A posterior sclerotomy is a surgical procedure to immediately lower intraocular pressure when all other medical methods have failed. It can be used as a primary procedure (therapeutic) or secondary to other intraocular surgical interventions such as in relation to anterior segment surgery.
The different conditions or circumstances that may necessitate the use of posterior sclerotomy include:
- Phacolytic glaucoma
- Anterior dislocated lens
- Before filtration surgery is done
- Intumescent lens with elevated IOP
- Corneal transplantation on aphakic eyes
- Treating intraoperative expulsive haemorrhage
- Treatment of malignant or ciliary body glaucoma
- Before a corneal graft or penetrating corneal transplantation
- In aphakia with pupil block that is not responding to medical treatment
- To restore a flat anterior chamber after an intraocular surgical procedure
A posterior sclerotomy is only an option when all possible medical treatment, which include systemic osmotic therapy and topical drops, have failed. If intraocular pressure fails to drop to lower than 40 mm Hg, then it must be performed.
Before the Procedure
The patient will discuss the procedure with the ophthalmologist. The benefits and risks of the procedure are explained. The patient's medical and ocular history is also taken. The ophthalmologist will administer Diamox to reduce the amount of fluid in the eye the night before the procedure, and in the morning as well.
The patient will be put under local or general anesthesia. The surgeon applies sustained pressure over the globe, which s/he releases every half a minute over a period of five minutes. The surgeon will use a tonometer to check intraocular tension after pressure application on the globe. Once a suitable pressure has been reached, the surgeon can open the anterior chamber where s/he will:
- Make an incision via the conjunctiva down to the sclera just behind the limbus
- Make a radial scleral incision down to the ciliary body
- Place a silk suture which s/he loops out
- Pass a needle with an artery forceps clamped onto it through the incision while aiming for the globe’s center
- Push in the needle until the clamp is flush with the sclera
- Slowly remove any vitreous fluid encountered, using a syringe attached to the needle
- Use a preferred method or instrument such as a Graefe knife to aspirate the fluid
- Withdraw the knife once the liquid has drained
- Not need to suture the scleral incision
Risks & Complications
Risks and complications may include:
- Retinal detachment
- Vitreous hemorrhage
- Trauma especially when an 18-gauge needle is used which can also plug with formed vitreous
- Loss of vitreous (usually if cataract extraction is involved) which results from inadequate drainage of the vitreous lakes occasioned by the sclerotomy
- If the pressure is not lowered, the surgeon needs to try another area by moving the point of the needle/knife to encounter a pocket of fluid that can drain easily
- Post operational hypotony (low intraocular pressure) and leakages which can lead to acute onset endophthalmitis (inflammation of the eye’s interior) resulting in loss of vision
- Vitreous incarceration can trap the vitreous within the site of incision, complicating the procedure and leading to further eye damage. Other complications arising from vitreous incarceration include fibrous ingrowth in the eye, retinal tears, and macular edema
Aftercare & Recovery
The patient's eye is padded for 24 hours after which the pad is removed. However, no padding is done if the second eye has no vision; a perforated eye shield will be used instead. The surgeon will prescribe postoperative medications to help with infection, inflammation, and pain, if any. The patient may experience a small reduction in vision, but it should gradually improve.
The patient requires good follow-up care, which is on a patient-by-patient case. Some patients have a follow-up period spread over three months, while others can go as long as 18 months. Generally, the first follow-up visit will take place on the day after the procedure. On this visit, the surgeon examines the eye to ensure that the aqueous has drained well. S/he also ensures that the bleb has formed adequately. S/he checks the IOP, which should be a good indication that a drainage channel has been created successfully.
On this first visit, the surgeon checks for early complications like hypotony, infection, choroidal detachment, a flat anterior chamber, hyphema, conjunctival leak, etc.
The patient should avoid touching the eye and keep the face clean. They should ensure clean hands before self-administration of medication.
Posterior sclerotomy results in lowering of intraocular pressure. It also produces an extremely soft eye, leading to uneventful removal of a cataract with satisfactory visual outcomes.