[Comparison of visual effects after LASIK in myopia between centered on the coaxially sighted corneal light reflex and line of sight].

OBJECTIVE: To compare visual acuity, refractive outcome, high order aberrations, contrast sensitivity and subjective symptom of myopia with laser in situ keratomileusis (LASIK) centered on the coaxially sighted corneal light reflex (CSCLR group) and the conventional ablation of line of sight (LOS group).

METHODS: With prospective, double-blind, randomized, controlled trial, the right eyes of patients were included and divided into two groups according to random stratified grouping. Two hundred and ten myopic eyes were treated with centration on the coaxially sighted corneal light reflex and 210 myopic eyes treated with centration on pupil center(line of sight). The parameters of visual acuity, refractive outcome, ablation center distance from visual axis, corneal high order aberrations, subjective discomfort glare and shadowing incidence rate, contrast sensitivity between the two groups were measured and compared up to 6months post operation. Consistent with the measurement data, normal distribution using the group t-test, non-normal distribution of measurement data using the group wilcoxon rank-sum test and count data using chi-square test.

RESULTS: The data of postoperative UCVA, BCVA, MRSE efficacy index and safety index showed no statistical difference between the CSCLR and the LOS group up to 6months post operation(P> 0.05). 3% lost one line or more of BCVA in the CSCLR group,and 9% in the LOS group postoperatively, χ(2)= 6.38, P=0.01. The ablation center deviation was (0.19±0.15) mm from visual axis(pentacam system default setting) in CSCLR group and (0.43±0.22) mm in the LOS group. Ablation center deviation was statistically significantly shorter in the CSCLR group (t=-2.59, P<0.01). The postoperative increased total cornea higher order aberrations was 0.150 μm in CSCLR group and 0.193 μm in LOS group, the difference was statistically significant, Z=3.21, P=0.03. The increased corneal vertical coma of CSCLR group was 0.321 μm,smaller than in the LOS group(0.464 μm), Z=4.33, P<0.01. The increased horizontal coma was 0.242 μm in CSCLR group and also smaller than the LOS group(0.353 μm), Z=4.54,P<0.01. Subjective discomfort glare and shadowing incidence rates were 8.5% and 17.5% respectively in the CSCLR and LOS group, χ(2)=7.16,P< 0.01. The one month postoperative contrast sensitivity visual acuity in the CSCLR was 1.157 ± 0.253, significantly higher than the LOS group (0.797±0.218) on 18 c/d spatial frequency, t=- 2.55, P=0.01, but with no significant difference between the two groups at 3 and 6 months.

CONCLUSIONS: Myopic LASIK centered on the CSCLR achieved significant lower induction of lost of BCVA, lower induction of high order aberrations, lower risk of subjective discomfort glare and shadowing and lower decline of early contrast sensitivity by comparison to centration on the LOS, improving the quality of vision after operation. (Chin J Ophthalmol, 2016, 52: 499-506).