Glaucoma research at Bascom Palmer
Tube Versus Trabeculectomy Study (TVT)
Bascom Palmer Eye Institute is one of the leading institutions (of fifteen participating centers) and is home to the Statistical Coordinating Center for the Tube Versus Trabeculectomy (TVT) Study. This study aims to improve our ability to care for glaucoma patients, and the results will guide us in recommending the best surgical procedures for our patients.
At present, two types of non-experimental glaucoma operations have been shown to be safe and effective surgical treatments. These procedures are known as tube shunt surgery and trabeculectomy. Both tube shunt surgery and trabeculectomy lower the intraocular pressure by creating a route for aqueous fluid to drain out of the eye.
Tube shunts (such as the Baerveldt glaucoma implant) —- A tube inserted into the eye shunts aqueous fluid to a silicone plate that is attached to the sclera (the white portion of the eye).
Trabeculectomy —- A hole, surgically created under a trap-door incision in the sclera, allows aqueous fluid to drain. Mitomycin, an anti-scarring medicine, is commonly applied at the operation site to reduce scarring that could close the trap door.
Similar success and complication rates have been reported for both tube shunt surgery and trabeculectomy when each has been studied separately. It is unclear if one operation is superior to the other in safety and efficacy. The TVT Study will examine the outcomes of a Baerveldt implant and trabeculectomy with Mitomycin C in patients who have had previous cataract surgery, glaucoma surgery, or a combination of both.
Ocular Hypertension Study
The Ocular Hypertension Study (OHTS), a major clinical investigation was conducted at 20 medical centers nationwide, including Bascom Palmer Eye Institute, which served as the Optic Nerve Reading Center. This study determined which patients would be better served by beginning treatment as soon as they are diagnosed with elevated intraocular eye pressure (thought to be the leading risk factor for the development of glaucoma) because their risk of developing optic nerve damage and visual field loss was so high.
The premise of OHTS is that high pressures may not lead to glaucoma. Researchers determined the risk factors for patients who have moderately elevated pressure, but normal optic nerves and visual fields.
Since only about one percent of patients per year who have elevated pressure and normal optic nerves and visual fields actually develop glaucoma, the critical issue is the identification of this small percentage. The National Eye Institute and the National Institutes of Health sponsored the significant work of the OHTS study.
In addition to evaluating the role of high intraocular pressure in the development of glaucoma, the OHTS study answered the following issues:
Is slightly elevated pressure normal in some patients?
Are African-Americans at greater risk for glaucoma damage?
Retinal Nerve Fiber Layer
Physicians and scientists at Bascom Palmer are focusing on developing advanced technologies to diagnose glaucoma. For the past twelve years, we have studied the optical properties of the retinal nerve fiber layer (RNFL) to aid doctors who are using RNFL as a diagnostic method. While visual field tests have long been the primary method for detecting glaucoma, recent studies show that examinations applying new optical technologies reveal more definitive diagnostic RNFL information.
Since nerve fiber loss may be the earliest sign of glaucoma, it is important to obtain precise, quantitative information on the condition of the RNFL. Researchers are evaluating two new technologies —- scanning laser polarimetry and optical coherence tomography —- to enhance the quality and reproducibility of the diagnostic information obtained.
Anterior Chamber Angle Anatomy
Through the support of a generous gift made possible by the Strobis Foundation, a high resolution ultrasonic biomicroscope (UBM) has been used to define the configuration of the drainage channels in a manner previously no possible. Based on quantitative analysis of anterior chamber angle, it may be possible to devise better diagnostic tests for patients at risk to devlop angle closure.
Pattern Electroretinogram (PERG)
The electroretinogram (ERG) for the eye can be thought of as being analogous to the electrocardiogram (EKG) for the heart. By studying the electrical activity pattern of the eye under different visual stimuli, scientists and clinicians at Bascom Palmer are designing new methods of diagnosing early glaucoma and for studying the progression of glaucoma.