[Curved lamellar keratotomy for correction of astigmatism. Experimental and initial clinical results]

The first experiments for surgical correction of higher astigmatism were reported more than 100 years ago. A lot of different procedures were strongly recommended at the beginning but then abandoned later on because they could not fulfill the expectations regarding the postoperative results and the complications. On the other hand, lamellar preparation of the cataract incision has been considered a major advance in ophthalmology. The main advantage of this incision is that it yields stable postoperative refraction as well as high mechanical stability very early (postoperatively). These findings prompted us to combine the advantages mentioned above with those of the arcuate transverse incision. In this report we present our experimental and clinical results with arcuate lamellar keratotomy.

Experiments were carried out on 22 cadaver bulbi. The optical zones ranged from 6 to 8 mm and the length of the arcuate incisions was between 2 and 7 mm. The clinical data presented here were obtained from 20 patients with a 4-week follow-up. These 20 patients had undergone cataract surgery previously with an induced astigmatism ranging from 2.5 to 5 D. Patients were treated with an optical zone of 7 mm or 8 mm. The length of the arcuate incision was 3 mm. All incisions were paired.

Our experiments (cadaver bulbi) showed an approximately linear decrease of the effect with increasing width of the optical zone and increasing are length. Our clinical results demonstrate that the astigmatism induced by our procedure (including potential overcorrection) was 3.41 +/- 1.33 D on the the first day postoperatively. All astigmatism was measured with the Zeiss keratometer. After 1 and 4 weeks the results were 3.98 +/- 1.35 and 3.71 +/- 1.29 D, respectively. The induced astigmatism also depended on the width of the optical zone. In the group with a 7 mm optical zone the induced astigmatism was 4.5 +/- 1.56 D after 4 weeks. This effect was remarkably higher than in the 8 mm group with an average of 3.35 +/- 0.94 D of induced astigmatism. There were no significant differences between visual acuity under glare conditions and the number of endothelial cells preoperatively and at 4 weeks follow-up, nor were there variations in refraction, depending on the time of day.

Due to the relatively high standard deviation of the induced astigmatism we must keep trying to make the results of our procedure more predictable.