Silicone Oil: Insertion/Removal
Silicone oil is a highly purified medical grade oil which is injected into the eye at the time of eye surgery for the following conditions:
- Proliferative vitreo retinopathy (scar tissue associated with retinal detachment).
- Proliferative diabetic retinopathy (scar tissue associated with diabetic retinopathy).
- Giant retinal tears.
- Certain retinal detachments that have breaks in the lower part of the retina and other types of retinal holes such as macular hole, inferior hole, large multiple retinal holes and recurrent retinal detachment.
The oil is used both as a tool to separate membranes and also as a sealant of retinal breaks.
The silicone oil replaces the vitreous gel which is removed at the time of operation. Other procedures may take place during the use of silicone oil, such as cataract extraction or laser treatment to the retina or the placement of a plastic external tyre which is sutured to the outside wall of the eye to indent the lower part of the wall of the eye towards the lower part of the oil bubble. Sometimes a tiny piece of iris is excised to allow the eye fluid to flow unimpaired by the oil.
After surgery it is usually necessary to posture face down for 12 to 24 hours, or longer in certain cases. This ensures that the oil bubble floats to the back part of the eye which then flattens the macula, part of the retina. (this is the seeing part of the retina)
Possible Side Effects
The only conditions where a definite causative link exists are the following:
- Keratopathy - this is where the oil may come in contact with the lining cells of the front window of the eye and the cornea. If this occurs then the nourishing fluid is prevented from bathing these lining cells (corneal endothelium). This can result in central deposition of calcium salts. However, this is reduced by performing a peripheral iridectomy, excision of iris in eyes that have had cataract extraction.
- Emulsification of oil - this complication is reduced by using a high viscosity oil which requires more energy to break the oil into globule. The presence of blood cells or inflammatory cells at the time of surgery or after surgery, can contribute to the emulsification process.
- Glaucoma - this is where high pressure can develop and threaten the blood supply of the optic nerve. This is prevented in patients' who have had cataract operation by performing a peripheral iridectomy. However, if there is a continued proliferate process in the eye, this can lead to closure of the iridectomy in about 10% of patients. There is probably a 5% chance of developing glaucoma. Emulsified oil may block the outflow of fluid from the eye. However, there is probably a greater risk of developing hypo Tony (low pressure), which might progress to phthisis (shrunken eye), due to the underlying proliferative process rather than as an effect from the oil, this scar forming process may alternatively contribute to chronic angle closure glaucoma.
- There is no good evidence of retinal toxicity from silicone oil.
Other Problems That May Develop Later, Unrelated to the Silicone Oil
- Retinal re-detachment after silicone oil surgery - the retina can re-detach again whether the oil is removed or not. 20% re-detachment if the oil is left eye and 20% if the oil is removed.
- Cataract is seen in patients' with eyes that have had silicone oil injected but it is thought to be more likely to be associated with the original problem, that of retinal detachment. That is, it is seen in 100% of eyes with proliferative vitreo retinopathy type retinal detachment.
- Corneal problems can still occur in 30% of patients', even if silicone oil is removed. This is usually a late onset problem.
Other Problems.
Of course it is possible to have eye problems unrelated to the retinal detachment or silicone oil such as continued diabetic circulation problems in diabetics or age related changes.
Glaucoma is a common condition, the population 2% over the age of 40 even without a history of retinal detachment or silicone oil injection.
Cataract occurs in 50% of eyes having vitrectomy by 5 years.
Success Rates
The success of surgery is approximately 60% in diabetic problems and 80% in other retinal problems requiring silicone oil but this clearly varies from patient to patient.
REMOVAL OF SILICONE OIL
At the end of surgery, the surgeon may plan to leave the oil in, if he feels that removing oil would have a significant risk of redetachment or phthisis. Or he may plan to remove it .
Removal of silicone oil will be considered if there appears to be oil related problems or if it is thought that vision will be improved by removing the oil but will not be done if the stability of the retina is suspect.
Nowadays pretreatment with argon laser may reduce the risk of redetachment. The timing of oil removal, that is 3 months versus later removal, has no impact on the rate of retinal re-detachment.
Oil removal takes about half an hour, the eye is entered at 2 sites : first to infuse fluid to replace the oil and second to remove the oil. These sites are sutured and further laser may be carried out. It can be done under local anaesthetic.
It is not possible to remove every last droplet of oil, so afterwards circular floaters may be seen in the centre of vision when the eye looks toward the ground. This isn't usually troublesome.
If there is re-detachment of the retina after silicone oil removal, then it may be necessary to undergo a further operation to re-inject the oil to re-attach the retina but of course this would be discussed in such an eventuality taking into consideration the risks (infection or sympathetic endophthalmitis) and benefits of further intervention.
This information site has been provided by varied UK and US eye doctors for patients with eye problems.
Once your eye doctor has made a diagnosis or recommended an investigation or treatment, then you will be able to find further explanation on this site.
It is not a self diagnosis centre. It should not be relied upon without taking professional advice.