medical retina Flashcards
what does the viterous humour contain
volume of it?
water, hyaluronic acid and type II collagen.
4.0-4.4mL
retina role
derived embryologically from
- Blood tissue barrier
- Facilitate neural transmission
- Facilitate pathway of pathogens
layer responsible for converting light energy into neural signals.
Derived embryologically from the diencephalon.
The diencephalon gives rise to the optic vesicle and then the optic cup.
what are the two parts of the retina
● The outer retinal pigment epithelium (RPE) layer – From the outer optic cup of the diencephalon.
● The inner neurosensory retina (NSR) (composed of nine layers) – From the inner optic cup of the diencephalon.
why may retinal detachment occur
long distance between RPE and NSR
what are the 9 layers of the NSR
- Internal limiting membrane: Separates the retina from the vitreous.
- Nerve fibre layer (NFL): Contains ganglion cell axons that come together to form the optic nerve. Presents in the macular area and travels nasally to the
optic nerve directly through the papillomacular bundle. - Ganglion cell layer: Contains the cell bodies of the ganglion cells. Involved in
transmitting visual information to the brain including the stimulus required
for light pupillary response. - Inner plexiform layer: Synaptic layer between second and third order neurons.
- Inner nuclear layer: Contains cell bodies of bipolar cells and cell bodies of
Müller cells (principal glial cells of the retina). - Outer plexiform layer: Synaptic layer between photoreceptors and bipolar cells.
- Outer nuclear layer: Contains cell bodies of rods and cones.
- External limiting membrane (ELM): Connections between photoreceptors
and Muller cells create the ELM. - Photoreceptor layer: Composed of rods and cones.
what is the role of RPE and composed of
single layer of cuboidal epithelial cells containing melanosomes
- Absorbs light and prevents the scattering of light within the eye.
● Replenishes the molecules needed for phototransduction.
● Contains a blood-retinal barrier, which provides a selectively permeable
membrane to supply nutrients to the photoreceptors and maintain homeostasis.
The blood-retinal barrier is maintained by the zonulae occludentes.
● Phagocytosis of photoreceptor outer segment membranes.
● Transport and storage of metabolites and vitamins.
what is macula lutea ALSO KNOWN AS MACULA
pigmented, rounded area at the posterior pole of the retina, located temporal to the optic disc.
central, high-resolution, colour vision.
several layers of ganglion cells in contrast to the peripheral retina, which contains only one layer.
what is the fovea
depression at the centre of the macula
contains only cones and represents the retina’s highest visual acuity.
The centre of the fovea is avascular and is dependent on the underlying choriocapillaris for blood supply via diffusion across the RPE from the choroid
how many rods location pigment wavelength bipolar connection function
120 million
highest density in the mid-peripheral retina
rhodopsin
498nm
One bipolar cell can receive stimuli from multiple rods
• Night vision – low threshold to light
- Sensitive in dark-dim illumination
- Responsible for night and peripheral vision
how many cones location pigment wavelength bipolar connection function
6 million
Highest density at the
macula (especially the fovea)
Iodopsin
Three types:
Short (420),
medium (534)
long (564) wavelength cones which are sensitive to blue, green and red light, respectively
Forms a 1:1 ratio with bipolar cells
- Sensitive to bright light
- Responsible for central and colour vision
The outer third of retinal layers, including photoreceptors and RPE and choroid are supplied by
short posterior ciliary artery (choroid).
The inner two-thirds of retinal layers are supplied by
central retinal artery
pathogenesis of diabetic retinopathy
hyperglycaemia -> increased retinal blood flow-> damages endothelial walls and pericytes.
endothelial dysfunction-> vascular permeability + hard exudate formation
(lipoproteins in the outer plexiform layer).
microaneruysms formation?
Pericyte damage predisposes to the formation of microaneurysms,
which are leakages of blood from capillary walls
flame haemorrhages formation?
due to rupture of the capillary walls which track along the nerve
fibre layer.
cotton wool spot formation
Axonal debris at margins of ischaemic infarcts.
neovascularisation formation
occurs through angiogenic factors such as vascular
endothelial growth factor (VEGF) in response to ischaemia.
CMO which layer os mpst affected
outer plexiform layer
RFs of DR
● Duration of diabetes: Most important risk factor.
● Poor diabetic control
- Smoking
- hyperlipidaemia
- hypertension
- ethnicity
- pregnancy
Ix
- Fluoroscein angiography
- OCT
For type 2 diabetics, a 37% reduction in progression rate of microvascular complications (e.g. retinopathy) can be achieved with 1% reduction in HbA1c (1).
For insulin-dependent diabetics, intensive glycaemic therapy showed
a 76% reduction in progression of retinopathy when compared to the control group.
Note, however, intensive diabetic control may transiently worsen retinopathy in the first few months
● Pregnancy.
● Other factors:
(for type 2
diabetics, a tight blood pressure control with a mean of 144/82 mmHg caused a 37% reduction of microvascular complications
gradual onset of features of DR
- Any type of diabetic retinopathy.
- Diabetic macular oedema: Most common cause of visual impairment.
- Cataract.
acute onset of features of DR
- Painless: Similar to vitreous haemorrhage or tractional retinal detachment (flashes and floaters may precede visual loss).
- Painful: Similar to neovascular glaucoma (NVG) precipitated by rubeosis iridis.
classficiation of nonproliferative DR
MILD
MODERATE
SEVERE
● Mild
- At least one microaneurysm, intraretinal haemorrhages, exudates or cotton wool spots.
● Moderate
- Intraretinal haemorrhages (in 1–3 quadrants) or mild intraretinal microvascular abnormality (IRMA-shunt vessels that arise to supply hypoperfused areas).
- Venous beading (in 1 quadrant only).
● Severe Follows the 4-2-1 rule; one or more of: – Intraretinal haemorrhages in 4 quadrants – Venous beading ≥ 2 quadrants – Moderate IRMA ≥ 1 quadrant
Classification of proliferative DR
● Non-high risk
Neovascularization on disc (NVD) or elsewhere (NVE)
● High risk Fulfils one of the following: – NV >1/3 disc area – NVD plus vitreous haemorrhage – NVE >1/2 disc area plus vitreous haemorrhage
● Advanced
Tractional RD
what is diabetic maculopathy and its classification
presence of diabetic macular oedema
● Centre involving DMO or
● Extra-foveal DMO meeting clinically significant macular oedema (CSMO)
defined by the ETDRS
- Hard exudates + other ‘background’ changes on macula (< 1DD of fovea) • Microaneurysms + haemorrhage (< 1DD of fovea if VA is < 6/12)
- Retinal thickening
- ̄ Visual acuity
- Oedema
commoner in T2DM
ix for diabetic maculopathy
● Optical coherence tomography (OCT) for assessing and monitoring DMO.
● Fluorescence angiography (FA) mainly used to assess for retinal ischaemia.
Mx for diabetic retinopathy or maculopathy
Glycaemic and blood pressure control (use effective antihypertensives such as lisinopril).
Mx for non-proliferative DR
Monitoring in screening programmes or secondary care ranging from annual (for mild-moderate) to 4 monthly (severe).
Consider pan-retinal photocoagulation (PRP) for severe nonproliferative in elderly patients with type 2 diabetes or if poor attendance or prior to cataract surgery.
mx for proliferative DR
non-high risk
high risk
Non-high risk: Regular routine review ± PRP.
High risk: PRP within 2 weeks. Treat DMO, if coexists, at the same time or before.
Mx for viterous haemorrhage
Tractional RD or persistent vitreous haemorrhage
treat as high-risk PDR
pars plana vitrectomy
Mx for maculopathy
- Steroids
- Anti – VEGF
- Laser
Treated with intravitreal anti-VEGF (ranibizumab or aflibercept, note the latter has a higher molecular weight and is second line) if there is DMO on OCT and the vision is affected.
Consider using modified ETDRS laser if anti-VEGF is contraindicated (e.g. pregnancy).
Mx for diabetic retinopathy and cataract surgery
Treat CSMO and PDR or neovascularization of iris before cataract surgery. If there is no fundal view perform B scan ultrasound.
what is hypertensive retinopathy
Atherosclerotic changes and vasoconstriction of retinal arteries in response to chronic hypertension causes endothelial damage and can lead to retinopathy
Chronic hypertensive retinopathy can include similar signs to diabetic retinopathy.
Mx is usually with BP control.
clinical stages of hypertensive retinopathy
- Arteriolar narrowing.
- Arteriovenous nipping (Figure 14.3) or atherosclerosis with thickening of
retinal arterioles (‘copper/silver wiring’). - Stage 2 plus flame haemorrhages, cotton wool spots or exudates.
- Stage 3 plus papilloedema.
classification of retinal vein occlusion
complications
non-ischaemia
ischaemic
● Central (CRVO) versus branch (BRVO): An occlusion at or proximal to the lamina cribrosa where the retinal artery exits the eye leads to CRVO. An occlusion of one of the branches of central retinal vein leads to BRVO
● Ischaemic versus non-ischaemic.
- Non ischaemic CRVO: chronic macular oedema leading to permanent central scotoma.
- Ischaemic CRVO: neovascularization, neovascular glaucoma, vitreous haemaorrhage, macular degermation and optic atrophy.
RFs of retinal vein occlusion
● Age ● Microvascular: Hypertension, hyperlipidaemia - DM ● Combined oral contraceptive pill ● Glaucoma - polycythaemia
non-ischaemic CRVO features
fundoscopy findings
● Sudden, painless dVA (>6/60).
● Fundoscopy:
- Tortuosity and dilatation of all branches of central retinal vein
- dot/blot and flame haemorrhages of all four quadrants, prominent in the periphery
- with optic disc and macular swelling.
ischaemic CRVO features
fundoscopy findings
● Sudden, painless severe dVA (<6/60).
● Relative afferent pupillary defect (RAPD).
● Significant tortuosity and dilatation of all four quadrants - with severe flame haemorrhages - disc and macular oedema. - cotton wool spots - swollen optic nerve - risk of neovascularisation
● Rubeosis iridis in about 50% of patients, which can lead to NVG.
Mx of non ischaemic CRVO
If VA is 6/96 or better and there is evidence of macular oedema on OCT:
● Commence intravitreal anti-VEGF or Ozurdex (dexamethasone) implant).
● Both treatments are first line
-> although younger phakic patients or with history of glaucoma should be started on anti-VEGF.
->Patients with high
cardiovascular profile should be started on Ozurdex implant.
Mx for ischaemic CRVO
● No neovascularization and open angle: Monitor for neovascularization and glaucoma.
● Neovascularization present: Urgent Pan-Retinal Photocoagulation ± cyclodiode laser therapy if angle closure.
most common location
features
complication
of BRVO
● Most common location: Superotemporal, followed by inferotemporal.
● dVA, metamorphopsia, VF defect (altitudinal).
● Retinal haemorrhage in the affected quadrant.
● Complication: CMO and neovascularization.
Mx of BRVO
macular oedem w minimal iscahemia
macular oedema w marked ischaemia
ischaemic BRVO w neovascularisation
● Macular oedema with minimal ischaemia
- Within 3 months of onset: Consider Ozurdex or anti-VEGF.
- After 3 months of onset: Consider macular grid laser or Ozurdex or anti-VEGF.
● Macular oedema with marked ischaemia: No immediate treatment.
● Ischaemic BRVO with neovascularization: PRP.
most common cause of CRAO
other causes
RFs
atherosclerosis.
Embolism:
• Carotid: this may be a cholesterol, fibrinoplatelet, or calcific embolus.
• Cardiac: this may be calcific, vegetations from the cardiac valves (endocarditis), or a
mural thrombus (eg, in atrial fibrillation).
• Aortic disease (including dissection) may be another embolic source
• Hypercoagulable states, sickle cell disease, leukaemia , lymphoma
Inflammatory/Arteritic: e.g. GCA (must rule out), PAN, SLE, etc
RFs
Smoking, hypertension, diabetes, hyperlipidaemia, CVD
Features of CRAO and fundoscopy findings
branches of central retina artery
● Sudden painless loss of vision (VA usually counting fingers, unless cilioretinal is spared) with marked RAPD.
- amaurosis fugax
● Fundoscopy:
- Swollen, pale and opaque retina
- RAPD
- ‘cherry red’ spot at the macula - POSTERIOR CILIARY ARTERIES
- arteriolar attenuation
Ischemic retinal whitening (immediately after an occlusion) - oedema
• Thin arteries, thin veins
• Sluggish blood flow
• Refractile lesion within blood vessel: Hollenhorst plaque- cholesterol), a whitish lesion within a section of the blood vessel usually at branching (platelet-fibrin ) or large calcific plaque (cardiac valvular disease).
• Systemic examination: carotid auscultation/check for bruit, radial pulse – AF, doppler ultrasound
• ESR/CRP – rule out GCA
branch of opthalmic -> CRA -> superior and inferior -> temporal and nasal
Mx of CRAO
Irreversible retinal infarction usually occurs within 90 minutes of occlusion of the artery
ocular massage - intermittent pressure is applied to the eye. Aqueous outflow is increased with pressure and retinal perfusion should improve. These maneuvers may dislodge the embolism.
AC paracentesis - can help to cause a sudden drop in IOP. This can dislodge the embolus + increase ocular perfusion
IOP-lowering - IV acetazolamide , IV mannitol outside of this window have questionable efficacy.
vasodilators - pentoxifylline, nitroglycerin, and isosorbide dinitrate
features of BRAO
● Most commonly due to embolic causes.
● Sudden painless altitudinal field loss.
● Swollen white retina along the affected vessel with arteriolar attenuation
major cause of ocular iscahemic syndrome
features of it
signs in anterior + posterior segments
atherosclerotic-stenosis of the carotid artery.
● Unilateral subacute dVA and periocular pain.
● Anterior segment: Conjunctival injection, AC cells and rubeosis iridis (IOP may remain low due to hypoperfusion).
● Posterior segment: Can be deceptively similar to CRVO. Cherry red macula,
retinal artery attenuation and neovascularization of the disc are seen.
what is sickle cell anaemia and pathophysiology
blood disorder that affects the beta haemoglobin subunit of red blood cells (RBCs)
- more prevalent in patients of African-Caribbean origin.
RBCs are exposed to hypoxia, they undergo a change in morphology resulting in a rigid, sickle-shaped cell. Intravascular sickling and haemolysis cause vascular occlusion and capillary nonperfusion, in both the anterior and posterior segment, leading to characteristic changes. Severity of ocular disease of different
forms of sickle cell mutations is: HbSC > HbSThal > HbSS.
features of
proliferative
non proliferative retinopathy
● Nonproliferative: Includes signs of intraretinal haemorrhages (‘salmon patches’) or patches of RPE hyperplasia (‘black sunbursts’).
● Proliferative retinopathy (Goldberg classification:
- Peripheral arteriolar occlusion
- Arteriovenous anastomosis
- Neovascularization with a ‘sea fan’ appearance
- Vitreous haemorrhage
- Tractional/rhegmatogenous retinal detachment
hallmark of the ARMD
macula of the eye, with large confluent soft drusen
pathological changes of
dry ARMD and features
Dry
● Drusen: Yellow deposits between Bruch’s membrane and RPE
● Atrophy of RPE, photoreceptor layers and choriocapillaries.
● Geographic atrophy: The end point of dry ARMD, characterized by large
atrophic areas with visibility of underlying choroid
Dry
● Gradual dVA and central scotoma.
● Intermediate or large soft drusen (≥63 microns or ≥125 microns). Note:
Small, hard drusen are of limited significance and may reflect normal age-
related changes.
● Geographic atrophy of RPE.
Pathological changes of polypoidal choroidal vasculopathy
● A variant of wet ARMD. Characterized by polypoidal dilatation of the choroidal vasculature. Progresses to subretinal haemorrhage and multiple PEDs.
● More common in middle-aged Asian populations and is unilateral in presentation.
RFs of ARMD
● Increasing age: Most important risk factor ● Genetics: CFH and ARMS2 genes - caucasian ● Smoking ● Hypermetropia ● Hypertension - hypercholestrolaemia ● Female ● White race
pathological changes of wet ARMD and features
Wet
● Ingrowth of choroidal vessels into RPE and subretinal space (choroidal neovascularization).
- leak exudate and fluid also cause haemorrhage
● Disciform macular degeneration is the end point of wet ARMD. This is fibrous scaring due to sub-RPE neovascularization (subretinal fibrosis).
features
● Decreased VA metamorphopsia
central scotoma of sudden onset.
● Subretinal or sub-RPE haemorrhage and exudation.
● RPE and/or exudative retinal detachment.
● CMO.
● Subretinal fibrosis (disciform).
Ix for ARMD
● OCT: monitor and identify drusen deposition and neovascular membranes
• Fundoscopy – deposition of drusen can be visualised along with areas of geographic atrophy is severe dry AMD.
• Fluorescein angiography can be performed to identify presence of neovascularisation
● ICG if PCV suspected: Branching vascular network may be seen on early
frames, with hyperfluorescence of polyps in late frames.
• Amsler grid – helps to identify the metamorphopsia
Mx of dry ARMD
wet ARMD
low vision aids
Dry
● Involves management of modifiable risk factors.
stop smoking
● Age-Related Eye Disease Study 2 (AREDS2) (9): Vitamin C, vitamin E, lutein,
zeaxanthin and zinc proved to reduce the progression of ARMD. Note: Beta-
carotene was removed as it increases the risk of lung cancer in smokers.
● AMSLER grid: To rule out progression to wet ARMD.
Wet
● Intravitreal anti-VEGF injections (e.g. ranibizumab or aflibercept).
Low vision aids
● Magnifiers: For reading, e.g. loop or spectacle magnifiers.
● Telescopes: For distance vision, e.g. Galilean telescopes.
what is choroidal neovascularisation and presentation of this
Abnormal growth of vessels from the choriocapillaries through Bruch membrane into sub-RPE (type 1) or subretinal (type 2) space.
Presentation of this disorder is with dVA, metamorphopsia and scotoma.
causes of choroidal neovascularisation
● Degenerative: ARMD (most common cause), myopic degeneration and angioid streak.
● Central serous chorioretinopathy.
● Inflammatory conditions: Birdshot choroidopathy, VKH, POHS.
● Best disease.
● Idiopathic.
what is degenerative myopia
progressive/pathological myopia. Those are a subset of patients with myopia >−6D in which the axial length of the eye may never stabilize. It can be associated with Stickler, Marfan, Ehlers-Danlos and Down syndromes.
features of degenerative myopia
● Chorioretinal atrophy with visibility of underlying choroidal vessels.
● CNV.
● Rhegmatogenous retinal detachment.
● Macular hole.
● Posterior staphyloma
An outpouching of the posterior wall of the eye that has a different radius of curvature than the rest of the eye.
One of the hallmarks of pathological myopia, associated with poor prognosis.
what is angoid streaks
bilateral symmetrical irregular atrophied streaks deep to the retina, radiating from the optic disc.
These result from breaks in the Bruch membrane. The condition presents as peripapillary atrophy with multiple irregular streaks radiating in a circular pattern.
The most common cause of visual loss is CNV.
causes of angoid streaks
● Idiopathic.
● Pseudoxanthoma elasticum: Most common systemic association. Mutation
in the ABCC6 gene. Presents with yellow papular lesions with excessive wrinkling (‘plucked chicken’ appearance) of skin usually in the neck, inguinal folds and antecubital fossa.
● Ehler-Danlos syndrome.
● Paget disease.
what is CMO
Sx
Ix
retinal thickening of the macula due to abnormalities of the blood-retinal barrier which leads to leakage of fluid within the intracellular spaces of the retina, typically in the outer plexiform layer
normal tight junctions in the retinal capillaries that form the inner blood retinal barrier breakdown
features dVA metamorphopsia scotoma. loss of foveal reflex cystic appearance to the fovea
Ix
OCT is useful in detecting CMO and measuring retinal thickening
The fluorescein leaks into the oedematous retina in a characteristic pattern - pettaloid
causes if CMO
Mx of cmo
● Diabetic macular oedema ● CRVO and BRVO ● ARMD ● Uveitis typically pars planitis but also occurs in anterior and posterior uveitis ● Retinitis pigmentosa ● Irvine-Gass syndrome ● Drugs
steroids (uveitis), acetazolamide (retinitis pigmentosa/IO surgery), NSAIDS
what is central serous chorioretinopathy
Breakdown of outer blood- retinal barrier between the choroid and retina.
buildup of central subretinal fluid due to retinal pigment epithelium dysfunction and choroidal hyperpermeability.
neuroretina separates from the RPE by fluid.
RFs of central serous chorioretinopathy
● Males aged 20–50.
● Type A personality.
● Corticosteroid related: Iatrogenic or Cushing disease.
features
examination
signs
Ix
Mx of
serous chorioretinopathu
features ● Unilateral drop in VA - metamorphopsia - central scotoma. ● Slow recovery from bright light. • Like AMD – micropsia, metamorphopsia, hyperopic or myopic shift, central scotoma, reduced contrast and colour saturation.
• Examination:
• Dome shaped elevation of the
retina
• “ink blot” leak under the neuroretina.
● Complications include serous (exudative) RD and CNV.
Ix
● OCT: Triangle-shaped subretinal fluid collection with neurosensory retinal detachment (Figure 14.12).
● FA: Progressive leakage with ‘inkblot’ or ‘smokestack’ appearance.
Mx
● Observe (spontaneous resolution), with management of risk factors.
● Consider photodynamic therapy (verteporfin) when there is significant
visual disturbance or chronic CSCR.
what is eales disease
presentation
RF
Idiopathic peripheral retinal periphlebitis that typically occurs in young Indian males.
Presentation is usually with recurrent vitreous haemorrhages.
Tubercular protein exposure (tuberculin sensitivity) may be a risk factor for developing this disease.
what is best disease
stages
BEST1 gene
Best vitelliform macular dystrophy is an AD degeneration of the macula associated with lipofuscin accumulation in the RPE and atrophy of the photoreceptor layer of the retina.
Stages
• Pre-vitelliform
• Vitelliform
• Pseudohypopyon • Vitelliruptive
features of Best disease
● Bilateral condition associated with hypermetropic patients.
● Egg yolk lesion in macula: Yellow-orange circular elevated lesion
(Figure 14.13).
● Electroretinogram (ERG): Normal.
● Electro-oculogram (EOG): Abnormal.
● Can be complicated by CNV which leads to dVA.
visual acuity drops in first 5-10 years of age
what is stargardt disease
An AR condition associated with a mutation in the ABCA4 gene on chromosome 1 that causes macular degeneration - normally clears away vitamin A by-products inside the photoreceptors
Usually, it presents with reading difficulties in patients under 20.
signs of stargardt disease
● Normal-appearing fundus in early stages of the disease.
● Late fundal appearance
- oval ‘snail slime’
- Beaten bronze appearance of the macula that can progress to
- geographic atrophy with a bull’s-eye pattern.
Yellow-white flecks in RPE.
● FA: ‘Dark choroid’ (reduced choroidal circulation).
what is lebers congential amaurosis and its presentations
An AR condition that presents with
- severe visual loss at birth
- nystagmus
- absent pupillary reflexes.
Enophthalmos and subsequent keratoconus may occur due to constant rubbing of the eye (oculodigital syndrome).
fundoscopy findings of lebers congenital amaurosis
● Early disease: Normal.
● Late disease: Salt-and-pepper retinopathy and bull’s-eye maculopathy.
what is albinism
hereditary group of diseases that affects melanin synthesis of the eye only (ocular albinism – XL inheritance) or, more commonly, the eye, skin and hair (oculocutaneous albinism – AR inheritance).
Sx & signs of albinism
● Symptoms: dVA due to foveal hypoplasia.
● Signs: Nystagmus, strabismus and iris/fundal hypopigmentation resulting in
a ‘pink eye’ appearance.
● The optic chiasm contains more crossed fibres than normal.
what is retinitis pigmentosa
A condition that is characterized by photoreceptor dysfunction (rods, then cones) and progressive atrophy/degeneration of retinal tissue.
Most commonly due to a mutation in the rhodopsin gene in the long arm of chromosome 3. Inheritance can be
AD (most common, least severe),
AR or XL inheritance (worst prognosis).
features of retinitis pigmentosa
● Symptoms:
- Nyctalopia (night blindness)
- peripheral vision loss (tunnel vision in late disease).
- loss of depth perception
● Triad: Pale optic disc (waxy disc)
- bone-spicules pigmentation
- arteriolar attenuation
● ERG (confirms diagnosis and monitors disease progression) and EOG are abnormal.
ass of retinitis pigmentosa
Optic disc drusen, myopia, posterior subcapsular cataract, CMO, open-angle glaucoma and keratoconus.
all retinitis pigmentosa related conditions present w
nyctalopia and tunnel vision with associated extraocular features.
AR - photoreceptor dysfunction with similar features to RP
what is usher syndrome
● Most common inherited cause of combined deafness (sensorineural) + blindness.
what is refsum syndrome
● Accumulation of phytanic acid.
● Associated anosmia, peripheral neuropathy and ichthyosis.
what is bardet-biedl syndrome
● RP-like retinopathy or bull’s-eye maculopathy (cone-rod dystrophy more common).
● Associated learning disability, polydactyly and obesity.
what is bassen kornzweigh syndrome
● Abnormal absorption of fat-soluble vitamins.
● Associated spinocerebellar ataxia and acanthocytosis.
causes of leukocoria
white pupil or the absence of red reflex
● Congenital cataract ● Retinoblastoma ● Persistent fetal vasculature ● Retinopathy of prematurity (ROP) ● Coats’ disease ● Toxocariasiscoria
what is retinoblastoma
common primary intraocular malignancy in children. It arises from embryonal photoreceptor cells of the retina with a mutation in the tumour suppressor gene RB1 on the long arm of chromosome 13. Most commonly sporadic in inheritance but can be AD.
histopathology of retinoblastoma
Flexner rosettes are classic, but Homer-Wright rosettes and fleurettes may exist.
features of retinoblastoma
fundoscopy findings
US findings
● The average age of diagnosis is 3 years. Parents often notice loss of red reflex on photographs.
● Unilateral (sometimes bilateral) leukocoria + strabismus ± red eye and dVa.
● Funduscopy: White round mass with either endophytic (towards vitreous) or exophytic growth (towards RPE/choroid).
● Ultrasound scan (USS): Can show calcification with high internal reflectivity
and can help determine tumour thickness.
what is persistent fetal vasculature
presentation
persistent hyperplastic primary vitreous and is the failure of the fetal hyaloid vasculature to regress.
This condition is associated with prematurity and development of cataract and retinal detachment.
presentation
Patients present within the first 2 weeks of life with unilateral leukocoria, micro-ophthalmia and cataract (Mittendorf dot).
what is retinopathy of prematurity
main RF
Blood vessels grow from the optic disc towards the periphery of the retina in utero, and this growth is driven through a relative hypoxic state.
• Increased metabolic demand by growing eye allows excessive VEGF production neovascularisation
The main risk factor for the development of ROP is being born prematurely.
The retinal vessels reach the nasal ora serrata (junction between retina and pars plana) at 32 weeks gestation and the temporal at 40 weeks. Hence, in ROP the temporal periphery is the first affected area
RFs of retinopathy of prematurity
● Prematurely born infant (<32 weeks gestation).
● Weight less than 1500 g.
● Extended oxygen treatment; for example, in neonatal respiratory distress
syndrome.
international classification of ROP revisited
Location
● Zone I: A circle with a radius of twice the distance from the disc to fovea
with the optic disc being the centre.
● Zone II: Edge of zone I to nasal ora serrata.
● Zone III: From zone II to the remaining retina.
Stages
1. White demarcation line separating vascular from avascular areas.
2. Ridge: Elevated and thickened demarcation line
3. Extraretinal fibrovascular proliferation or neovascularization infiltrating the
vitreous.
4. Partial retinal detachment: (a) extrafoveal; (b) foveal.
5. Total retinal detachment (most commonly tractional).
Plus disease
Additional signs of increased venous dilatation and/or arteriolar tortuosity of the posterior retinal vessels can increase the severity of the condition.
screening for retinopathy of prematurity
<=32 weeks or weighing < 1500 g
High-risk children should be screened via an indirect ophthalmoscope with 28D lens, as complications and permanent visual loss can occur if the disease is not treated early.
UK ROP screening recommendations (11) include:
● All infants born at less than 32-weeks gestation and/or weighing less than 1501 g should be screened.
- If born <27-weeks gestation, screen at 30–31 weeks postmenstrual age.
- If born ≥27- and <32-weeks gestation or born >32-weeks gestational age but weigh <1501 g, screen after 4–5 weeks postnatal age.
● Screen weekly if stage 3 disease, plus disease or if vessels end at zone 1 or posterior zone 2. Otherwise, screen every 2 weeks.
Mx of retinopathy of prematurity
Treatment is usually within 48 hours with transpupillary diode laser. Treat if:
● Zone I, any stage with plus disease.
● Zone II, stage 3 with plus disease.
● Zone I, stage 3 without plus disease.
what is coats disease
This is a unilateral condition of unknown aetiology that is characterized by telangiectasia and neovascularization. Commonly affects young boys.
features of coat’s disease
complications
● dVA, strabismus and leukocoria.
● Retinal telangiectasia and microaneurysms.
● Intra/subretinal exudation
● Complications: Exudative retinal detachment and NVG.
What is von hippel-lindau
AD condition affecting the von Hippel-Lindau (VHL) gene on the short arm of chromosome 3. This condition affects multiple organs including the brain, spinal cord, retina, kidneys, adrenal glands and pancreas.
features of von hippel-lindau
● Retinal capillary haemangioma with tortuous feeder vessels
● Renal cell carcinoma ● Pheochromocytoma
● CNS haemangioblastoma
what is choroidal melanoma
presentation
signs
metastasise where
Uveal tract malignant melanomas arise from melanocytes in either the iris, ciliary body or choroid. Choroidal melanoma is the most common.
P
This tumour is usually unilateral in presentation and can be asymptomatic or cause dVA and exudative retinal detachment.
signs
They can appear pigmented (lipofuscin) with a ‘collar-stud’ configuration if Bruch’s membrane is ruptured.
Metastatic spread is usually to the liver. Chromosome 3 monosomy is an indicator of poor prognosis.
choroidal circulation
flow rate
level of 02
type of cells
- high flow rate (150 mm/s) • low oxygen exchange
* fenestrated capillary bed
retinal circulation
flow rate
level of 02
type of cells
- Low flow rate (25 mm/s) • high oxygen exchange.
* Endothelial cells – tight junction which are impermeable to protein forming an inner blood retinal barrier
what is stickler syndrome
AD - COL2A1 gene on chromosome 12q13.11., defective collagen production
• Vitreous syneresis in a membranous or beaded configuration
• High risk of retinal tears and rhegmatogenous retinal detachment in the 1st decade
• Additional eye abnormalities include cataracts, astigmatism and strabismus.
• Cleft palate, hearing loss, osteoarthritis
Best vitelliform macular dystrophy
• AD, BEST1 gene • Stages
• Pre-vitelliform
• Vitelliform
• Pseudohypopyon • Vitelliruptive
• ABNORMAL EOG (even in carriers), NORMAL ERG
• VA drops in first 5-10 years of age.
