Binocular Visual Performance After LASIK

Abstract

PURPOSE:To analyze binocular visual function after LASIK.METHODS: Eye aberrometry and corneal topography was obtained for both eyes in 68 patients (136 eyes). To evaluate visual performance, monocular and binocular contrast sensitivity function and disturbance index for quantifying halos were measured. Tests were performed under mesopic conditions. RESULTS: Binocular summation and disturbance index diminished signifi cantly (PϽ.0001) after LASIK with increasing interocular differences in corneal and eye aberrations. Binocular visual deterioration was greater than monocular deterioration for contrast sensitivity function and disturbance index.CONCLUSIONS: Binocular function deteriorates more than monocular function after LASIK. This deterioration increases as the interocular differences in aberrations and corneal shape increase. Improvements in ablation algorithms should minimize these interocular differences. [J Refract Surg. 2006;22:679-688.] V arious studies have demonstrated that corneal and eye aberrations 1-4 as well as night vision disturbances 5,6 can increase after refractive surgery, while contrast sensitivity function can diminish after refractive surgery. [7][8][9] In general, studies on postoperative deterioration have concerned only monocular function, analyzing the results for each eye, with postoperative binocular function rarely being considered. 10 Interocular differences are known to affect visual performance. [11][12][13][14][15][16] Jimenez et al 16 demonstrated binocular summation measured by contrast sensitivity function in emmetropic subjects is reduced when the asphericities of the cornea differ. After surgery, pronounced changes such as an increase in aberrations and differences in corneal shape 1,2,5,8,17,18 occur in the eye; these changes partially explain the monocular deterioration in contrast sensitivity. 7 In the binocular case, a reduction in postoperative binocular summation can be expected when large interocular differences appear in eye aberrations and corneal shape.In this study, we analyzed the role of interocular differences in aberrations and corneal shape on binocular visual function. Although many different visual functions can be used to evaluate binocular vision performance, this study examined contrast sensitivity function and the disturbance index for halos (a measure for quantifying night vision disturbances). Constrast sensitivity is a common and useful function to JRS0906JIMENEZ.indd 679 JRS0906JIMENEZ.indd 679

Corneal Aberrations, Contrast Sensitivity, and Light Distortion in Orthokeratology Patients: 1-Year Results

“…Compared to our previous study [14] we did not measure binocular functions of LD and CS in the present study. This does not reflect the actual viewing conditions of the patients, but we aimed to maximize the potential changes to be observed and we know that they would be more likely detected under monocular conditions, as binocular summation will tend to improve the results of LD [14, 37] and CS [38]. We also aimed to explore the correlations with HOA specific to each eye, which forced us to do follow a monocular analysis in this part of the study.…”

Binocular visual performance and summation after correcting higher order aberrations

“…In the present study, the relatively low interocular difference in optical quality in the normal subjects with baseline correction did not affect binocular summation. However, in clinical cases of laser refractive surgery, large interocular asymmetries are observed post-op leading to reduced binocular summation and stereopsis [23,25]. In such cases, binocular higher order aberration correction to improve the optical quality and reduce the interocular difference in aberrations will substantially improve binocular visual performance.…”

“…This is evident from previous studies of binocular vision in the presence of interocular difference in optical quality, pertaining to anisometropia [18,19], addition of monocular defocus [20], interocular differences in higher order aberrations [21], corneal shape [22,23], contrast and spatial frequency [24]. Such interocular differences in optical aberrations occur routinely after clinical procedures such as laser refractive surgery [23,25]. In general, binocular summation has been observed to decrease with increasing interocular difference in optical quality [20,22].…”

Technical Note: Pre‐surgical anisometropia influences post‐LASIK binocular mesopic contrast sensitivity function

“…Although it is known that the mesopic contrast sensitivity function (CSF) can deteriorate monocularly after surgery, this deterioration is even greater in the binocular case when large interocular differences arise in corneal and total eye aberrations. The average deterioration of the binocular CSF was found to be 28%, exceeding 40% in any cases (Jiménez et al. , 2006).…”

“…, 2006). Recently, some authors have shown (Jiménez et al. , 2005, 2006) that the interocular differences in corneal and total aberrations and corneal asphericity correlate with a greater deterioration of binocular vision after refractive surgery under mesopic conditions.…”