Histology after lamellar keratoplasty and corneal excimer laser ablation.

PURPOSE: To correlate clinical and histological findings after lamellar keratoplasty, phototherapeutic keratectomy, and application of a donor lenticule on a human cornea. METHODS: A cornea was obtained during penetrating keratoplasty. The specimen was fixated, dehydrated and embedded in Epon resin. The tissue was cut in 0.5-microm-thick semi-thin sections, stained with toluidine blue, and studied with light microscopy. RESULTS: The central part of the photoablated cornea, which was covered by the donor lenticule, did not differ from a normal cornea. Peripherally, a hazy ring was found clinically. Histology showed an irregular epithelium. Where it was thickened, the epithelium was hyperplastic and showed an increased number of cell layers. In the hazy region, Bowman's layer was absent, indicating that the donor lenticule did not cover this part of the photokeratectomized cornea. The anterior-most part of the corneal stroma was vacuolized and contained amorphous extracellular material; swollen keratocytes were present in this region. Beneath this layer, collagen lamellae were wavy and interwoven and keratocytes were increased in number, appeared swollen, and some had assumed an atypical shape. Peripheral to the haze, the cornea was clear. Histologically, the epithelium was irregular and hyperplastic, Bowman's layer was absent, and stromal collagen lamellae were abnormally organized, but no vacuolization was found. CONCLUSIONS: The formation of haze after excimer laser photokeratectomy can be minimized if the ablated stroma is covered by a corneal lenticule.

Comparison of objective and subjective refraction before and after laser in situ keratomileusis.

PURPOSE: To compare the accuracy and reliability of objective and subjective refractions before and after laser in situ keratomileusis (LASIK) for myopia, hyperopia, and astigmatism. SETTING: Augenchirurgie und Laserzentrum Hochrum, Innsbruck, Austria. METHODS: In this prospective study, the objective refraction obtained with the Nidek AR-K 900 autorefractor was compared with the subjective refraction in 159 eyes (125 with myopia and 34 with hyperopia) operated on with 2 different lasers. Refractions were done before and 6 months after LASIK. RESULTS: Preoperatively, the objective and subjective refractions correlated better in eyes with low myopia than in those with high myopia (P < .01). Postoperatively, objective refraction was less accurate and reliable than preoperatively. The difference between the objective and subjective spherical refractions was statistically significant (P < .0001) after LASIK in eyes with hyperopia. The correlation between the objective and subjective cylindrical refractions was stronger preoperatively. Especially after LASIK for hyperopia, the objective refraction did not reliably assess the magnitude and axis of the cylinder. The preoperative refractive error did not significantly affect the preoperative and postoperative difference between the objective and subjective refractions or the change between the preoperative and postoperative mean differences. The type of excimer laser used significantly affected the difference between the objective and subjective refractions. CONCLUSIONS: Especially after LASIK for hyperopia, the objective refraction determined with the Nidek AR-K 900 autorefractor delivered erroneous results, which have implications for postoperative care and preoperative measurements for ocular surgery such as enhancement procedures or cataract surgery.

[Laser in situ keratomileusis (LASIK) for correction of myopia and astigmatism]. / Laser-in-situ-Keratomileusis (LASIK) zur Myopie- und Astigmatismuskorrektur.

PATIENTS AND METHODS: In order to better define the potential advantages and risks of laser in situ keratomileusis (LASIK), we designed a prospective study including 73 eyes. RESULTS: After 6 months, 62 eyes were examined. Myopia was corrected from -6.10 +/- 3.12 (mean +/- standard deviation) to +0.04 +/- 0.66 D, with 54 eyes (87.1%) being within +/- 1.00 D of emmetropia. Astigmatism was corrected from -1.07 +/- 1.02 to -0.32 +/- 0.89 D. Uncorrected visual acuity was 0.5 or better in 59 eyes (95.2%) and 1.0 or better in 27 eyes (43.5%) 6 months postoperatively. More than one line in best-corrected visual acuity was lost by 6 eyes (9.7%), with most of these eyes being highly myopic. There was no change or a gain in lines in best corrected visual acuity in 42 eyes (66.1%). Intraoperative complications arose in two eyes (2.7%); in one eye, visual acuity was temporarily decreased. More treatments were performed in 7 eyes (9.6%). Postoperatively, no haze, scars or central islands were detected. Patient satisfaction after LASIK was high: 97.3% were pleased or very pleased with the result. CONCLUSIONS: In conclusion, LASIK is effective in the correction of myopia and myopic astigmatism. Although complications more frequently occurred in the correction of higher refractive errors, LASIK seems to be relatively safe compared with other refractive methods.

Laser in situ keratomileusis for myopia and myopic astigmatism.

PURPOSE: To evaluate the precision and safety of myopia and astigmatism correction using laser in situ keratomileusis (LASIK). SETTING: Augenchirurgie und Laserzentrum Hoch-Rum (Sanatorium der Kreuzsch-western), Innsbruck, Austria. METHODS: In this prospective study, LASIK was performed on 66 eyes of 39 patients with myopia ranging from 1.50 to 16.00 diopters (D). Astigmatism, ranging from -0.00 to -3.00 D, was treated simultaneously. Surgery was performed with the Chiron Keracor 117 excimer laser and the Chiron Automated Corneal Shaper microkeratome. During the 6 month follow-up, manifest refraction as well as best corrected and uncorrected visual acuities were measured; corneal topographies were produced and slitlamp biomicroscopy was performed. Changes in visual acuity and corneal topography were evaluated. RESULTS: After 6 months, mean myopia had decreased from 6.78 D +/- 3.48 (SD) to 0.40 +/- 0.98 D. Fifty-one of 63 eyes (81.0%) were within +/- 1.00 D of spherical emmetropia and 61 of 63 (96.8%) within +/- 1.00 D of cylindrical emmetropia. Uncorrected visual acuity improved in all eyes; it was 20/40 or better in 82.5% 6 months postoperatively. Best corrected visual acuity did not change in most eyes; 9.5% lost two or more Snellen lines. No central islands or corneal scars were detected postoperatively. Haze was noted in only 6 eyes (9.1%); it was transient and less than grade 1. No sight-threatening complications occurred intraoperatively. CONCLUSION: Laser in situ keratomileusis was an exact and predictable procedure for correcting low, moderate, and high myopia and myopic astigmatism.

Laser in situ keratomileusis after automated lamellar keratoplasty and penetrating keratoplasty.

We present three patients who had laser in situ keratomileusis (LASIK) after corneal surgery as follow: 15 months after automated lamellar keratoplasty (ALK) for hyperopia, 6 months after ALK for hyperopia, and 2 years after penetrating keratoplasty (PKP). Although the first case was uneventful, intraoperative complications arose in the second case because the connection of the ALK-related flap to its stromal bed was insufficient. In the third case, the refractive error caused by PKP was corrected as shown by corneal topography and visual acuity measurement. In conclusion, LASIK after PKP can be considered a precise and safe procedure if 2 to 3 years pass between the procedures. An interval of 6 months between ALK and LASIK was too short, whereas 15 months after ALK for hyperopia, LASIK was performed without problems and delivered a good result.