular oedema, retinopathy), so do refractive status and visual function. Spectacles must be kept up to date and a range of low vision aids, some of which are designed to enhance contrast, provided. Advice on a wide range of visual rehabilitation strategies and various forms of 62
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A
B Figure 3.1 A & B (Plates 5 & 6) Treated diabetic retinopathy in a 24-year-old woman. The patient has been treated with panretinal photocoagulation for proliferative retinopathy (scars in the peripheral retina of the left eye – B) and with bilateral grid laser for maculopathy (subtle scars in the macular areas – A & B).
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C Figure 3.1 C (Plates 5 & 6) Corresponding ‘binocular Estermann’ fields show both peripheral and central field loss secondary to laser photocoagulation. This patient would not be eligible to hold a driving licence. Black rectangles indicate loss of function.
assistive technology (both low and high tech) should be provided.
3.1.5 The St Vincent’s Declaration In 1989, the World Health Organization and the International Diabetes Federation for Europe drew up a joint initiative on diabetes care and research into diabetes mellitus.8 Central to the initiative was the inclusion of 5-year targets for improvement in all diabetic complications, including the reduction of diabetic blindness by one-third. Following the St Vincent’s Declaration, a uniform pro64
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Table 3.2 Side-Effects of Argon Laser Panretinal Photocoagulation Transient side-effects
Permanent side-effects
Blurring of vision
Loss of visual acuity
Choroidal detachment
Accommodative defects (due to damage to long ciliary nerves and resulting recession of the near point)
Macular oedema – can persist for weeks but usually settles. More common in type II diabetes after PRP
Dimness of vision (dose related if >2000 burns at one sitting)
Headache
Nyctalopia Loss of colour vision Photophobia Loss of peripheral field Inadvertent foveal burn
tocol was developed in a joint venture by 21 European countries for the screening of diabetic retinopathy. This protocol includes guidelines for examination and a data collection sheet.9 To date, little progress appears to have been made in addressing these aims in a practical way.
3.2 Pathological myopia 3.2.1 Clinical presentation The prevalence of myopia varies between 11% and 36% of the general population, with 30% of the myopic population and 1–4% of the general population exhibiting high myopia, which is defined as more than 6 dioptres of myopia. Pathological myopia can be considered to be greater that 15 dioptres of refractive correction. Myopia is thought to be transmitted in a dominant fashion. Females seem to be at greater risk of high myopia and degenerative changes; the main risk threatening central vision is macular disease with lacquer cracks and haemorrhages associated with choroidal neovascularisation. The following fundal changes are found in those with pathological myopia: 65
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• Chorioretinal atrophy • Choroidal neovascular membranes (CNVMs) are thought to occur in 5–10% of myopes with more than 5 dioptres of myopia • Difficulty in viewing the foveal limits • Haemorrhage associated with a lacquer crack (can occur in the absence of a CNVM) • Lacquer cracks – linear or stellate • Myopic conus • Myopic crescents are usually temporal to the disc • Thinned retinal pigment epithelium and choroid.
Practical advice Owing to the large degree of direct ophthalmoscope magnification when examining the myope, full examination of the fundus is virtually impossible unless indirect ophthalmoscopy or a fundus lens is used.
The appearance of a CNVM in myopia varies with the age of the lesion. It begins as a dark brown spot at the centre of the fovea, which is representative of a collection of blood. As the lesion degenerates, it evolves into a yellowish-grey rounded or pigmented lesion, known as a Forster–Fuchs’ spot. The visual prognosis in CNVM in myopia remains controversial, with results on prognosis for patients with myopic CNVM varying from study to study. Hampton et al10 reported that 60% of patients do not improve beyond logMAR 1.0 (6/60) at best, and that 43% lose at least two lines of vision. It is generally agreed that a rapid decrease in vision occurs at the onset of the disease, thought to be due to a short neovascular growth phase. In general, CNVMs in myopia remain smaller and more confined than those in age-related macular degeneration (AMD), and many heal with resultant reasonable vision unless the CNVM is subfoveal. Pathological myopia is associated with a 34% rate of of legal blindness in the long term. Laser photocoagulation has been used to treat these lesions. A randomised controlled trial of the use of krypton red laser in extrafoveal CNVMs in myopes under the age of 55 years who have had a CNVM 100–1000 μm from the fovea has been reported.11 From the practical viewpoint, the operators had great difficulty in 66
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localising the fovea during treatment. The results showed that 40% in the treated group versus 13% in the untreated group had an increase of two lines of visual acuity. Some 40% of the treated and 77% of the untreated group had a drop of two lines, indicating that treatment is probably beneficial. Following early experience of treating CNVMs it was noted that the laser scar often enlarged after treatment. This is known as ‘run-off’. However, studies have shown that treatment ‘run-off’ does not necessarily decrease vision, even if it extends into the foveal area. Krypton red was chosen for this study because of its better absorption by choroidal melanocytes; it is therefore thought to be useful in the lightly pigmented fundus of the myope. Myopes are, of course, predisposed to other ophthalmic conditions such as retinal detachments, cataract and chronic open angle glaucoma. It must also be remembered that the magnitude of myopia is prone to increase, and high myopes should be re-refracted regularly and provided with an optimal correction in either spectacle or contact lens form. Highly myopic, visually impaired, spectacle wearers benefit from the easily accessible magnification of near objects achieved by removing their correction. This is not such a viable option for the contact lens wearer.
3.3 Acute optic neuritis The incidence of acute optic neuritis varies significantly between geographical areas. Studies estimate the prevalence of optic neuritis to be 46 per 100 000 in the USA, 93 per 100 000 in England and Wales, and 0.77 per 100 000 in Hong Kong.12 Patients with optic neuritis present with sudden blurring of vision, which is usually unilateral and of gradual onset, but progressive. The visual loss is characteristically associated with pain on ocular movement. Clinical examination shows deceased visual acuity, an afferent pupillary defect, loss of appreciation of the colour red and optic disc swelling, if the nerve head is involved. Most cases are due to retrobulbar pathology, so that the optic disc appears normal.
Practical advice There are only two causes of pain on ocular movement, in the presence of normal orbit and globe: influenza and optic neuritis.
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The management of optic neuritis has for many years been controversial. The recent report on the 10-year follow-up of the Optic Neuritis Treatment Trial (ONTT) has helped to give guidance in this area. The following is a synopsis from the 2004 report of the ONTT:13 The criteria for entry into the ONTT included a diagnosis of acute unilateral optic neuritis with visual symptoms for 8 days or less, age between 18 and 46 years, no previous history of optic neuritis or ophthalmoscopic signs of optic atrophy in the affected eye, and no evidence of a systemic disease other than MS that might be associated with the optic neuritis. Patients who experienced prior episodes of optic neuritis in the other (fellow) eye or prior demyelinative attacks of MS were eligible only if corticosteroids had not been prescribed. This minimised the number of patients enrolled who had a prior diagnosis of MS, and those diagnosed as having MS at the time of enrolment had minimal or no neurologic disability. At study entry, patients were randomly assigned to receive a short course of oral prednisilone, oral placebo, or intravenous methylprednisolone sodium succinate followed by oral prednisone. Patients were examined at eight follow-up visits within the first year and then at yearly intervals until 1997. From 2001 to 2002, the consenting patients were recalled for a further examination. The 10-year review of the ONTT showed the following: Examinations were completed on 319 patients. In most patients, visual function test results in the eyes that experienced optic neuritis at study entry (‘affected eyes’) were normal or only slightly abnormal after 9.9 to 13.7 years. Visual acuity in the affected eyes was > or = 20/20 in 74%, 20/25 to 20/40 in 18%, <20/40 to 20/200 in 5%, and <20/200 in 3%. On average, visual function was worse in patients with multiple sclerosis (MS) than in those without MS. Recurrent optic neuritis in either eye occurred in 35% of patients. Such attacks were more frequent in patients with MS (P<.001). The National Eye Institute Visual Function Questionnaire scores were lower when visual acuity was abnormal and when MS was present. CONCLUSIONS: Most patients retained good to excellent vision more than 10 years after an attack of optic neuritis . . . Although a significant proportion of patients presenting with isolated optic neuritis go on to develop MS in the future, the exact number varies between studies and length of 68
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follow up. Recurrences are, however, more frequent in patients with MS.13
Practical advice Red desatuaration is a very easy but important test to perform in a patient suspected of having optic neuritis. The progression or regression of red desaturation is also a sensitive indicator of the clinical progression or regression of the episode.
3.4 Posterior uveitis Posterior uveitis, an inflammatory process of the uveal tract (iris, cilary body and choroid), is a rare condition with an incidence of 15 per 100 000 and a prevalence of 40 per 100 000 population. Although rare, posterior uveitis accounts for 10% of blind registration in developed countries. The successful management of posterior uveitis is dependent upon an accurate diagnosis of ‘infective’ or ‘non-infective’ causes. Treatment of infective retinopathies such as toxoplasmosis is primarily with the appropriate anti-infective agent, whereas management of non-infectious posterior uveitis is with immunosuppressive agents. More recently the availability of new non-steroid-based immunosuppressants has improved the visual prognosis and quality of life for these patients, who often require medication for many years. Three of the more common causes of visual loss and visual disability are discussed below.
Toxoplasma retinochoroiditis Toxoplasma gondii is an obligate intracellular parasite whose natural host is the cat.14 The disease is transmitted to humans through cat faeces. In the UK, most of those affected are immunocompetent and present with reactivation of congenital toxoplasma scars that have been present since birth and were acquired through maternal infection in pregnancy. Interestingly these lesions seem to reactivate only during early adulthood; reactivation before the age of 18 years and after the age of 45 years is very rare. Treatment is with a combination of either clindamycin and oral corticosteroids, or pyrimethamine, sulfonamides, folinic acid and steroids. As the condition is self-limiting, not all patients with active lesions require treatment. Treatment is indicated only if the lesion is threatening 69
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the optic disc, the macula or a major vessel. If the lesion is close to the fovea, the pyrimethamine regimen detailed above is recommended, because final scar size has been shown to be reduced with this treatment. Until quite recently, the diagnosis of a primary acquired as opposed to a secondary or congenital toxoplasmosis invoked questions about the immune status of the individual. However, more recently apparently healthy people have presented with primary or acquired toxoplasmosis. The acquired toxoplasma lesion is clinically different from the reactivated congenital lesion. The cardinal features of a primary toxoplasma lesion are: a white, smooth, elevated retinochoroidal lesion usually found at the posterior pole; the relative absence of the vitritis usually associated with a reactivated lesion; and no evidence of chorioretinal scarring either at the edge of the lesion or elsewhere in the fundi. In contrast, in secondary toxoplasmosis the fundal lesion will show evidence of an old pigmented scar with an active white edge or fresh lesion. This is usually accompanied by significant vitritis. The clinical management is the same for both lesions, with due consideration for the patient’s immunocompetence status.
Punctate inner choroidopathy Punctate inner choroidopathy is a bilateral inflammatory condition that affects young adults.15 The clinical features of the syndrome include moderate myopia, blurring of vision associated with photopsia and scotoma. The condition usually presents in young women. The clinical findings are multiple yellow–white lesions of the inner choroid and retina, largely confined to the posterior pole. Usually the eyes are quiet with no signs of intraocular inflammation. These lesions heal and leave atrophic scars that are prone to neovascularisation, which occurs in 40% of eyes, and are usually responsible for loss of vision. The underlying aetiology remains unknown, although fundal changes found in this condition are similar to those found in the presumed ocular histoplasmosis syndrome (POHS), and therefore a viral aetiology has been assumed.
Practical advice Patients with punctate inner choroidopathy usually present only when the complication of choroidal neovascularisation occurs in a central scar, causing blurring and distortion of vision.
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The natural history of these lesions is more favourable than in AMD. Laser photocoagulation for extrafoveal lesions, and more recently photodynamic therapy (PDT) for juxtafoveal or subfoveal lesions, can further aid resolution. The role of steroids remains contentious, but they may have a place in dampening the inflammatory response in the stage of neovascularisation. The prognosis for vision is relatively good, with 50% of eyes retaining a visual acuity of 6/18 [LogMAR 0.5] or better. The clinical distinguishing features of the more common inflammatory retinopathies are shown in Table 3.3.
Serpiginous chorioretinitis This is a bilateral progressive inflammatory disease of the inner choroid, retina and retinal pigment epithelium.16 The lesions, which begin in the peripapillary area and spread centrifugally in a jig-saw-like pattern, are well circumscribed gray–white lesions. The patient is typically a healthy young or middle-aged individual. The signs are accompanied by inflammatory cells in approximately one-third of cases. Clinically, serpiginous chorioretinitis can easily be confused with acute multifocal placoid pigment epitheliopathy (AMPPE). The lesions can initially be similar in appearance; however, serpiginous chorioretinitis is recurrent whereas AMPPE is not. Serpiginous chorioretinitis is a chronic, relapsing condition with progressive loss of the visual field and sometimes central visual acuity. Some 25% of these patients develop choroidal neovascularisation.
3.5 Cytomegalovirus retinitis The incidence of cytomegalovirus (CMV) retinitis has risen dramatically over the past 10 years. Although approximately 80% of the normal population have been infected with CMV systemically, in those who have normal immunity (i.e. are immunocompentent) CMV causes no problem. CMV retinitis is an opportunistic infection affecting those who have compromised immune systems due to either immunosuppressant drug therapy or infection with human immunodeficiency virus (HIV).17 The retinitis presents with retinal necrosis and intraretinal haemorrhage. The appearance has been graphically described as ‘tomato ketchup and mayonnaise’ retinopathy. Those infected with HIV gradually 71
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None
Few cells
Brisk iritis
Quiet
Quiet
Punctate inner choroidopathy (PIC)
Acquired toxoplasmosis
Congenital toxoplasmosis
Serpiginous choroiditis
Acute multifocal placoid pigment epitheliopathy (AMPPE)
Anterior uveitis
Vitreous cells 50%
Posterior vitreous cells 30%
Vitritis +++
Quiet vitreous – few cells only
None
Vitreous cells/vitritis
Irregular clumps of pigment
Jig-saw pattern from optic disc
Usually bilateral pigmented chorioretinal scars
No previous scars
Punctate lesions throughout fundus
Chorioretinal scars
Table 3.3 Fundal Changes in the Inflammatory Retinopathies
Gray–white lesions
Retinal pigment epithelium mottling and pigmentation with active edge white for months
Pale active lesion at border of old scar
White focal elevated retinal lesion
Usually CNVM
Appearance of acute lesions
No
Yes
Yes
No
Yes
Choroidal neovascular membrane (CNVM)
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lose the function of their T cells (required to fight infections). CMV retinitis rarely occurs until the patient is severely immunocompromised.
Practical advice Studies have shown that, if an immunocompromised patient with a T4 count <50 cells per cubic millimetre of blood complains of floaters, the probability of CMV retinitis being present is approximately 80%.
CMV retinitis can initially affect either the posterior pole or the peripheral retina. Either type of lesion leads rapidly to blindness if untreated. CMV retinitis is reported to progress at a rate of one disc area every 6 weeks. Those with peripheral retinal lesions are more at risk of retinal detachment, which occurs in 20% of these patients. The treatment of CMV retinitis has improved, as has treatment of the underlying illness. Several years ago the survival of a patient once diagnosed with CMV retinitis could be measured in terms of 4–5 months, whereas today survival can be indefinite. Interestingly, since the advent of highly active antiretroviral therapy (HAART) for those infected with HIV, the incidence of CMV retinitis has fallen dramatically.18 Treatment for CMV retinitis, when it occurs, can be given intravenously, by repeated intravitreal injections or by a long-acting intravitreal delivery ganciclovir implant (Retisert).19 Each method of treatment has its own advantages and disadvantages. In the era before HAART was readily available, some patients proceeded to be visually impaired, despite aggressive therapy. These patients often benefit from the use of low vision aids. Despite the multiple problems that these patients have, one of the overriding fears is that they will go blind before they die. Maintenance of useful visual acuity and independence is therefore of paramount importance.
3.6 Trauma Trauma is an unusual cause of bilateral blindness, although nonbelted car occupants in road traffic accidents, electrocutions, chemical injuries and self-inflicted injuries can cause bilateral and 73
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significant visual impairment. Reductions in visual impairment resulting from trauma are achieved primarily through the dissemination of health and safety information to those undertaking potentially hazardous activity when in employment and at home (DIY). All of those involved in the provision of ‘eye care’ must play their part in this process. Cortical blindness from head injuries can also cause bilateral visual loss, although the nature of the loss can be complex, involving both visual and perceptual components. The rate of bilateral perforating eye injuries sustained through road traffic accidents has been reduced to almost negligible proportions since the advent of seat belt enforcement.
3.7 Low vision aids 1. As they get older, management of those with a stable childhood condition involves: a. The provision of low vision aids for new tasks (employment), CCTVs, computer systems with speech recognition or large print computer access programs, and distance monoculars as their world becomes bigger and motility needs increase. b. The consideration and discussion of registration as adult ‘state benefits’ often kick-in for those on the Blind Register. c. Discussion of changes in accommodation power in those with nystagmus, albinism, etc. These patients may no longer cope purely by accommodating but may now need near vision aids or suffer from headaches, eyestrain and limited concentration. d. Remembering that those who suffer from heritable conditions may develop progressive myopia, but might not need it corrected until 18 or 20 years of age. 2. Those with adult-onset blindness or visual impairment need follow-up advice on lighting and good posture. In particular, diabetics who have progressive and variable visual loss need regular follow-up and versatile low vision aids with good contrast enhancement. 3. Adults who need low vision aids for home use may also require more discrete portable folding hand magnifiers, miniature monoculars or spectacle magnifiers as portable low vision aids. 74
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3.8 Summary The young adult who presents with visual impairment is often the most difficult to manage. Patients in this age group are often the breadwinner, and visual impairment results in loss or change of employment, driving, and often in profound changes in interpersonal relationships and roles. It is important to remember that, for the younger adult, honest and practical advice is imperative in terms of prognosis and future career choices. Those who have had problems since childhood are often coping well and can proceed with appropriate careers; it is the newly diagnosed who require much support and also detailed genetic counselling regarding transmission of the disease to future offspring.
References 1. Frank RN. On the pathogenesis of diabetic retinopathy. Ophthalmology 1984; 91:626–634. 2. Klein R, Klein BE, Moss SE, Cruickshanks KJ. The Wisconsin Epidemiologic Study of Diabetic Retinopathy: XVII. The 14-year incidence and progression of diabetic retinopathy and associated risk factors in type 1 diabetes. Ophthalmology 1998; 105:1801– 1815. 3. Kohner EM. The evolution and natural history of diabetic retinopathy. International Ophthalmology Clinics 1978; 18:1. 4. Nasr CE, Hoogwerf BJ, Faiman C, Reddy SS. United Kingdom Prospective Diabetes Study (UKPDS). Effects of glucose and blood pressure control on complications of type 2 diabetes mellitus. Cleveland Clinic Journal of Medicine 1999; 66:247–253. 5. Diabetic Retinopathy Study Research Group. Photocoagulation treatment of proliferative diabetic retinopathy: the second report of diabetic retinopathy study findings. Ophthalmology 1978; 85:82–106. 6. Early Treatment Diabetic Retinopathy Study Research Group. Photocoagulation for diabetic macular edema: Early Treatment Diabetic Retinopathy Study Report No. 1. Archives of Ophthalmology 1985; 103:1796–1806. 7. Diabetic Retinopathy Vitrectomy Study Research Group. Early vitrectomy for severe vitreous haemorrhage in diabetic retinopathy: two year results of a randomized clinical trial. Diabetic Retinopathy Vitrectomy Study Report 2. Archives of Ophthalmology 1985; 103:1644–1652. 8. International Diabetes Federation. Diabetes Care and Research in Europe: The St Vincent Declaration 1989. Online. Available:
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9.
10. 11.
12.
13.
14.
15. 16.
17. 18.
19.
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http://www.idf.org/webdata/docs/SVD%20and%20Istanbul%20 Commitment.pdf [21 March 2006]. Kohner EM, Porta M. Protocols for screening and treatment of diabetic retinopathy in Europe. European Journal of Ophthalmology 1991; 1:46–54. Hampton GR, Kohen D, Bird AC. Visual prognosis of disciform degeneration in myopia. Ophthalmology 1983; 90:923–926. Pece A, Brancato R, Avanza P, Camesasca F, Galli L. Laser photocoagulation of choroidal neovascularization in pathologic myopia: long-term results. International Ophthalmology 1994–95; 18:339–344. Chan CK, Lam DS. Optic neuritis treatment trial: 10-year follow-up results. American Journal of Ophthalmology 2004; 138:695; author reply 695. Beck RW, Gal RL, Bhatti MT et al. Visual function more than 10 years after optic neuritis: experience of the optic neuritis treatment trial. American Journal of Ophthalmology 2004; 137:77–83. Hogan MJ. Ocular toxoplasmosis; clinical and laboratory diagnosis: evaluation of immunologic tests; treatment. Archives of Ophthalmology 1956; 55:333. Watzke RC, Packer AJ, Folk JC et al. Punctate inner choroidopathy. American Journal of Ophthalmology 1984; 98:572–584. Weiss H, Annesley WH Jr, Shields JA et al. The clinical course of serpiginous choroiditis. American Journal of Ophthalmology 1979; 87:133–142. Kramer M, Lynn W, Lightman S. HIV/AIDS and the eye. Hospital Medicine 2003; 64:421–424. Roels P. Ocular manifestations of AIDS: new considerations for patients using highly active anti-retroviral therapy (HAART). Optometry 2004; 75:624–628. Driot JY, Novack GD, Rittenhouse KD, Milazzo C, Pearson PA. Ocular pharmacokinetics of fluocinolone acetonide after Retisert intravitreal implantation in rabbits over a 1-year period. Journal of Ocular Pharmacology and Therapeutics 2004; 20:269–275.
3
Visual impairment in the working age person Giuliana Silvestri
Many of the conditions causing visual loss in persons of working age are not exclusive to this age group and have therefore been described elsewhere. Visually impaired persons in this age group may, however, reach a critical stage in their disease process and therefore experience significant changes in visual function with resulting changes in circumstances and/or employment. The conditions described in this chapter are those that cause unexpected visual compromise in the previously normally sighted adult.
3.1 Diabetic retinopathy 3.1.1 Clinical presentation Patients with diabetes mellitus may develop none, some or all of the following retinal changes throughout life: microaneurysms, dot and blot haemorrhages, venous dilatation, venous beading and loops, hard exudate formation, cotton-wool spots, vascular occlusion, vasoproliferation, vitreous haemorrhage and tractional retinal detachment. Although dilatation of the retinal veins is the earliest clinical sign of diabetic retinopathy, this can be difficult to detect on ophthalmoscopy. The earliest easily detectable sign of diabetic retinopathy is the appearance of a few tiny red dots in the retina; histological studies have shown these to be microaneurysms. 56
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Practical advice The earliest clinical changes – microaneurysms – are usually found in the area of retina just temporal to the macula. This is the vascular ‘watershed’ zone.
The temporal macular area represents a watershed zone, where the medial and lateral posterior ciliary arteries meet; this is an area of potential vascular weakness. In health, the retinal capillary walls contain pericyte cells, which are responsible for maintaining tone in the capillary walls. Death of the pericytes is the first histological change in diabetic retinopathy and is responsible for the formation of outpouchings of the capillary walls, known as microaneurysms.1 Once the pericytes are lost, the endothelial cells also lose their tight junctions and leakage of blood and protein into the retina occurs. Microaneurysms and small punctate haemorrhages cause no symptoms as long as the central fovea remains uninvolved. Microaneurysms are particularly obvious on fluorescein angiography and are easily distinguished from punctate haemorrhages owing to differing angiographic features. The retinopathy may remain stable for many years with minor background changes or, alternatively, progression may occur. Macular oedema is the commonest cause of impaired visual acuity in patients with early diabetic maculopathy. Intraretinal oedema, particularly when minor in nature, does not change the retinal transparency and is difficult to recognise by monocular ophthalmoscopy. A stereo view is required to detect clinically significant macular oedema (CSMO). In the clinical setting, use of the simple macular photostress recovery test is helpful in deciding whether CSMO is a possibility.
Practical advice The superfield non-contact Volk lens affords the observer a wideangled stereo view of the posterior pole and peripheral retina, and is useful in the diagnosis of diabetic retinopathy and, in particular, CSMO. The resolution of the lens can be enhanced using a contact lens adaptor.
Deposits of hard yellowish-white material are frequently seen at the periphery of oedematous areas; these represent lipid and/or 57
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protein that has ‘precipitated out’ from the oedematous fluid (hard exudates). Unfortunately, these changes characteristically occur in the posterior pole near the macula and can cause loss of central vision. As the disease progresses, other features become apparent on ophthalmoscopy. Cotton-wool spots, which represent areas of focal ischaemia and further dilatation and beading of the retinal veins, indicate progression of retinopathy. The mechanism whereby this occurs is obscure, but is probably related to hypoxia and venous stasis. Studies indicate that approximately 30% of patients with diabetes progress to either proliferative retinopathy or macular oedema over a 14-year period.2 New vessels arise most frequently on the optic disc or along the course of the major retinal veins. Unfortunately, wherever the vessels grow on the surface of the retina, they become adherent to the vitreous. When the vitreous contracts, it cannot easily separate from the retina and the vitreous pulls on the fragile new vessels, causing rupture of their walls and vitreous haemorrhage. Subsequently tractional retinal detachment may also ensue. A fuller description of the clinical grading of diabetic retinopathy is shown in Table 3.1. Before the availability of laser photocoagulation, 50% of eyes with fully developed proliferative retinopathy progressed to marked reduction of vision and often complete blindness.3 In the past, considerable controversy existed regarding the role of accurate control of diabetes in the prevention of retinopathy, as well as nephropathy and other vascular complications. The recent United Kingdom Prospective Diabetic Study has confirmed that good control of blood sugar levels is important in the prevention of both microvascular and macrovascular complications.4 This study also highlighted the importance of attending to the other ‘bad companions’ of diabetes – hypertension, hypercholesterolaemia and smoking. It is essential that all those involved in managing patients with diabetes have a thorough understanding of its complications and that they are willing to devote considerable time to education of their patients.
Practical advice Patient education is absolutely essential, as it is the patient who must understand and manage their disease from day to day and from hour to hour. In some diabetic units, a diabetic education centre and a diabetic liaison nurse are available to improve diabetic knowledge.
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Table 3.1 Grading of Diabetic Retinopathy Grade of retinopathy
Clinical signs
Features on angiography
Background
Venous dilatation (can be preclinical); microaneurysms; dot haemorrhages; blot haemorrhages; hard exudates
Leakage from microaneurysms; masking due to haemorrhages and exudates
Microaneurysms; hard exudates – diffuse or circinate
Diffuse or focal leakage from microaneurysms; little, if any, capillary fall-out
Oedematous
Retinal thickening – focal or diffuse; microaneurysms; dot and blot haemorrhages
Predominantly intraretinal leakage ± ischaemia
Ischaemic
Microaneurysms; large blot and blotch haemorrhages ± retinal thickening
Widespread areas of capillary fall-out often involving the perifoveal arcade
Pre-proliferative
All features of background retinopathy plus cottonwool spots; widespread intraretinal haemorrhages; venous dilatation, beading and venous loops; intraretinal microvascular abnormalities (IRMAs)
Widespread inner retinal ischaemia; masking from large haemorrhages; IRMAs
Proliferative
New vessels on the disc or elsewhere; fibrous tissue; pre-retinal and vitreous haemorrhage; ‘raspberry’ or abortive neovascular outgrowth
Widespread inner retinal ischaemia; profuse early leakage from new vessels
Maculopathy Exudative
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3.1.2 Prevalence of diabetic retinopathy The prevalence of diabetic retinopathy increases with duration of diabetes. In type 1 (juvenile) diabetes, retinopathy is virtually never present in the first 5 years. However, 27% of those who have had diabetes for 5–10 years and 71% of those who have had diabetes for 10 years or longer will have diabetic retinopathy. After 30 years the incidence rises to 90%, with 30% of these patients having proliferative diabetic retinopathy (PDR).5 Times of added risk are around puberty and during pregnancy. In adult onset diabetes, maculopathy is more common than proliferative retinopathy but may in some cases be associated with neovascularisation. Often in patients with type 2 diabetes, maculopathy can be the presenting feature of the disease. Adult-onset diabetes can remain undiagnosed for many years, with severe damage to the retinal capillaries resulting in subsequent irreversible visual loss.
Practical advice Visual acuity may appear good even in the presence of PDR or extensively treated non-proliferative retinopathy.
3.1.3 Laser photocoagulation and surgery for diabetic retinopathy Laser photocoagulation of the diabetic retina utilises an argon or krypton laser to coagulate ischaemic retina, rendering the ischaemic retina non-viable and thereby removing the stimulus for neovascularisation. Recent randomised controlled studies have shown that laser photocoagulation is effective in preserving vision and slowing the rate of visual decline in diabetic patients with pre-retinal and papillary neovascularisation and early maculopathy.5–7 Advanced retinal neovascularisation and macular oedema respond less favourably to photocoagulation; thus, it is imperative to detect disease in its early stages by meticulous screening and careful observation of diabetic patients. Persistent dense vitreous haemorrhage, fibrovascular membranes and traction detachments, which threaten macular function, may be treated by vitrectomy. This technique may dramatically improve visual function by irrigating blood from the vitreous cavity using an intraocular infusion and suction system, fitted with a cutting head. Fibrovascular 60
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membranes may also be carefully dissected from the retinal surface.7
3.1.4 The management of diabetic retinopathy The management of diabetic retinopathy has been the subject of many excellent randomised controlled trials, with the result that many management questions have been answered conclusively. Some questions that are of paramount importance to both the patient and the surgeon are discussed below.
Q.1 Does laser photocoagulation have any impact on the progression of retinopathy? Yes. Laser photocoagulation has been shown to reduce blindness in diabetic retinopathy by 50%.
Q.2 When should laser be applied in proliferative retinopathy? The Early Treatment Diabetic Retinopathy Study (ETDRS) has shown that panretinal laser photocoagulation (PRP) (Fig. 3.1 [Plates 5 & 6]) should be applied when ‘high risk’ criteria are present. High-risk criteria are as follows and indicate the need for prompt and aggressive PRP: • NVD (new vessels on the disc) covering more than onequarter to one-third of the disc area • NVD covering less than one-quarter to one-third of the disc area in the presence of pre-retinal or vitreous haemorrhage • NVE (new vessels elsewhere) with pre-retinal or vitreous haemorrhage.
Q.3 Is laser treatment equally helpful for all types of maculopathy? No. Unfortunately laser therapy is not helpful in all types of maculopathy. Exudative maculopathy responds best, in particular for patients who have circinate patterns of hard exudates. Oedematous maculopathy responds, at best, with stabilisation of vision in 30% of patients. No treatment has 61
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been found to be of help in ischaemic maculopathy; in fact, laser photocoagulation can sometimes exacerbate the situation. The outcome for patients with mixed maculopathies depends on the degree of each of the above components. Patients are often disappointed if they are told that they are unsuitable for laser treatment, or that it would not be of benefit. These patients usually have an ischaemic type of maculopathy.
Q.4 Should laser treatment be applied in pre-proliferative retinopathy? No, although it would appear sensible to pre-empt complications. The reason that laser treatment is not automatically indicated in all patients who develop to preproliferative retinopathy is that only 50% will progress to fullblown PDR. In addition, PRP is not without side-effects.
Q.5 Are there any side-effects to laser photocoagulation? Yes. The potential side-effects of laser treatment, whether permanent or transient, are many (Table 3.2). In practice, the most common side-effects of PRP are night blindness and loss of the peripheral field. These side-effects are, however, well tolerated by patients and are often accepted as a necessary pay-off against the preservation of what can often be excellent central acuity. Patients who have had successful PRP often maintain 6/6 [LogMAR 0.0] vision 20–30 years later. What is often most annoying for patients is the photophobia associated with scatter PRP. This is thought to be due to internal scattering and reflection of light from the laser scars.
In providing low vision support for those with visual impairment resulting from diabetes, the key is versatility. As aspects of the underlying condition change (lens hydration, macular oedema, retinopathy), so do refractive status and visual function. Spectacles must be kept up to date and a range of low vision aids, some of which are designed to enhance contrast, provided. Advice on a wide range of visual rehabilitation strategies and various forms of 62
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A
B Figure 3.1 A & B (Plates 5 & 6) Treated diabetic retinopathy in a 24-year-old woman. The patient has been treated with panretinal photocoagulation for proliferative retinopathy (scars in the peripheral retina of the left eye – B) and with bilateral grid laser for maculopathy (subtle scars in the macular areas – A & B).
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C Figure 3.1 C (Plates 5 & 6) Corresponding ‘binocular Estermann’ fields show both peripheral and central field loss secondary to laser photocoagulation. This patient would not be eligible to hold a driving licence. Black rectangles indicate loss of function.
assistive technology (both low and high tech) should be provided.
3.1.5 The St Vincent’s Declaration In 1989, the World Health Organization and the International Diabetes Federation for Europe drew up a joint initiative on diabetes care and research into diabetes mellitus.8 Central to the initiative was the inclusion of 5-year targets for improvement in all diabetic complications, including the reduction of diabetic blindness by one-third. Following the St Vincent’s Declaration, a uniform pro64
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Table 3.2 Side-Effects of Argon Laser Panretinal Photocoagulation Transient side-effects
Permanent side-effects
Blurring of vision
Loss of visual acuity
Choroidal detachment
Accommodative defects (due to damage to long ciliary nerves and resulting recession of the near point)
Macular oedema – can persist for weeks but usually settles. More common in type II diabetes after PRP
Dimness of vision (dose related if >2000 burns at one sitting)
Headache
Nyctalopia Loss of colour vision Photophobia Loss of peripheral field Inadvertent foveal burn
tocol was developed in a joint venture by 21 European countries for the screening of diabetic retinopathy. This protocol includes guidelines for examination and a data collection sheet.9 To date, little progress appears to have been made in addressing these aims in a practical way.
3.2 Pathological myopia 3.2.1 Clinical presentation The prevalence of myopia varies between 11% and 36% of the general population, with 30% of the myopic population and 1–4% of the general population exhibiting high myopia, which is defined as more than 6 dioptres of myopia. Pathological myopia can be considered to be greater that 15 dioptres of refractive correction. Myopia is thought to be transmitted in a dominant fashion. Females seem to be at greater risk of high myopia and degenerative changes; the main risk threatening central vision is macular disease with lacquer cracks and haemorrhages associated with choroidal neovascularisation. The following fundal changes are found in those with pathological myopia: 65
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• Chorioretinal atrophy • Choroidal neovascular membranes (CNVMs) are thought to occur in 5–10% of myopes with more than 5 dioptres of myopia • Difficulty in viewing the foveal limits • Haemorrhage associated with a lacquer crack (can occur in the absence of a CNVM) • Lacquer cracks – linear or stellate • Myopic conus • Myopic crescents are usually temporal to the disc • Thinned retinal pigment epithelium and choroid.
Practical advice Owing to the large degree of direct ophthalmoscope magnification when examining the myope, full examination of the fundus is virtually impossible unless indirect ophthalmoscopy or a fundus lens is used.
The appearance of a CNVM in myopia varies with the age of the lesion. It begins as a dark brown spot at the centre of the fovea, which is representative of a collection of blood. As the lesion degenerates, it evolves into a yellowish-grey rounded or pigmented lesion, known as a Forster–Fuchs’ spot. The visual prognosis in CNVM in myopia remains controversial, with results on prognosis for patients with myopic CNVM varying from study to study. Hampton et al10 reported that 60% of patients do not improve beyond logMAR 1.0 (6/60) at best, and that 43% lose at least two lines of vision. It is generally agreed that a rapid decrease in vision occurs at the onset of the disease, thought to be due to a short neovascular growth phase. In general, CNVMs in myopia remain smaller and more confined than those in age-related macular degeneration (AMD), and many heal with resultant reasonable vision unless the CNVM is subfoveal. Pathological myopia is associated with a 34% rate of of legal blindness in the long term. Laser photocoagulation has been used to treat these lesions. A randomised controlled trial of the use of krypton red laser in extrafoveal CNVMs in myopes under the age of 55 years who have had a CNVM 100–1000 μm from the fovea has been reported.11 From the practical viewpoint, the operators had great difficulty in 66
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localising the fovea during treatment. The results showed that 40% in the treated group versus 13% in the untreated group had an increase of two lines of visual acuity. Some 40% of the treated and 77% of the untreated group had a drop of two lines, indicating that treatment is probably beneficial. Following early experience of treating CNVMs it was noted that the laser scar often enlarged after treatment. This is known as ‘run-off’. However, studies have shown that treatment ‘run-off’ does not necessarily decrease vision, even if it extends into the foveal area. Krypton red was chosen for this study because of its better absorption by choroidal melanocytes; it is therefore thought to be useful in the lightly pigmented fundus of the myope. Myopes are, of course, predisposed to other ophthalmic conditions such as retinal detachments, cataract and chronic open angle glaucoma. It must also be remembered that the magnitude of myopia is prone to increase, and high myopes should be re-refracted regularly and provided with an optimal correction in either spectacle or contact lens form. Highly myopic, visually impaired, spectacle wearers benefit from the easily accessible magnification of near objects achieved by removing their correction. This is not such a viable option for the contact lens wearer.
3.3 Acute optic neuritis The incidence of acute optic neuritis varies significantly between geographical areas. Studies estimate the prevalence of optic neuritis to be 46 per 100 000 in the USA, 93 per 100 000 in England and Wales, and 0.77 per 100 000 in Hong Kong.12 Patients with optic neuritis present with sudden blurring of vision, which is usually unilateral and of gradual onset, but progressive. The visual loss is characteristically associated with pain on ocular movement. Clinical examination shows deceased visual acuity, an afferent pupillary defect, loss of appreciation of the colour red and optic disc swelling, if the nerve head is involved. Most cases are due to retrobulbar pathology, so that the optic disc appears normal.
Practical advice There are only two causes of pain on ocular movement, in the presence of normal orbit and globe: influenza and optic neuritis.
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The management of optic neuritis has for many years been controversial. The recent report on the 10-year follow-up of the Optic Neuritis Treatment Trial (ONTT) has helped to give guidance in this area. The following is a synopsis from the 2004 report of the ONTT:13 The criteria for entry into the ONTT included a diagnosis of acute unilateral optic neuritis with visual symptoms for 8 days or less, age between 18 and 46 years, no previous history of optic neuritis or ophthalmoscopic signs of optic atrophy in the affected eye, and no evidence of a systemic disease other than MS that might be associated with the optic neuritis. Patients who experienced prior episodes of optic neuritis in the other (fellow) eye or prior demyelinative attacks of MS were eligible only if corticosteroids had not been prescribed. This minimised the number of patients enrolled who had a prior diagnosis of MS, and those diagnosed as having MS at the time of enrolment had minimal or no neurologic disability. At study entry, patients were randomly assigned to receive a short course of oral prednisilone, oral placebo, or intravenous methylprednisolone sodium succinate followed by oral prednisone. Patients were examined at eight follow-up visits within the first year and then at yearly intervals until 1997. From 2001 to 2002, the consenting patients were recalled for a further examination. The 10-year review of the ONTT showed the following: Examinations were completed on 319 patients. In most patients, visual function test results in the eyes that experienced optic neuritis at study entry (‘affected eyes’) were normal or only slightly abnormal after 9.9 to 13.7 years. Visual acuity in the affected eyes was > or = 20/20 in 74%, 20/25 to 20/40 in 18%, <20/40 to 20/200 in 5%, and <20/200 in 3%. On average, visual function was worse in patients with multiple sclerosis (MS) than in those without MS. Recurrent optic neuritis in either eye occurred in 35% of patients. Such attacks were more frequent in patients with MS (P<.001). The National Eye Institute Visual Function Questionnaire scores were lower when visual acuity was abnormal and when MS was present. CONCLUSIONS: Most patients retained good to excellent vision more than 10 years after an attack of optic neuritis . . . Although a significant proportion of patients presenting with isolated optic neuritis go on to develop MS in the future, the exact number varies between studies and length of 68
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follow up. Recurrences are, however, more frequent in patients with MS.13
Practical advice Red desatuaration is a very easy but important test to perform in a patient suspected of having optic neuritis. The progression or regression of red desaturation is also a sensitive indicator of the clinical progression or regression of the episode.
3.4 Posterior uveitis Posterior uveitis, an inflammatory process of the uveal tract (iris, cilary body and choroid), is a rare condition with an incidence of 15 per 100 000 and a prevalence of 40 per 100 000 population. Although rare, posterior uveitis accounts for 10% of blind registration in developed countries. The successful management of posterior uveitis is dependent upon an accurate diagnosis of ‘infective’ or ‘non-infective’ causes. Treatment of infective retinopathies such as toxoplasmosis is primarily with the appropriate anti-infective agent, whereas management of non-infectious posterior uveitis is with immunosuppressive agents. More recently the availability of new non-steroid-based immunosuppressants has improved the visual prognosis and quality of life for these patients, who often require medication for many years. Three of the more common causes of visual loss and visual disability are discussed below.
Toxoplasma retinochoroiditis Toxoplasma gondii is an obligate intracellular parasite whose natural host is the cat.14 The disease is transmitted to humans through cat faeces. In the UK, most of those affected are immunocompetent and present with reactivation of congenital toxoplasma scars that have been present since birth and were acquired through maternal infection in pregnancy. Interestingly these lesions seem to reactivate only during early adulthood; reactivation before the age of 18 years and after the age of 45 years is very rare. Treatment is with a combination of either clindamycin and oral corticosteroids, or pyrimethamine, sulfonamides, folinic acid and steroids. As the condition is self-limiting, not all patients with active lesions require treatment. Treatment is indicated only if the lesion is threatening 69
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the optic disc, the macula or a major vessel. If the lesion is close to the fovea, the pyrimethamine regimen detailed above is recommended, because final scar size has been shown to be reduced with this treatment. Until quite recently, the diagnosis of a primary acquired as opposed to a secondary or congenital toxoplasmosis invoked questions about the immune status of the individual. However, more recently apparently healthy people have presented with primary or acquired toxoplasmosis. The acquired toxoplasma lesion is clinically different from the reactivated congenital lesion. The cardinal features of a primary toxoplasma lesion are: a white, smooth, elevated retinochoroidal lesion usually found at the posterior pole; the relative absence of the vitritis usually associated with a reactivated lesion; and no evidence of chorioretinal scarring either at the edge of the lesion or elsewhere in the fundi. In contrast, in secondary toxoplasmosis the fundal lesion will show evidence of an old pigmented scar with an active white edge or fresh lesion. This is usually accompanied by significant vitritis. The clinical management is the same for both lesions, with due consideration for the patient’s immunocompetence status.
Punctate inner choroidopathy Punctate inner choroidopathy is a bilateral inflammatory condition that affects young adults.15 The clinical features of the syndrome include moderate myopia, blurring of vision associated with photopsia and scotoma. The condition usually presents in young women. The clinical findings are multiple yellow–white lesions of the inner choroid and retina, largely confined to the posterior pole. Usually the eyes are quiet with no signs of intraocular inflammation. These lesions heal and leave atrophic scars that are prone to neovascularisation, which occurs in 40% of eyes, and are usually responsible for loss of vision. The underlying aetiology remains unknown, although fundal changes found in this condition are similar to those found in the presumed ocular histoplasmosis syndrome (POHS), and therefore a viral aetiology has been assumed.
Practical advice Patients with punctate inner choroidopathy usually present only when the complication of choroidal neovascularisation occurs in a central scar, causing blurring and distortion of vision.
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The natural history of these lesions is more favourable than in AMD. Laser photocoagulation for extrafoveal lesions, and more recently photodynamic therapy (PDT) for juxtafoveal or subfoveal lesions, can further aid resolution. The role of steroids remains contentious, but they may have a place in dampening the inflammatory response in the stage of neovascularisation. The prognosis for vision is relatively good, with 50% of eyes retaining a visual acuity of 6/18 [LogMAR 0.5] or better. The clinical distinguishing features of the more common inflammatory retinopathies are shown in Table 3.3.
Serpiginous chorioretinitis This is a bilateral progressive inflammatory disease of the inner choroid, retina and retinal pigment epithelium.16 The lesions, which begin in the peripapillary area and spread centrifugally in a jig-saw-like pattern, are well circumscribed gray–white lesions. The patient is typically a healthy young or middle-aged individual. The signs are accompanied by inflammatory cells in approximately one-third of cases. Clinically, serpiginous chorioretinitis can easily be confused with acute multifocal placoid pigment epitheliopathy (AMPPE). The lesions can initially be similar in appearance; however, serpiginous chorioretinitis is recurrent whereas AMPPE is not. Serpiginous chorioretinitis is a chronic, relapsing condition with progressive loss of the visual field and sometimes central visual acuity. Some 25% of these patients develop choroidal neovascularisation.
3.5 Cytomegalovirus retinitis The incidence of cytomegalovirus (CMV) retinitis has risen dramatically over the past 10 years. Although approximately 80% of the normal population have been infected with CMV systemically, in those who have normal immunity (i.e. are immunocompentent) CMV causes no problem. CMV retinitis is an opportunistic infection affecting those who have compromised immune systems due to either immunosuppressant drug therapy or infection with human immunodeficiency virus (HIV).17 The retinitis presents with retinal necrosis and intraretinal haemorrhage. The appearance has been graphically described as ‘tomato ketchup and mayonnaise’ retinopathy. Those infected with HIV gradually 71
72
None
Few cells
Brisk iritis
Quiet
Quiet
Punctate inner choroidopathy (PIC)
Acquired toxoplasmosis
Congenital toxoplasmosis
Serpiginous choroiditis
Acute multifocal placoid pigment epitheliopathy (AMPPE)
Anterior uveitis
Vitreous cells 50%
Posterior vitreous cells 30%
Vitritis +++
Quiet vitreous – few cells only
None
Vitreous cells/vitritis
Irregular clumps of pigment
Jig-saw pattern from optic disc
Usually bilateral pigmented chorioretinal scars
No previous scars
Punctate lesions throughout fundus
Chorioretinal scars
Table 3.3 Fundal Changes in the Inflammatory Retinopathies
Gray–white lesions
Retinal pigment epithelium mottling and pigmentation with active edge white for months
Pale active lesion at border of old scar
White focal elevated retinal lesion
Usually CNVM
Appearance of acute lesions
No
Yes
Yes
No
Yes
Choroidal neovascular membrane (CNVM)
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lose the function of their T cells (required to fight infections). CMV retinitis rarely occurs until the patient is severely immunocompromised.
Practical advice Studies have shown that, if an immunocompromised patient with a T4 count <50 cells per cubic millimetre of blood complains of floaters, the probability of CMV retinitis being present is approximately 80%.
CMV retinitis can initially affect either the posterior pole or the peripheral retina. Either type of lesion leads rapidly to blindness if untreated. CMV retinitis is reported to progress at a rate of one disc area every 6 weeks. Those with peripheral retinal lesions are more at risk of retinal detachment, which occurs in 20% of these patients. The treatment of CMV retinitis has improved, as has treatment of the underlying illness. Several years ago the survival of a patient once diagnosed with CMV retinitis could be measured in terms of 4–5 months, whereas today survival can be indefinite. Interestingly, since the advent of highly active antiretroviral therapy (HAART) for those infected with HIV, the incidence of CMV retinitis has fallen dramatically.18 Treatment for CMV retinitis, when it occurs, can be given intravenously, by repeated intravitreal injections or by a long-acting intravitreal delivery ganciclovir implant (Retisert).19 Each method of treatment has its own advantages and disadvantages. In the era before HAART was readily available, some patients proceeded to be visually impaired, despite aggressive therapy. These patients often benefit from the use of low vision aids. Despite the multiple problems that these patients have, one of the overriding fears is that they will go blind before they die. Maintenance of useful visual acuity and independence is therefore of paramount importance.
3.6 Trauma Trauma is an unusual cause of bilateral blindness, although nonbelted car occupants in road traffic accidents, electrocutions, chemical injuries and self-inflicted injuries can cause bilateral and 73
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significant visual impairment. Reductions in visual impairment resulting from trauma are achieved primarily through the dissemination of health and safety information to those undertaking potentially hazardous activity when in employment and at home (DIY). All of those involved in the provision of ‘eye care’ must play their part in this process. Cortical blindness from head injuries can also cause bilateral visual loss, although the nature of the loss can be complex, involving both visual and perceptual components. The rate of bilateral perforating eye injuries sustained through road traffic accidents has been reduced to almost negligible proportions since the advent of seat belt enforcement.
3.7 Low vision aids 1. As they get older, management of those with a stable childhood condition involves: a. The provision of low vision aids for new tasks (employment), CCTVs, computer systems with speech recognition or large print computer access programs, and distance monoculars as their world becomes bigger and motility needs increase. b. The consideration and discussion of registration as adult ‘state benefits’ often kick-in for those on the Blind Register. c. Discussion of changes in accommodation power in those with nystagmus, albinism, etc. These patients may no longer cope purely by accommodating but may now need near vision aids or suffer from headaches, eyestrain and limited concentration. d. Remembering that those who suffer from heritable conditions may develop progressive myopia, but might not need it corrected until 18 or 20 years of age. 2. Those with adult-onset blindness or visual impairment need follow-up advice on lighting and good posture. In particular, diabetics who have progressive and variable visual loss need regular follow-up and versatile low vision aids with good contrast enhancement. 3. Adults who need low vision aids for home use may also require more discrete portable folding hand magnifiers, miniature monoculars or spectacle magnifiers as portable low vision aids. 74
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3.8 Summary The young adult who presents with visual impairment is often the most difficult to manage. Patients in this age group are often the breadwinner, and visual impairment results in loss or change of employment, driving, and often in profound changes in interpersonal relationships and roles. It is important to remember that, for the younger adult, honest and practical advice is imperative in terms of prognosis and future career choices. Those who have had problems since childhood are often coping well and can proceed with appropriate careers; it is the newly diagnosed who require much support and also detailed genetic counselling regarding transmission of the disease to future offspring.
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