Faculty Bibliography

The effect of the vasoactive peptide, endothelin, on facility of outflow, accommodation, and pupil diameter was measured in the monkey eye in vivo. Endothelin increased the outflow facility 22-71% at approximate anterior chamber concentrations ranging from 10(-10)-10(-7) M. Endothelin-induced accommodation was modest but consistent and statistically significant ranging from 1.61 to a maximum of 2.43 diopters at 10(-9) M and 10(-7) M endothelin, respectively. No change in pupil diameter was noted with any of the administered doses. These data demonstrate an action of endothelin on outflow facility and, together with prior evidence indicating the presence of endothelin receptors on the ciliary muscle, suggest that, like cholinergic agonists, the observed effects of endothelin on outflow facility may be mediated, at least in part, through an action on the ciliary muscle.

We investigated the effects of semiconductor diode laser contact transscleral cyclophotocoagulation in human cadaver eyes by gross examination, light microscopy, and scanning electron microscopy to determine optimum clinical treatment parameters. Irradiation was performed using a continuous-wave semiconductor diode laser with a fiber-optic probe. At 1.0 to 1.25 mm posterior to the limbus, spots were centered on the pars plicata by gross examination. Exposures of less than 2 J produced no visible damage. A 2- to 3-J exposure produced mild whitening of the ciliary processes, while 4- to 5-J exposures created more intense whitening of the pars plicata. Energies higher than 5 J frequently produced explosive tissue damage. Light microscopy of tissue treated with 1.8 to 6 J at 1.0 to 1.25 mm posterior to the limbus revealed coagulation necrosis of the nonpigmented and pigmented epithelium, with evidence of thermal coagulation of the ciliary stroma and stromal vasculature. Coagulation necrosis was more intense with longer exposure times. We found the optimum parameters for contact transscleral diode laser cyclophotocoagulation in cadaver eyes to be 3 to 4.5 J of energy delivered with the anterior edge of the probe 1.0 to 1.25 mm posterior to the limbus.

Topical carbonic anhydrase inhibitors MK-507 and sezolamide hydrochloride (previously known as MK-417) were compared in a double-masked, randomized, placebo-controlled study in 82 patients with bilateral primary open-angle glaucoma or ocular hypertension. MK-507 was given every 8 or 12 hours, sezolamide every 8 hours, or placebo every 8 or 12 hours for 4 days. Both drugs lowered intraocular pressure (IOP) substantially. MK-507 was somewhat more active than sezolamide, with a peak mean IOP reduction of 26.2% for MK-507 versus 22.5% for sezolamide, although the difference between the treatments was not statistically significant. These drugs may have potential in the treatment of glaucoma.

Advanced glaucoma in 140 eyes of 136 patients was treated with contact transscleral continuous wave neodymium:YAG (Nd:YAG) laser cyclophotocoagulation (CYC) with a sapphire-tipped probe. The anterior edge of the probe was placed 0.5 to 1.5 mm posterior to the limbus, using 7 to 9 W of power for 0.7 seconds with 32 to 40 applications, sparing the 3 and 9 o'clock meridians. Patients were studied prospectively. The mean preoperative intraocular pressure (IOP) of 36.7 +/- 0.97 mmHg decreased to 21.2 +/- 0.99 mmHg (P = 0.004) after treatment (mean follow-up, 3.2 +/- 0.35 months) for a mean decrease in IOP of 15.5 +/- 1.21 mmHg and a mean percent decrease of 39%. Forty-one eyes were followed 6 or more months (mean, 6.7 +/- 0.25 months). The CYC reduced IOP to 25 mmHg or less in 71% of eyes, to 22 mmHg or less in 62% of eyes, and to 19 mmHg or less in 49% of eyes. Maximum lowering of IOP occurred 1 week to 1 month after treatment and remained at that level through 6 months of follow-up. Retreatment was required in 11% of patients; only one patient was retreated more than once. Four patients treated with 9 W of power developed IOPs below 5 mmHg; two of these patients had an IOP of 0 mmHg. Other complications of therapy were minimal, and patients had little pain. There was no significant change in visual acuity. Early results of this newly available therapy are encouraging.