Jonathan I. Macy

One-year results of excimer laser photorefractive keratectomy for myopia

BACKGROUND Excimer laser photorefractive keratectomy for the correction of myopia is presently under investigation in the United States by the Food and Drug Administration (FDA). The Phase II-B FDA study is being conducted on 75 normally sighted myopic eyes utilizing three currently available excimer lasers. This report presents the 1-year results on 12 myopic eyes treated with the VISX excimer laser system at the Ellis Eye Center at Cedars-Sinai Medical Center in Los Angeles under the Phase II-B FDA protocol. METHODS Twelve eyes of 12 patients with myopia between -1.75 and -5.00 diopters underwent 193 nm argon/fluoride excimer laser photorefractive keratectomy. The epithelium was mechanically removed, and fixation was accomplished with a suction ring which provided nitrogen flow across the corneal surface. The computer controlled corneal ablations were 5.00 mm in diameter and were accomplished with an iris diaphragm closing from large to small. RESULTS The preoperative spherical equivalent myopia was -3.50 D (SD = 1.02) and the postoperative myopia was -0.25 (SD = 0.48). Eleven of the 12 patients achieved an uncorrected visual acuity of 20/30 or better and were corrected to within +/- 0.50 D of emmetropia. All corneas demonstrated a mild reticular subepithelial haze which was barely visible at 1 year. There were no vision-threatening complications and none of the eyes experienced a loss of best corrected visual acuity. CONCLUSIONS In this small trial, the excimer laser appears to be capable of accurately changing the refractive power of the cornea for the correction of myopia with minimal side effects. Only when larger numbers of patients undergo the procedure will we be able to determine the safety and efficacy of photorefractive keratectomy as a refractive surgical procedure.

The Effect of Globe Fixation on Ablation Zone Centration in Photorefractive Keratectomy

PURPOSE For optimal vision, the ablation zone in photorefractive keratectomy should be centered over the entrance pupil. During ablation, the globe can be immobilized by the surgeon, with a suction ring around the corneoscleral limbus. Alternatively, the globe can be immobilized by patient fixation on a target, unassisted by the surgeon. We investigated which method results in better centration of the ablation zone over the entrance pupil, by using an objective, mathematical method to determine the ablation zone center. METHODS Forty-eight eyes from 48 patients who underwent photorefractive keratectomy by the two techniques were studied retrospectively. The centers of the ablation zones were objectively determined by a weighted center of mass algorithm applied to the preoperative minus postoperative difference maps. The validity of the objective method was confirmed by comparison to subjective estimates of ablation zone centers made by independent human observers. RESULTS The 19 eyes treated by surgeon fixation had an average decentration of the ablation zone of 0.63 +/- 0.31 mm (range, 0.01 to 1.00 mm), and the 29 eyes treated by patient fixation had an average decentration of 0.41 +/- 0.23 mm (range, 0.11 to 1.18 mm) (P = .027). CONCLUSIONS The center of the ablation zone can be determined mathematically from the topographic map, to avoid observer bias. In this study, unassisted patient fixation during photorefractive keratectomy produced more accurate centration of the ablation zone than did surgeon fixation and has the potential for maximizing the quality of vision postoperatively.

A Retrospective Study of Disposable Extended-wear Lenses in 100 Patients

A retrospective evaluation of 100 patients who wore disposable extended-wear contact lenses is presented. The patients were selected at random and were fitted with one of three lens brands approved for extended wear. There were 37 males and 63 females in the study. The mean age was 40.1 years (range, 14 to 76 years). Sixty-seven of the patients wore nondisposable extended-wear soft contact lenses before being fitted with disposable lenses. Complications were noted and included two instances of infectious ulcerative keratitis and six cases of peripheral corneal infiltrates. It is believed that the rate of complications is due to the ongoing hypoxic effect of prolonged use of extended-wear or other contact lenses and may be improved by providing a greater variety of lens fitting parameters. Disposable extended-wear lenses may be a reasonable means of vision correction in the appropriately selected patient and with proper follow-up. At the same time, caution should be exercised in the fitting and wear of disposable extended-wear lenses.

Mechanism of gastrointestinal hemorrhage in a case of mushroom poisoning by Chlorophyllum molybdites.

Abstract A twenty-seven year old female evaluated for gastrointestinal bleeding following ingestion of C. molybdites was found to have hematologic abnormalities consistent with disseminated intravascular coagulation. We suggest that the gastrointestinal hemorrhage was due to disseminated intravascular coagulation, a toxic effect of the mushroom.

Effect of Nitrogen Flow on Recovery of Vision After Excimer Laser Photorefractive Keratectomy Without Nitrogen Flow

BACKGROUND Excimer laser (VISX) photorefractive keratectomy was performed using nitrogen flowing through the ocular fixation ring. It was felt that eliminating nitrogen flow may provide faster early visual rehabilitation. METHODS Two groups of 50 consecutive eyes underwent photorefractive keratectomy with (N2 flow) and without (no N2 flow) nitrogen flow, and were evaluated at 1 month postoperatively. RESULTS There were more under- or overcorrections exceeding 1.00 diopter (D) in the N2 flow than in the no N2 flow groups. Eighteen eyes in the N2 flow and 11 in no N2 flow groups saw 20/50 or less, without correction. Fourteen eyes in the N2 flow and nine eyes in the no N2 flow groups lost two or more lines of best spectacle-corrected visual acuity. Four eyes in the N2 flow and none in the no N2 flow groups increased more than 1.00 D of astigmatism. CONCLUSION The elimination of nitrogen flow in photorefractive keratectomy performed with the VISX laser appears to improve visual results in the early postoperative period.

Broken Semiflexible Intraocular Lens Implant

The haptic of a semiflexible anterior chamber intraocular lens (Kelman Quadraflex) broke inside the eye of a 70-year-old man. No history of major eye or head trauma could be elicited from the patient. Clinical manifestations included inferior corneal edema progressing toward the optical axis resulting from a free-floating haptic segment of the lens implant inside the anterior chamber. A significant decrease in endothelial density was documented over a short period of time. The surgical management of this case included removal of the free-floating haptic segment, removal of the lens implant, penetrating keratoplasty, and vitrectomy. Final visual acuity was 20/70.

8. Orbital Cellulitis

Orbital cellulitis secondary to sinusitis has been the most common cause of proptosis in children. A case report is presented which emphasizes that the signs and laboratory findings in orbital cellulitis may be confusing, especially when modified by prior antibiotics. When orbital cellulitis is a possibility, adequate antibiotic therapy should be instituted while diagnostic studies are being performed. CT scanning is a new and useful modality for the evaluation of these patients, but cautious and experienced interpretation is essential. In patients who do not respond promptly to appropriate medical therapy, surgical intervention is indicated for drainage and biopsy.

A Retrospective Study of Disposable Extended Wear Lenses in 100 Patients: Year 3

We present the results of the third year of follow-up of a group of 100 patients wearing disposable contact lenses on an extended wear basis. Thirty-seven males and 63 females participated in the study. The mean patient age was 41.76 years (SD: 14.5), and the mean patient follow-up time was 37.73 months (SD: 5.25). Twenty-three patients were lost to follow-up. Most of those lost to follow-up decided to purchase their lenses at discount outlets. A case of recurrent corneal ulcers in a patient wearing lenses obtained from a discount outlet is described. A significant decrease in events defined as complications (14 events) was noted as compared with the second year (32 events) of the study. One corneal infiltrate and one corneal ulcer were noted. Disposable extended wear lenses may be a reasonable means of vision correction in the properly selected patient with appropriate follow-up provided by a well-trained eye care practitioner.

Update on excimer laser photorefractive keratectomy (PRK) at Cedars-Sinai Medical Center: two-year experience

Our two year experience with excimer laser photorefractive keratectomy for the correction of myopia on 160 eyes of 128 patients is described. All eyes were treated with a VISX Twenty- Twenty excimer laser, with the following parameters: radiant exposure 160 mJ/cm2, frequency 5 Hz, ablation zone diameter 5.0 to 5.5 mm, and stromal ablation rate 0.18 to 0.33 (mu) /pulse. A suction fixation ring was used in all cases either with nitrogen flow (79 eyes) or without nitrogen flow (81 eyes) across the cornea. Follow-up ranged from one month (152 eyes) to 24 months (12 eyes). The results are stable between 3 and 24 months with less than 0.25 D change in the mean postoperative spherical equivalents. In eyes with a follow-up of 6 to 24 months, 77% to 100% were 20/40 or better uncorrected, and 84% to 92% were corrected to within +/- 1 D of emmetropia. Further follow-up is needed to assess the long term safety and efficacy of the procedure.

Preliminary results of VISX excimer laser myopic photorefractive keratectomy at Cedars-Sinai Medical Center

Sixty-two eyes underwent excimer laser photorefractive keratectomy (PRK) for the correction of myopia at Cedars-Sinai-Medical-Center. The first group of 12 patients are presented with follow up data of ten months postoperatively. The second group of 50 patients are presented with follow up data of three months postoperatively. An in-depth comparison of pre and postoperative refractive data is presented. Comparisons between pre and postoperative corrected and uncorrected Snellen visual acuities are provided in order to asses the functional visual result of the procedure.