The retina, the light sensitive layer at the back of the eye, is only loosely attached to the layer beneath. The retinal pigment epithelium is considered a layer of the retina, it brings nutrients to the outer layers of the retina, and removes old, worn discs from the photo-receptors. The Retinal Pigment Epithelium (RPE) is sticky, which helps to keep the retina attached, but mainly the retina stays where it should because of the pressure of the Vitreous Humor, a colourless clear jelly, which fills the large chamber at the back of the eye. As a child this jelly is very firm, and fills the entire rear chamber of the eye. Because this jelly is one piece, even if a child falls out of a tree and tears their retina, the pressure from the jelly will likely keep the retina attached.
In everyone the Vitreous jelly undergoes certain changes with age. The vitreous shrinks, and parts of it become more dense, other parts more liquid. As it shrinks, the vitreous detaches from the retina at the back of the eye, moving forward and the space it leaves behind becomes filled by liquid. Usually this Vitreous detachment is asymptomatic, and is nothing to worry about- it is a normal part of the ageing process. However, in some people there can be areas where the adherence between the vitreous and the retina can be abnormally strong. This can cause traction on the retina as the vitreous peels away, causing flashes of light, particularly noticeable when the eyes are moving. Most symptomatic vitreous detachments will resolve without any problem, but approximately 1 in 10 may develop a retinal tear. The torn retina allows the fluid to seep underneath, and so the pressure difference, which keeps it attached is lost, allowing it to detach.
Left untreated a retinal detachment may progress until the entire retina comes off. If the retina is detached from the pigment epithelium, it will not function properly, and will eventually permanently cease to function.
Retinal detachments are quite rare- about 1 in 10000 people could have a spontaneous detachment, others may be caused by trauma, such as a bang to the head or the eye. Highly Myopic (Short Sighted) eyes are more prone, as the eyeball is larger and the retina consequently thinner in these eyes. Some people have degenerative changes in the periphery of the retina, some of these might merit prophylactic treatment to prevent tearing and detachment- often either laser treatment from inside, or cryotherapy- using a freezing wand, externally can “glue” or spot weld these weakened areas down.
Symptoms of retinal detachment are usually flashing lights, called photopsias, increased amounts of floaters, or new floaters, or obscuration of part of the vision- like a curtain coming across part of the vision. Any symptoms such as these should be investigated as soon as possible- retinal detachments are an emergency and if one was detected in practice it would normally be sent straight on to casualty. Usually retinal detachment requires surgical intervention, but sometimes they may try for a spontaneous reattachment by having the person lie still in a certain position- in an attempt to get the retina to fall on rather than fall off. Most retinal detachments will be admitted to hospital, so that they can be bed rested and postured correctly until surgery can be done.
Not all complaints of flashing lights will be a retinal detachment, but symptoms such as these should be checked, sooner rather than later. Because we will require dilating drops to thoroughly examine the back of the eyes, it is advisable to ensure you have a lift home- you should not drive when the drops are in effect in your eyes. It can take 4 – 6 hours for the effect of the drops to wear off.