Glaucoma is a disease that causes damage to the nerve of the eye, the optic nerve, and gets worse over time if not recognised. It's often associated with an increase in eye pressure. Glaucoma tends to be inherited and may not show till mid age. The optic nerve transmits images to the brain. Permanent loss of vision can occur over several years, if glaucoma is not properly treated.
The Silent Thief of Sight
The pressure in the eye can increase when eye fluid isn't circulating normally in the front part of the eye. This nourishing fluid, called aqueous humor, is produced by the Ciliary body, flows through pupil and than out of the eye through a mesh-like channel called Trabecular meshwork. If this channel gets blocked, fluid pressure builds up, causing glaucoma. There are several types of primary glaucoma. In the primary open angle glaucoma (POAG - the direct cause of the blockage is unknown, but doctors do know that it can passed from parents to children. In the primary closed angle glaucoma, decreased spaces and the crowding of structures in the front of the eye causes blockage at the pupil and the trabecular meshwork, causing sudden increase in the pressure.
Other causes of glaucoma are a blunt or chemical injury to the eye, eye infections, blockage of retinal blood vessels, inflammatory conditions, and occasionally eye surgeries. Glaucoma usually occurs in both eyes, but may involve each eye to a different extent.
Damaged Optic nerve due to Glaucoma
There are more than 40 types of glaucomas, but most fall into three principal categories; open angle, angle closure and congenital. These categories can be sub -classified as primary (occurring without a known cause) or secondary (due to an underlying cause, such as injury or illness).
Open angle glaucoma is the most prevalent form of glaucoma and accounts for about 60% all glaucoma. In open angle glaucoma, the aqueous humor cannot get out through the trabecular meshwork.
The onset of open angle glaucoma is slow with almost no symptoms. However, as time progresses, there is gradual loss of peripheral vision, a persistent elevation in IOP, optic-nerve atrophy, retinal ganglion cell atrophy etc. Blindness is the outcome unless surgery or drug treatment is initiated. Vision lost due to glaucoma is permanent and can never be recovered. Several conditions are known to be associated with open angle glaucoma, like pigmentory dispersion syndrome, high myopia, retinal detachment, and diabetes mellitus etc.
Angle closure glaucoma is a more severe form of glaucoma, and is seen more often in our country. The increase in IOP is related to sudden papillary blockage of aqueous humor circulation. This condition can be chronic (progressing slowly or occurring persistently) or acute (occurring suddenly). During an acute attack, the iris balloons forwardsand blocks the outflow channels suddenly and completely. IOP over 60 mmhg is not uncommon. It can lead to severe eye pain, headache, nausea, vomiting, stomach upsets, blurred vision accompanied by visions of colored halos around lights, and rapid loss of vision.
Thisvmay develop as a result of a dislocated or swollen lens, post-surgery, Ciliary block or post-inflammatory conditions. Certain eye drops like atropine, pupil dilating medicines etc. can precipitate angle closure glaucoma in susceptible patients.
Both subtypes congenital glaucoma—infant and juvenile- frequently require surgical intervention in preference to other, less effective medical treatments.
Although anyone can get glaucoma, some people are at higher risk than others. They include :
At first, open angle glaucoma has no symptoms. Vision stays normal, and there is no pain. As glaucoma usually remains untreated for many years, people may notice that although they see things clearly in front of them, they miss objects to the side of their eye field of sight. At the end stages, it may seem as though they are looking through a tunnel. Over time, the remaining forward vision may decrease until there is no vision left.
If you have any of the following symptoms, seek immediate medical care:
Your Ophthalmologist can suspect glaucoma during a routine eye test. Remember it's easy to manage glaucoma with your Ophthalmologist's advice and medications. It is also easy to miss Glaucoma, if you avoid consulting your Ophthalmologist. A spectacle check up or an eye screening in a camp, without a complete Ophthalmologists eye check up can easily miss the diagnosis.
Several procedures are used for diagnosing glaucoma. They, include the evaluation of IOP (tonometry), Optic nerve head and RNFL changes on slit lamp stereo biomicroscopy using high magnifying lens, visual field changes (perimetry), optic-disk analysis (OCT) and angle evaluation (gonioscopy).
Several tonometry techniques can be used for the measurement of IOP. Applanation tonometry measures the force applied to the cornea per unit area. Air puff tonometry measures IOP by sending a "puff of air" onto the cornea to measure IOP. ICare tonometry measures the IOP by magnetic rebound method.
By this technique the ophthalmologist can directly evaluate the optic nerve using an biomicroscope or ophthalmoscope. Changes in morphology of the optic disk may point to glaucomatous damage.
This procedure tests for visual field defects, a defining feature of glaucomatous optic nerve damage. Isolated of impaired vision, surrounded by normal areas in a vision filed, are indicative of open angle glaucoma. Classical patterns are suggestive of glaucoma, but it is said that Perimetry becomes positive only after about 40 percent of ganglion cells are damaged!
This technique allows the ophthalmologist to view the anterior chamber angle directly. Both open angles and angle closure glaucomas need this test.
Ziess visual fields test
The leader in HD OCT, Optovue, at Karthik Netralaya is a modern spectral OCT equipment. It incorporates ocular coherence tomography technology. The Optovue OCT is the gold standard in vivo imaging device for glaucoma and offers proven reproducibility for diagnosis & follow ups. Very critical analysis of small changes in glaucoma damage is possible so that the treatment can be modulated. It has several unique objective glaucoma analysis modes. This includes RNFL thickness & TSNIT maps for nerve fiber layer analysis, GCC (Ganglion cell complex) mapping & analysis, and optic disc cup analysis.
Optovue OCT at Karthik Netralaya has updated normative database to compare patients test results. GCC analysis, one of the most recent criteria that can detect glaucoma in very early stages is extensively used. The OCT provides real-time cross-sectional images and quantitative analysis of glaucoma damage, and optimizes the diagnosis and monitoring of glaucoma defects.
Optovue OCT test
Glaucoma treatment may include prescription eye drops, LASER surgery, or microsurgery.
These either reduce the formation of fluid by the ciliary body or increase its outflow. Side effects of glaucoma drops may include allergy, redness of the eyes, itching, stinging, blurred vision or irritated eyes. Some glaucoma drugs may affect the heart and lungs. Be sure to tell your doctor about any other medications you are currently taking or are allergic to. If you have Asthma, cardiac diseases, hypertension or allergies, do mention to the doctor. Eye drops have to be used strictly as advised. Timings and dosages have to be maintained.
Half hearted treatment leads to blindness, which cannot be reversed. Attend to your follow ups as advised. Use the drops even on the date of your next visit. After instilling one drop, keep the eyes closed for 2 to 3 minutes, with the inner corners of the lids kept pressed, so that the eye drop is retained in the eyes, instead of draining into nose and throat. If there are any untoward effects after starting eye drops, do inform your doctor.
LASER surgery for glaucoma (ALT or SLT) slightly increases the outflow of the fluid from the eye in open-angle glaucoma or eliminates fluid blockage in angle-closure glaucoma. Types of LASER surgery for glaucoma include Trabeculoplasty, in which a LASER is used to pull open the trabecular meshwork drainage area; iridotomy, in which a tiny hole is made in the iris, allowing the fluid to flow more freely; and cyclophotocoagulation, in which a laser beam treats ciliary body, reducing the production of fluid.
In an operation called a Trabeculectomy, a new channel is created to drain the fluid, thereby reducing intraocular pressure. Sometimes this surgery fails due to the body's healing mechanisms closing the new channel, needing a redoing of the surgery. For some patients, a glaucoma implant is the best option. Other complications of microsurgery for glaucoma include temporary or permanent loss of vision, as well as bleeding or infection.
If you are diagnosed to have glaucoma, just do not worry.
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