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OP7.1-5 | Glaucoma — PBL Case

CLINICAL SETTING

It is a Friday evening at a district general hospital eye casualty. Two patients arrive within one hour of each other. Patient 1 — Radha, 58F: arrives in acute distress, brought by her husband who found her clutching her right eye after returning from a late-night cinema screening. She reports sudden onset severe right eye pain, headache, nausea, and seeing rainbow-coloured haloes around the theatre lights just before the pain started. On examination: right eye is red and congested, cornea appears steamy and hazy, pupil is mid-dilated and unresponsive to light, IOP is 56 mmHg right eye vs 14 mmHg left eye, anterior chamber appears very shallow. Patient 2 — Ravi, 65M: presents 40 minutes later, referred urgently by a community optometrist who noticed a cup-to-disc ratio of 0.75 with inferior rim notching bilaterally at a routine check. Ravi has had no visual symptoms. On gonioscopy: both angles are wide open. IOP: 27 mmHg right, 25 mmHg left. Humphrey visual field testing shows an arcuate scotoma in the right eye. Ravi's father was blind from glaucoma. Both patients are now sitting in the waiting room and the consultant asks the team to manage both simultaneously.

Trigger 1: Diagnosis and Emergency Triage

The registrar reviews both patients. Radha's gonioscopy is attempted but the corneal haze limits the view. The available slit-lamp findings are: right eye — hazy cornea, very shallow anterior chamber, fixed mid-dilated pupil, IOP 56 mmHg, marked conjunctival congestion. Left eye is normal. For Ravi: bilateral wide-open angles on gonioscopy, no symptoms, cup-to-disc ratio 0.75 with inferior notching, arcuate scotoma on visual field, IOP 25-27 mmHg, family history of glaucomatous blindness.

DISCUSSION POINTS

Diagnose each patient. What specific type of glaucoma does Radha have, and what type does Ravi have? What anatomical difference between the two conditions explains their completely different clinical presentations?
Why did Radha's attack begin specifically at the cinema? What physiological mechanism links the darkened environment to the acute attack in her type of glaucoma?
Radha's husband asks if she can be given pilocarpine drops that were prescribed to his neighbour who also has glaucoma — the neighbour uses them daily and is doing fine. Is this appropriate? Explain why miotics are used differently in Radha's vs the neighbour's likely condition.
What is the normal range of intraocular pressure, and at what level does IOP pose an urgent threat to the optic nerve? For Ravi, is his IOP normal, and does a normal IOP exclude glaucoma?

Click to reveal Trigger 2: Emergency Management and Treatment Decision-Making (discuss previous trigger first!)

Trigger 2: Emergency Management and Treatment Decision-Making

The team initiates treatment for Radha. The registrar prescribes a combination of medications: intravenous acetazolamide 500 mg stat, intravenous mannitol 20% (1 g/kg body weight) because IOP remains above 50 mmHg, topical pilocarpine 2% to both eyes (affected and fellow eye prophylaxis), topical timolol 0.5%, and topical apraclonidine. She is told she will need a laser procedure once the cornea clears. Meanwhile, for Ravi, the consultant asks the team: which drug class should be prescribed first, and why? The team must also explain to Ravi why he needs treatment when he has no visual symptoms.

DISCUSSION POINTS

For Radha: explain the mechanism of action of each drug in her treatment regimen — how does pilocarpine work in angle-closure, how does acetazolamide lower IOP, and what is mannitol doing to aqueous dynamics?
Why is the fellow (left) eye also given pilocarpine in Radha's case? What risk does the fellow eye carry?
For Ravi: which drug class is first-line for POAG and why? Name a specific drug in that class. Why is pilocarpine NOT appropriate for Ravi even though it was used for Radha?
What is the definitive surgical/laser procedure for Radha once IOP is controlled? What procedure is available for Ravi if medical therapy fails? Compare the two procedures and their mechanisms.
A medical student on the team suggests adding a prostaglandin analogue immediately to Radha's treatment. Is this an appropriate suggestion in the emergency setting? Why or why not?

Click to reveal Trigger 3: Secondary Glaucoma Consult and Counselling (discuss previous trigger first!)

Trigger 3: Secondary Glaucoma Consult and Counselling

One week later, the registrar reviews Radha (who is now post-laser peripheral iridotomy, IOP controlled) and Ravi (started on latanoprost, IOP now 19 mmHg). During the same clinic, a third patient, Sunita, 60F, is referred by her general physician. She is a long-term steroid inhaler user who also uses topical dexamethasone eye drops for chronic allergic eye disease. IOP is 32 mmHg bilaterally with open angles on gonioscopy, normal discs, and no field loss yet. Additionally, Ravi's son (35M) has accompanied his father and asks if he should be screened — his grandfather (Ravi's father) was blind from glaucoma. Both Radha and Ravi have questions about their prognosis and the need for lifelong treatment.

DISCUSSION POINTS

What type of secondary glaucoma does Sunita have? What is the mechanism — how do corticosteroids elevate IOP? Classify it as open-angle or closed-angle and explain what investigation findings confirm this.
Enumerate at least six other causes of secondary glaucoma (excluding steroid-induced). For each, classify as open-angle or closed-angle and state the mechanism in one sentence.
How would you counsel Radha about her prognosis after laser PI? Can the other eye be protected? How would you explain this in simple language?
How would you counsel Ravi about his POAG? Address his likely unstated concern: that the drops are unnecessary because he feels normal. Use the most powerful counselling message for POAG adherence. What monitoring schedule would you recommend?
Should Ravi's son be screened for glaucoma? What makes him higher risk than the general population? At what age and with what tests would you screen him?

Learning Issues

Research these questions and bring your findings to the discussion.

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