Glaucoma

Question 1

What is the ‘angle’?

Answer 1

The space between the posterior surface of the cornea and the anterior surface of the iris

It’s where the aqueous fluid leaves the eye

Question 2

What is the aqueous? Describe where its produced and where it goes around the eye?

Answer 2

Fluid that circulates around and nourishes the lens

Produced in ciliary body, passes through pupil into anterior chamber, leaves the eye via the trabecular meshwork and enters the episcleral veins

Question 3

What is a normal IOP?

Answer 3

10 to 21mmHg

Question 4

What types of glaucoma are there and whats the difference between them?

Answer 4

Chronic open angle glaucoma (COAG): a problem with trabecular meshwork, so aqueous can’t be drained properly

Closed angle: the angle is closed, i.e. there’s no space between the iris and the cornea for the aqueous to go through

Question 5

Describe pathophysiology of COAG?

Answer 5

Raised IOP caused by a problem with trabecular meshwork drainage system and canal of schlemm

Results in chronic progressive optic neuropathy, caused by gradual loss of nerve fibres

Question 6

Presentation of open angle glaucoma? (signs and symptoms)

Answer 6

Painless
Progressive loss of visual field
Leading to tunnel vision
Usually bilateral

Enlarged optic disc cup

Question 7

Investigations of COAG?

Answer 7

Often asymptomatic until late

Visual acuity

Slit lamp: enlarged cup, bayonetting of vessels

Gonioscopy: is angle open or closed

Tonometry: IOP (resistance of cornea to indent)
Pachymetry (corneal thickness: influences IOP reading

Visual fields (perimetry)

Question 8

Management of COAG?

Answer 8

Medical: eye drops or oral

Laser therapy:

• trabeculoplasty (open up drainage tubes)
• iridotomy (holes in iris for drainage)

Surgery: trabeculectomy (create a bleb - new outflow tract from a. chamber)

Question 9

What is the medical treatment of COAG?

Describe.

Answer 9

Decrease aqueous production:

1. B blockers: timolol
2. Carbonic anhydrase inhibitors: dorzolamide (TOP), acetazolamide (PO)
3. Alpha adrenergics: brimodine

Increase aqueous outflow:

1. Prostaglandin analogues: latanoprost
2. Cholinergics
3. Alpha adrenergics: brimodine

Question 10

Pathophysiology of closed angle glaucoma?

Answer 10

Primary:

• In some people angles are naturally narrow
• As we get older the lens grows which pushes iris forwards

Secondary:
- to eye surgery

Peripheral iris bows forward ‘closing the angle’ i.e. obstructing aqeuous access to the trabecular meshwork

Leading to a sudden raise in IOP

Question 11

Presentation of closed angle glaucoma?

Answer 11

Red, painful eye
Usually unilateral

Decreased visual acuity, vision acutely blurred

Haloes around lights

Fixed, mid-dilated pupil

N+V, abdo pain

Question 12

Investigation of closed angle glaucoma?

Answer 12

Examination: hazy cornea, fixed mid-dilated pupil

Tonometry: raised above 21mmHg

Slit lamp: shallow anterior chambers

Question 13

What are the complications of closed angle glaucoma?

Answer 13

Irreversible loss of vision within hrs-days

Permanent angle closure

Question 14

Management of closed angle glaucoma?

Answer 14

Ocular emergency

1. Pilocarpine: miotic drops to constrict pupil
2. Decrease Aq production:
   - B blocker (timolol)
3. Increase Aq outflow:
   - Prostaglangin analogue (latanoprost)
4. Prednisolone drop regularly
5. IV acetazolamide, then PO
6. Hyper-osmotic agents: PO glycerol or IV mannitol
7. Laser or surgical iridotomy

Question 15

What is a hyperosmotic agent and how does it help in closed angle glaucoma?
Example?

Answer 15

A drug which makes blood plasma hypertonic

So it draws fluid out of the eye, reducing IOP

IV mannitol

Question 16

Investigations in glaucoma?

Answer 16

Visual acuity testing

Slit-lamp exam to see if angle is open, and anterior chamber depth

Ophthalmoscopy to look at disc

Tonometry (to measure IOP)

Visual field testing

Pachymetry (measure corneal thickness)

Question 17

Risk factors for open angle glaucoma?

Answer 17

A FIAT

Age
Family history
IOP
African descent
Thin cornea