Ординатура / Офтальмология / Английские материалы / Clinical Ophthalmology A Systematic Approach 7th Edition_Kanski, Bowling_2011

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Fig. 15.53 Snowflake degeneration

Dominant neovascular inflammatory vitreoretinopathy

1Inheritance is AD mapped to 11q13.

2Presentation is in the 2nd–3rd decades with vitreous floaters due to vitritis.

3Signs

•Panuveitis.

•Peripheral vascular closure and pigment migration.

•Peripheral and then disc neovascularization.

•Epiretinal and subretinal fibrocellular membranes.

4Complications include vitreous haemorrhage, tractional retinal detachment, cystoid macular oedema, cataract and neovascular glaucoma.

5ERG shows selective loss of b-wave amplitude.

6Prognosis is guarded. Peripheral retinal photocoagulation and vitreous surgery may be required to preserve vision.

Dominant vitreoretinochoroidopathy

1Inheritance is AD; maps to the BEST1 gene on 11q13.

2Presentation is in adult life if symptomatic, but frequently the condition is discovered by chance.

3Signs

•Fibrillary vitreous degeneration and cells.

•A non-progressive or very slowly progressive encircling band of pigmentary disturbance between the ora serrata and equator with a sharply defined posterior border.

•Within the band there is arteriolar attenuation, neovascularization, punctate white opacities and later chorioretinal atrophy.

4 Complications, which are uncommon, include cystoid macular oedema, vitreous haemorrhage and cataract.

5ERG is variably reduced.

6 EOG is subnormal with a reduced Arden ratio.

7Prognosis is good.

Kniest dysplasia

1 Pathogenesis. Defect in the type II collagen gene, COL2A1, also involved in Stickler syndrome type 1.

2Inheritance is AD but most cases represent a fresh mutation.

3Systemic features. Flat face, enlarged joints, platyspondyly and disproportional short stature; neonates display short, stiff limbs and have apparently large heads.

4Ocular features include high myopia, vitreous degeneration, retinal detachment and ectopia lentis.

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Albinism

Introduction

Albinism is a genetically determined, heterogeneous group of disorders of melanin synthesis in which either the eyes alone (ocular albinism) or the eyes, skin and hair (oculocutaneous albinism) may be affected. The latter may be either tyrosinase-positive or tyrosinase-negative. The different mutations are thought to act through a common pathway involving reduced melanin synthesis in the eye during development. Tyrosinase activity is assessed by using the hair bulb incubation test, which is reliable only after 5 years of age. Patients with albinism have an increased risk of cutaneous basal cell and squamous cell carcinoma that usually occurs before the fourth decade.

Tyrosinase-negative oculocutaneous albinism

Tyrosinase-negative (complete) albinos are incapable of synthesizing melanin and have white hair and very pale skin (Fig. 15.54A) throughout life with lack of melanin pigment in all ocular structures.

1Inheritance is usually AR; the condition is genetically heterogeneous.

2Signs

aVA is usually <6/60 due to foveal hypoplasia.

bNystagmus is typically pendular and horizontal. It usually increases in bright illumination and tends to lessen in severity with age.

cThe iris is diaphanous and translucent (Fig. 15.54B), giving rise to a ‘pink-eyed’ appearance (Fig. 15.54C).

dThe fundus lacks pigment and shows conspicuously large choroidal vessels. There is also foveal hypoplasia with absence of the foveal pit and lack of vessels forming the perimacular arcades (Fig. 15.54D).

eThe optic chiasm has fewer uncrossed nerve fibres than normal so that the majority of fibres from each eye cross to the contralateral hemisphere. This can be demonstrated by visual evoked potential which shows predominance in the response to monocular stimulation.

fOther features commonly seen include high refractive errors of various types, positive angle kappa, squint and absence of stereopsis.

Fig. 15.54 Tyrosinase-negative oculocutaneous albinism. (A) White hair and very pale skin; (B) marked iris translucency; (C) ‘pink eye’ appearance; (D) severe fundus hypopigmentation and foveal aplasia

(Courtesy of L Merin – fig. D)

Tyrosinase-positive oculocutaneous albinism

Tyrosinase-positive (incomplete) albinos synthesize variable amounts of melanin. The hair may be white, yellow or red and darkens with age. Skin colour is very pale at birth but usually darkens by 2 years of age (Fig. 15.55A).

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Fig. 15.55 Tyrosinase-positive oculocutaneous albinism. (A) Fair hair and normal skin colour; (B) mild fundus hypopigmentation

(Courtesy of B Majol – fig. A)

Ocular features

1 Inheritance is usually AR with at least two gene loci.

2 Signs

a VA is usually impaired due to foveal hypoplasia.

b Iris may be blue or dark-brown with variable translucency. c Fundus shows variable hypopigmentation (Fig. 15.55B).

Associated systemic syndromes

1Chediak–Higashi syndrome

•Inheritance is AR with the gene locus on 1q42.

•Mild oculocutaneous albinism.

•Leucocytic abnormalities resulting in recurrent pyogenic infections.

•The vast majority of patients eventually develop a lymphoproliferative syndrome (accelerated phase) characterized by fever, jaundice, hepatosplenomegaly, pancytopenia and bleeding that requires bone marrow transplantation.

•Prognosis for life is generally poor with demise in the 2nd decade.

2Hermansky–Pudlak syndrome is a lysosomal storage disease of the reticuloendothelial system.

•Inheritance is AR.

•Mild oculocutaneous albinism.

•Platelet dysfunction resulting in early bruising.

•Pulmonary fibrosis, granulomatous colitis and renal failure in some cases.

3Waardenburg syndrome is an AD condition of which there are four types.

•The main systemic features are white forelock, cutaneous hypopigmentation, poliosis, sensorineural deafness (particularly in type 2), and synophrys or an unusual hair distribution. Upper limb defects, flexion contractures and syndactyly in type 3 and neurological anomalies in type 4.

•Ocular features include lateral displacement of the medial canthi (not present in type 2), broad nasal bridge, hypochromic irides with segmental or total heterochromia (Fig. 15.56), and segmental or total choroidal depigmentation.

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Fig. 15.56 Waardenburg syndrome with iris heterochromia and synophrys

Ocular albinism

Involvement is predominantly ocular with normal skin and hair although occasionally hypopigmented skin macules may be seen.

1Inheritance is usually XL and occasionally AR with multiple gene loci identified.

2Female carriers are asymptomatic although they may show partial iris translucency, macular stippling and mid-peripheral scattered areas of depigmentation and granularity (Fig. 15.57).

3Affected males manifest hypopigmented irides and fundi.

Fig. 15.57 Carrier of XL ocular albinism

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Cherry-red spot at macula

Pathogenesis

A cherry-red spot at the macula (Fig. 15.58) is a clinical sign seen in the context of thickening and loss of transparency of the retina at the posterior pole. The fovea, being the thinnest part of the retina and devoid of ganglion cells, retains relative transparency, allowing persistent transmission of the underlying highly vascular choroidal hue. This striking lesion occurs in the sphingolipidoses, which comprise a group of rare inherited metabolic diseases characterized by the progressive intracellular accretion of excessive quantities of certain glycolipids and phospholipids in various tissues of the body, including the retina. The lipids accumulate in the ganglion cell layer of the retina, giving the retina a white appearance. As ganglion cells are absent at the foveola, this area retains relative transparency and contrasts with the surrounding opaque retina. With the passage of time the ganglion cells die and the spot becomes less evident. The late stage of the disease is characterized by degeneration of the retinal nerve fibre layer and consecutive optic atrophy. The following diseases are associated with a cherry-red spot.

Fig. 15.58 Cherry-red spot at the macula

GM1 gangliosidosis (generalized)

1Inheritance is AR.

2Defect. Deficiency of beta-galactosidase 1.

3Systemic features include coarse facies, stiff joints, growth deficiency and severe cerebral degeneration leading to death by the age of 2 years.

4Ocular features are macular cherry-red spot in 50% of cases and very subtle corneal clouding.

Mucolipidosis type I (sialidosis)

1Inheritance is AR.

2Systemic

aLate-onset (after the age of 7 years) with myoclonus and seizures, compatible with normal life span.

bSevere starts before the age of 2 years and is characterized by severe neurodegeneration Hurler-like facies, hepatosplenomegaly, deafness, severe neurodegeneration and death in early childhood.

3Ocular features include corneal clouding, macular cherry-red spot, optic atrophy and occasionally punctate lens opacities.

GM2 gangliosidosis

Tay–Sachs disease

1Inheritance is AR.

2Pathogenesis. Deficiency of hexosaminidase A leads to accumulation of GM2 ganglioside in the brain and retina.

3Systemic features are progressive neurological deterioration starting within 6 months or birth with death by 2–4 years.

4Ocular features include a macular cherry-red spot that is present by 3 months and optic atrophy after 1 year, with blindness by the age of 2 years.

Sandhoff disease

1 Inheritance is AR.

2 Pathogenesis. Hexosaminidase A and B deficiency.

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3 Systemic features. Neurological degeneration similar to Tay–Sachs disease. 4 Ocular features are macular cherry-red spot and early-onset blindness.

Niemann–Pick disease

There are three main types of Niemann disease (A–C) but only the first two are associated with a cherry-red spot. The main ocular features of type C (chronic neuropathic) are gaze palsy and abnormal eye movements.

Type A (acute neuronopathic)

1Inheritance is AR.

2Systemic features present in infancy and are characterized by severe psychomotor deterioration, massive hepatosplenomegaly and death by the 4th year.

3Ocular features are macular cherry-red spot in 50% and subtle corneal clouding.

Type B (chronic non-neuronopathic)

1Inheritance is AR.

2Systemic features present in the teenage years or early adulthood and are characterized by hepatosplenomegaly, and involvement of lungs and bone marrow. CNS disease does not occur and survival for up to 20 years after presentation is possible.

3Ocular features are macular cherry-red spot and bull's eye maculopathy.

Farber disease

1Inheritance is AR.

2Pathogenesis. Lysosomal storage disease due to defective ceramidase.

3Systemic features include hoarseness, aphonia, dermatitis, lymphadenopathy, psychomotor retardation, and renal and cardiopulmonary disease.

4Ocular features include macular cherry-red spot, pingueculum-like conjunctival lesions and nodular corneal opacity.

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Chapter 16 – Retinal Detachment

INTRODUCTION 688

Anatomy of the peripheral retina 688 Innocuous peripheral retinal degenerations  689

Definitions 689

Clinical examination 692 Ultrasonography 697

RHEGMATOGENOUS RETINAL DETACHMENT 698 Pathogenesis 698

Symptoms 704

Signs 705 Differential diagnosis  709 Prophylaxis 710 Surgery 715

TRACTIONAL RETINAL DETACHMENT 721 EXUDATIVE RETINAL DETACHMENT 722 PARS PLANA VITRECTOMY 723

Introduction 723

Indications 725

Technique 725 Postoperative complications  727

Introduction

Anatomy of the peripheral retina

Pars plana

The ciliary body starts 1 mm from the limbus and extends posteriorly for about 6 mm. The first 2 mm consist of the pars plicata and the remaining 4 mm comprises the flattened pars plana. In order not to endanger the lens or retina, the optimal location for a pars plana surgical incision is 4 mm from the limbus in phakic eyes and 3.5 mm from the limbus in pseudophakic eyes.

Ora serrata

The ora serrata forms the junction between the retina and ciliary body and is characterized by the following (Fig 16.1):

1Dentate processes are teeth-like extensions of retina onto the pars plana; they are more marked nasally than temporally and can have extreme variation in contour.

2 Oral bays are the scalloped edges of the pars plana epithelium in between the dentate processes.

3A meridional fold is a small radial fold of thickened retinal tissue in line with a dentate process, usually located in the superonasal quadrant (Fig. 16.2A). A fold may occasionally exhibit a small retinal hole at its apex. A meridional complex is a configuration in which a dentate process, usually with a meridional fold, is aligned with a ciliary process.

4An enclosed oral bay is a small island of pars plana surrounded by retina as a result of meeting of two adjacent dentate processes (Fig. 16.2B). It should not be mistaken for a retinal hole because it is located anterior to the ora serrata.

5Granular tissue characterized by multiple white opacities within the vitreous base can sometimes be mistaken for small peripheral opercula (Fig. 16.2C).

At the ora, fusion of the sensory retina with the retinal pigment epithelium (RPE) and choroid limits forward extension of subretinal fluid. However, there being no equivalent adhesion between the choroid and sclera, choroidal detachments may progress anteriorly to involve the ciliary body (ciliochoroidal detachment).

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Fig. 16.1 The ora serrata and normal anatomical landmarks

Fig. 16.2 Normal variants of the ora serrata. (A) Meridional fold with a small retinal hole at its base; (B) enclosed oral bay; (C) granular tissue

Vitreous base

The vitreous base is a 3–4 mm wide zone straddling the ora serrata (Fig. 16.3). An incision through the mid-part of the pars plana will usually be located anterior to the vitreous base. The cortical vitreous is strongly attached at the vitreous base, so that following acute posterior vitreous detachment (PVD), the posterior hyaloid face remains attached to the posterior border of the vitreous base. Pre-existing retinal holes within the vitreous base do not lead to RD. Severe blunt trauma may cause an avulsion of the vitreous base with tearing of the nonpigmented epithelium of the pars plana along its anterior border and of the retina along its posterior border.

Fig. 16.3 The vitreous base

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Innocuous peripheral retinal degenerations

The peripheral retina extends from the equator to the ora serrata and may show the following innocuous lesions.

1Microcystoid degeneration consists of tiny vesicles with indistinct boundaries on a greyish-white background which make the retina appear thickened and less transparent (Fig. 16.4A). The degeneration always starts adjacent to the ora serrata and extends circumferentially and posteriorly with a smooth undulating posterior border. Microcystoid degeneration is present in all adult eyes, increasing in severity with age, and is not in itself causally related to RD, although it may give rise to retinoschisis.

2Pavingstone degeneration is characterized by discrete yellow-white patches of focal chorioretinal atrophy which is present to some extent in 25% of normal eyes (Fig. 16.4B).

3Honeycomb (reticular) degeneration is an age-related change characterized by a fine network of perivascular pigmentation which may extend posterior to the equator (Fig. 16.4C).

4Peripheral drusen are characterized by clusters of small pale lesions which may have hyperpigmented borders (Fig. 16.4D). They are similar to drusen at the posterior pole and usually occur in the eyes of elderly individuals.

Fig. 16.4 Innocuous peripheral retinal degenerations. (A) Microcystoid seen on scleral indentation; (B) pavingstone; (C) honeycomb (reticular); (D) drusen

(Courtesy of U Rutnin, CL Schepens, from American Journal of Ophthalmology 1967;64:1042 – fig. A)

Definitions

Retinal detachment

A retinal detachment (RD) describes the separation of the neurosensory retina (NSR) from the retinal pigment epithelium (RPE). This results in the accumulation of subretinal fluid (SRF) in the potential space between the NSR and RPE. The main types of RD are:

1Rhegmatogenous (rhegma – break), occurs secondarily to a full-thickness defect in the sensory retina, which permits fluid derived from synchytic (liquefied) vitreous to gain access to the subretinal space.

2Tractional in which the NSR is pulled away from the RPE by contracting vitreoretinal membranes in the absence of a retinal break.

3Exudative (serous, secondary) is caused neither by a break nor traction; the SRF is derived from fluid in the vessels of the NSR or choroid, or both.

4Combined tractional-rhegmatogenous, as the name implies, is the result of a combination of a retinal break and retinal traction. The retinal break is caused by traction from an adjacent area of fibrovascular proliferation and is most commonly seen in advanced proliferative diabetic retinopathy.

Vitreous adhesions

1Normal. The peripheral cortical vitreous is loosely attached to the internal limiting membrane (ILM) of the sensory retina. Stronger adhesions occur at the following sites:

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•Vitreous base, where they are very strong (see above).

•Around the optic nerve head, where they are fairly strong.

•Around the fovea, where they are fairly weak, except in eyes with vitreomacular traction and macular hole formation.

•Along peripheral blood vessels, where they are usually weak.

2Abnormal adhesions at the following sites may be associated with retinal tear formation as a result of dynamic vitreoretinal traction associated with acute PVD.

•Posterior border of islands of lattice degeneration.

•Retinal pigment clumps.

•Peripheral paravascular condensations.

•Vitreous base anomalies such as tongue-like extensions and posterior islands.

•‘White with pressure’ and ‘white without pressure’ (see below).

Vitreoretinal traction

Vitreoretinal traction is a force exerted on the retina by structures originating in the vitreous, and may be dynamic or static. The difference between the two is crucial in understanding the pathogenesis of the various types of RD.

1Dynamic traction is induced by eye movements and exerts a centripetal force towards the vitreous cavity. It plays an important role in the pathogenesis of retinal tears and rhegmatogenous RD.

2Static traction is independent of ocular movements. It plays a key role in the pathogenesis of tractional RD and proliferative vitreoretinopathy.

Posterior vitreous detachment

A posterior vitreous detachment (PVD) is a separation of the cortical vitreous from the internal limiting membrane (ILM) of the NSR posterior to the vitreous base. PVD can be classified according to the following characteristics:

1Onset. Acute PVD is by far the most common. It develops suddenly and usually becomes complete soon after onset. Chronic PVD occurs gradually and may take weeks or months to become complete.

2Extent

aComplete PVD in which the entire vitreous cortex detaches up to the posterior margin of the vitreous base.

bIncomplete PVD in which residual vitreoretinal attachments remain posterior to the vitreous base.

Rhegmatogenous RD is usually associated with acute PVD; tractional RD is associated with chronic, incomplete PVD; exudative RD is unrelated to the presence of PVD.

Retinal break

A retinal break is a full-thickness defect in the sensory retina. Breaks can be classified according to (a) pathogenesis, (b) morphology and

(c) location.

1Pathogenesis

aTears are caused by dynamic vitreoretinal traction and have a predilection for the superior fundus (temporal more than nasal).

bHoles are caused by chronic atrophy of the sensory retina and may be round or oval. They have a predilection for the temporal fundus (upper more than lower).

2Morphology

aU-tears (horseshoe, flap or arrowhead) consist of a flap, the apex of which is pulled anteriorly by the vitreous, the base remaining attached to the retina (Fig. 16.5A). The tear itself consists of two anterior extensions (horns) running forward from the apex.

bIncomplete U-tears, which may be linear (Fig. 16.5B), L-shaped (Fig. 16.5C) or J-shaped, are often paravascular.

cOperculated tears in which the flap is completely torn away from the retina by detached vitreous gel (Fig. 16.5D).

dDialyses are circumferential tears along the ora serrata with vitreous gel attached to their posterior margins (Fig 16.5E).

eGiant tears involve 90° or more of the circumference of the globe. They are most frequently located in the immediate postoral retina (Fig. 16.6A) or, less commonly, at the equator. Giant tears are a variant of U-shaped tears with the vitreous gel attached to the anterior margin of the break (Fig. 16.6B).

3Location

aOral breaks are located within the vitreous base.

bPost-oral breaks are located between the posterior border of the vitreous base and the equator.

c Equatorial breaks are at or near the equator. d Post-equatorial breaks are behind the equator.

e Macular breaks (invariably holes) are at the fovea.

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