In eyes with axial lengths longer than or equal to 27.0 mm, current third- and fourth-generation lens calculation formulas have a tendency to over minus patients between -1.0 and -4.0 D. The formulas appear to perform better for plus-power IOL implantation than for minus-power IOL implantation. The use of B-scan ultrasonography to locate posterior pole staphylomas may improve the accuracy of IOL calculations in eyes with extreme myopia.

PURPOSE: To determine the efficacy, predictability, safety, and short term stability of laser in situ keratomileusis (LASIK) in treating patients with low myopia and astigmatism using the Chiron Technolas Keracor 117 PlanoScan excimer laser. METHODS: We retrospectively studied the results of our initial 83 eyes with myopia ranging from -1.13 to -7.25 diopters (D) and astigmatism of no more than 4.00 D that underwent LASIK with the Chiron Technolas Keracor 117 PlanoScan. Follow-up was at 1 day, 1 month, and 3 to 6 months. RESULTS: Mean baseline spherical equivalent refraction was -3.54 ± 1.41 D and cylinder -1.64 ± 1.14 D. Mean postoperative spherical equivalent refraction was -0.52 ± 0.50 D at 1 month and -0.65 ± 0.62 D at 3 to 6 months; mean postoperative refractive cylinder was -0.45 ± 0.54 D at 1 month and -0.50 ± 0.63 D at 3 to 6 months. Fifty-three percent (44 eyes) achieved a spherical equivalent refraction within ± 0.50 D and 81% (67 eyes) within ± 1.00 D of emmetropia at the last examination. Fifty-seven percent (47 eyes) achieved a refractive cylinder of =s0.50 D, and 27% (22 eyes) had an undercorrection of their refractive cylinder at the last examination. An uncorrected visual acuity of 20/40 or better was achieved in 86% (71 eyes) of patients on postoperative day one, in 81% (67 eyes) at 1 month, and in 76% (63 eyes) at 3 to 6 months. Twenty-eight percent (23 eyes) saw 20/20 or better uncorrected at the last visit (41% [34 eyes] had a baseline spectaclecorrected visual acuity of 20/20). There was no statistically significant difference in the refractions or uncorrected visual acuities between the different postoperative examinations. No eye experienced a loss of spectacle-corrected visual acuity of more than one line at the last examination. CONCLUSION: LASIK with the Chiron PlanoScan excimer laser appears to be an effective, safe, and reasonably predictable means to reduce low myopia and astigmatism. Adjustment of computer algorithms is needed to decrease the number of undercorrections. [J Refract Surg 1997;13:614-619]