Glaucoma causes visual loss starting in the periphery and moving centrally as the disease progresses. Worldwide, glaucoma is the second leading cause of blindness after cataracts. It is also the leading cause of blindness among peoples of African descent. Glaucoma affects one in 200 people aged fifty and younger, and one in 10 over the age of eighty. If the condition is detected early enough, it is possible to arrest the development or slow the progression with medical or surgical means.
The cause of glaucoma is not completely understood although it results in progressive damage to the optic nerve ( shown as an increase in cupping and pallor) this damage is probably cause by a reduction in blood supply in the eye itself and this reduction is linked to the pressure in the eye- the intra ocular pressure. The standard treatment for glaucoma is the reduction of intra-ocular pressure by drugs ( as eye drops ) or surgery .
There are two distinct types of glaucoma, acute and chronic.
Acute Glaucoma is much less common and is caused by a sudden blockage to the drainage channel located at the extreme outer periphery of the iris, (the canal of schlemm). This is the drainage channel for the the aqueous humor, a clear fluid in the anterior chamber of the eye, responsible for maintaining eye pressure and providing nutrients to the cornea. When blockage occurs, almost always in one eye only, there is a rapid increase in intra ocular pressure, causing a single red painful eye with a fixed pupil. ( the pain may be severe) As with all acute eye symptoms it is important to seek professional advice urgently. With acute glaucoma there is frequently no warning that it will develop although unlike chronic glaucoma which is largely symptom free it is much easier to detect when it does occur.
Chronic Glaucoma is much more difficult to detect, particularly in the early stages, when even at consultant level, diagnosis may be made based on the balance of probabilities. Chronic glaucoma causes slow progressive damage to the optic nerve, causing slowly increasing loss to the peripheral visual field. The pressure in the eye is usually raised above normal levels but glaucoma may still be present with normal or even low pressures. Diagnosis is made on the basis of several criteria, the four major factors are intra-ocular pressure, appearance ( particularly changing appearance of the optic nerve) changes in visual field and family history. With glaucoma it is virtually impossible to pick it up the day you develop it, the aim is to detect it before it causes significant damage. It is normal practice for optometrists to start actively looking for glaucoma in your forties or earlier if there are additional risk factors. Digital retinal photography ( available in this practice) is a valuable tool in detecting subtle early changes in optic nerve pallor and cupping.