Can Glaucoma Occur Even With Normal Eye Pressure?

Glaucoma is diagnosed by evaluating the health of the optic nerve and the factors responsible for vision loss. Glaucoma is also possible with normal eye pressure, and the condition is known as normal-tension glaucoma. In some patients, optic nerve damage can develop even with normal eye pressure, and in some patients, eye pressure increases without causing glaucoma.

The glaucoma specialist evaluates the optic nerve, eye pressure, corneal thickness, peripheral vision and other risk factors during the comprehensive examination of glaucoma.

What is eye pressure?

• The fluid is present in the front part of the eye, and that fluid gets produced and drains continuously, but if the fluid is not drained properly, then it can increase the pressure, and this is known as intraocular pressure.
• Continuously increasing eye pressure is a risk factor for glaucoma because it may damage the optic nerve that carries the information from the eye to the brain. Eye pressure is only a part of glaucoma assessment.

Does eye pressure exclude glaucoma?

No, eye pressure does not exclude glaucoma. Eye pressure can change during the day and is influenced by various factors:

• Corneal thickness
• Time of measurement
• Technique of measurement
• Medicines including steroids
• Past eye surgery
• Structure of the eye

The normal level of pressure that appears safe can also cause optic nerve damage. That's why, during glaucoma testing, the optic nerve and visual field are examined along with measuring the pressure.

Normal tension glaucoma

• It is the form of open-angle glaucoma in which visual field loss and optic nerve damage occur even though the measured eye pressure is within the normal range.
• The situation progresses gradually. Side or peripheral vision gets affected first, and the central vision may remain clear during the initial stage. As the brain easily adapts to the small changes in the visual field, the person may not notice the developing damage.

Normal glaucoma is diagnosed when:

• The optic nerve shows changes that are associated with glaucoma
• Visual field testing identifies the matching pattern of vision loss
• The drainage angle is open
• Eye pressure is not recorded above the normal or expected range
• Considering the possible cause of the optic nerve damage

Why does glaucoma develop at normal pressure?

• The exact reason is not clear. Some optic nerves can be vulnerable to the pressure even if the pressure doesn't appear high. Blood supply to the optic nerve can also be relevant in some patients. Conditions associated with changes in blood or oxygen supply can influence the ability of nerves to tolerate pressure. However, having these conditions does not mean that person is dealing with normal tension glaucoma.
• The main point is that the optic nerve responds differently from person to person. Therefore, glaucoma care needs proper evaluation and assessment instead of depending on safe pressure.

Factors that increase the risk of glaucoma:

High eye pressure is the major risk factor, but it's not the only one. The development of glaucoma can also depend on the other factors suggested by the specialist for normal tension glaucoma in Phagwara:

• Increasing age
• Family history
• Thin cornea
• Diabetes and vascular health
• Use of steroid
• Past eye injury or surgery

Early symptoms of normal-tension glaucoma guide:

• Patchy areas of missing side vision
• Difficulty noticing objects at the edge of vision
• Difficulty navigating crowded spaces and stairs
• Reduced contrast sensitivity
• Tunnel vision

Clear central vision does not mean that the optic nerve is healthy.

Tests to detect normal tension glaucoma with normal eye pressure:

• Tonometry
• Pachymetry
• Optic nerve examination
• Optical coherence tomography
• Visual field testing
• Optic disc photography
• Gonioscopy

Why is eye pressure not enough?

From the pressure test, the doctor can determine the intraocular pressure at that time. It doesn't show whether the optic nerve is damaged or not.

The assessment gives the answers to the normal-tension glaucoma questions, which include:

• What is the level of eye pressure?
• Is the optic nerve damaged or not?
• Has the patient developed functional vision loss?

Monitoring normal tension glaucoma

Monitoring is important because glaucoma is a long-term condition. The eye specialist can create baseline records and repeat the selected tests at intervals:

Follow-up may include:

• Monitoring intraocular pressure
• Review the use of prescribed eye drops
• Evaluate optic nerve
• Repeat OCT scan
• Compare results of visual field test
• Revising target eye pressure
• Review medicine changes and general health

The appointment interval depends on the rate of progression, stage of glaucoma, age, treatment plan and condition of the eye. Patients should attend the appointments when they feel a change in their vision.

Glaucoma can progress with any symptoms that are easy to recognise.

Final takeaway

Normal eye pressure is not reassuring, but it will not exclude glaucoma. This condition is identified by assessing the peripheral vision, examining the optic nerve and interpreting the pressure. If you have been told that your optic nerve is suspicious or have a glaucoma risk factor, then consult with the eye specialist Dr. H. Mitra at Mitra Eye Hospital & LASIK Laser Centre for detailed testing and a proper monitoring plan.

FAQ'S

Is it possible to have glaucoma with normal eye pressure?

Yes, it's completely possible that glaucoma can also occur with normal eye pressure.

Can eye pressure change during the day?

Yes, eye pressure can change throughout the day.

Can vision loss because of glaucoma be reversed?

Side vision is already lost due to glaucoma, and it is permanent. But early diagnosis and proper treatment help protect central vision.

After how much time does the glaucoma test repeat?

There is no fixed schedule for everyone; it depends on results, diagnosis and treatment response.

Can high eye pressure always mean glaucoma?

High eye pressure is not always glaucoma, and it is also due to unpredictable damage to the optic nerve.

Data Sources:

• Nethra Eye Care
• American Academy Of Ophthalmology