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Raised Eye Pressures; But not Glaucoma!
Mr Shah*, a 50 years old businessman wished to have his eyes checked as a routine screening. He did not have any complaints of any eye troubles. When his eyes were examined, his sharpness of vision was found to be normal. Mr Shah’s eyes were then examined using a Slit Lamp microscope, upon which no abnormalities were found. However when his eye pressures were tested they revealed raised eye pressure in both eyes (26 and 28 mm hg as opposed to the normal 8-21 mm hg).
Glaucoma is an eye condition where there is damage to the optic nerve usually due to raised eye pressures. Keeping this in mind, Mr Shah was referred to the Glaucoma Specialist at Advanced Eye Hospital. Gonioscopy was done which is a test to study the area where fluid is drained inside the eye (called the angle). This test is usually done in Glaucoma as Glaucoma can be of two types depending on whether there is a block in this area (called closed angle / open angle glaucoma).
Unexpectedly, this too turned out to be normal. This was followed by an examination of his retina (the photosensitive layer at the back of our eye). The vertical cup to disc ratio (this ratio reveals the damage to the optic nerve as seen in glaucoma) was 0.4
A ratio of 0.6 – 0.7 is suspicious of Glaucoma. There seemed to be no defects in the nerve fibre layer of the retina too.
Considering Mr Shah’s high eye pressures, he was further investigated for Glaucoma since all the previous tests seemed to be pointing against Glaucoma. The thickness of his central cornea was examined so that accurate readings of his eye pressures could be obtained. Those having thinner central corneas may cause a lower estimation of the eye pressure and vice versa. However, the readings in Mr Shah’s case were 570 and 573 microns in the right and left eye respectively which are higher than the average 530 - 550 microns.
His visual fields were then tested to see if Glaucoma had caused any decrease in the peripheral vision. This turned out normal despite a repeat test 2 days later.
As he had not had any eye injury in the past or consumed any steroids, it seemed apparent that a diagnosis of Glaucoma be ruled out.
A very surprised Mr Shah was handed a diagnosis of Ocular Hypertension.
Ocular Hypertension is when the pressure in one’s eyes is higher than normal (more than 24 mm hg in both the eyes). Ocular hypertension is not the same as glaucoma. Some people can have normal vision despite having high eye pressure. However, if ignored, this can lead to glaucoma or even permanent vision loss in some others. Hence, people with ocular hypertension are considered as ‘glaucoma suspects’.
The Ocular Hypertension Treatment Study found that the about 9% of people who had untreated ocular hypertension over 5 years developed glaucoma, compared to 4.4% in treated persons.
There seems to be no absolute way of predicting which of these patients will go on to develop glaucoma, but risk factors include:
· Older age
· Higher IOP
· Larger cup:disc ratio
· Thinner central corneal thickness
Take Home Message
Ocular Hyper Tension can happen to anybody above 35 years of age.
If diagnosed early and judiciously treated Glaucoma can be prevented.
* Name changed to protect privacy