Glaucoma is an eye disease that damages the optic nerve due to pressure build-up inside the eye which can lead to loss of vision or blindness. It is the second leading cause of blindness. The types of glaucoma are:
- Primary open-angle glaucoma this is the most common form of glaucoma. This happens when the drainage canals or trabecular meshwork are blocked, causing the fluid or aqueous humor to drain out to slowly which can cause increase eye pressure or intraocular pressure.
- Angle-closure glaucoma/narrow angle glaucoma/closed-angle glaucoma occurs when the iris (the colored part of the eye that surrounds the pupil) is pushed or pulled forward which narrows/blocks the drainage canals, causing the slow flow of fluid. This results to rise of pressure in the eye.
- Normal-tension glaucoma/low-tension glaucoma/normal pressure glaucoma happens when optic nerves are damaged but eye pressure remains within the normal range of 12-22 mmHg. The reason as to which this occurs is unknown, but some eye specialists say that it may be due to sensitive optic nerves or a lack of blood supply to the optic nerve.
- Secondary glaucoma is caused by other diseases or factors that can increase eye pressure such as eye injury, eye inflammation, cases of cataract or diabetes and certain drugs.
- Pigmentary glaucoma is a form of secondary open-angle glaucoma that occurs when pigment granules from the iris blocks the drainage canal which increases eye pressure.
- Traumatic glaucoma is caused by injuries that bruise or penetrate the eyes.
- Neovascular glaucoma is caused by abnormal formation of new blood vessels over the drainage canals and on the iris.
- Developmental glaucoma or childhood glaucoma occurs to infants born with glaucoma (congenital glaucoma), toddlers who develop glaucoma (infantic glaucoma) or children after 4-5 years old (juvenile glaucoma).
Commonly Prescribed Drugs
- Ophthalmic prostaglandin analogs (latanoprost, bimaprost) increase the fluid outflow from the eye. Side effects: Eye irritation, change in color of the eye, blurred visions. Drug interactions: Beta-adrenergic blocking agents, other ophthalmic prostaglandin analogs, epinephrine, anti-arrhythmic drugs.
- Topical beta blockers (timolol) decrease fluid production in the eye. This drugs can be used in combination with an alpha adrenergic agonist or a carbonic anhydrase inhibitor to reduce eye pressure. Precaution: Patients with history of respiratory and cardiac failure, depression. Pregnant and lactating women and infants. Side effects: Eye allergies and irritations, blurred vision, low blood pressure and pulse rate, fatigue.
- Alpha adrenergic agonists (brimonidine) help decrease fluid production and increase the outflow of the drainage canal. Side effects: Eye irritations, drowsiness, headache, fatigue, dry mouth and nose, allergic reactions. Drug interactions: Beta blockers, CNS depressants, antihypertensives and/or cardiac glycosides.
- Carbonic anhydrase inhibitors (brinzolamide, dorzolamine, acetazolamide) help lower fluid production in the eye. These drugs can be used in combination with beta blockers to reduce eye pressure. These are available in eye drops and oral preparations. Precaution: Patients with hepatic, renal, respiratory and cardiac impairment. Pregnant and lactating women and children. Side effects: Drops: Eye irritations, distortion of sense of taste. Oral dosage form: Frequent urination, depression, stomach upset, tingling in hands and feet.
Treatment and Management
Laser surgery has become popular as an intermediate treatment for glaucoma. There are several types of laser surgery:
- Argon Laser Trabeculoplasty (ALT) for open angle glaucoma, where laser beam opens the drainage canal or trabecular meshwork to increase the fluid outflow.
- Selective Laser Trabeculoplasty (SLT) for open angle glaucoma, uses low levels of laser energy to treat selective portions of the drainage canal.
- Laser Peripheral Iridotomy (LPI) for narrow/closed angle glaucoma. This type of laser surgery makes an opening in the iris to allow fluid to flow behind the iris and exit directly to the anterior chamber of the eye.