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

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Rhegmatogenous retinal detachment

Pathogenesis

Rhegmatogenous RD affects about 1 in 10 000 of the population each year and both eyes may eventually be involved in about 10% of patients. It is characterized by the presence of a retinal break held open by vitreoretinal traction that allows accumulation of liquefied vitreous under the NSR, separating it from the RPE. The retinal breaks responsible for RD are caused by interplay between dynamic vitreoretinal traction and an underlying weakness in the peripheral retina referred to as predisposing degeneration. Even though a retinal break is present, a RD will not occur if the vitreous is not at least partially liquefied and if the necessary traction is not present.

Dynamic vitreoretinal traction

1Pathogenesis. Syneresis defines liquefaction of the vitreous gel (Fig. 16.20A). Some eyes with syneresis develop a hole in the posterior hyaloid membrane and fluid from within the centre of the vitreous cavity passes through this defect into the newly formed retrohyaloid space. This process forcibly detaches the posterior vitreous and the posterior hyaloid membrane from the ILM of the sensory retina as far as the posterior border of the vitreous base (Fig. 16.20B). The remaining solid vitreous gel collapses inferiorly and the retrohyaloid space is occupied entirely by synchytic fluid. This process is called acute PVD with collapse (Fig. 16.21) and will subsequently be referred to as acute PVD.

2Age at onset is typically 45–65 years in the general population but may occur earlier in myopic or otherwise predisposed individuals (e.g. trauma, uveitis). The fellow eye frequently becomes affected within 6 months to 2 years. The symptoms are discussed below.

Fig. 16.20 (A) Vitreous syneresis; (B) uncomplicated posterior vitreous detachment

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Fig. 16.21 Biomicroscopy showing posterior vitreous detachment with collapse

(Courtesy of CL Schepens, CL Trempe and M Takahashi, from Atlas of Vitreous Biomicroscopy, Butterworth-Heinemann, 1999)

Complications of acute PVD

Following PVD, the sensory retina is no longer protected by the stable vitreous cortex, and can be directly affected by dynamic vitreoretinal tractional forces. The vision-threatening complications of acute PVD are dependent on the strength and extent of pre-existing vitreoretinal adhesions.

1No complications occur in most eyes because vitreoretinal attachments are weak so that the vitreous cortex detaches completely without sequelae.

2Retinal tears may develop as a result of transmission of traction at sites of abnormally strong vitreoretinal adhesion as previously described (Fig. 16.22A and B). Although tears usually develop at the time of PVD, occasionally they may be delayed by up to several weeks. Patients with isolated PVD should therefore be re-examined after 1–6 weeks depending on risk factors. Tears associated with acute PVD are usually symptomatic, U-shaped, located in the upper fundus and may be associated with vitreous haemorrhage resulting from rupture of a peripheral retinal blood vessel. After a tear has formed, the retrohyaloid fluid has direct access to the subretinal space.

3Avulsion of a peripheral blood vessel resulting in vitreous haemorrhage in the absence of retinal tear formation may occur.

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Fig. 16.22 (A) U-tear and localized subretinal fluid associated with acute posterior vitreous detachment; (B) the vitreous shows syneresis, posterior vitreous detachment with partial collapse, and retained attachment of cortical vitreous to the flap of the tear

(Courtesy of CL Schepens, ME Hartnett and T Hirose, from Schepens’ Retinal Detachment and Allied Diseases, Butterworth-Heinemann, 2000)

About 60% of all breaks develop in areas of the peripheral retina that show specific changes. These lesions may be associated with a spontaneous breakdown of pathologically thin retinal tissue to cause a retinal hole, or they may predispose to retinal tear formation in eyes with acute PVD. Retinal holes are round or oval, usually smaller than tears and carry a lower risk of RD. Retinal detachment without PVD is usually associated with either retinal dialysis, or round holes predominantly in young female myopes.

Lattice degeneration

1Prevalence. Lattice degeneration is present in about 8% of the population. It probably develops early in life, with a peak incidence during the second and third decades. It is found more commonly in moderate myopes and is the most important degeneration directly related to RD. It is usually bilateral and most frequently located in the temporal rather than the nasal fundus, and superiorly rather than inferiorly. Lattice is present in about 40% of eyes with RD.

2Pathology. There is discontinuity of the internal limiting membrane with variable atrophy of the underlying NSR. The vitreous overlying an area of lattice is synchytic but the vitreous attachments around the margins are exaggerated (Fig 16.23).

3Signs

•Spindle-shaped areas of retinal thinning, commonly located between the equator and the posterior border of the vitreous base.

•A characteristic feature is an arborizing network of white lines within the islands (Fig. 16.24A).

•Some lattice lesions may be associated with ‘snowflakes’ (remnants of degenerate Müller cells – Fig 16.24B).

•Associated hyperplasia of the RPE is common (Fig. 16.24C).

•Small holes within lattice lesions are common and usually innocuous (Fig. 16.24D).

4Complications

a No complications are encountered in most patients (Fig. 16.25A).

bTears may occasionally develop in eyes with acute PVD. A small area of lattice may be seen on the flap of the tear, representing strong vitreoretinal attachment (Fig. 16.25B). Tears may also develop along the posterior edge of an island of lattice (Fig. 16.25C). They typically occur in myopes over the age of 50 years and the SRF progresses more rapidly than in RD caused by small round holes.

cAtrophic holes (Fig. 16.25D) may rarely lead to RD, particularly in young myopes. In these patients the RD may not be preceded by symptoms of acute PVD (photopsia and floaters) and the SRF usually spreads slowly so that the diagnosis may be delayed until central vision is involved. The fellow eye often has a ‘mirror-image’ distribution of holes.

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Fig. 16.23 Vitreous changes associated with lattice degeneration

Fig. 16.24 Clinical features of lattice degeneration. (A) Small island of lattice with an arborizing network of white lines; (B) lattice associated with ‘snowflakes’; (C) lattice associated with RPEchanges; (D) small holes within lattice seen on scleral indentation

(Courtesy of NE Byer, from The Peripheral Retina in Profile, A Stereoscopic Atlas, Criterion Press, Torrance, California, 1982 – figs B and D)

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Fig. 16.25 Complications of lattice degeneration. (A) Atypical radial lattice without breaks; (B) two U-tears, the larger one of which shows a small patch of lattice on its flap and is surrounded by a small puddle of subretinal fluid; (C) linear tear along the posterior margin of lattice; (D) multiple small holes within islands of lattice

Snailtrack degeneration

Snailtrack degeneration is characterized by sharply demarcated bands of tightly packed ‘snowflakes’ which give the peripheral retina a white frost-like appearance. The islands are usually longer than in lattice degeneration and may be associated with overlying vitreous liquefaction. However, marked vitreous traction at the posterior border of the lesions is seldom present so that tractional U-tears rarely occur, although round holes within the snailtracks may be present (Fig. 16.26).

Fig. 16.26 Islands of snailtrack degeneration, some of which contain holes

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Degenerative retinoschisis

1Prevalence. Degenerative retinoschisis is present in about 5% of the population over the age of 20 years and is particularly prevalent in hypermetropes (70% of patients are hypermetropic). Both eyes are frequently involved.

2Pathology. There is coalescence of cystic lesions as a result of degeneration of neuroretinal and glial supporting elements within areas of peripheral cystoid degeneration (Fig. 16.27A). This eventually results in separation or splitting of the NSR into an inner (vitreous) layer and an outer (choroidal) layer with severing of neurones and complete loss of visual function in the affected area. In typical retinoschisis the split is in the outer plexiform layer, and in reticular retinoschisis, which is less common, splitting occurs at the level of the nerve fibre layer.

3Signs

•Early retinoschisis usually involves the extreme inferotemporal periphery of both fundi, appearing as an exaggeration of microcystoid degeneration with a smooth immobile elevation of the retina (Fig 16.27B).

•The lesion may progress circumferentially until it has involved the entire fundus periphery. The typical form usually remains anterior to the equator although the reticular type may spread beyond the equator.

•The surface of the inner layer may show snowflakes as well as sheathing or ‘silver-wiring’ of blood vessels and the schisis cavity may be bridged by rows of torn grey-white tissue (Fig. 16.28).

•Microaneurysms and small telangiectases are common, particularly in the reticular type.

4Complications

aNo complications occur in most cases and the condition is asymptomatic and innocuous.

bBreaks. Inner layer breaks are small and round, whilst the less common outer layer breaks are usually larger, with rolled edges and located behind the equator (Fig 16.29).

cRD may occasionally develop in eyes with breaks in both layers (Fig. 16.30A), especially in the presence of PVD. Eyes with only outer layer breaks do not as a rule develop RD because the fluid within the schisis cavity is viscous and does not pass readily into the subretinal space. However, occasionally the schisis fluid loses its viscosity and passes through the break into the subretinal space, giving rise to a localized detachment of the outer retinal layer which is usually confined to the area of retinoschisis (Fig. 16.30B). The detachment is almost always asymptomatic, infrequently progressive and rarely requires treatment.

dVitreous haemorrhage is uncommon.

Fig. 16.27 Microcystoid degeneration. (A) Histology shows spaces in the nerve fibre layer delineated by delicate vertical columns of Müller cells; (B) circumferential microcystoid degeneration and mild retinoschisis in the inferotemporal and superotemporal quadrants

(Courtesy of J Harry and G Misson, from Clinical Ophthalmic Pathology, Butterworth-Heinemann, 2001)

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Fig. 16.28 Retinoschisis with breaks in both layers. The inner layer shows snowflakes and ‘silver-wiring’ of blood vessels, and the cavity is bridged by torn greywhite tissue

Fig. 16.29 Retinoschisis with multiple outer layer breaks

(Courtesy of J Donald M Gass, from Stereoscopic Atlas of Macular Diseases, Mosby, 1997)

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Fig. 16.30 Retinoschisis. (A) Large breaks in both layers but absence of retinal detachment; (B) linear break in the outer layer associated with localized subretinal fluid

‘White with pressure’ and ‘white without pressure’

1‘White with pressure’ is a translucent grey appearance of the retina, induced by indenting the sclera (Fig 16.31A). Each area has a fixed configuration which does not change when the scleral indenter is moved to an adjacent area. It is frequently seen in normal eyes and may be associated with abnormally strong attachment of the vitreous gel (Fig. 16.31B). It is also observed along the posterior border of islands of lattice degeneration, snailtrack degeneration and the outer layer of acquired retinoschisis.

2‘White without pressure’ has the same appearance but is present without scleral indentation. On cursory examination a normal area of retina surrounded by ‘white without pressure’ may be mistaken for a flat retinal hole (Fig. 16.32A). Giant tears occasionally develop along the posterior border of ‘white without pressure’ (Fig. 16.32B). For this reason, if ‘white without pressure’ is found in the fellow eye of a patient with a spontaneous giant retinal tear, prophylactic therapy should be performed. It is advisable to treat all fellow eyes of non-traumatic giant retinal tears prophylactically by 360° cryotherapy or indirect argon laser photocoagulation, irrespective of the presence of ‘white without pressure’, if they have not developed a PVD.

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Fig. 16.31 (A) ‘White with pressure’; (B) extensive vitreous syneresis and strong attachment of condensed vitreous gel to an area of ‘white without pressure’

(Courtesy of NE Byer, from The Peripheral Retina in Profile, A Stereoscopic Atlas, Criterion Press, Torrance, California, 1982 – fig. A; CL Schepens, ME Hartnett and T Hirose, from Schepens’ Retinal Detachment and Allied Diseases, Butterworth-Heinemann, 2000 – fig. B)

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Fig. 16.32 (A) Pseudoholes within an area of ‘white without pressure’; (B) total retinal detachment caused by a giant tear

Diffuse chorioretinal atrophy

Diffuse chorioretinal atrophy is characterized by choroidal depigmentation and thinning of the overlying retina in the equatorial area of highly myopic eyes. Retinal holes developing in the atrophic retina may lead to RD (Fig. 16.33). Because of lack of contrast between the depigmented choroid and sensory retina, small holes may be very difficult to visualize without the help of slit-lamp biomicroscopy.

Fig. 16.33 Diffuse chorioretinal atrophy with holes and localized subretinal fluid

(Courtesy of CL Schepens, ME Hartnett and T Hirose, from Schepens’ Retinal Detachment and Allied Diseases, Butterworth-Heinemann, 2000)

Significance of myopia

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