Diurnal fluctuations of intraocular pressure in EX-Press Valve Blebs in Glaucoma Patients

Intraocular pressure (IOP) reduction is the mainstay of glaucoma management. (1) Open-angle glaucoma (OAG) is generally managed by decreasing the intraocular pressure (IOP) to a level that the physician believes will prevent further glaucomatous damage. However, in a significant proportion of patients, the visual fields continue to deteriorate in spite of office pressures within the range of normal values (8). It has been suggested that the progressive damage in some cases could be caused by peaks of IOP or diurnal IOP variability not detected by tonometry during office hours. It is possible that certain drugs or surgical interventions are more effective than others in dampening these fluctuations. The purpose of our study is to compare the diurnal IOP fluctuations in glaucoma patients treated with medications or Ex-press filtration surgery.

Diurnal fluctuations of intraocular pressure in EX-Press Valve Blebs in Glaucoma Patients

Department of Ophthalmology, Hillel-Yaffe Medical Center, affiliated with the Bruce Rappaport School of Medicine, The Technion, Haifa, Israel

Introduction:

Intraocular pressure (IOP) reduction is the mainstay of glaucoma management. (1) Medication alone is sometimes not sufficient to reduce excessively high IOP, and pharmaceutical intolerance may develop or damage can occur to the optic nerve, warranting surgical intervention. (2) The filtering bleb is considered to be the cornerstone of IOP control after glaucoma filtration surgery drainage device implantation. (3) It enables the flow of the aqueous humor from the anterior chamber to the subconjunctiva, episclera, sclera and choroid, thereby lowering the IOP. (4-6) Filtration and drainage devices, such as the EX-Press device (Alcon Laboratories, Fort Worth, Texas, USA), offer a surgical alternative to glaucoma medical therapy. (7) Open-angle glaucoma (OAG) is generally managed by decreasing the intraocular pressure (IOP) to a level that the physician believes will prevent further glaucomatous damage. However, in a significant proportion of patients, the visual fields continue to deteriorate in spite of office pressures within the range of normal values (8). It has been suggested that the progressive damage in some cases could be caused by peaks of IOP or diurnal IOP variability not detected by tonometry during office hours. (9, 10) In another study, Asrani et al. (11) showed that IOP fluctuations are an independent risk factor in patients with glaucoma and as such may need to be treated specifically. It is possible that certain drugs or surgical interventions are more effective than others in dampening these fluctuations. The purpose of our study is to compare the diurnal IOP fluctuations in glaucoma patients treated with medications or Ex-press filtration surgery.

Materials and Methods The study will include 20 open-angle glaucoma (OAG) patients underwent Ex-Press filtration surgery, and 20 OAG patients treated with medications alone. All patients will have 12 IOP measurements with 2 hours interval, starting at 10 AM until 10 AM of the following morning.

ICARE® PRO tonometer (Icare Finland Oy, Espoo, Finland) will be used for the measurement of IOP. The rebound motion of its light weighted probe will be recorded during contact of the probe with the cornea. (12, 13) The rate of deceleration of the probe is a function of IOP. The ICARE® PRO has a built-in inclination sensor that allows downward measurement of the eye in the supine position as well as in the normal upright sitting position. ICARE® PRO allows for measurement of IOP in the seated and supine positions. During IOP recording, patients will be supine or upright, and the tip of the probe will be applied perpendicular to the cornea. Two markers engraved on the piston of the probe indicated its ideal positioning. The reliability of the measurement is displayed on the ICARE® PRO tonometer screen and guided our measurements.

Fluctuations in IOP will be compared between the Ex-press filtration surgery eye and the fellow (intra-group comparison). Inter-group comparison of IOP fluctuation will be performed between the Ex-press filtration surgery eye and medically treated eye of different patients.

Inclusion Criteria: .

• Glaucoma patients that underwent EX-PRESS surgery

Exclusion Criteria:

• Angle closure glaucoma
• Neovascular glaucoma
• High refractive error

The study will include 20 open-angle glaucoma (OAG) patients underwent Ex-Press filtration surgery, and 20 OAG patients treated with medications alone.