What Is Glaucoma?
Glaucoma is optic neuropathy, which is a disease of the optic nerve that generally progresses over time. The optic nerve is the second cranial nerve that connects the eye to the brain. The optic nerve damage due to glaucoma is evident in the optic nerve head, the place where the optic nerve is connected to the back of the eye. Due to the optic nerve damage, there are changes in the visual field of the patient. The major modifiable risk factor in glaucoma is intraocular pressure (IOP).
What Causes Glaucoma?
The fluid inside the eye is called aqueous humor or aqueous. This fluid (99% water) is produced by the ciliary body in the eye. Most of the aqueous humor is drained through a structure known as the trabecular meshwork. The mechanical or functional block of trabecular meshwork leads to impaired drainage resulting in increased pressure inside the eye.
What Are the Types of Glaucoma?
Based on whether a good portion of the drainage site is visible on examination or not, glaucoma is categorized into,
Open-Angle Glaucoma (Visible): This is the common type of glaucoma. It is also called wide-angle glaucoma. In this type, the drain structure, known as the trabecular meshwork, will look fine in the eye, but the fluid does not flow out as it should.
Angle-Closure Glaucoma (Not Visible): It is also called acute or chronic angle-closure glaucoma or narrow-angle glaucoma. It is more common in Asians. The eye will not be able to drain like it should because of the narrow drain space between the iris and cornea. This causes a sudden build-up of eye pressure. This glaucoma type is linked to farsightedness and cataracts. The ophthalmologist performs a test called gonioscopy to view the angle of the front part of the eye. The trabecular meshwork is one of the structures that make up the angle.
Other common types of glaucoma are:
Secondary Glaucoma: This secondary glaucoma occurs when another condition, like diabetes or cataract, adds pressure to the eye.
Normal-Tension Glaucoma: This is said to be a form of open-angle glaucoma. It occurs when there are blind spots in the vision or when the optic nerve is damaged even though the eye pressure is within the average range.
Pigmentary Glaucoma: In pigmentary glaucoma, tiny bits of pigment from the iris, which is the colored part of the eye, enters into the fluid inside the eyes and clogs the drainage canals.
What Are the Risk Factors of Glaucoma?
Intraocular Pressure: It is directly proportional to the risk of developing glaucoma.
Family History: Peoplewith first-degree relatives having primary open-angle glaucoma are at a higher risk.
Age and Ethnicity: More in elderly and black individuals.
Others: Myopia and diabetes mellitus.
What Are the Symptoms of Glaucoma?
Most patients with glaucoma do not have any symptoms until it is too advanced. As a result, many patients are accidentally diagnosed with glaucoma during an eye check-up. Patients gradually lose their visual field till they are able to see only through a small island of vision. This is usually late in the course of the disease.
However, some patients who develop a sudden rise in IOP can have severe pain, headache, blurring of vision, colored halos, nausea, and vomiting. This usually occurs in an acute angle-closure attack when the patient suddenly develops closure of the angle leading to impaired aqueous drainage.
How Will the Ophthalmologist Examine?
Apart from the routine procedures, the IOP is checked using an applanation tonometer. This is done with a device attached to the slit lamp, the machine with which an ophthalmologist examines the eye. Gonioscopy is done using a lens suited for the purpose of visualizing the angle of the eye. For both the above tests, topical anesthetic medication is instilled to numb the eye.
The optic nerve head is examined using a lens to check for the characteristic changes of glaucoma. The area surrounding the optic disc is assessed to see if there are any obvious retinal nerve fiber layer defects. The optic nerve head assessment may require your pupils to be dilated using a dilating drop.
If there is a suspicion or evident glaucoma, further tests may be done. These tests can be done to assess the level of damage to the optic nerve as well as the functional damage (loss of visual field).
Visual field analysis using perimeter (Humphrey or Octopus or Goldmann).
Optical coherence tomography helps to assess the optic nerve head and the retinal nerve fiber layer.
Heidelberg retinal tomography gives a detailed analysis of the optic nerve head.
All these tests can be done periodically to assess the progression of the disease.
What Are the Treatment Options for Glaucoma?
1. Medical Treatment:
There are various eye drops, which decrease the production of aqueous or increase the drainage of aqueous from the eye, thus resulting in reduced IOP. As these usually give the desired decrease in IOP, they are usually preferred as the first-line treatment.
2. Surgical Treatment:
If the IOP is too high to be reduced with medicines or if maximal medical therapy does not result in the desired decrease in IOP, surgical management is opted for. A trabeculectomy is usually performed to reduce IOP. There are many newer techniques and implants that can also result in reduced IOP.
3. Laser Treatment:
Argon or selective laser trabeculoplasty is aimed at the trabecular meshwork to increase the outflow of aqueous. This can be done only for some types of glaucoma. A peripheral iridotomy (burning a small hole in the iris) using a laser is done in patients who are at the risk of developing angle-closure glaucoma.
How Is Glaucoma Prevented?
Glaucoma cannot be prevented. But when it is detected earlier, the risk of eye damage becomes lowered. The following steps help to protect the vision:
It is important to get frequent eye examinations, so the sooner the doctor spots the glaucoma signs, the earlier the treatment can be started. Adults should get tested for glaucoma every 3 to 5 years. Above 40 years of age and with a family history of the disease, a complete eye examination every 1 to 2 years is needed. When there are other health-related problems like diabetes or other eye diseases, an ophthalmologist visit is often required.
When the doctor has diagnosed a high eye pressure, drops to prevent glaucoma will be given.
Moderate activities like jogging or walking at least three times a week are required, and practicing regular exercise leads to a healthier life.
Use protective eyewear while working on home improvement projects, watching TV, using phones, playing sports, etc.
Going for a regular follow-up visit is paramount. It is wise to stick to the dates of follow-up visits as advised by the treating ophthalmologist. This is necessary to assess the reduction in IOP as well as the progression of optic nerve head changes. A negligent attitude in patients with glaucoma can prove to be costly. Adherence to treatment and follow-up schedule should be emphasized enough.
Frequently Asked Questions