Research On Low Contrast Visual Acuity In Scotopic Condition

【Objective】To investigate the distribution characters and related factors of Low contrast visual acuity(LCVA) in a scotopic condition and compare the changes before and after Laser in situ keratomileusis(LASIK) .【Methods】LCVA of 61 individuals of pre and post- LASIK in a scotopic condition with the ZyQv visual acuity chart; visual acuity, refractions, Q-value, keratometric(K-value) and wavefront aberration were evaluated in all cases.【Results】(1) The LCVA of 122 eyes(61 cases) were positive normal distribution with average as 0.34±0.12 logMAR(range:0.02 logMAR ~0.66 logMAR); The LCVA of low, moderate and high myopia groups were 0.28±0.11 logMAR, 0.33±0.10 logMAR, 0.42±0.11 logMAR respectively and there were significant differences among these groups. The LCVA showed positive line relation with pupil diameter(PD), total aberration and total high aberration, showed negative line relation with spherical lens and spherical equivalent(SE), but was not related with K-value, cylinder lens, Q-value and spherical aberration. (2) The LCVA were positive normal distribution at 1 week, 1 month and 3 months after surgery with average as 0.40±0.14 logMAR(0.04 logMAR ~0.84 logMAR),0.38±0.13 logMAR(0.10 logMAR ~0.82 logMAR),0.37±0.12 logMAR(0.1 logMAR ~0.8 logMAR) respectively. (3) The LCVA of the 3 groups increased significantly at 1week after surgery; As for the low myopia group, the LCVA recovered to the preoperative level at 1 month after surgery (P>0.05) and the LCVA of the moderate myopia group recovered to the preoperative level at 3 months after surgery(P>0.05), as for the high myopia group, the LCVA still greater than preoperative level at 3 months after surgery(P<0.05). (4) The LCVA at 3 months postoperation showed positive line relation with Q-value, total aberration, total high aberration and spherical aberration, but was not related with pupil diameter and K-value. TheΔLCVA showed a positive line relation withΔtotal high aberration,Δspherical aberration and Q-value, showed a negative relation with attempt refractions.【Conclusion】The LCVA shows positive normal distribution pre- and post- operation; The LCVA value of high myopia patients increase after LASIK; The LCVA value preoperation relates with pupil diameter, spherical equivalent, total aberration and total higher aberration; The LCVA value preoperation relates with Q-value, total aberration, total higher aberration and spherical aberration.Part two The effect on low contrast visual acuity with different corneal refractive surgery【Objective】To compare the effect of Q-value guided customized LASIK(Q-LASIK) and standardized LASIK(S-LASIK) on the low contrast visual acuity .【Methods】71 eyes of 37 patients were treated with S- LASIK and 62 eyes of 32 patients were treated with Q-LASIK. Preoperation and 1 week, 1 month and 3 months post operation, visual acuity, refractions, Q-value, spherical aberration(SA) and low contrast visual acuity were evaluated in all cases.【Results】(1) In the S-LASIK group, The LCVA of the low, moderate and high myopia groups increased significantly at 1week after surgery; As for the low myopia group, the LCVA recovered to the preoperative level at 1 month after surgery and the LCVA of the moderate myopia group recovered to the preoperative level at 3 months after surgery, as for the high myopia group, the LCVA still greater than preoperative level at 3 months after surgery. (2) In the Q-LASIK group, the LCVA after surgery appeared no differences at different time compared to that evaluated before surgery. (3) In Q3 group, theΔLCVA,ΔQ andΔSA were significantly lower than that in S-LASIK group at 3 months after surgery(P<0.05). (4) The incidence of vision quality's decrement in Q-LASIK group at different time after surgery was lower than that in S-LASIK group(P>0.05).【Conclusion】Q-LASIK has less effects on scotopic low contrast visual acuity than S-LASIK has for the patients, especially for the high myopia group.