Ophthalmology

Question 1

What are the 10 layers of the retina?

Answer 1

1. Inner limiting membrane
2. Nerve fibre layer
3. Ganglion cell layer
4. Inner plexiform layer
5. Inner nuclear layer
6. Outer plexiform layer
7. Outer nuclear layer
8. Outer limiting membrane
9. Photoreceptor layer
10. Retina pigmented epithelium

Question 2

Name the common forms of glaucoma.

Answer 2

1. Primary open angle glaucoma
2. Secondary open angle glaucoma
3. Primary angle closure glaucoma
4. Secondary angle closure glaucoma

Question 3

What is glaucoma?

Answer 3

Progressive optic neuropathy involving characteristic structual changes to the optic nerve head with associated visual field changes

Commonly associated with high IOP, but NOT REQUIRED FOR DIAGNOSIS

Question 4

What is an isolated increase in IOP called?

Answer 4

Ocular hypertension/Glaucoma suspect

Patients should be followed for increased risk of developing glaucoma

• 20-30mmHg: 10%
• 30-40mmHg: 40%
• >40%: most cases

Question 5

Up to 50% of patients with glaucoma do not have IOP >21mmHg

Question 6

In glaucoma, loss of peripheral vision (the classical ARCUATE DEFECT) commonly precedes central loss.

Question 7

What is the most common form of glaucoma?

Answer 7

Primary open angle glaucoma (95%)

Due to obstruction of aqueous drainage within the trabecular meshwork and its drainage into the Canal of Schlemm

Question 8

What are the major risk factors for primary open angle glaucoma?

Answer 8

A FIAT

• Age (prevalence at 80 years is 10%)
• Family history
• Increased IOP (>21mmHg)
• African descent
• Thin Cornea

Question 9

What are the minor risk factors for primary open angle glaucoma?

Answer 9

1. Myopia
2. Cataract
3. Previous ocular trauma
4. Chronic topical ophthalmic steroid use in steroid responders
5. Hypertension
6. Diabetes
7. Hyperthyroidism (Graves’ disease)
8. Anemia/hemodynamic crisis

Question 10

Yearly eye exams are recommended in patients with >4 weeks of topical ophthalmic steroid use.

Question 11

What is the earliest sign of primary open angle glaucoma?

Answer 11

Optic disc changes

• Normal: cup-disc ratio <0.4
• Increased vertical C:D ratio of >0.6
• Significant asymmetry in C:D ratios of >0.2
• Thinning and notching of the neuroretinal rim
• 360 degrees of peripapillary atrophy (PPA)
• Large vessels nasally displaced

Question 12

What is peripapillary atrophy (PPA)?

Answer 12

The thinning of the layers of retina and retinal pigment epithlium around the optic nerve – usually does not cause any symptoms or vision loss

1. Zona beta strophy: glaucoma
   >> Loss of retinal pigment epithelium
   >> Choriocapillaries in intact choroid vasculature
2. Zona alpha atrophy: normal
   >> On the outer surface of zona beta
   >> Areas of hyper/hypopigmentation with thinning of the choriocapillaries

Question 13

What is the characteristic visual field loss for primary open angle glaucoma?

Answer 13

1. Paracentral defects
2. Arcuate scotoma
3. Nasal step

Later: tunnel vision defect with temporal crescent sparing

Question 14

What is the treatment for glaucoma?

Answer 14

1. Medical treatment
   - Increase aqueous outflow
   >> Topical cholinergics: pilocarpine, carbachol
   >> Topical alpha-agonists: brimonidine
   >> Topical prostaglandin analogues: latanoprost, travaprost, bimatoprost
   - Decrease aqueous production
   >> Topical and oral carbonic anhydrase inhibitors: acetazolamide, brin/dorzolamide
   >> Topical beta-blockers: betaxolol
   >> Topical alpha-adrenergics: brimonidine
2. Surgical treatment
   - Trabeculectomy: create tract from anterior chamber to conjunctiva
   - Laser trabeculoplasty/Cyclophotocoagulation: selective destruction of ciliary bodies

Question 15

What is normal tension glaucoma?

Answer 15

Primary open angle glaucoma with IOP in the normal range – damage to the optic nerve may be due to vascular insufficiency

Usually found in women >60 years

Question 16

What are the secondary causes of open angle glaucoma?

Answer 16

1. Steroid-induced
2. Traumatic
3. Pigmentary dispersion syndrome
4. Pseudoexfoliation syndrome

Question 17

What is the rule of 4 regarding steroid-induced glaucoma?

Answer 17

1/4 of the general population using topical steroid for 4 weeks, 4 times a day will develop an increase in intraocular pressure.

Question 18

What are the risk factors for primary angle-closure glaucoma?

Answer 18

1. Age >70
2. Female
3. Family history
4. Hyperopia: small eye, big lens
5. Mature cataracts
6. Pupil dilation

Question 19

What are the clinical features of primary angle-closure glaucoma?

Answer 19

• Red, painful eye
• Decreased visual acuity with halo around lights
• Corneal edema – hazy cornea
• Fixed, mid-dilated pupil
• Nausea and vomiting
• Abdominal pain
• Shallow anterior chamber with cells in the chamber

Question 20

What are the complications of primary angle closure glaucoma?

Answer 20

• Irreversible loss of vision
• Permanent peripheral anterior synechiae

Question 21

What is the treatment for angle closure glaucoma?

Answer 21

BACH

• Beta-blockers
• Adrenergics
• Cholinergics: pilocarpine 1-4% Q5-15min topical
• Hyperosmotic agents: IV mannitol 1g/kg

Other medications

• IV acetazolamide 250-500mg
• Oral glycerine (hyperosmotic agents) 1g/kg

Surgery

• To decrease IOP: ALPI (argon-laser peripheral iridoplasty)
• To prevent recurrence: laser iridotomy

Question 22

What is the mechanism of treatment for ALPI (argon laser peripheral iridoplasty)?

Answer 22

Place contraction burns in the extreme iris periphery to contract the iris stroma between the site of the burn and the angle, physiclaly pulling the angle open

• In reversal of an angle-closure glaucoma attack
• Especially when medical treatment fails
• Does not necessarily prevent recurrences (VS. iridotomy)

Question 23

What are the causes for secondary angle-closure glaucoma?

Answer 23

• Uveitis: posterior synechiae
• Neovascular glaucoma
  >> Rubeosis iridis
  >> At the angle
  >> Within trabecular meshwork
  >> Due to retinal ischmia with proliferate DMR/CRVO
  >> Tx: laser therapy