If you have any concerns about your eye health, call us or drop in at the practice. An early professional examination offers you peace-of-mind and can ensure the most effective treatment if needed.
The eye is built in a similar fashion to an old (non digital) camera with a film. The back of the eye has a photosensitive lining called the retina (the equivalent of the Kodak film in the camera). If you were to open a camera, the main chamber is full of air, but in the eye there is a jelly like substance called the vitreous humour that fills the main chamber.This is described as jelly-like because as we age it starts to break up and become more liquid-like.
The jelly is attached to the retina in places. It is held firmly at the front of the eye and has quite a firm attachment at the fovea (the very centre of the retina) and around the optic disc (which is a hole in the retinal layer where the optic nerve leaves the eye to takes messages to the brain). Around the rest of the eye the attachment of the jelly to the retina is much less strong.
The natural ageing of the eye sees the jelly breaking down, when it does the following happens. It creates an area of liquid rather than jelly, often with debris in it from the broken down jelly. As the light passes through the eye to the retina, if it passes through this affected area, leaving a shadow like effect on the retina. Our brain interprets that shadow as a dark area. It can be dense, appearing as if a floating line or spot(s) or just a cloudy patch and is known as (vitreous) floater(s). This disturbance to the vision is not static and, if the eye is moved, the area of disturbance will move in roughly the same direction but not absolutely and often drifts after the eye movement has finished. The result to the jelly of this breakdown is that it shrinks slightly and when sufficient shrinkage has taken place it will start to pull away from the retina at the back of the eye.
If the vitreous pulls away there is what is called a ‘vitreous detachment’. In most cases this has no long term disadvantage (although will probably leave more floaters noticeable). When it pulls from the retina it causes tension on the photoreceptors and triggers a neural response from them as if they had a light flashed in that area. The result is that flashing lights are sometimes seen in the vision. These flashing lights are different from the lights people sometimes see with migraine attacks in that they only last for a second or so and are most commonly seen when the eyes are moved about. As mentioned before most of the retina/vitreous adhesion is not strong and after a short while the loose connections are broken and the lights stop, but the floaters remain. The flashing lights can last for up to a fortnight, until all the loose areas have come away and the firm anchorage areas are left.
There are concerns that sometimes the traction between the vitreous and the retina is strong enough that the retina is affected. If this happens then hospital review is URGENTLY needed. This could be either a retinal tear or a retinal detachment, both are which can be remedied but timely action is required.
If we examine your eye to try to assess this, we will dilate the eye to allow a better view, particularly of the peripheral retina. There are tell-tale signs in the anterior vitreous if there has been retinal damage and we will look for this as well as assessing the retina as far as we can see. If we see no signs of damage we will offer a guarded reassurance. But if symptoms deteriorate then further review is needed, probably at the hospital. In a hospital eye department a similar investigation is carried out but also they will probably see further to the extremity using a technique called indention where they manipulate the eye ‘casing’. Even when very skilled observers review eyes it is possible to miss very small tears that may in future progress so changes for the worse should always been considered for further review.
We have talked of the appearance of vitreous floaters which are a natural ageing change in almost all eyes over time, but generally greater at a time of vitreous detachment. These floaters move about in the vision and are not fixed. They move generally in the direction of eye movements but often lag movements and tend to drift after movement. If there has been a retinal detachment then there will be a symptom as if an area of the vision is blocked off and this does not come and go.
We suggest you think of your vision as if a theatre stage. Floaters are like flying trapeze artists moving about in the vision. A retinal detachment would appear as if a curtain is being drawn down / across / or upwards across the stage. If you experience the ‘curtain’ effect then URGENT review at a hospital eye department is called for.