Retinal detachment: which warning signs matter?

What is a retinal detachment?

The retina lines the inside of your eye the way wallpaper lines a room. It captures light and sends images to your brain via the optic nerve. In a retinal detachment this lining comes away from the layer beneath that nourishes it. The detached part stops working — you notice that as a grey or dark shadow in your vision.

How does it happen?

It usually starts with the vitreous: the clear gel that fills the eye. Over the years the gel becomes more liquid and contracts, at some point separating from the retina (a posterior vitreous detachment — harmless in itself and very common). During that separation the gel can pull too hard somewhere and create a tear. Fluid can then pass through the tear and lift the retina off.

Some eyes carry more risk: highly short-sighted eyes (longer eyes with a thinner retina), eyes that have taken a hard blow, eyes after cataract surgery, and eyes of people with retinal detachment in the family.

Which signs matter?

Three signs deserve attention. First: flashes of light, often brief sparks at the edge of your vision, most noticeable in the dark. Second: a sudden increase in floaters — not the familiar drifting specks you have known for years, but a new shower, sometimes described as soot or a cobweb. Third, and most urgent: a shadow, smudge or curtain sliding in from the edge of your visual field.

Flashes and new floaters usually only mean the vitreous is separating — nine times out of ten that ends harmlessly. But only an examination with dilated pupils can distinguish 'harmless separation' from 'there is a tear'. So: with sudden flashes or a shower of new floaters, have your eyes examined within a day or two. With a curtain or shadow, call immediately.

Why does time count so much?

As long as the centre of the retina (the macula, where you see sharpest) is still attached, surgical results are at their best. Once the detachment spreads across that centre, full recovery of sharpness becomes less certain. That is the whole story behind the urgency: not panic — pace.

How is it treated?

A tear without detachment can often be treated with laser in the outpatient clinic: the laser 'welds' the retina down around the tear so fluid cannot get underneath. An actual detachment requires surgery, usually a vitrectomy: the surgeon removes the vitreous, repositions the retina and secures it with laser or freezing, often with a gas or oil fill that holds the retina in place temporarily. With a gas bubble there is a temporary posturing advice and you must not fly. Most retinas are reattached after one operation; sometimes a second procedure is needed.

And afterwards?

How much sight returns depends mainly on whether the macula was involved and how long the detachment existed. The other eye deserves attention afterwards: anyone who has had a detachment in one eye has an increased risk in the other, and will receive monitoring advice.