Understanding Glaucoma, the Sneak Thief of Sight
Dr Vanita Pathak-Ray, FRCS (Ed), FRCOphth (Lon) Consultant VST Centre for Glaucoma, In-Charge Zeiss International Academy for Advanced Ophthalmic Education, L V Prasad Eye Institute (LVPEI), Faculty, Bausch and Lomb School of Optometry and Visiting Faculty, Hyderabad Central University
Eye is a complex and sensitive organ that allows us to receive, process and understand images with the help of special sensors in the brain. Damage to any part of the eye can decrease the vision.
Glaucoma is a disease that affects the optic nerve of the eye and is characterized by shrinkage of the field of vision. In India, 11.2 million are estimated to be affected by the disease, with 1.1 million rendered blind. Worryingly, almost 90% of glaucoma in the community is undetected, because in most cases apart from the acute ones, there are no symptoms until the person experiences loss of vision. That is why glaucoma is also referred to as the ‘sneak thief of sight’.In the acute variety, patients may complain of coloured halos preceding pain and loss of vision. However, in the majority of chronic glaucoma cases, patients can tell only after side vision is severely affected (tunnel vision), which occurs in well established glaucoma. Based on the status of the drainage of the fluid (aqueous), responsible for high pressure, out of the eye, glaucoma can be roughly divided into two main categories, "open angle" and "closed angle" (or "angle closure") glaucoma. The acute variety of angle closure can appear suddenly and is often painful; visual loss can progress quickly, but the discomfort often leads patients to seek medical attention before permanent damage occurs. Chronic glaucoma, which can be both open angle and angle closure, tends to progress at a slower rate and patients may not notice they have lost vision until the disease has progressed significantly.
Glaucoma slowly affects side vision (peripheral vision) first. It occurs in both eyes, but usually unequally, as a result the better eye keeps ‘filling-in’ for the eye that is affected more. Due to extreme constriction of side vision, tunneling of vision occurs. Central vision continues to remain relatively good till the very last stage. That is why, early on in the disease, patients fail to realize that they have a problem.
Glaucoma is a blinding disease but can be prevented if detected early.Chronic glaucoma is 4-10 times more common in blood relations of patients diagnosed with glaucoma. It is recommended that all individuals above the age of 35 have eye checks every 2 years. If there is a suspicion of glaucoma, then a visual field test (perimetry) is done to check for peripheral vision. In diagnosed cases of glaucoma, perimetry is usually repeated annually as well. Imaging (scans) may also be done, especially when there is suspicion of early disease. Thus, in either case, early detection is of great importance.
If glaucoma is discovered early enough, and is treated, then the likelihood of losing sight is small. If left untreated, there is progressive damage, leading to tunnel vision and eventually loss of central vision too. The best way to improve the condition of a glaucoma patient is by regular use of eye drops, as prescribed, without fail, and also regular checkup.
What are the risk factors?
Family history, as mentioned above, increasing age (above 35 years), high degree of short-sightedness (myopia) and usage of any type of steroid medication (eye drops, inhalers, tablets, ointments etc) are all risk factors. In some parts of India, angle closure disease is quite common.
What are the tests required?
Tests that are specific to glaucoma are:
- Tonometry (measurement of eye pressure)
- Gonioscopy (viewing of the drainage angle)
- Bio-microscopic fundoscopy (viewing of the optic nerve head in 3-D at the slit lamp with special lens)
Can glaucoma be cured?
Glaucoma affects the nerve and hence the ensuing damage is permanent. There is no cure, but we can control it and help to prevent any further loss of vision.
How is glaucoma treated?
Current treatment of glaucoma is directed towards control of eye pressure by means of eye drops (sometimes tablets for short duration), laser and glaucoma surgery. For the majority of chronic open angle disease, it is controlled with eye drops; when this fails then laser or surgery is contemplated. For all angle closure disease cases, laser is done first. Laser Peripheral Iridotomy helps create a ‘hole’ in the peripheral part of the coloured portion (iris) of the eye, in order to try and open up the drainage angle. Once this is done, it is treated like open angle glaucoma. Surgery carries greater risk of complications and morbidity and, in any case, cannot restore the vision that is already lost. Moreover, there is no 100% guarantee that it will help control eye pressure in the long term, hence most Ophthalmologists reserve this form of treatment as the last resort.
How long is the treatment?
Treatment, once started, has to be continued indefinitely. As such, it has to become a part of one’s daily routine. Also, lifelong monitoring is required (follow-up at regular intervals, usually 3-6 months), similar to diabetes management. Even if surgery is done, lifelong follow-up at regular intervals (3-6 months) is mandatory.
Lastly, glaucoma is not a very lifestyle sensitive disease. However, if you practice yoga, shirshaasana or the head-down position should be avoided. Also, consumption of more than 4 standard glasses of water (approx. 1 litre) at one time should be avoided. Apart from this, alcohol, if consumed, should be in moderation. Diet should be normal and balanced. Unfortunately, other than this, there is little else one can do to modify the course of glaucoma.
It cannot be stressed any less that though glaucoma is a blinding disease, it can be prevented if detected early, through dissemination of knowledge and creation of awareness, not only in the general publicbut also in the ophthalmic community responsible for the delivery of primary eye care.