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Glaucoma: Symptoms, Tests, Treatment, and Why Diabetics Are at Higher Risk

Glaucoma is one of the most common causes of permanent blindness worldwide — and one of the most preventable. It is called the “silent thief of sight” because it gradually damages the optic nerve without producing any symptoms until significant peripheral vision has already been lost. Once vision is lost from glaucoma, it cannot be restored — but if detected early, progression can almost always be stopped. Our eye care team at MCR Diabetes & Eye Care, Kannur, explains everything you need to know.

Glaucoma is a family of conditions, not a single disease. The common feature is damage to the optic nerve — the cable that sends visual information from the eye to the brain — most often associated with elevated pressure inside the eye. Early detection through regular eye examination is the only way to catch glaucoma before vision is affected. People with diabetes have approximately double the risk of glaucoma, making annual eye screening even more important. Visit our eye care service in Kannur for comprehensive glaucoma testing.

What Is Glaucoma?

The eye continuously produces a clear fluid called aqueous humour, which nourishes the front of the eye and then drains out through a meshwork in the angle between the iris and cornea. If this drainage system becomes blocked or inefficient, fluid backs up and pressure inside the eye rises. Over time, this pressure damages the optic nerve fibres, starting with the peripheral (side) vision.

Types of Glaucoma

Primary Open-Angle Glaucoma (POAG)

The most common type, accounting for about 75% of glaucoma cases. The drainage angle appears normal but functions inefficiently. Pressure rises slowly over years, and vision loss is gradual and painless. Without screening, it can progress to significant peripheral vision loss before being noticed.

Angle-Closure Glaucoma

The drainage angle becomes physically blocked by the iris. Can be chronic (slow) or acute (sudden). Acute angle-closure is an ophthalmic emergency with severe eye pain, headache, nausea, halos around lights, and red eye — requires immediate treatment to prevent blindness within hours.

Normal-Tension Glaucoma

Optic nerve damage occurs despite normal eye pressure. Common in patients of Japanese descent and increasingly recognised in Indians. Other factors — blood flow to the optic nerve, vascular disease — contribute.

Secondary Glaucoma

Glaucoma caused by another condition: diabetic neovascular glaucoma, steroid-induced glaucoma, pigmentary glaucoma, pseudoexfoliation glaucoma, traumatic glaucoma, and others.

Congenital Glaucoma

Rare form present from birth or developing in early childhood. Requires specialist paediatric care.

Why People with Diabetes Are at Higher Risk

Diabetes increases glaucoma risk through several mechanisms:

• Vascular dysfunction — diabetes damages small blood vessels, including those supplying the optic nerve
• Neovascular glaucoma — advanced diabetic retinopathy can cause new blood vessels in the drainage angle, blocking outflow
• Cataract surgery — needed earlier in diabetics, occasionally complicating glaucoma
• Reduced corneal sensitivity — making detection of symptoms harder

People with diabetes should have glaucoma screening as part of every annual eye examination.

Risk Factors for Glaucoma

• Age over 40 (risk doubles each decade after 60)
• Family history of glaucoma (4-9× increased risk)
• Diabetes
• High blood pressure or low blood pressure
• Severe nearsightedness or farsightedness
• Long-term steroid use (oral, inhaled, or eye drops)
• Previous eye injury
• Thin cornea
• Indian ethnicity (somewhat higher rates)
• Sleep apnoea

Symptoms: The Late Warning Signs

Open-angle glaucoma typically has no symptoms at all until significant vision is lost. When symptoms do appear, they include:

• Gradual loss of peripheral (side) vision
• “Tunnel vision” in advanced disease
• Difficulty adjusting to dark rooms
• Occasional blurred vision
• Halos around lights

For angle-closure glaucoma, symptoms are sudden and severe:

• Severe eye pain and headache
• Nausea and vomiting
• Sudden blurred vision
• Halos and rainbows around lights
• Red eye, hard to touch

Glaucoma Tests: What Happens at Screening

A comprehensive glaucoma evaluation includes the following tests, most of which are painless and take only a few minutes each.

At MCR’s eye care service, we perform comprehensive glaucoma screening as part of every adult eye examination, with detailed testing for higher-risk patients.

Modern Treatment Options

Eye Drops (First-Line)

Several classes of eye drops effectively lower eye pressure. They are often used in combination to achieve target pressure.

• Prostaglandin analogues (latanoprost, travoprost, bimatoprost, tafluprost) — first choice for most patients; once daily; very effective
• Beta blockers (timolol, betaxolol) — twice daily; effective but cautioned in asthma/heart disease
• Alpha agonists (brimonidine, apraclonidine) — two-to-three times daily
• Carbonic anhydrase inhibitors (dorzolamide, brinzolamide) — two-to-three times daily
• Rho kinase inhibitors (netarsudil) — newer class

Laser Treatments

• Selective laser trabeculoplasty (SLT) — first-line for many patients; opens drainage angle
• Laser peripheral iridotomy — for angle-closure; creates an opening in the iris
• Cyclophotocoagulation — reduces aqueous production in refractory cases

Surgical Options

• Trabeculectomy — creates a new drainage channel; gold standard for advanced glaucoma
• Glaucoma drainage devices (Ahmed, Baerveldt) — implanted shunts
• Minimally invasive glaucoma surgery (MIGS) — newer, less invasive; often combined with cataract surgery

Living with Glaucoma

A glaucoma diagnosis is not a death sentence for vision. With consistent treatment and regular monitoring, most patients maintain functional vision for life. Key principles:

• Take drops exactly as prescribed — missed doses cause silent damage
• Attend all follow-up appointments — pressure changes are usually invisible
• Don’t stop treatment because you “feel fine” — glaucoma is silent
• Tell family members — they have a higher risk and should be screened
• Maintain general health — control diabetes, blood pressure, sleep apnoea
• Avoid head-down positions for prolonged periods — yoga inversions, for example

Glaucoma at a Glance

Frequently Asked Questions

Below are the questions our patients ask most often. If you have additional questions, our specialist team at MCR Diabetes & Eye Care, Kannur, is always available to help.

Final Takeaway: Annual Screening Prevents Blindness

Glaucoma cannot be felt, often cannot be seen until late, and cannot be reversed. However, it can almost always be stopped — if detected early through routine screening. For Indians over 40, particularly those with diabetes, family history, or other risk factors, annual eye examination including glaucoma screening is the single most important investment in long-term vision.

At MCR Diabetes & Eye Care, Kannur, glaucoma screening is part of every adult eye examination. If you are over 40, have not had an eye examination in the past year, or have any glaucoma risk factors, please book a comprehensive eye examination today.

You May Also Find Helpful

• Diabetic Retinopathy: Stages and Treatment
• Cataract Surgery in Kannur
• Dry Eye Syndrome: Causes and Treatments
• Annual Health Check-Up Guide

Tags: Glaucoma · Eye Care · Eye Pressure · Vision Loss · Preventive Health