Keeping sight of glaucoma: cases rising in Trinidad and Tobago

Glaucoma is becoming more prevalent worldwide, and according to ophthalmologist Dr Debra Bartholomew, the rate at which it is developing in TT is insidious as many people are unaware they have the condition.

Glaucoma is an eye disease that causes damage to the optic nerve. This stems from fluid build-up that results in abnormally high pressure in the eye. Eye pressure is measured in millimetres of mercury (mm Hg), and normal pressure ranges from ten to 21 mm Hg. Symptoms of glaucoma include eye pain, nausea and vomiting, headaches, red eyes, blurred vision, seeing rings around lights and tenderness around the eyes. There is no cure for glaucoma and it is one of the leading cause of blindness in people over the age of five.

Bartholomew said there are two categories of glaucoma – primary and secondary.

Primary glaucoma develops due to unknown causes and there are different types:

• Open-angle glaucoma is the most common type and has a strong genetic link. It usually develops in people with a history of glaucoma in their family.
•  Angle closure or narrow-angle glaucoma is usually found in people of east Asian descent.
•  Normal tension glaucoma is more common among people with hypertension and diabetes
• Congenital glaucoma occurs in babies or young children.

Secondary glaucoma develops from known causes such as eye injuries, inflammation, and certain types of drugs.

“The most common type in TT is neovascular or rubeotic glaucoma, where the eye is affected by the growth of new blood vessels…With this type of glaucoma the pressure can go above 50 and 60 mm Hg, and this tends to cause severe pain. This is a long, complex condition to treat,” Bartholomew said.

In diagnosing glaucoma, whether primary or secondary, she said two things are always considered as vitals – vision and your eye pressure.

“Testing vision is very important because you may have blurred or reduced vision. After we check the vision, we touch the cornea with something called a tenometer to get the pressure...One of the things we also do is a pachymetry test to check the thickness of the cornea. We do this test because based on studies, in people who have thicker cornea you will have to insert more force to check the pressure and you may get a falsely higher reading.”

She said certain tests, like the optical coherence tomography (OCT) have revolutionised how glaucoma is now detected and managed. The OCT is a non-invasive imaging test that uses light to take cross-section images of the retina, allowing the ophthalmologist to map and measure its thickness.

"I like using the OCT because I can sit with my patient and show them exactly what I see and why it needs to be treated.”

She said in the old days doctors relied heavily on the visual field tests or perimetry to diagnose and manage glaucoma. The test produces a map of the complete field of vision. During this test, the patient is required to look straight ahead as spot of lights repeatedly appear in different areas of the peripheral vision. The patient is given a clicker which they are asked to press every time they see a spot of light. But because of the nature of this test, Bartholomew said there are some patients who, if they take it, may not get an accurate reading.

“Patients with arthritis in the neck and fingers, those who can’t concentrate, I can’t ask them to take this test. The OCT is a fantastic test. With it you can pick up glaucoma before a visual field test picks it up.”

But, she said, there are instances in which the visual field test takes precedence over the OCT.

“If, for example, you’re a driver, I need to know if your peripheral vision is affected. The OCT will give me a lot of other information, but will not tell me exactly how much of your vision is affected.”

Bartholomew said a patient’s history is also a very important aspect of a consultation.

“If they wear glasses, if they have diabetes or high blood pressure, all these things can affect the management of their condition. So we want an entire history before we do an examination.”

The examination involves looking at the nerve at the back of the eye.

“We look for thinning, if it’s pale, if they are symmetrical, among other things. If the pressure is high and we suspect it’s glaucoma, we may start treating immediately.”

Over the years, Bartholomew said, glaucoma treatment options have changed. There was a time when there was only a limited variety of medications available to treat the disease, and people had no choice but to use what was available, most of which came with a number of side effects.

“In people of African and Indian descent there tends to be a lot of scarring. This meant that back then surgery failed a lot…Then eye drops became the first-line management option, but over time drops too can fail. Plus, the idea of having to use eye drops for the rest of your life can be a daunting thought.”

She said there has been a shift towards selective laser trabeculoplasty (SLT), an in-office procedure that reduces intraocular pressure in patients with glaucoma.

“It reshapes the trabecular meshwork where the fluid drains. It reduces the amount of eyedrops you will need to use and is now offered as first-line management treatment option. But it may not be suitable for everyone.”

Bartholomew practises at both the Trinidad Eye Hospital and the Caribbean Eye Institute, and said she always takes the time to talk with her patients about their options.

“It’s important for you to have these conversations with your patients, to explain to them about how the treatments work in managing the disease so they can make an informed decision, and to discuss why they will need regular assessment.”

She said as the number of people needing treatment continues to increase, she envisions the development of newer and better treatment options. “We want to hit at blindness. Blindness caused by glaucoma is irreversible, but it can be avoided with early detection and better management.”