Refractive outcome following radial keratotomy and combined radial and astigmatic keratotomy

Penetrating and Intrastromal Corneal Arcuate Incisions in Rabbit and Human Cadaver Eyes: Manual Diamond Blade and Femtosecond Laser-Created Incisions

OBJECTIVES

To compare morphologic differences between freehand diamond or femtosecond laser-assisted penetrating and intrastromal arcuate incisions.

METHODS

Freehand diamond blade, corneal arcuate incisions (180° apart, 60° arc lengths) and 150 kHz femtosecond laser (80% scheimpflug pachymetry depth corneal thickness) arcuate incisions were performed in rabbits. Intrastromal arcuate incisions (100 μm above Descemet's membrane, 100 μm below epithelium) were performed in rabbit corneas (energy 1.2 μJ, spot line separation 3 × 3 μm, 90° side cut angle). Eyes were examined by slit lamp and light microscopy up to 47 days post-procedure. Freehand diamond blade penetrating incisions, and femtosecond laser penetrating and intrastromal arcuate incisions (energy 1.8 μJ, spot line separation 2 × 2 μm) were performed in cadaver eyes. Optical coherence tomography was performed immediately after surgery and the corneas were fixed for light scanning and transmission electron microscopy.

RESULTS

The rabbit model showed anterior stromal inflammation with epithelial hyperplasia in penetrating blade and laser penetrating wounds. The laser intrastromal and penetrating incisions showed localized constriction of the stromal layers of the cornea near the wound. In cadaver eyes, penetrating wound morphology was similar between blade and laser whereas intrastromal wounds did not affect the cornea above or below incisions.

CONCLUSION

Penetrating femtosecond laser arcuate incisions have more predictable and controlled outcomes shown by less post-operative scarring than incisions performed with a diamond blade. Intrastromal incisions do not affect uncut corneal layers as demonstrated by histopathology. The femtosecond laser has significant advantages in its ability to make intrastromal incisions which are not achievable by traditional freehand or mechanical diamond blades.

Implantation of spheric phakic posterior chamber intraocular lenses in astigmatic eyes

PURPOSE

To evaluate the simultaneous correction of spherical and cylindrical ametropia through implantation of phakic posterior chamber (PC) intraocular lenses (IOLs) combined with a limbal incision.

SETTING

Eye Department, Schlosspark-Klinik, Charité University Berlin, Berlin, Germany.

METHODS

In 5 hyperopic and 7 myopic eyes with varying astigmatic measurements, a refractive correction was achieved by implanting phakic PC IOLs (Staar Surgical Co.) and performing limbal incisions of different lengths. The incisions were placed approximately 1.0 mm from the limbus with a mean depth of 600 microm and a length of 6.0 mm +/- 0.9 (SD). The phakic PC IOLs were implanted after the limbal incisions were placed.

RESULTS

In the 5 hyperopic eyes, the astigmatism decreased from 2.7 diopters (D) preoperatively to 0.5 D at a mean of 7.5 +/- 1.7 months without alteration of the axis of highest bowing. In the 7 myopic eyes, it decreased from 2.2 D preoperatively to 0.7 D at 7.2 +/- 2.6 months. In 3 hyperopic eyes and 1 myopic eye, the limbal incisions were repeated.

CONCLUSIONS

The observed mean postoperative spherical equivalent was close to emmetropia. Repeat incisions were necessary in eyes exhibiting astigmatism greater than 2.5 D. The advantage of limbal incisions in combination with phakic PC IOL implantation is demonstrated not only by the astigmatic reduction but also by the axis stability. It will be interesting to see whether toric phakic lenses can achieve the same postoperative results, especially in axis stability and reduction of higher degrees of astigmatism.

Advances in refractive surgery: 1975 to the present

PURPOSE

To review the major advances in the field of refractive surgery occurring over the past 25 years.

METHODS

Literature review.

RESULTS

The major developments in refractive surgery over the past 25 years are reviewed.

CONCLUSIONS

The past 25 years have witnessed great changes in refractive surgery. As a result of advancements in technology, instrumentation, and technique, we have seen improvements in the treatment of all types of ametropias. In this article, we review some of the successes and failures of the past quarter-century.