Retinal detachment Flashcards
what is the definition of retinal detachment?
RD refers to separation of the neurosensory retina (NSR) from the retinal pigment epithelium (RPE) 🡪 results in accumulation of subretinal fluid (SRF) in the potential space between the NSR and RPE.
what is the definition of rhegmatogenous retinal detachment?
RRD is characterised by presence of retinal break + vitreoretinal traction that allows accumulation of liquified vitreous under the NSR (subretinal space), thus separating it from the RPE.
Retinal breaks result from posterior vitreous detachment or trauma (also caused by vitreous traction on the retina but the traction does not directly pull the retina off the underlying tissue, like in traction detachment).
what is the definition of tractional RD?
NSR is pulled away from the RPE by contracting vitreoretinal membranes, in the absence of a retinal break.
what is the definition of exudative RD?
Exudative RD is characterised by accumulation of SRF in the absence of retinal breaks or traction.
As long as the RPE is able to compensate by pumping the leaking fluid into the choroidal circulation (normal function of RPE), RD does not occur. However, when the mechanism is overwhelmed or functions subnormally, fluid accumulates in the subretinal space.
what is the definition of posterior vitreous detachment?
PVD refers to the separation of the cortical vitreous, along with the delineating posterior hyaloid membrane (PHM), from the neurosensory retina (NSR) posterior to the vitreous base.
what is the pathophysiology of posterior vitreous detachment?
PVD occurs due to vitreous gel liquefaction with age (synchysis) to form fluid-filled cavities, and subsequently condensation (syneresis), with access to the preretinal (postvitreous) space allowed by a dehiscence in the cortical gel and/or PHM.
what are the risk factors for posterior vitreous definition?
Prevalence of PVD increases with age (reaches 60% by age 80s).
Myopia – longer axial length of eye
Typically spontaneous, but can be induced by cataract surgery, trauma, uveitis, pan-retinal photocoagulation (PRP).
what are the symptoms of posterior vitreous detachment?
Floaters (myodesopsia) (most common complaint of PVD): Vitreous opacities (e.g. blood, glial cells or aggregated collagen fibres torn from the margin of the optic disc) most evident against a bright pale background
Flashing lights (photopsia): almost always seen in temporal periphery, caused by physical stimulation of the retina from vitreoretinal traction
Blurred vision: diffuse haze – may be due to dispersed vitreous haemorrhage (arise from torn retinal blood vessel, or from retinal break) or can also be caused by Posterior hyloid membrane or floaters in the visual axis
what are the signs of posterior vitreous haemorrhage?
Detached PHM can often be seen clinically on slit lamp examination as a crumpled translucent membrane in the mid-vitreous cavity behind which the cavity is optically clear
Haemorrhage – presence prompts careful search for retinal break (40-90%)
Retinal breaks
what are the investigations for posterior vitreous haemorrhage?
B scan U/S – can demonstrate extent of PVD
OCT – can show posterior pole separation
what is the management of posterior vitreous haemorrhage?
If vitreous haemorrhage is non-clearing 🡪 consider vitrectomy
F/U fundus examination to r/o retinal tear, retinal detachmen
what are the symptoms of retinal detachment?
- Floaters: caused by particles in vitreous (e.g. blood cells, retinal pigment cells)
- Flashes (photopsia): occurs due to tugs on the retina (from the separating vitreous) 🡪 mechanical depolarisation of axons running through the nerve fibre layer 🡪 interpreted as a flash of light
- Visual field defect -> usually in the far periphery of the retina, “curtain-like”, may not be visible on direct fundoscopy 🡪 probably means detachment, not just retinal break
- Blurring of vision
what is the management of retinal breaks without retinal detachment?
Retinal breaks without retinal detachment can be treated with laser retinopexy
MOA: apply laser to the region surrounding the lesion 🡪 induces adhesive chorioretinitis (chorioretinal adhesion) 🡪 preventing liquid vitreous access from travelling through the hole into the subretinal space 🡪 prevents expansion of the retinal break
After treatment, pt should avoid strenuous physical exertion for a week, until adequate adhesion has formed (takes 1-3 weeks); review after 1-2 weeks
Laser retinopexy does not work for retinal detachment, because the retina needs to be relatively attached to the underlying layer first (Mx of retinal detachment is by vitrectomy, see below) (same technology as PRP)
what is the risk factors for rhegmatogenous retinal detachment?
high myopia (> 6D), FHx of retinal detachment, trauma
Retina is more thinly stretched in people with severe myopia (longer axial length); risk of RD is higher with increasing myopia
If trauma, retinal detachment will occur generally within 6 weeks of trauma
what are the surgeries for retinal detachment?
- Trans pars plana vitrectomy + tamponade (air/silicone oil), OR
- Scleral buckling (indents sclera towards middle of the eye, relieving sclera traction) + cryotherapy or laser photocoagulation (to heal any breaks)
