by Dr Shilpa Kodkany
World Glaucoma week is a global event organised every year between the 2nd and 3rd week of March to create awareness among people about this ‘Silent Thief of Sight’.
The pressures within the eye increase and cause damage to the Optic Nerve (the nerve carrying the visual signals from the eye to the brain). This occurs very gradually and so very often we don’t realise that our vision is getting affected.
The optic nerve is basically a group of Retinal Ganglion cells. Retinal ganglion cells are the neurons that link the eye to the brain. The retinal ganglion cells’ job is to take those electrical signals and send them into the brain. The way they do that is by little wires that we call axons that actually exit the back of the eye in the area we call the optic nerve head. They comprise the optic nerve, and they’re literally like wires that plug the retina to the brain.
Then the brain makes sense of those neural signals so that it can understand, or you can understand, what a person’s face is and who that person is. All our vision is dependent on the electrical activity of retinal ganglion cells, the really incredible cells.
In Glaucoma there is death of these retinal ganglion cells. Why it affects some people and not others is still not known. There is a hereditary component to it. Those of you whose parents or siblings have Glaucoma should be screened for it. It usually affects people after the age of 40, although very rarely it has been detected in Newborns called Congenital Glaucoma or in childhood called Juvenile onset Glaucoma.
To diagnose glaucoma and to know the extent of damage to the optic nerve, there are various computerised tests. These tests not only detect the extent of damage but can also detect the progression of the disease. So these tests need to be done on a 6 monthly or yearly basis.
It is extremely important to detect if there is progression of damage to the optic nerve, because this determines the line of treatment which is required. Only checking the eye pressures at a given time will not determine progression.
To standardise detection and progression of glaucoma there are certain guidelines introduced globally. The ICO ( International Council Of Ophthalmology ) Guidelines suggest IOP ( Intra ocular Pressure) checks repeated periodically along with the assessment of the Optic Nerve which require computerised machines.
What are these tests?
1. Visual Field Analysis : The newer machines can detect defects in the field of vision and also detect progression when serial tests are done at regular intervals. The print outs obtained are analysed. With this newer technology a test which earlier took almost 20 – 30 mins is now possible in 10 minutes and is also much more accurate. It is also less tiring for the patient.
2. Optic Nerve Photographs : These are taken on a regular basis to look for progression of the disease.
3. OCT ( Optical Coherence Tomography ) : The actual defects in the Optic Nerve fibres ( retinal Nerve fibre layers ) are seen here and also have a colour coding.
Last year, a new analysis procedure, the Glaucoma Progression Index (GPI), was introduced. This procedure requires a minimum of five visual fields obtained over time. The test calculates a Mean Deviation (MD) to define a rate of progression of visual field loss and provides an estimate of the amount of damage that has occurred from glaucoma over time.
So, along with detection of glaucoma the manner in which progression of the disease is analysed is very important. Only then a proper treatment analysis can be done.
Newer Treatment Options for Glaucoma :
Most patients with glaucoma can be treated with eye drops alone. There are many new drugs in the market today. These newer drugs like Latanoprost / Bimetaprost not only control the eye pressures but also improve the blood circulation inside the nerve and help to maintain the function of the optic nerve. These are called Neuroprotective drugs. Newer drugs also reduce the number of drops to once a day instead of the conventional 2-3 times a day dosages.
Surgery for glaucoma is now a days only restricted to very advanced cases or in those patients who are unable to put eye drops.
The new surgical treatment is called MIGS ( Minimally Invasive Glaucoma Surgery ) just like all surgeries which have turned towards key hole surgeries. There are new stents which are the size of a hair which are undergoing clinical trials.
There is a lot of research going on to improve the drugs and also the drug delivery systems, since glaucoma is a life time disease just like diabetes and hypertension. Certain drug implants, very small in size are being implanted which slowly release the drug into the eye so a person does not need to remember to put the drops. The efficacy of such implants is still under research.
In the next few years we will see a lot of innovations in the treatment of Glaucoma which will help patients see better and lead a normal life with no restriction in the visual field as well as lifestyle. People will not get bogged down by this disease and hopefully when detected in early stages glaucoma will no longer be called ‘The Silent Thief Of Sight’.