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The pigmented retina: C-19518 O/D.

Choroidal naevus and CHRPE

Choroidal naevus and congenital hypertrophy of the retinal pigment epithelium (CHRPE) account for a high proportion of pigmentary lesions referred to secondary care. Naevi are common, occurring in about 10% of the Caucasian population. They become evident during the first three decades of life, darkening over that time. This is one reason why some may not have been noticed at the first examination. They may be located anywhere in the fundus and may be up to six disc diameters in size. They are usually light grey in colour (but about 5% lack pigment), with a poorly defined perimeter, and minimal apparent thickness (Figure 1). There may be overlying drusen. Serous detachment of the overlying retina is a very rare finding. Some naevi result in visual field defects. The chief concern about naevi is that of transformation to, or confusion with, choroidal melanoma. Important features in this regard are: documented increase in size or thickness; the accumulation of orange pigment (lipofuscin) on the surface of the lesion; a large area of serous retinal detachment; photopsia in association with a suspiciously large lesion.

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By deinition CHRPE are present from birth. Like naevi, they can be located anywhere in the fundus, and range considerably in size, from a tiny speck of pigment to a lesion many disc diameters in size. They are usually darker and better defined than naevi (Figure 2a) and whereas naevi are often single, CHRPE often presents as multiple pigmented patches (sometimes clustered to give a "bear-track" appearance) (Figure 2b). There may be some areas of "punched-out" hypopigmentation within the lesion. Careful visual field testing can reveal scotomata corresponding to the CHRPE.

Melanoma and indeterminate melanocytic lesions

Suspicion of malignant melanoma drives much of the referral of congenital benign lesions to secondary care. Melanoma is the most common primary malignant tumour of the eye in adults, but it is rare in optometric practice. It is typically an elevated, pigmented mass (Figure 3a) but it can be mottled in appearance and occasionally amelanotic. It may break through Bruch's membrane to give a mushroom-shaped ("collar stud") mass (Figure 3b) and there may be serous retinal detachment. Orange pigment (lipofuscin) in the overlying retinal pigment epithelium is common.

Retinitis pigmentosa

Retinitis pigmentosa represents a group of hereditary disorders characterised by a genetically determined degeneration of the photoreceptors. This results in night-blindness and constricted visual fields. There is a variable degree of pigmentation of the fundus. The pigmentation is typically perivascular; it is often described as "bone spicule" because it has a pattern that resembles the histological appearance of bone. A striking feature is the marked attenuation of the retinal vasculature (Figure 4). In later stages, the optic nerve head becomes pale. The age of onset of symptoms and the rate of progression depend upon the nature of the underlying genetic defect. Recessive and X-linked defects generally present earlier and progress more rapidly than autosomal dominant defects.

Laser photocoagulation

With the increasing incidence of diabetes in the UK, and the adoption of a national screening programme for diabetic retinopathy, it is increasingly likely that optometrists will encounter individuals who have undergone laser photocoagulation treatment. Freshly applied laser burns are pale white lesions. Over the course of weeks to months, the burns become pigmented, particularly around their periphery, resulting in a somewhat speckled fundal appearance (Figure 5). The treated area may be confined to the posterior pole if it has been carried out for diabetic maculopathy, or dispersed throughout the periphery for proliferative retinopathy. Not all laser photocoagulation is carried out for diabetes though; treatment may have been applied for other vasculopathies, or for retinal tears or detachment.

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Pigmentation associated with retinal detachment

Both retinal detachment and its treatment may result: in pigmentary abnormalities in the fundus. Spontaneouos resolution of a chronic retinal detachment, occurring following serous detachment or in rhegmatogenous detachment where tee vitreous has provided tamponade, may result in a profound pigmentary disturbance in the area of the previously detached retina. Furthermore, in areas of chronic detachment, a pigment line (often referred to as a "tidemark") may form at the boundary of the detached retina. Such tidemarks persist, even when the retina has been surgically re-attached (Figure 6). Surgical treatment also gives rise to peripheral pigmentary abnormalities from laser or cryopexy treatment of retinal tears. These are most commonly equatorial or peripheral, and most commonly in the superior quadrants.

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Inflammatory pigmentation

Any retinal or choroidal inflammation may give rise to pigmentary changes. One of the more common examples is Toxoplasma retinochoroiditis. This is usually acquired in utero and results in an asymptomatic pigmented lesion in the fundal periphery. Vision is only affected if this occurs at the macula and so it is normally a chance finding. Encysted organisms can reactivate, typically when the patient is 20-40 years old, and this results in an area of "fluffy" white retinitis (Figure 7). Other inflammatory conditions, eg active uveitis, can give rise to pigmentation, or even hypopigmentation, which is most striking (Figure 8).

Degenerative pigmentation

Central pigmentary changes are a hallmark of early dry age-related macular degeneration (AMD), and therefore, increasingly seen in optometric practice.

Pigmentary changes resulting from degeneration may also be seen peripherally. Perhaps the most important is lattice degeneration. This has a number of subtypes, but it is usually in long patches in the periphery, parallel to the ora, with a pale "crisscross" appearance. One common feature is associated pigment stippling. Not infrequently, areas of lattice degeneration harbour small atrophic retinal holes. Lattice degeneration is also associated with the development of horseshoe retinal tears when posterior vitreous detachment (PVD) occurs, and hence, this poses a pre-disposition to retinal detachment.

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Subretinal blood

There are various causes of subretinal blood, but the most common is a bleed from a subretinal neovascular membrane, often associated with age-related changes. With a fresh bleed, the retina is elevated to a varying degree (sometimes quite markedly) and there is an obvious red colour. Over time, the colour changes to become pale, with areas of hyperpigmentation (Figure 9).

Naevus of Ota

Some congenital abnormalities may be encountered very rarely. They result from altered migration of pigment cell precursors during embryological development. Perhaps the most extraordinary is the naevus of Ota, wherein hyperpigmentation of the lids, sclera and iris is associated with a corresponding increase in pigmentation off the fundus.

History

Most pigmentary abnormalities in the fundus are not associated with clinical symptoms. If the patient has diabetes, practitioners should ask if they have had laser treatment. If there is a history of surgery for retinal detachment, then pigmentary changes associated with the detachment are likely to be observed and will almost always be seen peripherally, associated with laser or cryosurgical retinopexy.

A history of AMD alerts you to the likely presence of pigmentary changes in the posterior pole.

Choroidal naevi and CHRPE do not produce symptoms. In the presence of a large or atypical "naevus" a history of photopsia is a cause for concern. It may be the result of growth of the abnormality, which may actually be a melanoma.

Individuals with retinitis pigmentosa may complain of visual field loss and/or night-blindness. But if the disease is the autosomal dominant type, which usually presents late and is often mild, then they may not have significant problems in this regard. Sometimes in such patients there are symptoms, but this only becomes apparent on close questioning: can they walk from bedroom to bathroom at night without putting the light on? How is their night driving? Do they cope in town at night where there is no street lighting? Of course, no-one sees as well at night as by day, but a discussion with affected individual suggests more problems than one would regard as "normal". There may be a known family history because of the genetic nature of the disease, but this is so in only about 50% of cases.

Examination

Is there unusual pigmentation of the lids, or does the sclera look pigmented? This would suggest a congenital pigmentary abnormality such as the rare naevus of Ota. In such cases, the iris on the affected side will show a deep pigmentation, either in whole or in part.

If the pigmentary abnormality is solely in the fundus, is it centred on the macula, or is it in the periphery, either as a single patch, multiple areas, or in a sectorial distribution? Fine pigment spots grouped around the posterior pole suggest AMD or focal laser treatment. Look for drusen and atrophic changes to confirm AMD, and look at the other eye, which is highly likely to show similar changes or evidence of previous "wet" AMD. Subretinal membranes can be pigmented, although this is not usually very marked in AMD and more apparent in choroidal neovascular membranes, CNV) associated with inflammation or myopia. If there has been Clewing from CNV, then the subretinal blood gives an elevated pigmented area (Figure 1b).

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Retinitis pigmentosa produces a widespread patchy pigmentation throughout the equatorial regions of both fundi. It tends to be more prominent in the vicinity of blood vessels. VA may be normal, but examination of the visual field is likely to show/ marked constriction.

Pigmented lines beneath the retina in the form off "tidemarks" suggest previous retinal detachment, which can also produce clumps of pigmentation in the previously detached are there has been previous retinal detachment surgery, it is likely that the retina is now secure. If there has been no surgery, then dilated examination of the peripheral retina is mandatory, since, even if there has been some spontaneous reattachment, there ma y be areas of retina teat area still detached, or open U-tears, which require prompt treatment. If yon see an area off elevated, thin retina in the periphery, with a pigmented demarcation line at its boundary with non-elevated retina, this is NOT a retinoschisis; it is a chronic retinal detachment (and you will find pigment in the vitreous). if there has been prior surgery for retinal detachment then you will see large patches of hyper- and hypo-pigmentary change in the periphery, from laser or creopexy. The eye lacks f vitreous (most retinal reattachment surgery in the UK is now carried out using a vitrectomy technique) or there will be indentation of the retina and external conjunctival scarring and bulging resulting from scleral buckling (sometimes as a sole treatment, and sometimes as an adjunct to vitrectomy surgery).

Examination off the retinal periphery through a dilated pupil with a hand-held condensing lens, or indirect ophthalmoscope may reveal a number of peripheral retinal or vitreo-retinal degenerations, particularly! lattice degeneration, which can lead to U-tears when PVD occurs (is there pigment in the vitreous, and can you see a Weiss ring?). Another common finding is reticular subretinal pigmentation, which is of no pathological significance Some people, with completely healthy eyes, show an interesting striped pigmentation to the fundus, known as a tigroid fundus. This has no pathological connotations.

The well-defined and deeply pigmented lesions of CHRPE may occur as a single tiny or large patch, or it may emprise a number of patches, clustered or widely scattered. The overlying retina is not elevated. it is of no pathological significance, although there is an extremely rare association in Gardener's Syndrome, which comprises multiple pigmentary abnormalities in the fundus, multiple "lumps and bumps" elsewhere on trie body, and papillomatosis of the large bowel, which leads to carcinoma. This is a hereditary condition.

With choroidal naevi, look for drusen overlying the pigmented area and assess the thickness of the lesion. Elevation of the retina is not usual, and is at most barely discernible. Choroidal melanoma, by contrast, produces an (often marked) elevation of She retina. There may be an orange pigmentation overlying the melanotic lesion, and an area of retinal detachment, usually inferiorly.

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Management

Of course, no practitioner wishes to "miss" a choroidal melanoma. However, given the limited resources available to the NHS, it is not appropriate to refer every patient with a choroidal naevus or CHRPE (> 10% of the population) for assessment in secondary care. Photography can, however, help to determine if a lesion has enlarged. If the lesion is a typical, in terms of its size, thickness, or associated features, particularly if there is a suggestion that it may be symptomatic, then a referral should be made. Same-day attendance at an acute ophthalmic centre is not necessary, since the patient will, in any case, be redirected to a medical retina or oncology clinic. Referral to a retina clinic using an established written referral route (eg by fax) is appropriate. If you really think the lesion may be a melanoma (eg it is clearly elevated and/or is associated with sub-retinal fluid or photopsia) then you must be confident that the secondary care unit will see the patient within days, not weeks, otherwise a same-day referral may be appropriate Patients with retinitis pigmentosa, or similar retinal dystrophies, require assessment in secondary care to allow for prognostication, genetic counselling, and access to support services etc. There is no heed foe urgent attention, and routine referral to your local ophthalmic clinic, particularly ho a retinal specialist, is appropriate.

Pigment lines at the boundary (leading edge) of a retinal detachment indicate chronicity. Such patients still need prompt attention, since detachments can and do extend beyond these "tidemarks" at intervals However, in there is no fluid beyond the pigment line, then an urgent written referral is appropriate. If fluid has extended beyond the tidemark, or you are not sure about this, then manage as for acute retinal detachment, with same day referral to the ophthalmic emergency department. Untreated U-tears in lattice degeneration need urgent attention, preferably within 24 hours Atrophic holes within lattice degeneration do not require treatment, so no referral is necessary as a rule, but non-urgent referral is advisable if the patient has presented with symptoms of posterior vitreous detachment (floaters, photopsia). Asymptomatic patients with lattice degeneration (8% of the populetion) do not require referral. Pigmentary chants associated with other stigmata of dry AMD necessitate counselling regarding smoking cessation, diet, the possible role of antioxidants, and the importance and significance of distortion of vision us a symptom. This is particularly the case if the fellow eye has already been affected by significant AMD. In myopes, and patients with inflammatory disease, CNV are frequently pigmented. Increasing use of optical coherence tomography (OCT) makes diagnosis in the case of myopes complaining of distortion, much more straightforward. Such cases should be referred to rapid access macula clinics in secondary care, using established referral protocols.

Pigmentation associated with inflammatory lesions is usually a late event, occurring with regression of the inflammation. If there are no symptoms, no cells in tee vitreous, and the lesion has clearly-defined borders, then no action is required. Patients with a reactivated toxoplasma lesion are likely to preset with reduced vision and floaters. They have flare and cells in the anterior chamber and in the vitreous, and in the fundus "fluffy", ill-defined pale lesions are seen, usually at the border of an older hypopigmepted lesion with a hyperpigmented surround. Such cases warrant same-day referral to the ophthalmic department for urgent work-up and treatment.

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Module questions Course code: C-19518 O/D

PLEASE NOTE There is only one correct answer. All CET is now FREE. Enter online. Please complete online by midnight on October 5, 2012--You will be unable to submit exams after this date. Answers to the module will be published on www.optometry.co.uk/cet/exam-archive. CET points for these exams will be uploaded to Vantage on October 15, 2012. Find out when CET points will be uploaded to Vantage at www.optometry.co.uk/cet/vantage-dates

1. Which of the following is the MOST appropriate management of choroidal naevi?

a) They should be referred if there is documented increase in size

b) They should be referred if they are large and associated with photopsia

c) They should be referred if accompanied by significant serious detachment of the retina

d) All of the above

2. Which of the following is the MOST appropriate management of CHRPE?

a) It should be referred if there is a "bear-track" configuration

b) It should be referred if it contains "punched-out" hypopigmented areas

c) It should be referred if there is an associated visual field defect

d) None of the above

3. Which of the following is a feature of choroidal melanoma?

a) The lesion is _at with overlying drusen

b) The lesion may be pale and elevated

c) It shows a peak incidence in the 7th decade

d) It is benign in most cases

4. Which of the following is a feature of tidemarks in the retina?

a) They are commonly seen around areas of macular oedema

b) They indicate that retinal detachment is no longer present

c) They indicate chronicity in a retinal detachment

d) They occur at the boundary of retinal detachment and retinoschisis

5. Which of the following is a feature of retinitis pigmentosa?

a) It is in an inactive stage if there are no cells in the vitreous

b) It may be caused by Toxoplasma gondii

c) It requires urgent referral to secondary care

d) It may be discovered in an asymptomatic patient

6. Which of the following is a feature of pigmented lattice degeneration?

a) It is present in about 8% of the population

b) It usually demands urgent assessment in secondary care

c) It is more likely to require laser treatment than non-pigmented degeneration

d) All of the above

References

See www.optometryico.ek/clinical. Click on the article title and then on 'references' to download.

Mark Benson, MB, ChB, MSc, FRCS, FRCOphth

Mark Benson is a director of the Midland Eye Institute, and consultant ophthalmic surgeon to the Heart of England NHS Trust for whom he runs retinal and cataract services. He is senior clinical lecturer to the University of Birmingham, a section editor for the journal Eye, and an examiner for the Royal College of Ophthalmologic.
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Title Annotation:CET: CONTINUING EDUCATION & TRAINING
Author:Benson, Mark
Publication:Optometry Today
Geographic Code:4EUUK
Date:Sep 7, 2012
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