SCLEROSTOMY GLAUCOMA SURGERY 2

Diagnosis
Open-angle glaucoma is not always diagnosed promptly because it is insidious in onset, which means that it develops slowly and gradually. Unlike closedangle glaucoma, open-angle glaucoma rarely has early symptoms. It is usually diagnosed either in the course of an eye examination or because the patient has noticed that they are having problems with their peripheral vision— that is, they are having trouble seeing objects at the side or out of the corner of the eye. In some cases the patient notices that he or she is missing words while reading; having trouble seeing stairs or other objects at the bottom of the visual field; or having trouble seeing clearly when driving. Other symptoms of open-angle glaucoma may include headaches, seeing haloes around lights, or difficulty adjusting to darkness. It is important to diagnose open-angle glaucoma as soon as possible because the vision that has been already lost cannot be recovered. Although open-angle glaucoma cannot be cured, it can be stabilized and controlled in almost all patients. Because of the importance of catching open-angle glaucoma as early as possible, adults should have their eyes examined every two years at least.

HIGH-RISK GROUPS.
Not everyone is at equal risk for glaucoma. People with any of the risk factors listed below should consult their doctor for advice about the frequency of eye checkups:
• Age over 40 (African Americans) or over 60 (other races and ethnic groups).
• Ocular hypertension. The normal level of IOP is between 11 mm Hg and 21 mm Hg. It is possible for people to have an IOP above 21 mm Hg without signs of damage to the optic nerve or loss of visual field; this condition is referred to as ocular hypertension. Conversely, about one out of six of patients diagnosed with open-angle glaucoma have so-called normal-tension glaucoma, which means that their optic nerve is being damaged even though their IOP is within the “normal” range. Ocular hypertension does, however, increase a person’s risk of developing glaucoma in the future.
• Family history of glaucoma in a first-degree relative. As of 2003, at least six different genes related to glaucoma have been identified.
• An unusually thin cornea (the clear front portion of the outer cover of the eye). A recent National Eye Institute (NEI) study found that patients whose corneas are thinner than 555 microns are three times as likely to develop glaucoma as those whose corneas are thicker than 588 microns.
• Extreme nearsightedness. People who are very nearsighted are two to three times more likely to develop glaucoma than those who are not nearsighted. ,
• Diabetes.
• History of traumatic injury to the eye or surgery for other eye disorders .
• Use of steroid medications.
• Migraine headaches or sleep-related breathing disorder.
• Male sex.

Some patients should not be treated with filtration surgery. Contraindications for a sclerostomy include cardiovascular disorders and other severe systemic medical problems; eyes that are already blind; or the presence of an intraocular tumor or bleeding in the eye.
DIAGNOSTIC TESTS. Ophthalmologists use the following tests to screen patients for open-angle glaucoma:
• Tonometry.
Tonometry is a painless procedure for measuring IOP. One type of tonometer blows a puff of pressurized air toward the patient’s eye as the patient sits near a lamp; it measures the changes in the light reflections on the patient’s corneas. Another method of tonometry involves the application of a local anesthetic to the outside of the eye and touching the cornea briefly with an instrument that measures the fluid pressure directly.

• Visual field test.
This test measures loss of peripheral vision. In the simplest version of this test, the patient sits directly in front of the examiner with one eye covered. The patient looks at the examiner’s eye and indicates when he or she can see the examiner’s hand. In the automated version, the patient sits in front of a hollow dome and looks at a central target inside the dome. A computer program flashes lights at intervals at different locations inside the dome, and the patient presses a button whenever he or she sees a light. At the end of the test, the computer prints an assessment of the patient’s responses.

• Gonioscopy.
Gonioscopy measures the size of the angle in the anterior chamber of the eye with the use of a special mirrored contact lens. The examiner numbs the outside of the eye with a local anesthetic and touches the outside of the cornea with the gonioscopic lens. He or she can use a slit lamp to magnify what appears on the lens. Gonioscopy is necessary in order to distinguish between open- and closed-angle glaucoma; it can also distinguish between primary and many secondary glaucomas.

• Ophthalmoscopic examination of the optic nerve.
An ophthalmoscope is an instrument that contains a perforated mirror as well as magnifying lenses. It allows the examiner to view the interior of the eye. If the patient has open-angle glaucoma, the examiner can see a cupshaped depression in the optic disk.

Newer diagnostic devices include a laser-scanning microscope known as the Heidelberg retinal tomograph (HRT) and ultrasound biomicroscopy (UBM). UBM has proved to be a useful method of long-term follow-up of sclerostomies.

Preparation
Preparation for a sclerostomy begins with the patient’s decision to undergo incisional surgery rather than continuing to take medications or having repeated laser procedures. Three factors commonly influence the decision: the present extent of the patient’s visual loss; the speed of visual deterioration; and the patient’s life expectancy. With regard to the procedure itself, patients may be asked to take oral antibiotic and anti-inflammatory medications for several days prior to surgery.