Understanding vitreous haemorrhage surgery

What is a vitreous haemorrhage?
What causes a vitreous haemorrhage?
How does vitreous haemorrhage affect your sight?
When should you have surgery for vitreous haemorrhage?

 

What is a vitreous haemorrhage?

The term vitreous haemorrhage implies bleeding into the vitreous cavity of the eye. The degree of visual loss depends upon the extent of bleeding and can range from mildly troublesome “floaters” to a complete loss of all useful vision.

It is helpful to know a little about the eye and how it works in order to understand what effect vitreous haemorrhage has on the vision, and how it can be treated.

Anatomy of a normal eye

The wall of the eye is formed by three layers, the retina, the choroid and the sclera.

The retina is the light-sensitive nerve tissue that lines the inner wall of the eye. Rays of light enter the eye, passing through the cornea, pupil and lens before focusing on to the retina. The retina contains photoreceptors which convert light into electrical impulses.

In the healthy eye these impulses are sent via the optic nerve to the brain where sight is interpreted as clear, bright, colourful images. The retina can be likened to photographic film in a camera.

The macula is a small area at the centre of the retina. It is very important as it is responsible for our central vision. It allows us to see fine detail for activities such as reading, recognising faces, watching television and driving. It also enables us to see colour.

The choroid is the underlying vascular (blood vessel) layer of the eye, from which the retina receives oxygen and nutrients.

The vitreous is the clear jelly-like substance which fills the hollow space behind the lens. As we age this vitreous gel opacifies and shrinks away from the retina. This is very common, occurring in about seventy-five per cent of people over the age of sixty-five.

Separation of the vitreous gel from the retina is known as posterior vitreous detachment or “PVD”. It does not itself cause any permanent loss of vision, although some patients are immediately troubled by floaters or a generalised mistiness. Very occasionally PVD results in tearing of the retina, with the risk of retinal detachment. Tearing of the retina, with or without retinal detachment, is one possible cause of vitreous haemorrhage.

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What causes a vitreous haemorrhage?

The vitreous cavity of a healthy eye is filled with nothing other than clear vitreous gel. Bleeding can come either from normal retinal vessels which have been subjected to some kind of trauma, or from abnormal blood vessels which have developed on the surface of the retina in response to an underlying retinal pathology.

Normal blood vessels can be torn when the vitreous separates from the retina at the time of posterior vitreous detachment. This is more common in short-sighted (myopic) eyes and always raises the possibility that the retina may have been torn. This puts the eye at risk of retinal detachment.

Direct trauma to the eyeball can cause bleeding, but the eye is remarkably resilient and even a hefty knock may not cause a vitreous haemorrhage.

Bleeding from abnormal retinal vessels occurs in a number of conditions, many of which will have been diagnosed prior to the vitreous haemorrhage and for which some treatment may already have been initiated.

The common causes are;

  • diabetic retinopathy; abnormal blood vessels grow on the surface of the retina in response to poor retinal blood flow. This may have already been diagnosed and in some cases laser treatment applied;

  • retinal vein occlusion; blockage of the retinal vein or one of its branches results in poor blood flow to an area of the retina. The retina responds by growing abnormal blood vessels, which unfortunately do little to help retinal function, but are fragile and susceptible to bleeding;

  • age-related macular degeneration; about ten per cent of patients with macular degeneration develop the “wet” form of the disease, with an abnormal meshwork of blood vessels growing beneath the central macular retina. Although very uncommon, patients with severe wet macular degeneration can develop a “breakthrough” bleed into the vitreous cavity of the eye.

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How does vitreous haemorrhage affect your sight?

Vitreous haemorrhage causes a spectrum of visual symptoms of varying severity;

  • floaters, which may be anything from small dots to large clouds of “debris”;

  • a haziness of the entire visual field;

  • profound visual loss, preventing even “hand movements” vision.
Example of vision with floaters

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When should you have surgery for vitreous haemorrhage?

This depends upon a number of factors, but important considerations are;

  • if a pre-existing abnormality has been documented, for example abnormal blood vessels in diabetic retinopathy, it may be appropriate to wait a few weeks for spontaneous clearing;

  • if a severe bleed with profound visual loss has occurred, resulting in no clear view of the retina, more urgent surgery will be recommended;

  • those patients with no pre-existing ocular disease, the concern being that bleeding may be a result of posterior vitreous detachment and that shrinkage of the vitreous jelly, sufficient to cause bleeding, may have also torn the retina. If the peripheral retina, where tears normally occur, cannot be clearly visualised urgent surgery is essential. The risk of retinal detachment accompanying vitreous haemorrhage is increased in cases of short-sightedness or when the fellow eye has already suffered a retinal detachment.

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