[Contrast sensitivity function in myopic LASIK].

OBJECTIVE

To evaluate near contrast sensitivity function before and after myopic laser in situ keratomileusis (LASIK).

METHODS

With FACT 101 test chart, static near contrast sensitivity was measured in randomly selected 47 subjects (93 eyes) before, 1 month and 6 months after LASIK. The contrast sensitivity was measured at 1.5, 3.0, 6.0, 12.0 and 18.0 cycles per degree (c/d) spatial frequency respectively and made comparison in them.

RESULTS

The patients achieved the mean uncorrected visual acuity (UCVA) of 1.07 +/- 0.18 and 1.12 +/- 0.20 at postoperative 1-month and 6-months respectively. There was a general reduction in near contrast sensitivity in all spatial frequencies at postoperative 1-month when they were compared with the preoperative contrast sensitivity. The difference at 12 and 18 c/d spatial frequency was statistically significant (t test, P < 0.01). By the 6-month visit, all eyes showed a recovery of static contrast sensitivity function. The group of high myopia (preoperative > or = -6.00 D) and group with complaining of glare and halos after the surgery had a higher decrease rate of contrast sensitivity compared with that of the group preoperative < - 6.00 D and the group of patients without such complaints respectively. The differences at 6.0, 12.0 and 18.0 c/d spatial frequency at 1-month visit was statistically significant (t test, P < 0.05).

CONCLUSIONS

The contrast sensitivity function test offers a more sensitive and comprehensive measure of functional vision than does standard Snellen acuity. The near contrast sensitivity in post-LASIK patients at early stage is reduced despite normal visual acuity and this can affect the quality of vision.