Retinal Disorders Flashcards
Outer surface attached to
Choroid
Inner surface attached to
Vitreous body
Macula
- Oval, yellowish area at centre of posterior part
- high concentration of cones
- fovea centralis
Optic Disk
- 3mm medial to macula
- pierced by central artery of retina
- blind spot
- leaves as optic nerve
What are the layers of retina?
outermost = retinal pigment epithelium (single layer)
innermost
- ganglion cell layer, axons form optic nerve
- bipolar nerve layer
- photoreceptors (cons & rods)
Functions of rods
- for night vision
- do not signal wavelength information
Function of Cones
- for daylight & color vision
- high threshold to light
- concentrated at fovea
Symptoms of Macular (central) dysfunction
significant visual impairment
- Blurred central vision
- Distorted vision (metamorphopsia)
- Areas of loss of central vision field (scotomata)
Distorted vision (metamorphopsia)
- micropsia/macropsia
- when photoreceptors gets stretched apart/close together
- straight lines = wavy, bent, irregular
Scotomata
- areas of loss of central vision field
- if part of photoreceptors layer becomes covered (by blood)
- if photoreceptors gets destroyed
Symptoms of peripheral retinal dysfunction
- loss of visual field (detected clinically)
- diseases predominantly affecting 1 type of photoreceptors (retinitis pigmentosa & night vision)
Age related maculopathy (AMD)
Collection of drusen (yellow lesions) in the macula
- overtime undigested lipid product that deposits in Burch’s membrane
Dry Form (AMD)
Neighboring retinal pigment epithelium & photoreceptors shows degenerative changes
Wet/Exudative form (AMD)
Angiogenic factors (ex. VEGF) stimulate new vessel formation from choroid through Bruch’s membrane & RPE into sub retinal space -> sub-retinal neovascular membrane
Symptoms of AMD
- symptoms of macular dysfunction
- progressive, gradual loss of central vision = difficulty reading, recognizing distant objects
- wet form = sudden visual disturbance
Signs of AMD
- Yellow, well-circumscribed drusen
- Areas of hypo/hyperpigmentation
- Loss of foveal reflex
- Wet = pre-retinal/subretinal hemorrhage
Investigations done for AMD
- Appearance of retina (through ophthalmoscope)
- Exudative AMD & vision not severely affected = fluorescein angiogram performed to delineate position of sub-retinal neovascular membrane
Prognosis for dry AMD
- progress very slowly
- increasing difficulty in reading
Prognosis of wet AMD
- marked deterioration in vision over 3 years (75%)
Treatment for Dry AMD
- no treatment
- vision magnified with low-vision aids (ex. Magnifier, telescopes)
- reassure peripheral vision won’t get affected
Treatment for wet AMD
- Argon laser treatment: if membrane is eccentric to fovea
- Photodynamic therapy (PDT): subfoveal membrane
- drugs - anti-VEGF (bevacizumab, ranibizumab) = inhibit angiogenesis
Conditions associated with formation of sub-retinal neovascular membranes
- AMD
- Myopia
- Pseudoxanthoma elasticum
Myopia
Loss of central vision (in young adulthood)
Pseudoxanthoma elasticum
Sub-retinal neovascular membrane grow through elongated cracks in Bruch’s membrane = angioid streaks
Pathogenesis of Macular holes
Blunt trauma/idiopathic -> traction by vitreous on thin macular retina -> well-circumscribed hole at center of macular -> loss of acuity
Pre-retinal glial membrane form over macular region -> contraction -> puckering of retina
Symptoms of macular holes
Early stages = distortion & mild blurring of vision
Treatment of macular holes
Microsurgical vitrectomy technique -> remove membrane -> improve symptoms
Macular edema
Accumulation of fluid within retina
Diagnosis of macular edema
- Ophthalmoscopy = loss of normal foveal reflex
- Confirmatory OCT scan
- Fluorescein angiogram
Causes of macular edema
- Intraocular surgery
- uveitis
- retinal vascular disease (e.g diabetic retinopathy)
- retinitis pigmentosa
Treatment for macular edema
- If its due to uveitis -> give steroids
- If due to retinitis pigmentosa/following Intraocular surgery -> give acetazolamide
Drugs causing macular damages
- Chloroquine
- Hydroxychloroquine
- Phenothiazines
- Tamoxifen
Ophthalmoscopy finding in chloroquine maculopathy
Bull-eye appearance
Posterior vitreous detachment
Vitreous gel undergoes degenerative changes in ptn in their 50s and 60s -> detach from retina
Symptoms of posterior vitreous detachment
- Photopsia (flashing lights)
- Shower of floaters
Most marked on bright days = small pupil throws sharper image on retina
Photopsia (flashing lights)
Detaching of vitreous -> traction on retina
Shower of floaters
Detaching of vitreous -> ruptures small vessels -> vitreous hemorrhage -> condensations within collapsed vitreous
Retinal detachment
Loss of position between the sensory retina & retinal pigment epithelium
Rhegmatogenous retinal detachment
Tear/break/hole in retina -> vitreous in sub-retinal space
Traction retinal detachment
Retina pulled away from pigment epithelium by contracting fibrous tissue grown on retinal surface
Exudative retinal detachment
Fluids in sub-retinal space (e.x tumors)
Without retinal break arising from inflammatory disease of choroid, retinal tumors & retinal angiomatosis
Risk factors for rhegmatogenous retinal detachment
- high myopes ptn
- cataract surgery complicated by vitreous loss
- detached retina in other eye
- recent severe eye trauma
Tear in sensory retina associated with
- posterior vitreous detachment
- lattice degeneration
Symptoms for rhegmatogenous retinal detachment
- progressive development of field defect (shadow/curtain)
- peripheral field loss (early)
- loss of central vision & marked decrease in visual acuity (if macula detached)
- loss of red reflex
Signs of rhegmatogenous retinal detachment
- Ophthalmoscopy = floating, diaphanous membrane (detached retina)
- Bullous detachment = marked accumulation of fluid in sub-retinal space
- Tear appears reddish pink (underlying choroidal vessels)
- Vitreous hemorrhage
Treatment for rhegmatogenous retinal detachment
- Surgery (by cryoprobe/laser) = close causative break & increase attachment
Surgeries done for rhegmatogenous retinal detachment
- External (conventional approach)
- Internal (vitreoretinal surgery)
External (conventional approach)
Relieves vitreous traction
Sclerostomy needed first
Internal (vitreoretinal surgery)
Through pars plana
- maintain head posture for several days
- avoid air traveling
Prognosis of rhegmatogenous retinal detachment
If surgery is successful -> excellent vision
If macula detached > 24 hrs = acuity not recovered completely, months to restore part of vision
Complications in rhegmatogenous retinal detachment surgery
Fibrotic changes in vitreous (proliferative vitreoretinopathy) -> traction on retina & further detachment
Traction retinal detachment seen in?
- proliferative diabetic retinopathy
- proliferative vitreoretinopathy
- vitreoretinal surgery
Exudative retinal detachment seen in
- posterior uveitis
- Intraocular tumors
- toxemia of pregnancy
- central serous retinopathy affecting macula
Retinoschisis
Degenerative splitting of retina with cyst formation between the 2 layers
