Glaucoma Screening - An Overview

What Is Glaucoma?

Glaucoma is a common eye disease that affects and damages the optic nerve. The optic nerve is responsible for sending images to the brain. Increased intraocular pressure is considered the reason for optic nerve damage. It is regarded as the second most common leading cause of impaired vision or blindness worldwide. Glaucoma is slow, progressive, chronic in nature, and one of the main causes of blindness in people aged above 60.

• Open-angle glaucoma and closed-angle glaucoma are the two main types of glaucoma.

• Open-angle glaucoma is one of the most common types of glaucoma in which the drainage canal of the eye becomes clogged over time, ultimately damaging the optic nerve.

• Primary angle-closure or narrow-angle closure is the other type of glaucoma in which increased eye pressure is seen due to the closed angle between the iris and the cornea.

• The other types of glaucoma are normal-tension glaucoma, pigmented glaucoma, secondary glaucoma, congenital glaucoma, exfoliative glaucoma, neovascular glaucoma and uveitic glaucoma, and traumatic glaucoma.

What Is Glaucoma Screening?

Glaucoma is an eye disorder that arises due to increased pressure build-up, and glaucoma screening is a group of tests available to detect the disease. Fluid accumulation in the front part of the eye and, thereby, an increase in eye pressure is known as glaucoma, which can eventually lead to damage of the optic nerve and loss of vision. Screening tests help identify the condition as early as possible, therefore preventing vision loss. There are several tests available. Tests for glaucoma include tonometry, ophthalmoscopy, pachymetry, perimetry, and gonioscopy.

What Are Causes of Glaucoma?

Glaucoma mostly occurs due to elevation or increase in the intraocular pressure that leads to an inability to drain. The nerve that connects the eye to the brain is called the optic nerve, which gets damaged due to increased pressure.

• Age: It is the most common factor of glaucoma, as older people are more likely to get affected as compared to younger people.

• Ethnicity: It is the other consideration in which African, Caribbean, or Asian origin has more chances of getting glaucoma.

• Family History: It plays a vital role as the individual may develop glaucoma if parents or siblings have the same condition throughout life.

• Other Medical Conditions: Such as diabetes, long-sightedness, and short-sightedness, can make the older age group people prone to glaucoma.

What Are Symptoms of Glaucoma?

Symptoms of glaucoma:

• Blurred vision.

• Nausea and vomiting.

• Severe headache.

• Intense eye pain.

• Redness of eyes.

• Tunnel vision.

• Upset stomach.

• Halo around lights or rainbow-colored rings.

• Dilated pupil.

• Sudden onset of visual disturbance, often seen in low light.

• Blindspot.

• Clouding of the normally transparent cornea.

• Squinting.

• Tenderness around the eye.

What Are Risk Factors of Glaucoma?

• People of African, American, Irish, Turkish, Russian, Japanese, Inuit, Hispanic, or Scandinavian descent origin are more likely to suffer from glaucoma.

• Family history of glaucoma.

• People suffering from diabetes, heart disease, and sickle cell anemia are prone to develop glaucoma.

• People who have cornea thinner than the usual one.

• Individuals with farsightedness and short-sightedness.

• People aged over 40 years are most at risk of glaucoma.

What Are Screening Tests of Glaucoma?

Glaucoma screening is done with tests that observe the changes in pressure of the eye's fluid, changes in the optic nerve, and changes in visual fields. The aim of screening is to diagnose early glaucoma. One or a combination of tests is done for the diagnosis of glaucoma. The procedure is non-invasive, quick, and painless.

Glaucoma tests involve -

• Angle Exam: Also known as the gonioscopy test, that shows the drainage system in relation to the angle where the cornea (clear outer layer of the eye ) meets the iris (colored part of the eye). In this test, the cornea is contacted with a special lens after numbing the eyes using eye drops. The angle is predicted whether it is open or closed from the lens. The drainage system is considered blocked or narrow if the angle is closed, which is indicative of glaucoma.

• Dilated Eye Exam: Is used to dilate (open) the pupil using bright light into the back of the eyes that magnifies the retina and optic nerve. Retina, optic nerve, size, shape, blood vessel, and color can easily be investigated by this test. It is helpful in estimating any damage caused to the optic nerve that might result in glaucoma.

• Corneal Thickness Measurement: Also known as pachymetry, it measures the thickness of the cornea after numbing the eye with an eye drop and uses a small probe to determine the risk of glaucoma.

• Eye Pressure Test: This is also known as tonometry or applanation. This test is done by using a tiny instrument that touches the surface of the eye and flattens the cornea in order to measure eye pressure. Increased eye pressure that is greater than 22 mm Hg is indicative of glaucoma.

• Visual Field Test: This is done to determine the severity of glaucoma. In this test, the patient is asked to cover one of his eyes and to look straight ahead at the object. Automated static perimetry can also be used, which requires looking into track lights and machines. The specific spot presence is seen when the vision gets blurry or blank.

• Optic Nerve Imaging: This is another test used to make a visual picture of the optic nerve and retina. The pupil is dilated, and then, with the help of optical coherence tomography, the images of each layer of eye tissue are obtained. Findings of optic nerve imaging, such as buckling or swelling of the optic nerve or bumpy retina, are examined in this test.

How to Treat Glaucoma?

Medical treatment involves eyedrops such as prostaglandin derivatives - Latanoprost, Travoprost, and Latanoprostene; beta-blockers, for example, Timolol; alpha-adrenergic agonists, for example, Apraclonidine (Iopidine) and Brimonidine. Oral medication is used when eye drops alone are not effective in bringing the eye pressure down; carbonic anhydrase is usually prescribed. Surgery includes laser therapy, filtering surgery, drainage tubes, and minimally invasive glaucoma surgery (MIGS). Lifestyles should be modified by eating a healthy diet, exercising regularly, limiting caffeine intake, and sleeping with the head elevated.

Conclusion:

Glaucoma is a medical condition that damages the optic nerve and can cause permanent blindness over the years. Timely treatment of glaucoma can only be done after the proper screening test. Increased community awareness of glaucoma and earlier detection of the disorder will result in a reduced number of glaucoma cases. A routine eye examination is important for protecting the eyes. Surgical intervention done in the early stage may reduce the risk of vision loss due to glaucoma. Management of glaucoma involves medical, laser, and surgical modalities.