Corneal Aberrations and Visual Performance After Radial Keratotomy

Abstract

BACKGROUND: Refractive surgery and videokeratography have allowed us to study the effects on visual performance of relatively large changes in corneal aberration structure induced by surgical changes in corneal shape. METHODS: We quantified in one eye of nine normal and 23 radial keratotomy patients, the area under the log contrast sensitivity function (AULCSF) and corneal first surface wavefront variance for two artificial pupil sizes (3 and 7 mm). Contrast sensitivity was measured with sine-wave gratings at six spacial frequencies. Wavefront variance was derived from videokeratographs using Zernike polynomials. RESULTS: For normals eyes there were no significant changes over time. For eyes that had radial keratotomy, there were significant pupil sizedependent changes. For the 3 mm pupil, there were significant surgery-induced changes in the corneal wavefront variance which became large (approximately 30 times preoperative values) at 7 mm. Significant correlated changes in AULCSF for the 7 mm pupil but not for the 3 mm pupil occurred immediately following surgery and remained. CONCLUSIONS: Radial keratotomy, like photorefractive keratectomy, shifts the distribution of aberrations from third order dominance (coma-like aberrations) to fourth order dominance (sphericallike aberrations). Radial keratotomy-induced aberrations and loss in contrast sensitivity are reduced with increasing clear zone diameter. Radial keratotomy induces an increase in the optical aberrations of the eye and the increase for large pupils (7 mm) but not small (3 mm) is correlated to a decrease in contrast sensitivity. [J Retract Surg 1998;14:397-4071

Changes in Contrast Sensitivity Function and Ocular Higher Order Aberration by Conventional Myopic Photorefractive Keratectomy

“…PRK, 4,11,12 similarly to after RK 5,13 and LASIK. 10,11,[14][15][16] Applegate et al 5 reported that the area under the contrast sensitivity function decreases as the wavefront variances increase after RK.…”

“…The area under the log contrast sensitivity function (AULCSF) was calculated from the data obtained with the CSV-1000E sine wave grading chart. AULCSF was determined according to the method of Applegate et al 5 The log of contrast sensitivity was plotted as a function of log spatial frequency, and thirdorder polynomials were fi tted to the data. The fi tted function was integrated between the fi xed limits of log spatial frequency of 0.48 (corresponding to 3 cpd) and 1.26 (18 cpd), and the resulting value was defi ned as the AULCSF.…”

“…10,11,[14][15][16] Applegate et al 5 reported that the area under the contrast sensitivity function decreases as the wavefront variances increase after RK. Studies using aberroscopy have demonstrated a signifi cant correlation between low-contrast visual acuity and ocular higher order wavefront aberration after PRK.…”

Effect of 1-year lutein supplementation on macular pigment optical density and visual function

“…The contrast level of the last correct response for each cpd was recorded as the contrast threshold in logarithmic value under full spectacle correction. We then calculated the area under the log contrast sensitivity function (AULCSF) as representative of the contrast sensitivity data according to the method of Applegate et al [41]. The log contrast sensitivity versus log spatial frequency data were fitted to a third-order polynomial curve.…”

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“…Contrast sensitivity function under the photopic condition was evaluated with best-spectacle correction at 3, 6, 12, and 18 cycles per degree (c/d) using the CSV-1000E chart (Vector Vision Co., Greenville, OH), and the area under the log contrast sensitivity function (AULCSF) was calculated according to the method of Applegate et al [14]. In brief, the log of contrast sensitivity was plotted as a function of log spatial frequency, and third-order polynomials were fitted to the data.…”