Written and Reviewed By Dr Md Maksude Mowla, FCPS

Glaucoma: Why Normal Vision and Normal Eye Pressure Are Not Enough

Glaucoma is a group of eye diseases that progressively damage the optic nerve—the structure that carries visual information from the eye to the brain. Early glaucoma commonly produces no pain, redness or noticeable reduction of central vision.

Because peripheral vision may deteriorate slowly, a person can feel that their eyesight is normal while optic-nerve damage is already developing. Vision lost from glaucoma usually cannot be restored, but timely diagnosis and appropriate treatment can often slow further damage. National Eye Institute⁠

Is glaucoma simply high eye pressure?

No, Easy Glaucoma screening in Khulna Focus eye Hospital can help you .

No. Raised intraocular pressure is the most important modifiable risk factor, but it is not the complete definition of glaucoma.

Some people have raised pressure without optic-nerve damage, a condition known as ocular hypertension. Others develop characteristic optic-nerve damage and visual-field loss despite measurements within the statistically normal pressure range. This is called normal-tension glaucoma.

Therefore, a pressure reading alone cannot reliably confirm or exclude glaucoma. NEI—Glaucoma and eye pressure⁠

What are the main types of glaucoma?

Primary open-angle glaucoma

This is a chronic condition in which optic-nerve damage generally progresses slowly. Most patients have no early symptoms. Peripheral vision may be affected before central reading vision.

Normal-tension glaucoma

The optic nerve and visual field show glaucomatous damage even though recorded eye pressure is not consistently above the usual range. Treatment still generally aims to lower pressure to a safer individual target.

Angle-closure glaucoma

The drainage angle between the cornea and iris becomes narrow or closed. Chronic angle closure may be silent, but an acute attack can cause:

• Severe eye or forehead pain
• Redness
• Blurred vision or coloured haloes
• Headache
• Nausea or vomiting

Acute angle closure is an emergency requiring immediate ophthalmic treatment.

Secondary glaucoma

Eye inflammation, trauma, advanced cataract, retinal vascular disease, previous eye surgery or corticosteroid use may produce secondary glaucoma.

Childhood and congenital glaucoma

These uncommon forms require specialist assessment. Excessive watering, light sensitivity, corneal cloudiness or enlargement of the eye in a child needs prompt examination.

Who should be particularly careful?

The likelihood of glaucoma is higher in people with:

• A parent or sibling with glaucoma
• Increasing age
• Raised intraocular pressure
• Thin central cornea
• Suspicious optic-disc appearance
• High myopia or, in some angle-closure eyes, hypermetropia
• Previous ocular trauma or surgery
• Prolonged corticosteroid use
• Certain retinal or inflammatory eye diseases

People with a strong family history may need assessment earlier and more frequently. The correct review interval should be based on the individual risk profile rather than a universal timetable.

What does a complete glaucoma assessment include?

Eye-pressure measurement

Tonometry measures intraocular pressure. Pressure varies during the day and is influenced by corneal thickness, technique and treatment; a single measurement gives only part of the picture.

Optic-nerve examination

The ophthalmologist assesses the neuroretinal rim, cup-to-disc relationship, disc haemorrhage, retinal nerve-fibre layer and differences between the two eyes.

Gonioscopy

Gonioscopy determines whether the drainage angle is open, narrow or closed. This distinction influences diagnosis and treatment.

OCT of the optic nerve

Optical coherence tomography measures retinal nerve-fibre layer and ganglion-cell thickness. It can help identify structural damage and monitor progression.

OCT must be interpreted alongside the clinical examination because high myopia, disc anomalies, segmentation errors and image artefacts can generate misleading results.

Visual-field testing

Automated perimetry assesses functional peripheral-vision loss. Reliable baseline tests and subsequent comparisons help determine whether glaucoma is stable or progressing.

Central corneal thickness

Pachymetry helps interpret pressure measurements and contributes to risk assessment. It does not simply provide a fixed number to add to or subtract from the measured pressure.

Contemporary guidance recommends combining optic-nerve assessment, pressure measurement, angle evaluation, visual-field testing and appropriate imaging rather than relying on one isolated test. NICE glaucoma guidance⁠

How is glaucoma treated?

Treatment aims to reduce the risk of further optic-nerve damage by lowering pressure to an individual target. The target depends on the degree of damage, baseline pressure, life expectancy, risk factors and documented progression.

Eye drops

Pressure-lowering drops may reduce fluid production or improve its drainage. Correct technique and regular use are essential.

Patients should inform their ophthalmologist about asthma, heart disease, pregnancy, medication allergies and other treatments before starting glaucoma drops. Burning, redness, eyelid changes or systemic adverse effects should be reported rather than stopping treatment without advice.

Laser treatment

Selective laser trabeculoplasty may be used for suitable open-angle glaucoma or ocular hypertension. Laser peripheral iridotomy is used in selected narrow-angle and angle-closure conditions. These procedures have different indications and should not be considered interchangeable.

Surgery

Trabeculectomy, glaucoma drainage devices or minimally invasive procedures may be considered when pressure remains unsafe, damage progresses or medication is unsuitable. Surgery lowers risk but cannot restore optic-nerve tissue already lost.

Why is long-term follow-up essential?

Glaucoma is usually a lifelong condition. A pressure that appears satisfactory does not always mean the disease is stable. Follow-up may include repeated pressure measurements, optic-disc photography, OCT and visual-field testing.

The ophthalmologist compares results over time and adjusts the target pressure or treatment when genuine progression is identified.

Patients should:

• Use drops exactly as prescribed
• Bring all current eye drops to appointments
• Learn the correct instillation technique
• Avoid sharing medication
• Inform doctors about steroid use
• Keep review appointments even when vision feels normal
• Encourage close relatives to undergo eye assessment

Frequently asked questions

Can glaucoma be cured permanently?

There is currently no routine treatment that reverses established optic-nerve damage. Treatment aims to preserve remaining vision by reducing the risk of progression.

Does normal eye pressure exclude glaucoma?

No. Normal-tension glaucoma can occur within the usual pressure range. The optic nerve and visual field must also be assessed. American Academy of Ophthalmology⁠

Is an air-puff pressure test enough?

No. It may be useful for screening, but glaucoma diagnosis requires a broader assessment. Some people with glaucoma have apparently normal pressure during screening.

Can I stop drops when the pressure becomes normal?

Not without medical advice. The pressure may be lower precisely because the medication is working.

Does cataract surgery cure glaucoma?

Cataract surgery may lower pressure in selected eyes, particularly some angle-closure cases, but it is not a universal cure for glaucoma.

Can glaucoma cause sudden painful vision loss?

Chronic open-angle glaucoma is usually painless. Sudden pain, redness, haloes, headache, nausea and blurred vision may indicate acute angle closure and require emergency care.

Clinical learning points for students and trainees

• Glaucoma is a progressive optic neuropathy, not merely an elevated IOP reading.
• Establish structure–function correlation using disc/RNFL assessment, OCT and standard automated perimetry.
• Perform gonioscopy before classifying glaucoma as open-angle.
• Consider CCT, diurnal variation, adherence and measurement technique when interpreting IOP.
• Set an individual target pressure and revise it if progression occurs.
• In apparent normal-tension glaucoma, exclude nonglaucomatous optic neuropathy when features are atypical.
• Acute angle closure requires immediate pressure control and definitive angle management.

Glaucoma and eye consultation in Khulna

Dr. Md Maksude Mowla
MBBS, BCS (Health), MCPS, FCPS (Eye), ICO (London)
Eye Specialist, Retina and Phaco Surgeon
Consultant and Long-term Vitreo-Retina Fellow, National Institute of Ophthalmology and Hospital

Khulna chamber: Focus Eye Hospital
43 KDA Avenue, Moylapota, Khulna
Opposite Khulna City Medical College Hospital
Consultation: Thursday, 3:00–7:00 PM
Appointment: 013 1329 2404