Unanswered questions on glaucoma, the silent thief of vision

Ladies and Gentlemen, please, listen attentively to my poem. It will answer nearly all the questions you have been asking about glaucoma,” I announced gleefully to the audience. I could see, my niece hew Celina raise up her hand. She looked a bit disappointed, so I asked, “Do you have anything important you want to say before I commence the recital? “Yes, sir,” she said, “I have many questions I have been yearning to ask you?” I maintained my stance, “I will answer all unanswered questions next week. Now, let us go straight to the poem.”

 

You silently destroy our eyes,

Nibbling at our optic nerves,

Providing no clue or warning,

Making us feel all’s well.

Reducing our visual field to a tunnel,

Like NEPA, you suddenly strike the final blow,

Leaving us in perpetual darkness and gloom,

You insolent thief of vision!

 

Yes, Glaucoma, you are a “quiet” devil causing an irreversible blindness by your action. You do not announce your presence until the damage is extensive. You are like a rat nibbling at one’s toe and blowing it. We only get to know it when you have done a great deal of damage. About six out of 10 people don’t know that they have glaucoma until the eye is almost blind.

 

Reducing our visual field to a tunnel,

You dig deeper and deeper,

And suddenly, you strike the final blow,

Leaving us in perpetual darkness and gloom,

Stealing our most valuable possession.

 

“How then does one know that he has glaucoma early enough to prevent blindness?”  There are three functions of the eye – the ability to see objects clearly which is called Visual Acuity; then the actual area which you can see in front of you – your scope of vision. We call this the Visual Field and often refer to it as your “island of vision in the sea of blindness”; the third is your ability to recognise colour – Colour Vision. Glaucoma strikes at the Visual Field, reducing it into a tunnel, leaving the Visual Acuity intact until later stages. It is when the Visual  Acuity is affected that the patient knows that something is wrong with his eyes.”

 

Why do you quench the light

And turn day to night?

Why are you so merciless

And refuse the sacrifice of drops and tablets

Offered daily for your appeasement?

Why? You silent destroyer of sight!

 

The pressure inside the eye, which we call the intraocular pressure, for unknown reasons, rises above what is needed to maintain the shape and integrity of the eye. This pressure which is higher than normal for that eye leads to damage to the optic nerve at the back of the eye. The optic nerve is the nerve of sight. It relays the information gathered about what you are looking at to the brain which makes the interpretation. The only way we treat glaucoma now is to reduce the intraocular pressure to a level at which it will cause no further damage to the eye. There is no pre-determined level and we have to gradually titrate our medications until there is no further damage to the eyes. Thus visual field tests are done at intervals to monitor the progression of damage.

We use eye drops and sometimes tablets to reduce the intraocular pressure (IOP). Often this may work for a while and later stop working. There are several reasons why a medication that was working would suddenly stop working for the patient. Since we do not know when this will happen, a patient on medications must keep his follow-up appointments. The doctor tries to answer three questions at each appointment. First, “Is the medication working well? The IOP will tell. The second is, “Despite the control of the IOP, is there still a loss of visual field?” Central Visual Field (CVF) would tell.

 

Even when we accept to worship at your feet,

And the surgeon carves out a channel in our eyes

That you may find your way out

And leave us in peace.

You ignore our pleas.

Why? You insolent thief of vision!

 

When medications don’t work or for some other reasons, we may decide to perform surgery to create a special channel through which the fluid inside the eye will drain out to maintain a steady IOP. Often the channel may seal up months or years later! So we must continue to keep patients who have had surgery under surveillance because the doctor never knows when it can happen.

Glaucoma is an enigma. The patient does not know he has it. It’s the doctor’s duty, during visits to the eye clinic, to make its presence known and once known, the patient must follow instructions, use his medications and submit himself for follow-up regularly. This is the only way to prevent blindness in glaucoma. Unlike in cataract, glaucoma blindness is irreversible. Are you still hesitating to have an eye examination?