Ophthalmology

Question 1

Describe the 3 layers of the eye

Answer 1

Fibrous / outer layer: sclera - tough outer layer, attachment for extraocular muscles, covered by thin transparent conjunctiva (also covers inner eyelids); cornea - avascular and highly innervated, dome that changes shape to focus light on the retina

Vascular layer: choroid - vascular tissue that provides oxygen + nutrients to outer layers of the retina; ciliary body - ciliary muscle (smooth) controls the shape of lens and contributes to the formations of aqueous humour, attached to lens by ciliary processes; iris - circular structure, smooth autonomic muscle control diameter of pupil

Inner / retina: pigmented - single layer of cells, attached to choroid, absorbs light to avoid scattering, whole inner surface of eye; neural - photoreceptors, posterior + lateral; centre of retina = macula, fovea centralis has high concentration of light detecting cells, responsible for high acuity vision; optic disc around optic nerve has no light detecting cells; anteriorly has pigmented but no neural - non-visual retina

Question 2

Describe presentations of eye cranial nerve palsies

Answer 2

III: down + out (unopposed lateral rectus + superior oblique), ptosis (eyelid drooping), diplopia, if parasympathetic too - mydriasis (dilated pupil) + loss of accommodation

IV: elevated + maybe extortion, worst when looking down + in - reading, walking downstairs; patients adopt compensatory head tilt to opposite side of lesion to minimise diplopia

VI: turned medially, horizontal diplopia when looking towards affected side, patients may turn toward affected side

Question 3

What is the pathophysiology and risk factors of acute angle closure and open angle glaucoma

Answer 3

Sight threatening emergency (optic nerve damage), rapid rise in intraocular pressure due to obstruction of aqueous humour outflow (pupillary block), increasing pressure pushes iris forward exacerbating the angle closure
Elderly females, hyperopic (farsighted), shallow anterior chamber / thick peripheral iris, FHx, east asian
Meds: adrenergic (noradrenaline), anticholinergics (oxybutynin), tricyclics

Gradual increase in resistance through trabecular meshwork (age related, debris, fibrosis)
Age, FHx, black, myopia (nearsighted). Most common form of reversible blindness

Question 4

Acute angle closure glaucoma Px, Ix, Mx

Answer 4

Presentation: severe ocular pain, headache, nausea, vomiting, red eye, hazy cornea. Peripheral visual acuity reduced + halos around lights, pupil can be fixed + mid dilated, increased cup-disk ratio

Early diagnosis essential: gonioscopy (special contact lens + slit lamp) to view angle, eye examination, Goldmann tonometry shows raised IOP (>40 mmHg, should be 10-21)

Emergency medical treatment:
Lie patient on back, pilocarpine eye drops (2% blue eyes, 4% brown), topical timolol (BB, alternatively alpha agonist or prostaglandins), oral acetazolamide (or dorzolamide drops), IV mannitol, analgesia + antiemetic

Definitive treatment (chronic): laser peripheral iridotomy, hole in iris to allow flow

(Pilocarpine - cholinergic agonist + miotic agent causes pupil + ciliary muscle contraction (opens channel)
Timolol - unknown but likely reduced production of aqueous
Acetazolamide: carbonic anhydrase inhibitor - reduced production of aqueous humour)

Question 5

Open angle glaucoma Px, Ix, Mx

Answer 5

Presentation: (asymptomatic if found early), gradual peripheral vision loss, fluctuating pain, headaches, blurred vision, halos around lights

Ix: tonometry (Goldmann GS, non contact most common), gonioscopy + slit lamp, examination

Mx (>24 mmHg): 360 degree laser trabeculoplasty for all patients - laser on trabecular meshwork; latanoprost (prostaglandin, increase uveoscleral outflow) FL medical treatment
Also: timolol, dorzolamide (carbonic anhydrase inhibitor), brimonidine (symp)
If ineffective - trabeculectomy, new channel from anterior chamber

Question 6

Describe the difference between dry and wet macular degeneration

Answer 6

Wet is 10%, neovascularisation, leakage of serous + blood, risk of rapid vision loss, is curable
Dry: 90%, RPE + photoreceptor atrophy, gradual vision loss, supportive treatment

Question 7

Age related macular degeneration Px, Ix, Mx

Answer 7

Px: reduction in bilateral central visual acuity (particularly close objects), difficulty in dark adaptation, fluctuation in visual disturbance, photopsia (flashing lights + glare), visual hallucinations, straight lines appear wavy
Ix: slit lamp (exudative or haemorrhagic changes in retina), fundoscopy (drusen), amsler grid (wavy lines), optical coherence tomography (cross sectional view of retina - diagnosis and monitoring)
Mx: early stage: observation + risk factor modification; intermediate: antioxidant vitamin supplementation (zinc, A, C, E), specialist referral;

Mx wet: anti-VEGF (vascular endothelial growth factor) injections into vitreous chamber

Question 8

Central retinal artery occlusion Px, Ix, MX

Answer 8

Sudden onset (seconds) monocular vision loss, painless, RAPD

Swinging light test (complete / relative afferent papillary defect), fundoscopy (cherry-red spot in centre of macula, white ischaemic retinal areas); causes: carotid doppler, heart auscultation + ECG, ESR + CRP (giant cell arteritis)

Mx: within 6h, urokinase thrombolysis through ophthalmic artery catheterisation, ocular massage (<90m), anterior chamber paracentesis, sublingual isosorbide dinitrate
If giant cell arteritis - IV steroids

Question 9

Diabetic retinopathy pathophysiology and fundoscopy findings

Answer 9

Hyperglycaemia damages retinal small vessels and endothelial cells; increased vascular permeability (leaking vessels, haemorrhages, hard exudates), microaneurysms, venous beading, damage to nerve vessels (cotton-wool spots), neovascularisation (due to ischaemia) and vitreous haemorrhage

Grading based on fundoscopy findings: non-proliferative (early): everything above other than; proliferative: neovascularisation and vitreous haemorrhage

Question 10

Diabetic retinopathy Px, Mx, complications

Answer 10

Px: asymptomatic, blurred vision, floaters, dark areas in field, vision loss

Mx: good diabetic control; proliferative: laser photocoagulation, anti-VEGF, vitrectomy; dexamethasone intravitreal implant for macular oedema

Complications; vision loss, retinal detachment, vitreous haemorrhage, optic neuropathy, cataracts
Diabetic maculopathy: oedema + protein on / under macula leading to vision loss

Question 11

Cataracts pathophysiology, Px, Ix, Mx

Answer 11

Opacification of crystalline lens, progressive decline in visual activity due to loss of light hitting retina, combination of factors - oxidative stress / osmotic imbalance (swelling) / glycation due to age
(Age, smoking, alcohol, diabetes, steroids, hypocalcaemia)

Px: asymmetrical, progressive loss of acuity + blurring, colours become faded / brown, starbursts around lights, change in prescription glasses. Loss of red reflex + opacification of lens

Fundoscopy (normal fundus + optic nerve), slit lamp (visible cataract)

Mx: conservative for mild, once symptoms unmanageable surgery only treatment; breaking apart of lens, removal and replacement with an artificial lens

Question 12

Conjunctivitis Px, Ix, Mx. Most common cause

Answer 12

Acute onset, typically unilateral (may progress to bi), exposure (contact lens, swimming, contact), discomfort / itching / burning, foreign body sensation. Eyelid swelling + erythema
Viral: serous discharge, recent URTI, preauricular lymph nodes
Bacterial: purulent discharge, eyes stick together (especially morning)

Usually resolves within 2w without treatment

Hygiene (avoid contact, washing with cool boiled water + cotton wool); bacterial: topical chloramphenicol every 3h (fusidic acid in pregnancy). No contact lenses

Viral > bacterial, adenovirus most common

Question 13

Retinal detachment Px, Ix, Mx

Answer 13

Px: new onset floaters / flashes, sudden onset painless + progressive visual field loss from periphery, if macula is involved will also affect central acuity

Examination, red reflex lost on fundoscopy + retinal folds pale / opaque

Mx: urgent referral, treat tear with laser / cryotherapy, reattach retina with vitrectomy / scleral buckle / pneumatic retinopexy

Question 14

Anterior uveitis Px, Ix, Mx

Answer 14

Px: painful (dull aching), red, reduced visual acuity, photophobia, excessive lacrimation. Ciliary flush (cornea outwards), miosis (constricted pupil) and abnormal shape, hypopyon (white fluid in anterior chamber due to inflammatory cells)

Ix: slit lamp (anterior chamber cells, flare, keratic precipitates), intraocular pressure and fundoscopy for complications. Cause: blood tests for infection, HLA B27, ANA, RF

Mx: topical prednisolone / dexamethasone, topical atropine (cycloplegics - ciliary spasm and pain), treat cause

Question 15

Scleritis vs epislceritis

Answer 15

Red sclera, severe (boring) pain exacerbated by movement, photophobia, excessive lacrimal production, reduced acuity, tenderness

Episcleritis (outermost layer): localised / diffuse redness, no pain, dilated vessels. No photophobia or discharge or change in acuity
Applying phenylephrine drops will cause blanching of vessels and cause redness to disappear, will not help scleritis

Question 16

Scleritis Px, Mx, associations

Answer 16

Red sclera, severe (boring) pain exacerbated by movement, photophobia, excessive lacrimal production, reduced acuity, tenderness

Mx: urgent referral, systemic steroids, oral NSAIDs (indomethacin), treatment of cause

Associated with connective tissue disorders (RA, vasculitis)

Question 17

Subconjunctival haemorrhage patho, Px, Mx

Answer 17

Rupture of vessels between sclera and conjunctiva, often after periods of strenuous activity and trauma
RF: hypertension, bleeding disorders, whooping cough, blood thinners

Px: bright red blood covering white of eye, painless and does not affect vision

Harmless + spontaneously resolve, lubrication if irritating, investigate for underlying cause

Question 18

Corneal abrasion Px, Ix, Mx

Answer 18

Painful red eye, photophobia, foreign body sensation, excessive tear production, blurred vision

Fluorescein stain will collect in abrasion

Treat with topical chloramphenicol (abx), simple analgesia, lubricating eye drops

Question 19

Keratitis Px, Ix, Mx, most common cause

Answer 19

Primary usually mild blepharoconjunctivitis (eyelid margins + conjunctiva). Painful red eye, vesicles, foreign body sensation, watery discharge, reduced visual acuity

Slit lamp exam, fluorescein staining - dendritic ulcer (branching), corneal scraping for viral testing

Simple Mx: lid hygiene, ocular lubricants, simple analgesia. Can use chloramphenicol + pred

Herpes: urgent referral, topical antiviral, corneal transplant if permanent scarring / vision loss

Herpes simplex most common, potentially sight threatening, in recurrent virus becomes dormant in trigeminal ganglion

Question 20

Blepharitis Px, Mx

Answer 20

Px: bilateral grittines/ discomfort, particularly around eyelid margins, sticky in the morning, red margins, styes + chalazions common

Mx: hot compresses one eyelid margin BD, lid hygiene to remove debris (boiled water / sodium bicarbonate), artificial tears

Question 21

Retinitis pigmentosa Px, Ix, Mx

Answer 21

(Genetic condition causing degeneration of photoreceptors (particularly rods))

Px: night blindness often first, peripheral vision loss

Fundoscopy - bone-spicule pigmentation concentrated around the mid-peripheral area, narrowing of arterioles, pale optic disc

Referral to ophthalmology and genetics, vision aids, sunglasses, inform DVLA
No current options to slow progression

Question 22

Orbital cellulitis pathophysiology, Px, Ix, Mx

Answer 22

Medical emergency (sight threatening), infection of fat and muscles posterior to orbital septum, (not involving globe); usually URTI from sinuses. Most common: strep, staph a, HiB
Risk of cavernous sinus thrombosis, infection spreads, inflammation causes thrombosis (sepsis and cranial nerve palsies)

Px - 5Ps: pain (deep, eye movements), proptosis, periocular swelling (chemosis, erythema), pupil involvement (blurred, diplopia, RAPD), palsy; fever, malaise, other systemic

Ix: exam, FBC, CT with contrast (looking for abscess), blood culture + swab

Mx: admission / senior review, IV abx, surgery for abscess

Question 23

Periorbital cellulitis Px, Ix, Mx

Answer 23

Px: eyelid swelling + erythema, partial / complete ptosis
Without: pain on movement, ophthalmoplegia, proptosis, visual disturbance, RAPD
Bloods, swab, contrast CT
Mx: oral co-amoxiclav (IV in severe - ceftriaxone), surgery for abscess

Question 24

Vitreous haemorrhage Px, Ix, Mx

Answer 24

Px: sudden painless vision loss / reduced acuity, floaters. Exam: diminished red reflex, fundoscopy blocked by blood

Ix: slit lamp, B-scan ultrasonography (retinal detachment, foreign bodies, tumours), optical coherence tomography. Looking for cause: fluorescein angiography (vascular abnormalities), FBC + coag, ESR + CRP (vasculitis), viral serology / PCR

Mx: mild - observation and follow up, treat underlying cause (laser photocoagulation for diabetic retinopathy, anti VEGF for wet AMD), vitrectomy for severe / persistent (also treat retinal pathology)

Question 25

Posterior vitreous detachment Px, Ix, Mx

Answer 25

Px: sudden appearance of of floaters + flashes of light, blurred vision, ‘cobweb’ across vision
Weiss ring on ophthalmoscopy

Ix: examination by ophthalmologist within 24h to rule out retinal tears / detachment

Mx: will resolve in around 6m so no treatment