The Effect of Laser in situ Keratomileusis on Low Contrast Vision

Factors affecting contrast sensitivity with the Artisan phakic intraocular lens for high myopia

PURPOSE

To evaluate the factors affecting postoperative visual function in eyes with Artisan phakic intraocular lenses (PIOLs).

METHODS

This study examined a retrospective noncomparative case series. Phakic IOLs were implanted in 60 eyes of 36 patients with high myopia. Contrast sensitivity for spatial frequencies of 1.1, 1.7, 2.6, 4.2, 6.6, and 10:4 cycles per degree with and without glare and wavefront aberrations were measured before and 3 months after surgery. The area under the log contrast sensitivity function (AULCSF) was calculated from the contrast sensitivity. Stepwise regression analysis was used to assess the factors that affected the postoperative AULCSF.

RESULTS

No significant difference was noted between the preoperative AULCSF without glare and the postoperative AULCSF without glare (P=.886). The mean AULCSF with glare improved significantly after surgery (P=.018). The variables affecting the postoperative AULCSF without glare were axial length (partial regression coefficient B=-0.101, P=.0002) and age (B=-0.008, P=.0063). The variables affecting the postoperative AULCSF with glare were axial length (B=-0.127, P<.0001) and age (B=-0.012, P=.0294). The preoperative refraction showed multicollinearity with the axial length, and coma-like aberration and spherical aberration showed multicollinearity with age.

CONCLUSIONS

Contrast sensitivity without glare was the same before and after surgery and contrast sensitivity with glare improved after surgery. Longer axial length and older age predispose patients to degradation of the postoperative visual function in eyes with Artisan PIOLs.

Takagi Glare Tester CGT-1000 for Contrast Sensitivity and Glare Testing in Normal Individuals and Cataract Patients

PURPOSE

To investigate the sensitivity and repeatability of the Takagi Contrast Glare Tester CGT-1000 in normal individuals and those with cataracts.

METHODS

A prospective observational study was performed. The Takagi Contrast Glare Tester measures contrast sensitivity (CS) at 6 target sizes and 13 contrast levels (2.00 to 0.34 logCS). Testing follows a method of descending limits paradigm with a single reversal determining threshold. The CGT-1000 was administered with and without glare in 95 eyes of 61 cataract patients and 13 controls. The percentage floor (unable to see the highest contrast) and ceiling (able to see the lowest contrast) effects and correlations between CS and cataract grades were determined. The repeatability was evaluated using Bland-Altman limits of agreement and expressed as the coefficient of repeatability (COR). Factor analysis was used to test for redundancy within the 6 spatial frequencies.

RESULTS

In normal individuals, a high rate of ceiling effect varying with target size was noted--for 6.3 degrees, 4.0 degrees, 2.5 degrees, 1.6 degrees, 1.0 degrees, 0.7 degrees, ceiling effects were 68%, 58%, 18%, 11%, 4%, 2%, respectively, for no glare, and 47%, 42%, 8%, 2%, 2%, 2%, respectively, with glare. In cataract patients, floor effects were noted--3%, 0%, 3%, 7%, 19%, 62%, respectively, for no glare, and 3%, 3%, 6%, 14%, 44%, 79%, respectively, with glare. Correlations with cataract grades ranged from 0.10 to 0.61, being best for nuclear cataract. Repeatabilities expressed as COR were +/- 0.11, +/- 0.14, +/- 0.28, +/- 0.38, +/- 0.38, +/- 0.47 logCS, respectively. All spatial frequencies loaded heavily on one factor, indicating no gain in information from testing multiple target sizes.

CONCLUSIONS

Sensitivity to the presence of cataract was good, but ceiling effects in normal individuals and floor effects in cataract patients limit accuracy. Repeatability was poor, but could be improved by testing less spatial frequencies more rigorously.