Picosecond neodymium:yttrium lithium fluoride (Nd:YLF) laser peripheral iridotomy.

PURPOSE: We evaluated the picosecond neodymium:yttrium lithium fluoride (Nd:YLF) laser for performing peripheral iridotomies of predetermined size and shape in various types of irides. METHODS: In the first part of the study, we determined operating parameters from performing 60 iridotomies in human cadaver eyes. Subsequently, using the parameters obtained in cadaver eyes, iridotomies were created in eyes of patients with primary angle-closure glaucoma. RESULTS: In the cadaver eyes, the optimal parameters were a rectangular cutting pattern of 0.3 x 0.3 mm, 500-microns cutting depth, 50-microns spot separation, 200 to 400 microJ of energy per pulse, 200 to 400 pulses per second, and no focal offset distance. In 18 eyes of 11 patients, iridotomies with well-defined margins and size were created. Minimal hemorrhage occurred intraoperatively in ten of 18 eyes (55.6%), which did not affect the outcome of the procedure. Increases of postoperative intraocular pressure at one hour averaged 3.5 +/- 5.1 mm Hg, with an increase of more than 10 mm Hg in three eyes (16.7%), and a maximum of 12 mm Hg. We observed no corneal or retinal damage. CONCLUSION: The picosecond Nd:YLF laser seems to be an effective instrument for reliably performing peripheral iridotomies of precise size and shape using low energy per pulse levels. This laser, unlike the argon laser, is successful independent of iris thickness or color and can easily make a larger iridotomy than is often possible with the Nd:YAG laser.

Gonioscopic ab interno Nd:YLF laser sclerostomy in human cadaver eyes.

We explored the potential of the picosecond Nd:YLF laser to perform gonioscopic ab interno sclerostomy in human cadaver eyes. Full-thickness sclerostomies were created in 12 such eyes and confirmed by external scleral and histopathologic examination. Optimum parameters for successful completion of a sclerostomy were: a rectangular pattern of 0.3 mm by 0.3 mm, a repetition rate of 1000 pulses per second, an energy-per-pulse of 400 mJ, and a spot separation between 10 and 50 microns, with no focal offset. The Nd:YLF laser reliably created successful gonioscopic sclerostomies with minimal adjacent thermal damage in human cadaver eyes.

A human cadaver eye model for anterior and posterior segment laser applications.

We have developed a cadaver eye model that allows anterior and posterior segment laser procedures to be performed under closely simulated in vivo conditions. The model consists of a reusable container with an artificial cornea with a refractive power and an anterior radius of curvature similar to those of the human cornea, and a fresh cadaver eye, prepared by removing the cornea and adjusting the biometric parameters to normal values. This cadaver eye model appears to be a valuable tool for teaching and practicing anterior and posterior segment laser procedures, as well as for research on new laser systems and applications.

A clinical evaluation of the potential acuity meter in 210 cases.

The potential acuity meter (PAM) has been reported to be a useful instrument for predicting postoperative visual acuity after cataract extraction surgery. In this study, 210 eyes were tested with the PAM before surgery, and the best postoperative visual acuity was obtained. The PAM accurately predicted the postoperative visual acuity to within three lines in 85.2% of the cases. Further, the PAM was able to predict whether or not an operation would be successful (success defined as a final visual acuity of 20/40 or better) in 91.6% of the cases. It was found that senile macular degeneration may cause false-positive tests (predicted acuity better than final acuity), and this should be watched for when the test is used. When the test is in error, the tendency is for the PAM to underestimate the final acuity rather than to overestimate.

Pseudophakic cystoid macular edema: a revised comparison of the incidence with intracapsular and extracapsular cataract extraction.

A previous study by one of the authors found no significant difference in the incidence of cystoid macular edema with an intracapsular cataract extraction and the implantation of an iris-supported posterior chamber optic lens, compared with the incidence of cystoid macular edema with an extracapsular extraction and the implantation of a Shearing lens. To test the validity of that conclusion, the charts of 686 patients operated on by one of the authors were reviewed. It was determined that the incidence of both transient and persistent cystoid macular edema was significantly higher in patients who had an intracapsular cataract extraction. Reasons for the contradictory findings are discussed.