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Normotension Glaucoma - a Disease on the Rise

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Normotension Glaucoma - a Disease on the Rise

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Glaucoma is a group of diseases causing long-standing progressive optic nerve damage. This article describes the essential features of this disease, how the disease progresses, and what measures need to be taken to detect and manage this problem.

Medically reviewed by

Dr. K. Shobana

Published At August 30, 2018
Reviewed AtDecember 27, 2023

Introduction:

Glaucoma is a group of diseases causing long-standing progressive optic nerve damage. Glaucoma is thus a sort of generic name, referring to the plethora of diseases causing optic nerve damage with one common feature, a higher intraocular pressure (higher pressure inside the eye than the normal limits). A few patients belong to a lesser-known, smaller subgroup among the broader classification of glaucoma called normotension glaucoma. This peculiar disease is one where, as the name suggests, the intraocular pressure is normal. But, is classified as a type of glaucoma as it produces eye changes that are characteristic of glaucomatous damage. This article describes the essential features of this disease, how the disease progresses, and what measures need to be taken to detect and manage this problem.

What Is Normotension Glaucoma?

Glaucoma is a disease that causes damage to the optic nerve, which connects the eye to the brain and allows it to see. The disorder is typically brought on by too high eye pressure. The "normotension" kind, however, is distinct. The area around the front of the eye usually contains fluid. That fluid does not drain as well as it should in many forms of glaucoma. As a result, it backs up like water in a blocked drain. As a result, the pressure inside the eye increases. The optic nerve begins to suffer damage over time.

However, even when the eye pressure remains normal, the optic nerve is destroyed in normal-tension glaucoma. It is also called "low-tension" or "normal-pressure" glaucoma.

What Are the Causes of Normotension Glaucoma?

The cause of normotension glaucoma is proposed to be due to blood flow changes causing damage to the optic nerve (the nerve of sight), from blood vessels that are presumed to be more sensitive to blood flow changes than normal. This damage, just like in all glaucomas, affects the field of vision (refers to how much of the whole world around us we can see with our eyes regarding size). Thus, only the extent of vision and not the clarity of vision is affected, even in advanced cases.

To give the readers a sense of perspective, a patient with advanced optic nerve damage due to normotension glaucoma will be able to see as clearly as any normal person, but he will only be able to perceive the things around him as if he is looking through a tiny hole (also called in medical terms as tubular vision), because of massive constriction of his visual field.

What Are the Symptoms in a Patient with Normotension Glaucoma?

A patient with normotension glaucoma is usually asymptomatic, and the condition will only be detected by screening.

What Are the Risk Factors of Normotension Glaucoma?

There are groups of people who have a higher risk of developing glaucoma, the most common being genetic. A few races are known to have a higher incidence of normotension glaucoma than the global average. The number is steadily increasing with awareness about the disease and adequate screening modalities being made available. The second group is relatives of known glaucoma patients and patients with hypertension and disease related to blood vessels (stroke, heart disease, diabetes). It is recommended to visit an ophthalmologist for getting screened for glaucoma.

What Are the Investigations Available to Detect Normotension Glaucoma?

During the screening, a preliminary examination of visual acuity (when the doctor or optometrist asks individuals to read a few letters which decrease in size as each line progresses and checks the individuals for glasses) is performed. Then the examination continues with a check of the color vision using Ishihara's charts, and an estimation of the intraocular pressure using applanation tonometry. The examination then includes a thorough examination of the eyes using a slit lamp with special emphasis on the angle of the anterior chamber and optic disc.

The next most important test is the visual field test. This test is the main “treatment-deciding” factor in all glaucomatous diseases. This test, when performed correctly by patients, enables doctors to get an idea of the exact extent of optic nerve damage. Hence even if the pressure-lowering drugs are working and reducing the intraocular pressure, the optic nerve damage does not go down. Then, the treatment must be considered inadequate and must be reviewed.

Since the examination of the retina can be confused as it is a subjective assessment, to maximize effectiveness, it is recommended to supplement the examination with objective investigations. A few of these tools are stereoscopic optic disc photographs, these are just objective supplements to the appearance of the disc and have supportive value with the findings of the other tests.

Central corneal thickness measurement is also done because any variation in the thickness of the cornea can have a corresponding variation in intraocular pressure. Retinal nerve fiber layer analysis is also an objective assessment of optic nerve fiber layer thickness in comparison to age and race-matched normative data. This imaging is done with a machine called optical coherence tomography (OCT). A similar imaging method used to estimate optic nerve fiber thickness is the GDX VCC (glaucoma detection with variable corneal compensation), although it operates on a different mechanism.

In earlier days, doing a diurnal variation test was in vogue. In this test, a patient has to stay overnight at the hospital, and his eye pressure would be measured at regular intervals throughout the night. This is still considered an inexpensive and excellent test to detect normotension glaucoma.

These tests and investigations may not all be required, and they may be adjusted based on different patient-related aspects. As previously mentioned, the reason for this extreme attention and high volume of testing is that the condition has no symptoms, thus the earlier a patient can be diagnosed, the earlier they can begin therapy and prevent optic nerve damage.

What Are the Treatment Methods Available for Normotension Glaucoma?

Treatment modalities available mainly include eyedrops which reduce the pressure of the eyes (antiglaucoma drugs). A few cases may also be prescribed drugs that alter blood flow such as calcium channel blockers. It is quite rare for a patient to require surgery, but that may be necessary depending on the optic nerve damage progression.

Once a patient has been diagnosed to be glaucomatous, he has to be on follow-up until there are no visual field changes for a prolonged period. So more often than not, the treatment is started and progression monitored by visual field test results, and this makes follow-up essential as the disease is not one where the damage is caused and can be prevented in one go. The entire process of follow-up, monitoring, and personalizing treatment takes years, with follow-ups every six months to assess progress.

Thus, the best way to deal with normotension glaucoma is screening and early diagnosis coupled with prompt and regular follow-ups.

Conclusion:

Unfortunately, glaucoma cannot be prevented. However, if the illness is identified and treated at an early stage, blindness from it is frequently avoidable. Therefore, continue to schedule frequent eye checkups with the eye doctor.

Frequently Asked Questions

1.

What Is the Reason for Normotensive Glaucoma?

Normotensive glaucoma occurs secondary to conditions like chronic low vascular perfusion, Raynaud’s phenomenon, migraines, nocturnal systemic hypotension, and over-corrected systemic hypertension. Mediation like systemic steroids and beta-blockers contribute to creating a normotensive glaucoma condition.

2.

Is It Possible for Stress to Increase Glaucoma Pressure?

According to a specific hypothesis, stress can induce glaucoma, as acute and chronic stress can lead to vascular dysregulation of the optic microvasculature and cranial vessels, which may lead to partial hypoxia and hypoglycemia. Stress can also induce other cranial degenerative changes affecting the visual pathway.

3.

Is There a Cure Available for Glaucoma?

It is with great expectation that humanity looks up to scientists and researchers to find a cure for glaucoma. As of now, there is no absolute cure for glaucoma. The glaucoma research foundation is actively involved in finding new treatment means to improve patient care.

4.

Is Normal Pressure Glaucoma a Serious Condition?

Normal pressure glaucoma is a glaucomatous neuropathy with intraocular pressures within the normal range. Unchecked, this can lead to severe visual morbidities, including bilateral blindness. Secondarily, people may present with migraines and cold hands and feet.

5.

How Many People Suffer From Normal Pressure Glaucoma?

The condition was first described in the 19th century, and the first extensive review of the disease was not done until 1980. In normal-pressure glaucoma, the pressure stays within the range of 12 to 22 mm Hg covering nearly 30 to 40 percent of all glaucoma cases.

6.

What Worsens Glaucoma?

Certain foods and activities can further deteriorate the conditions that precipitate glaucoma, like caffeine, saturated fats, trans fats, excess salt, weight lifting, scuba diving, bungee jumping, yoga, and playing wind instruments.

7.

Is Walking Helpful in Glaucoma?

Aerobic exercises, including walking, swimming, biking, and treadmills, have been proven beneficial in lowering the risk of glaucoma. These activities benefit the heart and brain health as well. Walking at a brisk pace can reduce the risk of glaucoma by up to 73 percent.

8.

How to Prevent the Worsening of Glaucoma?

Certain lifestyle modifications are necessary to prevent the deterioration of glaucomatous conditions:
- Inculcate a healthy and balanced diet.
- Exercise, but only the safe routines.
- Limit caffeine intake.
- Watch the fluid intake.
- Take prescribed medications.
- Consume vitamins and elements supplementation.

9.

What Is the Pace of Progression of Normal Tension Glaucoma?

Not everyone with normal tension glaucoma goes blind. About 65 percent of eyes with the condition showed no worsening over a five-year follow-up, even without any treatment. On average, in those with worsening visual defects, glaucoma-associated vision defects progressed at the rate of -0.2 to -2 dB (decibels) per year, which is more than -0.36 dB per year in early manifest glaucoma trials.

10.

How Many Glaucoma Patients Go Blind?

Glaucoma is the leading cause of irreversible blindness affecting more than 60 million people worldwide. According to an estimate, the incidence of single-eye blindness is between 14.6 and 54 percent and between 6.4 to 22 percent in both eyes.

11.

What Is Considered ‘Mild Glaucoma’?

Mild glaucoma is optic nerve damage with nil to minimal loss of peripheral vision. The mean deviation is below five. White-on-white field tests, short-wavelength automated perimetry, or frequency-doubling perimetry tests show no visual field deficits.

12.

What Are Normal Glaucoma Values?

Normally, intraocular pressure ranges between 10 to 21 mm Hg but can drop to as low as 0 mm and increase to 70 mm in ocular pathologies. Optic nerve damage caused over several years with intraocular pressure within the normal range is termed normal glaucoma pressure, which generally ranges from 20 to 30 mm. Rapidly progressing visual loss with retinovascular lesions have recorded pressures between 40 to 50 mm Hg.

13.

What Reading Is Considered Extremely High Eye Pressure?

Intraocular pressures above 40 mm Hg are considered extremely dangerous. Such high pressures can cause retinal vascular occlusion, a serious condition in which retinal blood vessels get damaged. This causes rapid loss of vision within 24 hours leading to permanent irreversibility. Pressures above 50 mm Hg cause extreme complications in increasing severity, requiring immediate intervention.

14.

What Does Glaucoma Vision Look Like?

Glaucoma vision is described as blurry tunnel vision or like looking through a straw. This is due to loss of peripheral vision, which leads to diminished vision towards the edges of the visual field.

15.

Can Sleep Reduce Eye Pressure?

Aqueous fluid production decreases during sleep which should decrease intraocular pressure, but the pressure actually increases during sleeping or laying flat as a supine position blocks the drainage system. Overall, intraocular pressure increases by 10 to 20 percent while sleeping.
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Dr. Manjunath Natarajan
Dr. Manjunath Natarajan

Ophthalmology (Eye Care)

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optic nerve damageeye pressureglaucoma
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