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At least 1,531 records · Page 85Linked to original sources
PubMedDate not supplied

Correction of astigmatism using positive and negative cylinder programs with the Nidek EC-5000 excimer laser.

BACKGROUND: The efficacy of a current program of positive cylinder treatment was evaluated and compared to a previous program of negative cylinder treatment. METHODS: The authors performed a comparative analysis of 123 eyes (72 patients) who underwent LASIK using the Nidek EC-5000 excimer laser with the formula developed by Chayet and the positive cylinder (71 eyes of 52 patients) and negative cylinder programs (52 eyes of 31 patients). RESULTS: A faster stabilization of correction and a marked reduction of stromal tissue ablated were obtained with the positive cylinder program than with the negative cylinder program. This was directly related to the amount of preoperative ametropia. CONCLUSION: The spectrum of ametropias that can be treated with LASIK is increased with the positive cylinder program because less tissue is ablated.

Astigmatism↗
PubMed2006

A correction formula for the real intraocular pressure after LASIK for the correction of myopic astigmatism.

PURPOSE: To create a correction formula to determine the real intraocular pressure (IOP) after LASIK considering the altered corneal thickness, corneal curvature, and corneal stability. METHODS: This prospective clinical trial comprised 101 eyes of 59 patients (34 women and 25 men) that underwent LASIK with a mean preoperative spherical equivalent refraction of -6.3 +/- 2.17 diopters (D) (-3.0 to -11.5 D). Mean patient age was 32 +/- 9 years. Preoperatively and 6 months postoperatively, IOP (by Goldmann applanation tonometry), keratometry (by topography), and central corneal thickness (CCT) (by ultrasound pachymetry) were evaluated. These parameters were measured in all patients between 8 and 11 o'clock in the morning. RESULTS: Due to the LASIK procedure, IOP was reduced from 16.5 +/- 2.1 mmHg (range: 12 to 22 mmHg) to 12.9 +/- 1.9 mmHg (range: 8 to 16 mmHg). Multiple linear regression analysis of the IOP values before and after LASIK showed a significant correlation between the measured IOP and CCT and keratometry values (R2=0.631; P<.001). After LASIK, the biomechanical bending strength of the cornea is reduced by the cut so that the measured IOP must be additionally corrected by 0.75 mmHg. An equation containing all three changes is given: IOP (real) = IOP (measured) + (540-CCT)/71 + (43-K-value)/2.7 + 0.75 mmHg. CONCLUSIONS: Intraocular pressure measurements after LASIK for the correction of myopia are inaccurate as a consequence of changes in CCT, corneal curvature, and corneal flap stability. After LASIK, the measured IOP should be corrected to avoid false low IOP applanation readings.

Adult↗
PubMedDate not supplied

[Comparative results evaluation of residual myopia and astigmatism correction after radial keratotomy by photorefraction keratectomy and laser specialized keratomileusis].

The results of correction of residual myopia by photorefraction keratectomy (PRK) (51 eyes) and laser specialized keratomileusis (LASIK) (36 eyes) after radial keratotomy (RK) are compared. The patients were observed for up to 12 months. After PRK, 7.3% patients developed late fleur of the cornea, evaluated by at least 2 points. The incidence of fleur directly depended on the value of residual myopia. After LASIK none of the patients developed such fleur. The best visual acuity (0.5 and higher without correction) was attained in 70.73% after PRK and RK, vs. 100% after LASIK. The results of photorefraction operations and severity of residual myopia after RK correlated. In residual myopia of up to -3 diopters the results of correction by PRK and LASIK were virtually the same. In residual myopia higher than -3 diopters, LASIK is preferable.

Adult↗