Glaucoma: The Silent Thief of Sight – A GP’s Role in Early Detection and Referral Types
- Ann Augustin
- Jun 2
- 4 min read
Updated: Aug 16
What my fellow doctor colleague asked:
In cases of chronic glaucoma with mild peripheral visual field changes, should we refer the patient urgently or routinely? Also, should IOP-lowering eye drops be initiated in primary care, or is that solely the responsibility of the specialist?
What is Glaucoma, why it happens, and what to do next
Glaucoma is a group of eye conditions that can lead to progressive, irreversible vision loss due to damage to the optic nerve — often linked to increased pressure inside the eye (intraocular pressure or IOP). It is one of the leading causes of blindness worldwide, yet many patients don’t know they have it until the damage is advanced.
💡 What Causes Glaucoma?
The eye produces a fluid called aqueous humour that nourishes the eye and maintains its shape. This fluid drains through a structure called the trabecular meshwork located at the anterior chamber angle — the space between the cornea and the iris.
Glaucoma occurs when this fluid doesn't drain properly, leading to increased intraocular pressure (IOP). This raised pressure damages the optic nerve at the back of the eye.
Types of Glaucoma & Why the Problem Arises
1. Open-Angle Glaucoma (OAG) / Primary Open-Angle Glaucoma (POAG)
The angle between the cornea and iris is open, but the drainage system (trabecular meshwork) becomes blocked or dysfunctional over time.
Aqueous fluid builds up slowly, leading to chronic, painless elevation of IOP.
The damage is gradual and silent, typically affecting peripheral vision first.
Why the problem arises:
Age-related degeneration of the drainage pathway
Genetic predisposition
Other modifiable and non-modifiable risk factors (see below)
2. Closed-Angle Glaucoma (CAG) / Acute Angle-Closure Glaucoma
The angle is narrowed or closed, and the fluid can’t drain at all.
This causes a sudden rise in IOP, triggering acute symptoms and threatening rapid vision loss.
Why the problem arises:
Anatomically shallow anterior chamber, often in smaller eyes
Iris bowing forward due to pupil dilation (e.g., in dim light or after medications)
Risk Factors for Glaucoma
📘 General Risk Factors (for both types)
East Asian descent → ↑ CAG risk || Raised IOP |
The most important modifiable risk factor
|| Diabetes | Associated with increased IOP and optic nerve vulnerability
|| Hypertension | May influence optic nerve blood flow
|| Steroid use (topical/systemic) | Can increase IOP |
🟦 Specific Risk Factors for Open-Angle Glaucoma
🟥 Specific Risk Factors for Closed-Angle Glaucoma
What Are the Tests for Glaucoma?
🏥 When and Why to Refer
GPs do not initiate glaucoma treatment — instead, they play a vital role in early detection, prompt referral, and patient reassurance.
💊 IOP-lowering medications (like prostaglandin analogues) are usually started by the specialist, not the GP.
However, if the patient presents with:
Ocular discomfort
Dry eyes
Concern/anxiety about vision
👩⚕️ What the GP can do:
🚫 GPs should not prescribe IOP-lowering eye drops unless instructed by ophthalmology, as inappropriate use may mask worsening or complicate diagnosis.
💊 Management
Open-Angle Glaucoma
First-line: Prostaglandin analogues (e.g., latanoprost) to lower IOP
Other drops: Beta-blockers, carbonic anhydrase inhibitors, alpha-agonists
Laser trabeculoplasty or surgical trabeculectomy if not controlled with drops
Regular monitoring of IOP, visual fields, and optic nerve
🩺 Started and managed by ophthalmologists — not initiated in primary care.
🚨 Red Flag Symptoms
IOP >= 35 mm of Hg without symptoms --> Urgent Referral
IOP >= 35 mm of Hg with symptoms --> Immediate Referral
Sudden, severe eye pain
Red, hard eye
Blurred vision, halos around lights
Headache, nausea, vomiting
Mid-dilated, fixed pupil
Cloudy cornea
Closed-Angle Glaucoma
Immediate treatment to lower IOP:
Acetazolamide (IV or oral)
Topical beta-blockers or alpha-agonists
Definitive treatment:
Laser peripheral iridotomy (creates a small hole in the iris to open the angle)
May require surgery if recurrent
🆘 Requires emergency ophthalmology referral.
These signs indicate an ophthalmic emergency — Immediate referral is essential.
Why Early Detection and Referral Matter
Vision loss from glaucoma is irreversible — but early treatment slows or halts progression.
Patients are often asymptomatic in the early stages (especially in open-angle glaucoma).
By the time symptoms are noticed, permanent damage may already be done.
Referring promptly ensures patients access specialist evaluation, accurate diagnosis, tailored treatment, and lifelong follow-up.
📝 Summary: Quick Glance Comparison
Key Takeaway for GPs and PLAB Candidates
Always refer suspected glaucoma — early detection saves sight.
Do not start treatment in primary care — it’s specialist-led.
Recognize red flags for acute angle-closure — these are true ophthalmic emergencies.
Reassure, educate, and support the patient through the referral process.
📚 References
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