Biomedical subjects

Kuang-mon Ashley Tuan

Publications and source records attributed to Kuang-mon Ashley Tuan.

3 recordsLinked to original sources

PubMed2006

Improved contrast sensitivity and visual acuity after wavefront-guided laser in situ keratomileusis: in-depth statistical analysis.

PURPOSE: To evaluate changes in contrast sensitivity and visual acuity following wavefront-guided laser in situ keratomileusis (LASIK) procedures with the Visx CustomVue system. SETTING: Six clinical sites that participated in an Investigational Device Exemption clinical study. METHODS: Two hundred seventy-four myopic astigmatic eyes (spherical equivalent range -0.63 to -6.00 diopters) completed 6 months of follow-up examinations. Wavefront-guided procedures using the WaveScan aberrometer and Star S4 excimer laser system with variable spot scanning were performed at 6 clinical locations. Visual acuity and contrast sensitivity under photopic, mesopic, and mesopic-with-glare lighting conditions were tested preoperatively and over a 6-month follow-up period. This study was a retrospective analysis of contrast sensitivity data with controls for the effects of retinal magnification, mesopic pupil size, and the influence of prior soft contact lens wear on visual outcome. RESULTS: Patients experienced statistically significant improvements in contrast sensitivity at all spatial frequencies and under all lighting conditions (P<.05, Student t test). Contrast sensitivity under mesopic conditions with glare improved in 40% of patients. There was more improvement at higher (12 cycles per degree [cpd], 18 cpd) than lower (3 cpd) spatial frequencies. No correlation was found between mesopic pupil size and contrast sensitivity. Results stratified by spectacle or soft contact lens wear were similar. Soft contact lens wearers had slightly higher disability glare scores than spectacle wearers. CONCLUSIONS: A significant number of patients experienced improved corneal optical quality after wavefront-guided LASIK. The contrast sensitivity in most patients was unchanged. Contrast sensitivity improved in a significant number of patients. There was no correlation between mesopic pupil size and mesopic or mesopic-with-glare contrast performance. Spectacle wearers improved more than soft contact lens wearers.

Adult↗

PubMed2006

Visual experience and patient satisfaction with wavefront-guided laser in situ keratomileusis.

PURPOSE: To determine the correlation between patient perception and clinical measurements after wavefront-guided laser in situ keratomileusis (LASIK). SETTING: Multicenter clinical trial. METHODS: In this retrospective analysis of clinical study results in 274 eyes, wavefront-guided LASIK procedures were performed in 274 myopic-astigmatic eyes at 6 sites. Comprehensive evaluations of vision and ocular health were conducted preoperatively and for 6 months postoperatively. Visual acuity and contrast sensitivity were measured, and questionnaires were administered. Questionnaire responses were compared with clinical measurements. RESULTS: The overall distribution shifted toward "more satisfied." The "very satisfied" population increased by as much as 70% in all areas. There was no significant change in frequency of visual symptoms. Patients were more expressive about visual decline than visual improvement. Perception of changes in vision appeared to be related to mesopic contrast sensitivity and mesopic contrast sensitivity under glare. Mesopic pupil diameter was not a major predictor of patient satisfaction. Contact lens wearers were more satisfied with postoperative vision than were spectacle wearers. Men were more likely to report visual symptoms and to complain about night vision, although their changes were the same as those of the women. Residual refractive error was a major predictor for most questionnaire items. CONCLUSION: Most patients were as satisfied or more satisfied with their postoperative uncorrected visual acuity than with their preoperative best corrected visual acuity. By continuing to minimize postoperative refractive error through the use of nomograms and improved technology, visual complaints such as night glare and halo could be diminished or even eliminated. The study shows that subjective experience affected satisfaction with results. Some dissatisfaction might be mitigated by being sure patients are educated and have realistic expectations before surgery.

Adult↗

PubMed2006

Corneal asphericity and visual function after wavefront-guided LASIK.

PURPOSE: In recent years, a theory has been advanced that corneal asphericity in and of itself determines visual function; that the natural, optimal shape of the cornea is prolate; and that changing the cornea from prolate to oblate negatively impacts visual results. This article presents an analysis of the impact of corneal asphericity on wavefront-guided LASIK. METHOD: A retrospective analysis was conducted of 160 myopic eyes that had undergone wavefront-guided LASIK. Surgical procedures and data collection were conducted at six clinical sites. Corneal topography, visual acuity, and contrast sensitivity data were collected before and 6 months after surgery. The topographically measured corneal surface of each eye was fitted to a conic, and a Q-value was computed for a 5.5-mm pupil. Multivariate regression analysis was performed to evaluate the correlation between Q-value and visual function. The relationship of changes in the corneal surfaces to visual performance was also investigated. RESULTS: Preoperative corneas exhibited negative (prolate) conic shape constants. Postoperative corneas were about equally divided between positive (oblate) and negative conics. There was no statistically significant correlation between corneal shape and visual acuity or contrast sensitivity function. Changes in corneal asphericity after surgery had no significant correlation with changes in visual acuity or contrast sensitivity. CONCLUSION: Visual acuity and contrast sensitivity after wavefront-guided LASIK are not dependent on corneal asphericity. Neither preserving nor inducing asphericity ensures better visual outcome. Better visual outcomes are more likely to result from the application of a customized shape than a standard conic shape.

Adult↗