Retinal detachment




Definitions





  • Retinal detachment (RD): separation of the neurosensory retina (NSR) from the RPE, with the accumulation of subretinal fluid (SRF).



  • Rhegmatogenous RD: occurs when a full-thickness defect in the NSR permits synchytic (liquefied) vitreous to gain access to the subretinal space.



  • Tractional RD: involves the contraction of vitreoretinal membranes in the absence of a retinal break.



  • Exudative RD: SRF is derived from retinal or choroidal vessels (e.g. inflammation, tumour).



  • Retinal break: full-thickness defect in the NSR, either (a) a tear, caused by dynamic vitreoretinal traction, or (b) a hole, caused by chronic retinal atrophy.



  • U-tear: consists of a flap with the apex pulled anteriorly by adherent vitreous, the base attached to the retina ( Figs. 16.1a–16.1c ).




    Fig 16.1



  • Operculated tear: flap has been completely torn away from the retina ( Fig. 16.1d ).



  • Dialysis: circumferential tear along the ora serrata with vitreous gel attached to its posterior margins ( Fig. 16.1e ).



  • Giant tear: involves 90° or more of the NSR ( Fig. 16.2 ).




    Fig 16.2





Rhegmatogenous retinal detachment





  • Pathogenesis: rhegmatogenous retinal detachment (RRD) affects approximately 1 in 10,000 of the population each year; both eyes are eventually involved in approximately 10%. Presentation is typically between 45 and 65 years of age but may be earlier, especially if predisposed (e.g. myopia).




    • Posterior vitreous detachment (PVD): (a) separation of the cortical vitreous from the internal limiting membrane (ILM) of the NSR posterior to the vitreous base with the remaining solid vitreous gel collapsing inferiorly (acute PVD; Figs. 16.3a and 16.3b ), (b) some eyes with acute PVD develop retinal tears ( Fig. 16.3c ), and subsequent RRD; (c) occasionally avulsion of a peripheral blood vessel may cause vitreous haemorrhage without a retinal tear ( Fig. 16.3d ).










      Fig 16.3



    • RRD without PVD: usually associated with a retinal dialysis or round holes.



    • Lattice degeneration: present in approximately 8% of the population and in approximately 40% of eyes with RRD: (a) spindle-shaped islands of retinal thinning with a characteristic network of white lines, (b) associated RPE hyperplasia; (c) small holes within islands are common ( Figs. 16.4a–16.4d ); (d) overlying gel is liquefied, but its adhesions around the margins of lattice are exaggerated ( Fig. 16.5 ); (e) tears typically occur at the posterior edge of an island.




      Fig 16.4



      Fig 16.5



    • Snailtrack degeneration: (a) sharply demarcated peripheral bands of tightly packed ‘snowflakes’ (see Fig. 16.4e ), (b) small holes; (c) overlying vitreous is liquefied but marked adhesions are seldom present so that tears are less common than in lattice.



    • Degenerative (acquired) retinoschisis: (see Fig. 16.4f and below).



    • White with pressure’: translucent grey appearance of a region of retina induced by indenting the sclera that may be associated with abnormally strong vitreous attachments.



    • ‘White without pressure’: same appearance without scleral indentation ( Fig. 16.4g ).



    • Significance of myopia: more than 40% of all RRDs occur in myopic eyes; (a) macular holes may give rise to RRD in highly myopic eyes, (b) vitreous loss and laser posterior capsulotomy are more likely to lead to RRD than in non-myopic eyes, and (c) predisposing factors are more common in myopic eyes (vitreous degeneration, PVD, lattice and snailtrack degenerations).



    • Other predisposing lesions: (a) pigment clumps (see Fig. 16.4h ), (b) diffuse chorioretinal atrophy (see Fig. 16.4i ), and (c) abnormal paravascular vitreoretinal adhesions (see Fig. 16.4j ).




  • Degenerative (acquired) retinoschisis




    • Pathogenesis: (a) coalescence of individual lesions within areas of peripheral microcystoid degeneration, (b) the NSR splits into inner and outer layers with severing of neurons and complete loss of visual function in the affected area (absolute scotoma); (c) the split in ‘typical’ retinoschisis is through the outer plexiform layer, and in the less common ‘reticular’ form at the nerve fibre layer.



    • Signs: (a) early retinoschisis appears as a shallowly elevated area of microcystoid degeneration, usually starting inferotemporally, (b) progresses to smooth immobile elevation of the retina ( Fig. 16.6 ), and (c) may extend circumferentially, the typical form usually remaining anterior to the equator although the reticular type may spread beyond.




      Fig 16.6



    • Associated features: (a) the inner layer surface may have a snowflake-like appearance, (b) vascular sheathing and sclerosis; (c) breaks in the inner layer are small and round, whereas the less common outer layer breaks are usually larger, with rolled edges ( Fig. 16.7 ).


Jul 11, 2019 | Posted by in OPHTHALMOLOGY | Comments Off on Retinal detachment
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