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 include:
- 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.
Retinal Tear with Vitreous Bleed
Most retinal tears are small and can be treated using laser or cryotherapy (freezing procedure). This seals the tear and reduces the risk of a retinal detachment.
This is a condition where the retina peels away from the wall of the eye. In most cases the retina detaches because a hole or a tear has formed in the retina allowing fluid to pass underneath the retina.
Treatment involves surgery whose main aim is to seal holes in the retina and reattach the retina. The two methods used in retinal detachment surgery are vitrectomy or scleral buckle or a combination of the two.
This procedure involves removing the vitreous gel (that has caused the retinal tear) from inside the eye. Then to seal the tear the surgeon uses either laser or a freezing probe to make a scar around the tear. A gas or silicone oil bubble is then inserted into the eye to support the retina while it heals. A gas bubble slowly absorbs over 2 to 8 weeks but a silicone oil bubble will need a small operation to remove it at a later date. Your vision will be very blurred initially due to the presence of the gas or oil bubble.
The retinal holes can also be sealed and supported by stitching a piece of silicone rubber or sponge to the outside of the eye. This acts as a ‘splint’ and produces a dent within the eye and pushes the outer wall of the eye up to the hole in the retina. The buckle is not visible on the outside of the eye and usually remains in place permanently.
Retinal detachment surgery can be performed under local anaesthetic or general anaesthetic. Under local anaesthetic you will be awake but you will not feel any discomfort as the eye will be numbed with an injection. You will not see the operation and the other eye will be covered. If a general anaesthetic is chosen then you will be fully asleep. The decision as to which type of anaesthesia is most suitable will be made following a discussion between you and your surgeon.
If you have been given any posturing instructions then these should be followed. You can bath or shower, but avoid splashing water near the eye. Generally you may do anything with which you are comfortable. Most people choose not to drive over the first few weeks. You must not fly until the gas bubble has gone and you must inform the anaesthetist if you require a general anaesthetic for any operation while there is gas in your eye.
Risks of Retinal Detachment Surgery
Retinal detachment surgery is not always successful. Every patient is different and some retinal detachments are harder to treat than others. Some patients may need more than one operation. These are the risks and benefits that will be explained to you before you give consent for surgery:
The success rate for retinal detachment surgery is approximately 90% with a single operation. This means that 1 in 10 people (10%) will need more than one operation. The reasons for this are new tears forming in the retina or the eye forming scar tissue which contracts and pulls off the retina again.
If a gas or oil bubble is used during surgery then you will usually develop a cataract in the eye within the first 18 months. A cataract is the lens of the eye becoming cloudy and will require a short operation to remove it.
Any surgical procedure carries a risk of haemorrhage and infection but in retinal detachment surgery this risk is very low (less than one in a thousand). Although it is rare, it does have serious consequences as it can cause blindness.
Diabetic Eye Disease
Patients with diabetes are more likely to develop eye problems such as cataracts or glaucoma, but the principal threat to vision is through diabetic retinopathy which is damage to the retina. Diabetes is a chronic metabolic disorder characterised by insufficient insulin production or insensitivity to insulin, which leads to too much sugar (glucose) in the blood.
Regulating blood glucose levels is extremely important. Untreated diabetes can result in damage to blood vessels, nerves and organs such as the kidney and the eye. The retina is situated at the back of the eye and responsible for detecting light and transmitting this signal to the brain, resulting in a visual image. Nutrients and oxygen are transported to the retina via numerous blood vessels. These vessels can be damaged by the high blood sugar levels often seen in non-treated diabetes or diabetes that is not completely controlled. This is known as diabetic retinopathy, which has several forms.
Most patients with diabetes will have developed some signs of diabetic change in the retina after 20 years. Treatments range from observation, laser, injections and vitrectomy surgery.