Ophthalmology Flashcards
Anatomy of the eye
Sclera white layer, goes all around and finishes at cornea
Iris is coloured, anterior chamber in front
Cornea is dome at the front (only bit covering the pupil)
Blood retinal barrier with tight junctions, so immune priveleged
Muscles of the eye and their innervation
Rectus muscles
- superior/inferior/lateral/medial
- superior and inferior tend to draw in medially
- medial, superior and inferior rectus - occulomotor nerve III
- lateral recuts - abducens nerve VI
Oblique
- superior/inferior
- allow rolling of eye when head to one side
- superior - down and out, intortion - trochlear nerve IV
- inferior - up and in, extortion - occulomotor nerve III
Light -> eye -> brain
Eye sees upside down image, visual cortex needs to convert
Need clear media to get light into retina - cornea, lens and vitreous fluid (so no blood supply to cornea, need nutrients from tears)
Light refracted at tear/air interface
Further refined at cornea through pupil by lens
Retina converts light signals to brain messages - by photoreceptors and supporting cells
Need muscles to align and coordinate
Need structures to protect and maintain (sclera, fascia, conjunctiva, lids)
Emmetropia
Myopia
Hypermetropia
Emmetropia = normal refraction Myopia = short sighted, eye too long Hypermetropia = long sighted, eye too short
Cataracts
‘A cataract is any congenital or acquired opacity in the lens capsule or substance, irrespective of effect on vision’
- but practically, ignore unless symptomatic
Can affect nucleus of lens, cortex of lens or back surface of lens
Presents - blurred vision worse on distance, glare, gradual onset, painless, monocular diplopia (double vision if just one eye)
Causes of cataracts
Mostly AGE - 70% of 70+yos
(lens made of multiple layers which are added to through life, accumulation of layers/metabolites -> opacity)
Also
- diabetes (glucose in aqueous humour, overhydrate lens, swell)
- trauma (direct penetrating/concussion/infrared)
- drug induced (steroids/chlorpromazine/gold)
- congenital (genetic/chromosomal/prenatal infection/metabolic/skeletal)
Cataracts surgery
Most common operation in UK
(may do both eyes in order to keep balance of short/long sightedness)
Involves removal of lens from capsule and replace with biometric artificial lens
Age related macular degeneration symptoms
Damage to retinal pigment epithelium (waste management zone)
Major cause of blindness
Symptoms
- loss of central vision
- metamorphosia (distortions in straight lines)
- change to colour vision
Age related macular degeneration - dry/wet
Dry form (atrophic)
- Atrophy of retinal pigment epithelium and cells immediately under and over it
- 90% of cases
- Progressive decline in vision over time, more metamorphopsia
- ‘Drusen’ - intracellular deposits
Wet form (exudative)
- Growth of underlying choroidal vessels, resulting in a neovascular membrane - new vessels leak and cause bleeds and fluid accumulation
- More acute and debilitating vision loss, more big spots knocked out due to haemorrhage
- 10% of cases
Risk factors and treatment for ARMD
Eye conditions- ARM, hypermetropia HTN, (not diabetes) Genetics Lifestyle Nutrition Anti-oxidants, obesity
Treat - anti-VGEF (vascular endothelial growth factor) injections, maybe monthly, to reduce existing vessels and stop new ones forming
+ glasses, low vision clinic, counselling (driving), support groups
Diabetic retinopathy and vasculopathy
Hyperglycaemia causes glycosylation of tissue proteins, small vessels disease
- Small vessel occlusion
- Increased permeability
- Neovascularisation following ischaemic tissue drive to compensate
See cotton wool spots
+ micro-aneurysms, exudates, oedema
+ retinal detachment in end stage disease
Should have yearly screening in T2DM (won’t necessarily get early symptoms but need early management)
Vascular occlusions
Sudden painless loss of vision, manifestation of underlying systemic disease
Arterial occlusion
- embolisation usually, or arteritis
- severity according to location
- cherry red spot over fovea (macula lost blood supply, fovea preserved)
- address underlying disease
Venous occlusion
- thrombosis in vessel lumen
- usually older age (if young consider SLE/myeloma etc)
- ‘clogged up’ looking retina with oedema and diffuse haemorrhage
- need anti-VGEF and laser
Hypertensive retinopathy
- only in very badly managed HTN (rare now)
- vasospastic reaction, then arteriosclerotic response
- macular star exudate, disc swelling, haemorrhage, exudate, cotton wool sports
- treat by managing HTN
Retinopathy of prematurity
Relative hypoxia intrauterine for retinal growth, so when premature birth into hyperoxic conditions, halts vascular growth
Eye continues to grow, so peripheral area of hypoxia, then compensatory pathological neovascularisation (fragile and leaky)
Risk of retinal detachment
Need laser therapy, or if severe then vitrectomy
Conjunctivitis
Mild-moderate pain, no vision loss
Can stain to see if corneal involvement
Bacterial or viral (very rarely fungal/amoebic)
Bacterial
- purulent, gunky
- unilateral
- staphylococcus/streptococcus
- broad spectrum topical abx (or oral if need be)
Viral
- less purulent/irritant, watery discharge
- bilateral
- much more contagious
- adenovirus/herpes simples/herpes zoster
- will go in 5 days ish (eye drops may help dry eye)
Keratitis
If involvement of cornea also (redness in sclera/conjunctiva, oedema around eye and discharge is just secondary)
More acute presentation in 24-48h
More painful, impacting vision earlier
May see fluid level of pus inside eye = hypopyon
Bacterial
- more acute, clearly demarcated lesion in cornea
- contact lens use associated
Viral
- more in older population
- herpes simples, herpes zoster, adenovirus
Fungal rare unless immunosupressed, or rotting vegetable contact with eye
Acanthamoeba if left contact lens in for several weeks, very agressive
