A New Night Vision Disturbances Parameter and Contrast Sensitivity as Indicators of Success in Wavefront-guided Enhancement

Abstract

PURPOSE: To determine the level of success of wavefront-guided repair of night vision disturbances after conventional (Munnerlyn) myopic LASIK using a new parameter to describe higher order aberrations, and to compare the improvements to matched myopic LASIK controls who were symptom-free. METHODS: We developed a single parameter metric to represent raw spherical aberration (RAWS) to functionally describe the cumulative spherical aberration for an eye over a range of physiological pupil sizes. To derive the RAWS parameter, spherical aberration is plotted over pupil analysis zones from 3000 to 6000 µm. The RAWS parameter (unit = µm p 2 ) is then equal to the area under the plot. Sixteen eyes treated for night vision disturbances by wavefront-guided repair were each compared to the mean of four matched control eyes (total 64 eyes) treated by aspheric myopic ablation and without night vision disturbances. Contrast sensitivity and RAWs parameter for spherical aberration were determined for each of the repair eyes and control eyes before and after surgery. RESULTS: Following wavefront-guided repair, 76% of eyes were subjectively reported to have night vision disturbances improved by at least 80%. The percentage of eyes within normal contrast range increased from 25% to 80% following wavefront-guided repair (P<.05). For the control eyes, LASIK increased RAWS by 126% (RAWS was 122 µm p 2 preoperatively and 276 µm p 2 post-operatively). For the night vision disturbances repair eye group, RAWS at presentation was 104% (563 µm p 2 ) above the respective postoperative RAWS control eyes. Following wavefront-guided repair, RAWS was decreased (P<.05) to only 49% (410 µm p 2 ) above the postoperative control group. CONCLUSIONS: The RAWS parameter enabled a single digit descriptor of overall higher order aberrations for an eye over the principal physiological pupil range. By comparing RAWS parameter changes in wavefront-guided repair eyes to matched postoperative asymptomatic eyes, we were able to determine the magnitude of the deficit in the symptomatic eyes and the relative efficacy of wavefront-guided repair. [J Refract Surg. 2005;21: S535-S540.]

Refractive and Topographic Errors in Topography-guided Ablation Produced by Epithelial Compensation Predicted by 3D Artemis VHF Digital Ultrasound Stromal and Epithelial Thickness Mapping

“…An irregular epithelial thickness profi le may often have a detrimental effect on the effectiveness of wavefront-or topography-guided custom ablation because the true stromal irregularity is partially masked by the epithelium. Compensatory epithelial remodeling and other, currently unpredictable, biomechanical responses are the likely explanation for the less than 50% effectiveness of wavefront- 18 or topography-guided 19 custom ablation profi les. This was demonstrated in the example case as, following Artemis-assisted transepithelial PTK, two additional topography wavefrontguided procedures were required to fully regularize the corneal topography.…”

Incidence and Outcomes of Optical Zone Enlargement and Recentration After Previous Myopic LASIK by Topography-Guided Custom Ablation

“…Wavefront-guided custom ablation is an alternative option for treating highly aberrated eyes, but the reduction in aberrations reported for wavefront-guided treatments has been lower than for topography-guided treatments. 41 Another disadvantage of wavefront-guided treatments is that these are forced to be centered on the entrance pupil because this is where the data are captured. These treatments are therefore less effective for recentration of the optical zone to the corneal vertex, and can actually increase the decentration in eyes with a large angle kappa.…”

Aberrometric, Keratometric, and Visual Outcomes After Trans-Epithelial Topography-Guided Phototherapeutic Keratectomy for the Treatment of Irregular Corneas

“…WG treatments have shown very good results for the treatment of regular astigmatism or normal refractive surgery cases, however because the aberrations measured by the aberrometry devices consider the ones of the whole eye, results are usually not satisfactory in irregular corneas. [1][2][3][4][5][6][7] Most cases of irregular astigmatism are secondary to corneal causes, and TG treatments have been used in these cases with satisfactory results. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]20,21 When the aberrations exist at the level of the cornea, the information provided by the topographer is then transferred to a laser platform, which subsequently plans a treatment based on the specific irregularity and higher order aberrations of that specific cornea.…”

“…[1][2][3][4][5][6][7] Most cases of irregular astigmatism are secondary to corneal causes, and TG treatments have been used in these cases with satisfactory results. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]20,21 When the aberrations exist at the level of the cornea, the information provided by the topographer is then transferred to a laser platform, which subsequently plans a treatment based on the specific irregularity and higher order aberrations of that specific cornea. The regularizing procedure itself may induce some refractive shift that will further need to be corrected.…”