Wayne F. March

Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study One Year After Surgery

The Prospective Evaluation of Radial Keratotomy (PERK) study is a nine-center, self-controlled clinical trial of a standardized technique of radial keratotomy in 435 patients who had physiologic myopia with a preoperative refraction between -2.00 and -8.00 diopters. The surgical technique consisted of eight incisions using a diamond micrometer knife with blade length determined by intraoperative ultrasonic pachymetry and the diameter of central clear zone determined by preoperative refraction. At one year after surgery, myopia was reduced in all eyes; 60% were within +/- 1.00 diopter of emmetropia; 30% were undercorrected and 10% were overcorrected by more than 1.00 diopter (range of refraction, -4.25 to +3.38 D). Uncorrected visual acuity was 20/40 or better in 78% of eyes. The operation was most effective in eyes with a refraction between -2.00 and -4.25 diopters. Thirteen percent of patients lost one or two Snellen lines of best corrected visual acuity. However, all but three eyes could be corrected to 20/20. Ten percent of patients increased astigmatism more than 1.00 diopter. Disabling glare was not detected with a clinical glare tester, but three patients reduced their driving at night because of glare. Between six months and one year, the refraction changed by greater than 0.50 diopters in 19% of eyes.

Inner Retinal Layer Thinning in Parkinson Disease

OBJECTIVE To quantify retinal thickness in patients with Parkinson disease (PD). METHODS Forty-five eyes of 24 PD patients and 31 eyes of 17 control subjects underwent a comprehensive ophthalmologic examination. We used optical coherence tomography to examine retinal thickness, separately quantifying the inner and outer retinal layers. Intraocular pressure was measured by Goldmann applanation tonometry. RESULTS The mean (SD) ages of the patients with PD and healthy subjects were 64.0 (6.5) years vs 63.5 (10.7) years (P = .77). The mean (SD) intraocular pressure was 13.6 (+/-2.7) mm Hg in the PD patients. No difference was found in either the superior or inferior outer retinal layer thickness of PD vs control eyes. The mean (SD) superior inner retinal layer thickness of PD vs control eyes was 88.79 (11.3) microm vs 103.5 (24.3) microm (P = .01), and the mean inferior inner retinal layer thickness was 89.83 (11.1) microm vs 104.0 (23.5) microm (P = .01). CONCLUSIONS The inner retinal layer is significantly thinner in PD patients than in healthy subjects. Idiopathic PD, distinct from glaucoma, needs to be considered in the differential diagnosis of retinal nerve fiber layer thinning.

Pathogenesis of Block of Rapid Orthograde Axonal Transport by Elevated Intraocular Pressure

Although axoplasmic flow blockage (AFB) with raised intraocular pressure (IOP) is well-established (1–11), its pathogenesis remains an enigma. AFB may be due to ischemia of the optic nerve fibers (6) or mechanical axonal compression (8). The present study was designed to determine whether the AFB is due to ischemia or mechanical compression of the optic nerve fibers in the optic nerve head.

Gonioscopic Ab Interno Laser Sclerostomy A Pilot Study in Glaucoma Patients

PURPOSE The purpose of this study is to evaluate the safety and efficacy of gonioscopic ab interno laser sclerostomy (GLS) in patients with glaucoma. METHODS The technique of GLS involves iontophoresis of methylene blue dye (1%) at the limbus to focally dye the sclera and to provide subsequent delivery of 10-microsecond pulsed laser energy to the dyed area through a goniolens. The laser emits at 660 nm, a wavelength that is maximally absorbed by the methylene blue dye. Patients were evaluated for fistula formation, intraocular pressure (IOP) reduction, and adverse sequelae. Thirty-eight treatments were performed in 35 eyes. RESULTS Successful complete sclerostomies were achieved in 21 eyes (55%), which was associated with an acute mean reduction in IOP of 23 mmHg. Mean preoperative IOP for all patients was 35 mmHg, and 1 hour after treatment it was reduced to 18.5 mmHg. In 4 of the 38 treatments, there was no acute IOP reduction, and these eyes were judged as failures. The mean follow-up time was 8.2 months with a maximum follow-up of 15 months. By 9 months, 50% of patients had an IOP of 22 mmHg or lower. The number of antiglaucoma medications decreased from 3.1 to 1.7 for all eyes over the 15-month follow-up period. Hyphemas (13%) were the only major complication, and these resolved spontaneously. In only one case did the IOP increase after the procedure. CONCLUSION The results of this trial indicate that GLS is technically feasible, and preliminary results of IOP control are promising.

Design of New Contact Lens for YAG Laser Filtering Procedures

A contact goniolens has been developed specifically for YAG laser filtering procedures both for use in unblocking failed surgical filtering procedures and for performing two-stage or one-stage YAG filtering procedures. The design concentrates the YAG energy and maintains a constant small angle with the cornea.

Proposal for a new contact lens for YAG laser posterior capsulotomies.

A contact lens designed for neodymium-YAG laser posterior capsulotomy which angulates the beam with respect to the posterior capsule is presented. This lens may minimize injury to the corneal endothelium.

Pathogenesis of acute ocular hypertension after laser trabeculoplasty

The effects of indomethacin on the acute rise of intraocular pressure (IOP) following argon laser irradiation of the iris and trabecular meshwork in pigmented rabbits have been studied. Acute pressure elevation of at least 12 mm Hg was noted in the experimental eye 15 minutes after photocoagulating either the iris or the angle meshwork. The pressure elevations lasted for more than two hours and were followed by a delayed hypotony at 24 hours. Prior treatment (1 hour) with indomethacin (30 mg/kg, IP) prevented the acute pressure rise following irradiation of the iris, but only partially blocked the pressor response after lasering the angle meshwork. These results suggest that prostaglandins (PG’s) are involved in mediating the IOP rise following iridotomy. In contrast, the role of PG’s in mediating the rise in IOP after lasering the trabecular meshwork in the rabbit remains unclear.The effects of indomethacin on the acute rise of intraocular pressure (IOP) following argon laser irradiation of the iris and trabecular meshwork in pigmented rabbits have been studied. Acute pressure elevation of at least 12 mm Hg was noted in the experimental eye 15 minutes after photocoagulating either the iris or the angle meshwork. The pressure elevations lasted for more than two hours and were followed by a delayed hypotony at 24 hours. Prior treatment (1 hour) with indomethacin (30 mg/kg, IP) prevented the acute pressure rise following irradiation of the iris, but only partially blocked the pressor response after lasering the angle meshwork. These results suggest that prostaglandins (PG’s) are involved in mediating the IOP rise following iridotomy. In contrast, the role of PG’s in mediating the rise in IOP after lasering the trabecular meshwork in the rabbit remains unclear.