Opthalmology

Question 1

Afferent Defect

Answer 1

Features -

• No direct response but intact consensual response
• Cannot initiate consensual response in contralateral eye.
• Dilatation on moving light from normal to abnormal eye

Causes

• Total CN II lesion

Question 2

Relative Afferent Pupillary Defect

Answer 2

= Marcus-Gunn Pupil Features

Features

• Minor constriction to direct light
• Dilatation on moving light from normal to abnormal eye

Causes

• Optic neuritis
• Optic atrophy
• Retinal disease

Question 3

Efferent Defect

Answer 3

Feature

• Dilated pupil does not react to light
• Initiates consensual response in contralateral pupil
• Ophthalmoplegia + ptosis

Cause

• 3rd nerve palsy
• The pupil is often spared in a vascular lesion (e.g. DM) as pupillary fibres run in the periphery.

Question 4

Differential of a fixed dilated pupil

Answer 4

• Mydriatics: e.g. tropicamide
• Iris trauma
• Acute glaucoma
• CN3 compression: tumour, coning

Question 5

Holmes-Adie Pupil

Answer 5

Features

• Young woman c¯ sudden blurring of near vision
• Initially unilateral and then bilateral pupil dilatation
• Dilated pupil has no response to light and sluggish response to accommodation.
• A “tonic” pupil

Ix

• Iris shows spontaneous wormy movements on slit-lamp examination
• Iris streaming

​Cause

• Damage to postganglionic parasympathetic fibres
• Idiopathic: may have viral origin

Holmes-Adie Syndrome - Tonic pupil + absent knee/ankle jerks + ↓ BP

Question 6

Horner’s Syndrome

Answer 6

Features:

• PEAS
• Ptosis: partial (superior tarsal muscle)
• Enophthalmos
• Anhydrosis
• Small pupil

Causes

• Central -MS, Wallenberg’s Lateral Medullary Syndrome
• Pre-ganglionic (neck), Pancoast’s tumour: T1 nerve root lesion, Trauma: CVA insertion or CEA
• Post-ganglionic, Cavernous sinus thrombosis, Usually 2^O to spreading facial infection via the ophthalmic veins, CN 3, 4, 5, 6 palsies

Question 7

Argyll Robertson Pupil

Answer 7

Features

• Small, irregular pupils
• Accommodate but doesn’t react to light
• Atrophied and depigmented iris

Cause

• DM
• Quaternary syphilis

Question 8

Acute Closed Angle Glaucoma

(RED EYE)

Answer 8

• Blocked drainage of aqueous from anterior chamber via angle of Schlemm
• Pupil dilatation (e.g. at night) worsens the blockage, IOP ->60mmHg
• RFs - hypermetropia, shallow anterior chamber, female, FH, increased age, drugs (anti-cholinergics, sympathomimetics, TCAs, anti-histamines)
• Symptoms - prodrome = ranbow haloes around lights at night
  
  • ​Severe pain, +/- N/V
  • Decreased acuity, blurred vision
• Examination - cloudy cornea +/- circumcorneal injection
  
  • ​Fixed, dilated, irregular pupil
  • Increase IOP -> hard feeling eye
• Ix - Tonometry - V V high IOP (>40mmHg)
• Acute Mx -
  
  • ​Pilocarpine 2-4% drops - miosis opens blockage
  • Topical beta-blockers e.g. timolol - decrease aqueous formation
  • Acetazolamide 500mg IV stat - decrease aqueous formation
  • Analgesia and antimetics
• Subsequent Mx -
  
  • ​Bilat YAG peripheral iridotomy once IOP decreases

Question 9

Sudden Loss of Vision

Key Questions

Answer 9

• Headache associated - GCA
• Eye movements hurt - optic neuritis
• Lights/flashes preceding visual loss - detached retina
• Like curtain descending - TIA, GCA
• Poorly controlled DM - vitreous bleed from new vessels

Question 10

Sudden Loss of Vision

AION

Answer 10

• Optic nerve damaged if posterior ciliary arteries blocked by inflammation or atheroma.
• Pale / swollen optic disc
• Causes
  
  • Arteritic AION: Giant Cell Arteritis
  • Non-arteritic AION: HTN, DM, ↑ lipids, smoking

Question 11

Sudden Loss of Vision

OPTIC NEURITIS

Answer 11

• Symptoms
  
  • Unilateral loss of acuity over hrs – days
  • ↓ colour discrimination (dyschromatopsia)
  • Eye movements may hurt
• Signs
  
  • ↓ acuity
  • ↓ colour vision
  • Enlarged blind-spot
  • Optic disc may be: normal, swollen, blurred
  • Afferent defect
• Causes
  
  • Multiple sclerosis (45-80% over 15yrs)
  • DM
  • Drugs: ethambutol, chloamphenicol
  • Vitamin deficiency
  • Infection: zoster, Lyme disease
• Rx
  
  • High-dose methyl-pred IV for 72h
  • Then oral pred for 11/7

Question 12

Sudden Loss of Vision

VITREOUS HAEMORRHAGE

Answer 12

• Source
  
  • New vessels: DM
  • Retinal tears / detachment / trauma
• Presentation
  
  • Small bleeds → small black dots / ring floaters
  • Large bleed can obscure vision → no red reflex, retina can’t be visualised
• Ix
  
  • May use B scan US to identify cause
• Mx
  
  • VH undergoes spontaneous absorption
  • Vitrectomy may be performed in dense VH

Question 13

Sudden Loss of Vision

CENTRAL RETINAL ARTERY OCCLUSION

Answer 13

• Presentation
  
  • Dramatic unilateral visual loss in seconds
  • Afferent pupil defect (may precede retinal changes)
  • Pale retina c¯ cherry-red macula
• Causes
  
  • GCA
    
    • Thromboembolism: clot, infective, tumour
• Rx
  
  • If seen w/i 6h aim is to ↑ retinal blood flow by ↓ IOP
  • Ocular massage
  • Surgical removal of aqueous
  • Anti-hypertensives (local and systemic)

Question 14

Sudden Loss of Vision

RETINAL VEIN OCCLUSION

Answer 14

• Central
  
  • Commoner than arterial occlusion
  • Causes: arteriosclerosis, ↑BP, DM, polycythaemia
  • Pres: sudden unilat visual loss c¯ RAPD
  • Fundus: Stormy Sunset Appearance
    
    • Tortuous dilated vessels
    • Haemorrhages
    • Cotton wool spots
  • Complications
    
    • Glaucoma
    • Neovascularisation
  • Prognosis: possible improvement for 6mo-1yr
• Branch
  
  • Presentation: unilateral visual loss
  • Fundus: segmental fundal changes
  • Comps: retinal ischaemia → VEGF release and neovascularisation
• ​Rx: laser photocoagulation

Question 15

Sudden Loss of Vision

RETINAL DETACHMENT

Answer 15

• Holes/tears in retina allow fluid to separate sensory retina from retinal pigmented epithelium
• May be 2^O to cataract surgery, trauma, DM
• Presentation: 4 F’s
  
  • Floaters: numerous, acute onset, “spiders-web”
  • Flashes
  • Field loss
  • Fall in acuity
  • Painless
• Fundus: grey, opalescent retina, ballooning forwards
• Rx
  
  • Urgent surgery
  • Vitrectomy + gas tamponade c¯ laser coagulation to secure the retina.

Question 16

Gradual Loss of Vision

CAUSES

Answer 16

• Common
  
  • Diabetic retinopathy
  • ARMD
  • Cataracts
  • Open-angle Glaucoma
• Rarer
  
  • Genetic retinal disease: retinitis pigmentosa
  • Hypertension
  • Optic atrophy
  • Slow retinal detachment

Question 17

Gradual Loss of Vision

AGE-RELATED MACULAR DEGENERATION

Answer 17

• Commonest cause of blindness >60yrs
• 30% of >75yrs will have dry AMD
• Risk Factors
  
  • _​_Smoking
  • ↑ age
  • Genetic factors
• Presentation
  
  • ​Elderly pts.
  • Central visual loss
• Dry ARMD: Geographic Atrophy
  
  • Drusen: fluffy white spots around macula
  • Degeneration of macula
  • Slow visual decline over 1-2yrs
• Wet ARMD: Subretinal Neovascularisation
  
  • Aberrant vessels grow into retina from choroid and → haemorrhage
  • Rapid visual decline (sudden / days / wks) c¯ distortion
  • Fundoscopy shows macular haemorrhage → scarring
  • Amsler grid detects distortion
• Ix
  
  • OCT: optical coherence tomography
    
    • Gives high resolution images of the retina
• Mx for Wet AMRD
  
  • Photodynamic therapy
  • Intravitreal VEGF inhibitors
    
    • Bevacizumab (Avastin)
    • Ranibizumab (Lucentis)
  • Antioxidant vitamins (C,E) + zinc may help early ARMD