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Biomedical subjects

W F March

Publications and source records attributed to W F March.

At least 19 recordsLinked to original sources
PubMed1992

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.

Adult↗
PubMed1990

Laser sclerostomy by pulsed-dye laser and goniolens.

We describe an ab-interno laser sclerostomy procedure using the method termed dye-enhanced ablation with a slit-lamp delivery system and special goniolens such that only the laser light beam penetrates the anterior chamber. The procedure uses a microsecond-pulsed-dye laser emitting at 666 nm and iontophoresis of methylene blue dye (absorption of 668 nm) into the sclera at the limbus to enhance the absorption of the laser light. We compared the number of pulses needed to perforate excised human sclera at pulse durations of 1.5, 20, and 300 microseconds. Pulse durations of 1.5 and 20 microseconds required 20 pulses or fewer to perforate excised human sclera with pulse energies of 75 to 100 mJ. The ab-interno laser sclerostomy procedure was performed in 54 eyes of Dutch-belted rabbits with pulse durations of 1.5 or 20 microseconds and a 100- or 200-microns incident spot diameter delivered using a CGF goniolens. Full-thickness fistulas were successfully created at both pulse durations in approximately 80% of eyes treated. A range of three to 25 pulses was required to perforate sclera with slightly fewer pulses and lower pulse energies at 1.5 microseconds compared with 20 microseconds. There were no significant complications from the procedure. This technique could permit filtration surgery to be performed on an outpatient basis.

Animals↗
PubMed1987

Safety of high-energy neodymium:YAG laser pulses in YAG sclerostomy.

YAG sclerostomy was performed in 15 eyes of nine cynomolgus monkeys. Individual pulse energies ranged between 10 and 135 millijoules. Total pulse energy ranged between 2,000 and 36,000 millijoules in order to test the extreme range of energy that might be required. Both acute effects and chronic effects were studied in the corneal endothelium, the lens capsule, the iris, the ciliary body, the retina, and the sclera. Techniques included flat preparations of the corneal endothelium, paraffin sections for light microscopy, and scanning and transmission electron microscopy. Our conclusion is that individual pulse energies of up to 135 millijoules with a total of up to 36 joules of energy are safe in monkey eyes when performing YAG sclerostomy.

Animals↗
PubMed1987

Silver oxide in YAG sclerostomy.

YAG sclerostomy is a filtering procedure performed entirely with the neodymium:YAG laser through a goniolens as an alternative to trabeculectomy in the treatment of glaucoma. Extremely large pulse powers have been required in the past to complete the procedure. We found that an injection of silver-stabilized protein intrasclerally prior to the procedure makes it possible to perform the procedure with low total power.

Animals↗
PubMed1986

Laser-induced glaucoma in rabbits.

Argon laser energy was applied to the trabecular meshwork of pigmented rabbits in an attempt to develop an animal model of 'glaucoma'. Laser energy was varied to determine the optimal level needed to produce sustained ocular hypertension. An initial response of ocular hypertension followed by hypotension was observed in all of the animals tested. Approximately half of the laser-treated rabbits developed a secondary buphthalmus and sustained ocular hypertension. In these animals outflow facility was decreased by approximately 60%. Histologic examination at 4- and 8 weeks after laser treatment demonstrated a wound-healing response resulting in closure of the intertrabecular spaces and obstruction of outflow to injected carbon particles. Optic nerve cupping and a loss of ganglion cells were also observed. Topical application of L-timolol (0.5%), pilocarpine (2.0%) and forskolin (1.0%) were found to be effective in decreasing intraocular pressure in the laser-treated, hypertensive eye with no significant effect in control non-laser-treated eyes, suggesting that this model can be a useful tool for screening potential antiglaucoma medications.

Animals↗
PubMed1985

Histologic study of a neodymium-YAG laser sclerostomy.

A glaucoma filtering procedure was performed with the YAG laser in an eye to be enucleated for malignant melanoma. Scanning electron microscopic examination shows the extent and position of the incision and the effects of the procedure on the cornea. To our knowledge, this article represents the first report of complete perforation of the sclera in a living human eye with the use of a laser alone.

Cornea↗
PubMed1985

Neodymium-YAG laser sclerostomy in primates.

A one-stage sclerostomy procedure was performed "noninvasively" in four cynomolgus monkeys solely with the neodymium-YAG laser. The neodymium (Nd)-YAG laser was focused, for the most part, a few diopters behind the focus of the helium-neon aiming beam. This enabled optical breakdown to occur entirely within the sclera to produce a perforating micropuncture of the scleral tissue. Two monkeys were treated with higher energy (23 and 24 joules) and two were treated at lower energy levels (12 and 14 joules). An immediate reduction of intraocular pressure in the treated eye was associated with a significant increase in outflow facility. The sclerostomy remained patent for more than 180 days, as determined by tonography and histologic examination. Scanning electron microscopic examination of the cornea revealed no significant damage to the central cornea or to tissue adjacent to the visual axis in any of the treated eyes. However, there was some endothelial cell loss at the site of the laser treatment at the peripheral cornea and in the area immediately posterior to the incision; there was also a focal break in Descemet's membrane.

Animals↗
PubMed1985

Ibuprofen in the treatment of uveitis.

Ibuprofen has gained widespread acceptance for the treatment of rheumatoid arthritis and other inflammatory disorders. We have used ibuprofen in the control of both anterior and posterior uveitis and have found it to be effective in the control of these disorders.

Administration, Oral↗
PubMed1985

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.

Contact Lenses↗
PubMed1984

Acute intraocular pressure elevation produced by argon laser trabeculoplasty in the cynomolgus monkey.

The short-term effect of argon laser trabeculoplasty (ALT) was studied in a nonhuman primate model. The ALT treatment produced a consistent intraocular pressure elevation in the treated eye for eight hours. A statistically significant indomethacin-resistant increase in aqueous humor protein concentration was also observed. Morphologic observations using light microscopy and scanning and transmission electron microscopy revealed evidence of a fibrinous material covering the trabecular openings four hours after ALT. Cells and tissue debris appeared to be trapped in this fibrinlike net and may be the cause of the acute rise in IOP. Twenty-eight hours after ALT, the fibrin net was shown to be discontinuous, with fewer cells and less debris present. These acute morphologic alterations were not seen in control eyes or the laser-treated eyes observed later.

Animals↗