Biomedical subjects

D S Durrie

Publications and source records attributed to D S Durrie.

41 records · Page 3Linked to original sources

PubMedDate not supplied

Holmium:YAG laser thermokeratoplasty for hyperopia.

Holmium:YAG laser thermokeratoplasty (LTK), a procedure using a solid-state infrared laser to treat hyperopia, was performed on 10 patients in phase I and 16 patients in phase II--in a total of 29 eyes at the Hunkeler Eye Clinic. Phase II was redesigned after phase I results showed undercorrection and regression. The follow-up period ranged from 1 to 24 months (mean 10.9 months). A total of 79% of phase II patients were within +/- 1.00 D of intended correction at the 6-month visit. Looking at both phases together, no patients had J2 or better near vision preoperatively, but 75% had J2 or better at the 6-month visit. A total of 43% of eyes in phase II lost 1 line and 7% lost two lines of best spectacle corrected visual acuity due to induction of irregular astigmatism. The surgical challenges are to insure appropriate centration of the procedure about the optical axis. Concerns about regression and stability will be defined as these patients are followed through their 2-year visits.

Cornea↗

PubMedDate not supplied

Photorefractive keratectomy for myopia using a 4.5-millimeter ablation zone.

BACKGROUND: Argon fluoride (193 nm) excimer laser photorefractive keratectomy for myopia is under evaluation by the United States Food and Drug Administration. METHODS: We report a consecutive prospective series of 100 patients (one eye per patient) treated as part of the Phase IIB FDA-approved protocol, with 80 patients followed for 1 year. Patients' ages ranged from 21 to 62 years (mean, 35 years). The Summit Technology, Inc ExciMed UV200LA with a 4.5-mm diameter ablation was used. RESULTS: Baseline spherical equivalent refraction ranged from -2.00 to -6.90 diopters (D) (mean -4.60 D). Ninety-five percent of eyes reepithelialized by 72 hours. At 1 year, the difference between attempted and achieved correction was +/- 0.50 D for 42 eyes (53%) and +/- 1.00 D for 60 eyes (75%). During the first 6 months, there was a trend toward overcorrection and the majority of eyes showed some loss of initial refractive correction; 10 eyes (14%) changed by 1.00 D or more between 6 and 12 months. An uncorrected visual acuity of 20/25 or better was achieved by 50 eyes (63%) and 20/40 or better by 61 eyes (77%). Of the 10 eyes (12%) that lost two or more Snellen lines of spectacle-corrected or glare visual acuity, two had visual acuity of worse than 20/25. Central subepithelial corneal haze was absent to mild in 77 (96%) eyes at 12 months. CONCLUSIONS: Excimer laser photorefractive keratectomy as performed in this study was generally effective and safe in reducing simple spherical myopia. Further studies of the effect of a larger diameter ablation zone, smoother transitional corneal contours, and the effect of postoperative topical corticosteroids may lead to further improvements in outcome.

Adult↗

PubMedDate not supplied

Arcuate keratotomy for the correction of spherical hyperopia in human cadaver eyes.

BACKGROUND: A new experimental surgical technique to correct spherical hyperopia by steepening of the central corneal curvature was performed on human cadaver eyes. METHODS: Ten eyes were used in the study. All were pretreated with glycerin to ensure a uniform corneal thickness between .55 and .65 mm on ultrasonic pachometry. A constant intraocular pressure of approximately 30 to 40 mm Hg was maintained in each eye by the injection of saline into the vitreous cavity. This was verified by pneumotonometry. A vertical blade diamond knife was set at 100% of the thinnest of four paracentral readings. Each eye underwent preoperative computed topography. One set of five eyes had 12 incisions made following a 5.75-millimeter diameter Mendez hexagonal marker that included unconnected T incisions at each junction (ie, "Hex T" pattern). The other set of five eyes had four arcuate incisions made following a 6-millimeter diameter zone marker; each incision was 60 degrees in arc. Immediately after surgery, computed topography was repeated. RESULTS: The hexagonal keratotomy set of eyes had an average steepening of the cornea of 0.80 D with a range of -1.05 to + 4.38 D. The arcuate keratotomy set had an average steepening of +2.12 D with a range of +1.27 to +3.27 D. CONCLUSIONS: This study suggests arcuate keratotomy may be a more effective procedure in the correction of spherical hyperopia when compared with hexagonal keratotomy. The amount of corneal steepening achieved in a cadaver eye model may not be the same as when performed in vivo.

Cornea↗

PubMedDate not supplied

Holmium:YAG laser thermokeratoplasty for hyperopia and astigmatism: an overview.

The holmium:YAG laser can be used to perform corneal collagen shrinkage and treat refractive errors. Studies are underway for the treatment of hyperopia by shrinking collagen in the peripheral cornea, which produces central and paracentral steepening. There is initial overcorrection followed by a regression of effect postoperatively, which appears to stabilize 4 to 6 months postoperatively. Refinement of current nomograms and definition of the amount of expected regression will enhance its accuracy. The holmium:YAG laser may be superior to radial thermokeratoplasty with a hot needle. Nearly 100 years ago, Lans was the first to report that heating of the cornea could induce collagen shrinkage with resultant corneal curvature changes. Various collagen shrinkage procedures have evolved since then. To date, the most well-known form of collagen shrinkage involves the hot needle and a technique developed by Fyodorov to do radial thermokeratoplasty for hyperopia. This article will review the current state of holmium:YAG laser technology and the advantages it may provide over radial thermokeratoplasty.

Astigmatism↗

PubMedDate not supplied

Philosophy and technique for excimer laser phototherapeutic keratectomy.

Phototherapeutic keratectomy (PTK) with the excimer laser has been shown to be effective in removing anterior corneal pathology and smoothing surface irregularities. Blocking agents are important in PTK. The techniques we present seek to balance therapeutic effect and refractive error change. Successful PTK depends on thorough preoperative assessment and attention to intraoperative detail. Clinical research has demonstrated that the excimer laser is an effective tool, not only for correcting myopic refractive errors, but also for treating various types of anterior corneal pathology. We present our PTK techniques that reflect recent refinements.

Cornea↗