[Safety of the automated microkeratome for Sub-Bowman's Keratomileusis on the flat cornea]

Use of the One Use-Plus SBK (Sub-Bowman's Keratomileusis) automated microkeratome (Moria, Antony, France) has been shown to be safe, predictable and comfortable for the creation of thin corneal flaps with a smooth and regular stromal bed.

To evaluate the use of the Moria One Use-Plus SBK (Moria, Antony, France) automated microkeratome on corneas with 180°-keratometry under 40 diopters (D).

We retrospectively studied cases that underwent SBK whose 180°-keratometry was under 40 D. We separated the cases between 39 and 40 D and those less than 39 D. The preoperative data, the procedure and the postoperative outcomes were analyzed. The Moria One Use-Plus SBK microkeratome with the 90-micron head was used for all cases.

Among the 2883 eyes that underwent SBK LASIK over the past six years, 80 eyes (2.77%) had a preoperative topographical 180°-keratometry of less than 40 D: 63 eyes (2.19%) between 39 and 40 D and 17 eyes (0.59%) between 38 and 39 D (38.13-38.97 D). The spherical equivalent was between -3.50 D (-2.25 sph -2.50 cyl. at 175°) and+6.00 D (+5.50 sph +1.00 cyl. at 85°). Fifty-eight eyes (72.5%) had hyperopia and/or hyperopic astigmatism; 18 eyes (22.5%) had mixed astigmatism; and 4 eyes (5%) had myopia and/or myopic astigmatism. Twenty-six eyes (32%) had a history of strabismus. Thirteen patients (27.66%) had a history of amblyopia. The "-1" ring was used in all cases, with a 7.5 stop (14%) or 8 stop (86%). The procedure went uneventfully in all cases with a stable vacuum between 117 and 123 mm Hg. The nasal hinge and the stromal bed were normal in size in all cases and sufficient to perform the photoablation laser safely with an optical zone between 6.00 and 7.00 millimeters. There were no intraoperative nor immediate postoperative complications: free cap 0%; incomplete flap 0%; button hole 0%; epithelial erosion 0%; bleeding 0%; irregular stromal bed 0%. Postoperative complications: flap displacement 0%; punctate keratitis: 8%; LASIK retreatments: 12%; safety: 100% (no loss of lines of visual acuity).

Corneas with a topographical 180°-keratometry under 40 D are a very small percentage of the total eyes that undergo LASIK (SBK). Those with a 180°-keratometry under 39 D are even more infrequent. Due to the characteristics of the flat cornea, the percentage of hyperopia is much larger in than in the general LASIK group. In addition, the percentage with a history of strabismus and amblyopia is higher.

The Moria One Use-Plus SBK microkeratome is an excellent device that allows the easy creation of thin corneal flaps and regular and smooth corneal beds, safely and predictably even in extremely flat corneas without complications. The safety, efficacy and predictability are quite comparable to the general LASIK group.