A sclerostomy is a type of glaucoma filtration surgical procedure whose goal is to reduce intraocular pressure (IOP) in open-angle glaucoma. The surgeon creates a small incision in the sclera (outer eyeball covering). Some patients do not respond to laser surgery or medications to reduce IOP and require further interventions, often surgical. A sclerostomy is also recommended for patients who are on a rapid progression toward vision loss and are intolerant to glaucoma medication.
Without medical intervention, glaucoma can progressively lead to blindness. It is caused by elevated IOP, which results from aqueous humor overproduction, optic nerve atrophy, and resistance to the normal fluid outflow. A sclerostomy is performed to reduce IOP so that aqueous humor outflow is improved. With the procedure, the fluid is allowed to collect under the conjunctiva and form a filtration bleb.
- Conventional sclerostomy
- Enzymic sclerostomy
Sclerostomy has also been classified as:
- Internal sclerostomy
- Laser sclerostomy
Before the Procedure
To ensure that a sclerostomy is the ideal procedure of choice, the ophthalmologist will need to undergo a complete ophthalmic examination to confirm open-angle glaucoma and rule out other coexisting eye diseases. These include:
- Tonometry to measure IOP
- Visual field test to measure peripheral vision loss
- Optic nerve examination using an ophthalmoscope which allows a view into the interior of the eye
- The Heidelberg retinal tomography (HRT), a laser scanning microscope, and ultrasound biomicroscopy (UBM) are also used. UBM is a useful tool to follow up sclerostomies in the long-term
- Gonioscopy to measure the size of the anterior chamber angle using a special mirrored contact lens. A gonioscopy distinguishes between open- and closed-angle glaucoma and between primary and secondary glaucoma
The ophthalmologist will discuss with the patients so that the latter gets adequate information to make an informed decision and to manage expectations and fears. The ophthalmologist will explain what can be achieved through a sclerostomy, which involves incision, and the associated risks. The decision to undergo a sclerostomy is influenced by the extent of the patient's loss of vision, how quickly the vision is deteriorating, and the patient's life expectancy.
The patient must provide the family’s medical history of glaucoma. The patient will take anti-inflammatory medications and oral antibiotics several days to the procedure. The procedure will be performed in an outpatient setting, and the patient should have a responsible adult drive them home.
The patient will be put under local or general anesthesia. In some situations, the eye doctor may administer an intravenous sedative for relaxation purposes.
In conventional sclerostomy, the surgeon will:
- Use medication or a speculum to prevent eye movement
- With the help of a microscope, use extremely tiny instruments to make a small opening in the sclera. The created hole acts as a passageway for aqueous humor. The surgeon also has the option of using an erbium YAG laser or Holmium laser to create the opening
- Apply an antimetabolite medication to minimize the risk of closure of the new drainage channel. The channel can close when new tissue grows
The sclerostomy hole created allows aqueous humor to flow through and form a filtration bleb on the eye's upper surface. The aqueous humor can now flow through in a controlled manner.
In enzymatic sclerostomy, a newer technique, the surgeon will:
- Apply collagenase, an enzyme, to the eye to increase the release of aqueous humor. The surgeon uses an applicator attached to the eye with tissue glue to apply the collagenase. The applicator is left on for 22-24 hours before being removed.\
Risks & Complications
The risks and complications of a sclerostomy may include the following:
- Bleb leak or failure which can occur even years after surgery
- Though extremely rare, a sclerostomy can lead to central vision loss
- Cataract formation which can occur in the first five years after surgery
- Hypotony (low IOP) which can result in failure of the bleb and subsequent formation of a cataract
- Suprachoroidal hemorrhage (massive bleeding behind the retina) which can occur intraoperatively or postoperatively
- The created hole in the sclera may be blocked by new tissue growth requiring a repeat sclerostomy if necessary
- Hyphema (accumulation of blood in the anterior chamber) which usually manifests in the first two to three days following the procedure. Corticosteroid medications will help to reduce inflammation
- Infection which develops in the bleb before spreading to the interior of the eye. The infection may come with redness in the eye, blurry vision, discharge, and watery eyes. An infection can lead to loss of vision; therefore, it must be treated promptly
Aftercare & Recovery
The surgeon prescribes certain medications to prevent infection, reduce inflammation, and manage pain. Blurry vision may persist for about a month, but a patient can go to work the day after surgery. However, driving is discouraged until vision has completely normalized. It takes about six weeks for complete recovery to take place.
The patient will have frequent check-ups in the initial weeks after the procedure. The first follow-up appointment is after 24 hours and then weekly for the next several weeks.
The patient should wear eyeglasses in the daytime and use an eye shield (on the operated eye) for the night. S/he should also avoid rubbing or wetting the operated eye. The patient must steer clear of heavy lifting and other strenuous activities.
Research indicates that approximately 80-90% of patients who undergo a sclerostomy have their eye pressure effectively lowered. Patients who have not undergone previous ocular surgery record the most success.
According to researchers, enzymatic sclerostomy helped reduce IOP in 80% of the subjects, and none developed any systemic complication.