Health examination
LAST TIME we considered the result of your sight test, but perhaps even more important is the result of the health examination of your eyes.
The eye is the only point at which we can see inside the body without resorting to surgery, so any condition of your body which affects the blood supply will show up in the blood vessels of your eye, which means that we are looking for and can diagnose not only malfunctions of your eyes but also of your whole body.
Cataract
From my previous article you may remember we use an instrument called a retinoscope to measure the prescription of your eye by focussing light on the retina and then placing correcting lenses in front of your eye until it comes back along its own path. A second function of this examination is that it shows the lens of your eye in silhouette against the orange background of the retina and we can readily observe any opacities or cataracts. This word often panics patients and, up to 20 years ago justifiably, when the whole lens was removed under general anaesthetic and entailed a four day hospital stay and bottle-bottom corrective lenses thereafter. However nowadays it is a relatively simple, quick and painless treatment using local anaesthetic, breaking up the opaque central portion of the lens using an ultrasonic probe, which is sucked out and replaced by a small soft contact lens to give instant correction, even of previous long-standing sight errors. The actual surgical procedure takes only about 10 minutes with your total hospital stay being all of four hours.
Glaucoma
This is one of the most dangerous eye conditions because it produces no symptoms at all until the very late stages and can only be detected as part of your eye examination. The anterior (front) section of your eye contains a watery fluid (aqueous) which is designed to lubricate and cool the working mechanisms of your eye. This is continuously being produced and escapes through micro-channels (canaliculi), if these get blocked up and the aqueous cannot escape as quickly as it is produced, then pressure builds up within your eyes and pushes back onto the retina damaging the delicate nerve endings. Once damaged these cannot be repaired and so, on detection it is imperative to lower the pressure to avoid further damage.
The diagnosis is by checking the pressure within your eye using a tonometer, observing the back of your eye where the increased pressure depresses the soft optic nerve head (disc) and by checking your field of vision using a field screener. Treatment is initially using drops in your eye, possibly combined with tablets, or if this does not work, either using a laser to produce artificial canaliculi or surgically producing a non-return flap/valve in your eye. The earlier the diagnosis, the better chance there is of your sight being saved!
The Fundus
(or back of your eye)
We use an instrument called an opthalmoscope to look through the pupil (the window of your eye) to examine the fundus, which is fascinating as it is a microcosm of the whole body and, as I mentioned earlier the only place we can examine your blood supply without surgery.
The diagnosable conditions are too many to fully cover in an article such as this but include diabetes, high blood pressure, toxaemia (poisoning of the blood by things such as lead, tabacco etc.), kidney malfunction and many cancers, although unfortunately they are nearly always secondary by the time occular signs occur.
Brain tumours
(both benign and malignant)
Often diagnosed first of all following routine eye examinations and, as with glaucoma, sometimes before symptoms have been experienced. Following a field of vision test it is often possible to pinpoint the problem and thus assist the neurologist.
Retinal detachments
Detected, mainly in very short-sighted people or following accidents, attacks or often following sporting (eg squash ball in the eye) incidents. Symptoms are of blurry, sometimes wavy, distorted vision and sometimes in the early stages, flashing lights. If you get any of these, do not hesitate in getting professional advice and a differential diagnosis.
Macular degeneration
Very common in the later stages of life and is due to the microscopic nerve endings of the retina literally dying off gradually. This diagnosis is one of the most depressing I have to make. There is no cure for the condition at the moment; the only good news is that it does not normally lead to complete blindness although the centre of your field of vision goes, almost as if you have a dirty mark in the middle of your spectacle lens.
Floaters
Annoying, but are not a disease or sight-threatening condition. The posterior two thirds of your eye is filled with a jelly like fluid (vitreous), particles of dead tissue come (normally) off the surface of your retina and into the vitreous where they gradually dissolve, if a piece comes into your line of vision before dissolving, a floater occurs. They are particularly noticeable when looking at a plain surface or a blue sky, play with them but do not worry about them!
I cannot cover all conditions in an article such as this but have tried to explain most of the commoner ones and hope I have not alarmed you too much, most are fairly rare, and if diagnosed early, treatable.
Next time I will deal with the front of the eye and contact lenses but until then, with summer coming on, protect your eyes with good quality UV absorbing sunglasses.
