Glaucoma

Question 0

Classify Glaucoma

Answer 0

A) congenital/developmental glaucoma

1. Primary congenital glaucoma (without assoc anomalies)
2. Developmental glaucoma (with associated anomalies)

B) primary adult glaucoma

1. Primary open angle glaucoma
2. Primary angle closure glaucoma
3. Primary mixed mechanism glaucoma

C) secondary glaucoma

Question 1

Define glaucoma

Answer 1

Group of disorders characterised by a progressive optic neuropathy resulting in a characteristic appearance of the optic disc and a specific pattern of irreversible Visual field defects that are associated frequently but not invariably with raised intraocular pressure.

Question 2

What is primary open angle glaucoma?

Answer 2

It is a type of primary glaucoma where there is no obvious systemic or ocular cause of rise in the intraocular pressure. Characterised by-

1. Slowly progressive raised intraocular pressure.
2. Open normal appearing anterior chamber angle
3. Characteristic Optic disk cupping
4. Specific visual field defects

Question 3

What are the drugs given for primary open angle glaucoma?

Answer 3

1. Topical beta blockers (DOC):
   Lower IOP by reducing aqueous secretion due to effect on beta 2 receptors in ciliary processes.

-Timolol Maleate (non selective beta blocker) 0.25, 0.5% 1-2 times a day.
CI in patients with heart block or asthma.
- Betaxolol (0.25,0.5% 1-2 times a day)
Selective beta blocker for patients with asthma and pulmonary problems.
- Levobunolol (0.25, 0.5% 1-2 times a day) action lasts longest
- Cartelol (1% 1-2 times a day)
Raises triglycerides and lowers high density lipoprotein least. Best choice for patients with hyperlipideamia or artherosclerotic cvs disease.

2. Prostaglandin analogues:
    Decrease IOP by incr uveoscleral outflow of aqueous. 
- Latanoprost
- Travoprost
- Bimaprost
- Unoprostone

3. Adrenergic drugs:
   - Epinephrine hydrochloride and Dipivefrine hydrochloride.
   Lower IOP by incr aqueous outflow by stimulating alpha receptors in the aq. Outflow system. High allergic rate.
   - Brimonidine
   Selective alpha 2 adrenergic agonist and lowers IOP by decreasing aq. Production
   Incr uveoscleral outflow
4. Dorzolamide:
   Topical carbonic anhydride inhibitor which lowers IOP by decr aq. Producn by altering ion transport along ciliary process epithelium.
5. Pilocarpine:
   Very effective. Sheet anchor drug. But not preferred anymore as doc because in younger patients causes spasms of accommodation and miosis.
   Contracts longitudinal muscle of ciliary body and opens spaces in trabecular meshwork thereby incr aq. Outflow.

Question 4

What is primary angle closure glaucoma?

Answer 4

Characterised by the apposition of peripheral iris against the trabecular meshwork resulting in obstruction of aqueous outflow by Closure of an already narrow angle of the anterior chamber. Not associated with any other ocular and systemic abnormalities.

Question 5

Signs of PCAG.

Answer 5

1. Lids- oedematous
2. Conjunctiva- chemosed and congested (conjunctival and ciliary vessels congested)
3. Cornea- oedematous and insensitive
4. Anterior chamber- very shallow. Aqueous flare or cells may be seen
5. Angle of anterior chamber- completely closed as seen in gonioscopy.
6. Iris - maybe discoloured.
7. Pupil- is semi dilated, vertically oval and fixed. Non reactive to both light and accommodation.
8. IOP- marked elevation of 40-70 mm hg
9. Optic disc- is oedematous and hyperaemic
10. Fellow eye- shows shallow anterior chamber and occludable angle.

Question 6

Management of PCAG? Immediate therapy ?

Answer 6

It is a serious emergency.
A) Immediate medical therapy:
1. Systemic hyper osmotic agents if IOP more than 40 mm of hg.
- IV mannitol 1gm/kg body weight
- oral hyperosmotics eg. Glycerol 1gm/kg body weight

2. Systemic carbonic anhydride inhibitors
   Eg. Acetazolamide 500mg stat iv followed by 250 mg tab 3x day
3. Topical anti glaucoma drugs include
   - Beta blocker- 0.5% Timolol maleate or 0.5% Betaxolol
   - Alpha adrenergic agonists eg. Brimonidine
   - Prostaglandin analogues eg. Latanoprost

Miotic therapy-
- pilocarpine 2% QID should be started 1 hour after commencement of treatment. When IOP is lowered coz at higher IOP sphincter is unresponsive to pilocarpine.

4. Analgesics and anti emetics
5. Compressive gonioscopy
   May help relieve pupil block and essential to determine of trabecular blockage is reversible.
6. Topical steroid
   Eg. Prednisolone acetate 1% or
   Decamethasone eye drops admin. 3-4 drops a day to reduce inflammation.

Question 7

Management of PCAG? Definitive treatment?

Answer 7

1. Laser peripheral iridotomy:
   As soon as cornea clears, perform gonioscopy. Laser PI should be performed if PAS are seen in < 270* angle. It reestablishes communication between posterior and anterior chamber so it bypasses pupillary block and relieves crowding of angle.

Laser iridotomy - always preferred over PI

2. Filtration surgery:
   Trabeculotomy should be performed incases where IOP is not controlled with the maximum medical therapy following an attack of acute PAC or if gonioscopy reveals PAS > 270 * angle and when PI not effective.
   Mechanism- filtration surgery provides an alternative to the angle for drainage of aqueous from anterior chamber to sub conjunctival space.
3. Clear lens extraction:
   By phacoemulsification with IOL lens implantation especially in prescence of cataract.