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S J Bechara

Publications and source records attributed to S J Bechara.

10 recordsLinked to original sources
PubMed1999

Corneal topography in asymptomatic family members of a patient with pellucid marginal degeneration.

PURPOSE: To report corneal topographic patterns in asymptomatic family members of a patient with pellucid marginal degeneration. METHODS: Computer-assisted corneal topography was used to study the corneas of five family members of a patient with pellucid marginal degeneration. RESULTS: In all five asymptomatic family members, corneal biomicroscopy was normal. Corneal topography, however, showed various abnormalities in different members of this family, particularly a topographic pattern suggesting keratoconus in one family member and a topographic pattern suggesting pellucid marginal degeneration in another family member. CONCLUSION: This study reinforces the hypothesis that corneal ectatic disorders may represent different manifestations of a clinical spectrum.

Adult↗
PubMed1996

Keratoconus in two pairs of identical twins.

We studied two sets of identical twins with keratoconus. The first 21-year-old pair had bilateral fully developed keratoconus and the second 35-year-old pair presented with early bilateral keratoconus detected by videokeratography. To our knowledge, these are the seventh and eighth sets of identical twins with keratoconus reported in the literature. They support the evidence of heredity as a factor in the etiology of keratoconus. Videokeratography proved to be a valuable adjunct for the detection of early keratoconus in a cornea with normal slit-lamp microscopy and photokeratoscopy results. Radial keratotomy in one eye produced an unstable refraction.

Adult↗
PubMed1995

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.

Algorithms↗
PubMed1992

Subepithelial fibrosis after myopic epikeratoplasty. Report of a case.

A 29-year-old man with a -22.00-diopter myopia in the right eye underwent a planar, nonfreeze myopic epikeratoplasty and postoperatively developed a central subepithelial opacity. The opacity recurred after two superficial keratectomies; finally, another epikeratoplasty was performed. Light microscopic examination of the original button showed that the epithelium was thickened, collagenous subepithelial fibrocellular tissue was present, and Bowman's layer was focally disrupted. The stroma was edematous and peripherally scarred with scattered keratocytes. Examination by transmission electron microscopy revealed keratocytes lying anterior and posterior to Bowman's layer. The subepithelial fibrocellular tissue corresponded to an area of a break in Bowman's layer and probably originated from the donor stroma. The break in Bowman's layer may have been caused by the microkeratome cuts, but its origin is not certain.

Adult↗
PubMed1987

Therapeutic use of contact lenses in alkali burns of the cornea.

Rabbit eyes submitted to alkali burns (in 1 N NaOH, 7 mm, for 2 min) were evaluated as to the effect of contact lenses on the corneal reepithelialization. Forty eyes were used, divided into two groups: 3 weeks and those observed for 5 weeks. In each group, 10 eyes received a contact lens while 10 served as controls. From the daily evaluation of the corneal surface as well as the microscopic examinations at the end of the two periods of observation, we concluded that hydrophilic contact lenses provide a beneficial effect on alkali burns of the cornea, reducing the incidence of epithelial defects to statistically significant levels.

Alkalies↗
PubMedDate not supplied

An independent evaluation of second generation suction microkeratomes.

BACKGROUND: Microkeratome designs for lamellar refractive surgery have changed significantly in recent years. Three microkeratome systems (Automatic Corneal Shaper (Steinway Instrument Company, Inc, San Diego, Calif), Draeger Lamellar Keratome (Storz Instrument GmbH, Heidelberg, Germany), and Microprecision test model (Microprecision Instrument Company, Inc, Phoenix, Ariz) were subjected to a concurrent and independent evaluation. METHODS: Three types of keratectomies (primary superficial stromal, secondary intrastromal, and primary deep stromal) were performed under identical conditions in human cadaver eyes. The resected discs and the beds were observed for uniformity, accuracy, centering, and smoothness. Scanning electron microscopy of the corneal beds and cutting blades was done. RESULTS: The three systems produced irregular surfaces with chatter lines that appeared least rough with the Draeger rotating machine. The average primary and secondary section diameters were undersized by 10% in all three systems. The average primary keratectomy thickness was more accurate with Steinway, but the variability was over 20 microns in all three systems. Regarding the average secondary keratectomy thickness, Steinway tended to cut thicker, whereas Draeger and Microprecision tended to cut thinner than attempted. The Draeger blade presented the smoothest edge. CONCLUSIONS: All three systems need substantial improvements to produce more accurate, reproducible, and smooth resections. More reliable methods to accurately measure the thickness of the resected cornea should be developed.

Cornea↗