Glaucoma is a degenerative disease that is characterized by the accelerated death of ganglion cells and damage to the optic nerve, which result in the loss of the field of vision (peripheral vision) in patients.
Glaucoma generally affects both eyes and begins in adulthood. Primary open-angle glaucoma is the most common type of glaucoma and affects aproximately 1% of the population over 40 years of age. Primary open-angle glaucoma is the most common type of glaucoma and affects about 1% of the population over 40 years of age. Primary open-angle glaucoma affects both men and women equally and is responsible for about 12% of all cases of blindness in North America.
Glaucoma is a silent disease that does not have any symptoms in its early stages, meaning it does not cause any significant visual impairment, pain, or discomfort. As glaucoma progresses, the patient will lose their peripheral vision and usually one eye is more severely affected than the other. In this early stage, the patient does not usually notice these vision changes because the less affected eye is able to compensate for the more affected eye. When the patient finally notices changes in their vision, they are usually at a more advanced stage of glaucoma which makes it more difficult to stop the progression of the disease and preserve the central vision.
The Vision of a Patient With Advanced Glaucoma
The main risk factors for glaucoma are:
High intraocular pressure is the most significant risk factor, but it is important to keep in mind that not every patient with glaucoma has high intraocular pressure. In fact, 16% of patients with glaucoma have normal intraocular pressure (less than 21 mmHg).
After a thorough eye examination, further studies should be performed to confirm a glaucoma diagnosis: 1) an optical coherence tomography (OCT) is usually requested to determine any structural changes in the optic nerve and to check the thickness of the nerve fiber layer, 2) a visual field to evaluate if there is loss of functional vision and 3) a corneal pachymetry to later calculate the real intraocular pressure.
OCT of the Optic Nerve in a Healthy Patient
Visual field of a Patient With Glaucoma
Once a diagnosis of glaucoma is confirmed, the patient should begin treatment with the objective of limiting visual impairment and slowing down the loss of ganglion cells. Currently, the best method to achieve this goal is to decrease intraocular pressure. The first line of treatment is usually with medicated drops (usually a prostaglandin analog or a beta-blocker) that are applied in both eyes. The medicated drops that are chosen should be used in the lowest concentration and whenever possible, according to the desired therapeutic effect. Ideally, the drug with the least possible side effects should be used.
The patient should return for a follow-up eye examination 4 weeks after starting treatment. While a decrease in intraocular pressure greater than 4 mmHg is considered significant, it is not always enough. If the patient seems to be responding well to the glaucoma treatment, the patient should return for the next evaluation in 2 months and then every 3 to 4 months. If the treatment is not working well, the patient can be given a different type of medicated drop.
Surgery may be necessary in cases of glaucoma where the patient does not respond to maximum therapy using 3 or 4 medications. These patients may have an intolerance to the treatment and/or are very specific cases where the patient would benefit from a more aggressive treatment at an early stage of the disease.
Most patients with primary open-angle glaucoma will not go blind during their lifetime. One glaucoma study found that over the 20-year follow-up period, 25% of patients developed blindness in one eye and 10% developed blindness in both eyes.
Neovascular glaucoma can occur in only one eye and be more aggressive than primary open-angle glaucoma. The treatment of neovascular glaucoma includes treating diabetic retinopathy or occlusion of the retinal veins with laser or intraocular injections to inhibit the formation of abnormal veins on the iris that caused obstruction of the angle or eye drainage.
Neovascular Glaucoma Seconday to Diabetic Retinopathy
There are different types of primary and secondary glaucoma, which is why it is important to see an eye specialist to properly diagnose it.
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