Glaucoma

Question 1

What is glaucoma?

Answer 1

-Progressive optic neuropathy
-Characteristic changes at optic nerve head

Question 2

Describe aqueous humour

Answer 2

-Nutrient-rich colourless fluid produced by the ciliary body
-Drains through the trabecular(¾) and uveoscleral (¼) routes

Question 3

Mechanism of open-angle glaucoma

Answer 3

Debris clogs up aqueous outflow tract (trabecular meshwork)
=Increased IOP, optic nerve compression and atrophy

Question 4

Risk factors for OAG

Answer 4

-Age >50
-Family history
-Black ethnicity
-Myopia (short sightedness)
-Hypertension, DM, corticosteroids

Question 5

Symptoms and signs of OAG

Answer 5

-Initially asymptomatic
-IOP >21 mmHg

-Visual field defects
=Peripheral vision loss (tunnel vision)
=Scotomata (nasal)
=Decreased VA

-Disc changes
=Cup-disc ratio >0.4/7 or asymmetry
=Notching of optic nerve cup
=Loss of nerve fibres, pallor
=Disc margin haemorrhage

Question 6

Investigation of glaucoma

Answer 6

-Tonometry (IOP measurement)- Goldmann applanation
-Ophthalmoscopy
-Slit-lamp examination (aqueous drainage angle examination)
-Fundoscopy (optic disc assessment)
-Visual field testing

Question 7

Treatment of OAG

Answer 7

URGENT REFERRAL IF IOP >30 mmHg

-First line:
=Topical (eye drops)
=Prostaglandin analogue/ Latanoprost (↑uveoscleral outflow). Darkens iris
=Timolol (↓aqueous production, beta blocker). Not asthmatic/ heart block
=Brinzolamide (↓aqueous production, carbonic anhydrase inhibitor)
=Brimonidine (↑outflow + ↓production, alpha adrenoreceptor)

-Second line: Laser trabeculoplasty/ IOP>24

Question 8

Mechanism of closed angle glaucoma

Answer 8

-Bowed iris blocks aqueous outflow tract

Question 9

Risk factors of CAG

Answer 9

-Age >40
-Female gender
-Asian ethnicity
-Hyperopia (axial length of eyeball anatomically too short)
-Dilating drops, medications inc some antidepressants- anticholinergic side effects so dilates pupils
-Family history
-Refraction (hypermetropia so small eyes, plus powered lenses)

Question 10

Symptoms and signs of CAG

Answer 10

-Pain (eye, headache, abdominal)
-Blurry vision
-Haloes
-Nausea, vomiting
-Red eye

-Hazy oedematous cornea
-Mid-sized fixed pupil (ischaemic so cannot contract)
-Injected eye
-Reduced VA
-IOP 50 –80 (raised)/ >21
-Shallow anterior chamber
-Occludable, narrow angle on contralateral side
-Afferent pupillary defect

Question 11

Diagnostic testing in CAG

Answer 11

Gonioscopy (examination of anterior chamber angle)
-Tonometry for IOP

Question 12

Treatment of CAG

Answer 12

-IV Acetazolamide 500mg STAT and eye drops as for OAG (stop production)
-Lie patient flat
-Topical pressure lowering therapy and topical steroids
-Topical pilocarpine (pupillary constriction) to BOTH eyes
-Urgent referral- laser peripheral iridotomy for definitive treatment (equalises anterior and posterior chamber pressure)- superior iris for cover by eyelid or double vision. Cataract surgery creates space (long term)

Question 13

What is angle closure?

Answer 13

Occlusion of the trabecular meshwork by the peripheral iris, obstructing aqueous outflow

-Primary= anatomically predisposed eye
-Secondary= due to ocular or systemic factor