Laser in situ keratomileusis for moderate and high myopia and myopic astigmatism

Abstract

Objective: This study evaluated the predictability, stability, and safety of laser in situ keratomileusis (LASIK) in myopia and myopic astigmatism.

Design: The study design was a prospective, unmasked, nonrandomized clinical trial.

Participants: Participating were 25 patients with myopia (37 eyes) with astigmatism of less than 1.00 diopter (D), divided into 3 subgroups (-5.00 to -9.90 D, 8 eyes; -10.00 to -14.90 D, 10 eyes; -15.00 to -29.00 D, 19 eyes), and 37 patients with myopia (56 eyes) with corneal astigmatism of 1.00 to 4.50 D, divided into 3 subgroups (-5.00 to -9.90 D, 12 eyes; -10.00 to -14.90 D, 24 eyes; -15.00 to -29.00 D, 20 eyes).

Intervention: LASIK was performed using the Automatic Corneal Shaper and the Keracor 116 excimer laser.

Main outcome measures: Visual acuity, manifest refraction, central corneal islands, ablation decentration, and patient satisfaction were measured.

Results: At 12 months, predictability, regression between 1 and 12 months, uncorrected visual acuity (UCVA), loss of two or more lines of corrected visual acuity, and patient satisfaction of the spherical (toric) groups are reported. Subgroups -5.00 to -9.90 D: 100% (75%) +1.00 D; regression less than or equal to 1.00 D in 100% (91.7%); UCVA greater than or equal to 20/40 in 87.5% (70%); none lost two or more lines; 100% (84%) highly satisfied. Subgroups -10.00 to -14.90 D: 60% (78.3%) +/-1.00 D; regression less than or equal to 1.00 D in 100% (87%); UCVA greater than or equal to 20/40 in 77.8% (86.4%); 10% (4.3%) lost two lines; 90% (91%) highly satisfied. Subgroups -15.00 to -29.00 D: 38.9% (21.4%) +/-1.00 D; regression less than or equal to 1.00 D in 72.2% (64.3%); UCVA greater than or equal to 20/40 in 33.3% (40%); 5.6% (7.1%) lost two lines; 78% (50%) highly satisfied. Differences of predictability and change of manifest refraction between subgroups of -5.00 to -9.90 D and -15.00 to -29.00 D were statistically significant. Central islands (decentrations) were observed in 17% (5.6%) of eyes of the spherical and in 16% (4.1%) of the toric group. Overall, the corneal interface was visible in 8.2%.

Conclusions: The LASIK method used in this study showed stability of manifest refraction and adequate uncorrected central visual acuity in a large percentage of patients with myopia up to -15.00 D. Corneal stability was not as uniform. Central corneal islands were observed in a sizable minority of patients despite pretreatment. For myopia greater than 15.00 D, accuracy and patient satisfaction were sufficiently poor to advise against using the authors' treatment technique in these groups. Visually significant microkeratome and laser-related problems were noted in a smaller percentage of patients. Patients with astigmatism correction were less pleased with results than were patients who received spherical corrections.