Assessment of nerve fiber layer thickness before and after laser in situ keratomileusis using scanning laser polarimetry with variable corneal compensation.

PURPOSE: To determine the effect of laser in situ keratomileusis (LASIK) on retinal nerve fiber layer (RNFL) thickness measurements obtained by scanning laser polarimetry with variable corneal compensation (SLP-VCC). SETTING: Gimbel Eye Centre, Calgary, Alberta. METHODS: Retinal nerve fiber layer thickness measurements were performed in both eyes of 25 consecutive healthy patients the day of LASIK surgery and 1 month after by trained examiners using the GDx-VCC nerve fiber analyzer. Thickness measurements and all other parameters provided by the software of the machine before and after LASIK were analyzed using the paired Student t test. RESULTS: Mean age of the patients was 39 years +/- 9.6 (SD) (range 24 to 57 years). The mean preoperative spherical equivalent was -4.15 +/- 1.76 diopters (D) (range -1.0 to -7.50 D) and the mean postoperative spherical equivalent, 0.12 +/- 0.39 D (range -0.75 to +1.00 D). Mean ablation depth was 62 +/- 23 mum. No statistically significant difference was found in SLP parameters after LASIK (P<.05). No clinically significant difference in RNFL thickness measurements was noted in any eye. CONCLUSION: These data suggest that SLP-VCC mean thickness measurements are not influenced by LASIK-induced alterations in corneal architecture. Measurements obtained with SLP-VCC before surgery may be used for future comparisons.

Wavefront-guided multipoint (segmental) custom ablation enhancement using the Nidek NAVEX platform.

PURPOSE: To present our clinical experience regarding enhancement (retreatment) of previously performed non-wavefront-guided refractive surgery by wavefront-guided multipoint (segmental) custom ablation utilizing the Nidek NAVEX platform. METHODS: Retrospective clinical analysis was conducted of 20 eyes (19 patients) with mixed myopic or hyperopic astigmatism who had undergone primary laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) and reported postoperative reductions in quality of vision. These vision disturbances correlated with clinically significant elevations in the root mean square of higher order aberrations (RMS of HOA) values. Before wavefront-guided multipoint (segmental) custom ablation enhancement with the NAVEX platform, all patients underwent testing with the Nidek Optical Path Difference Scan (OPD-Scan) and analysis with Final Fit Software. RESULTS: Twenty eyes showed improvement or resolution of visual symptoms following wavefront-guided multipoint (segmental) custom ablation enhancement. The postoperative root mean square of higher order aberration values were variable and not always related to improvement in visual function. No patient lost two or more lines of best spectacle-corrected visual acuity. CONCLUSION: Topography and wavefrontguided multipoint (segmental) custom ablation enhancements were safe and effective in improving visual symptoms following primary refractive surgery. In some eyes, improved visual function without correspondingly lower RMS of HOA values may be an effect of neutralizing some chromatic aberrations across the visible light spectrum, thereby improving the modulation transfer function.

Primary multipoint (segmental) custom ablation.

PURPOSE: We present our experience in resolving visual symptoms in refractive patients undergoing primary multipoint (segmental) custom ablation. METHODS: Twelve eyes with mixed myopic astigmatism underwent evaluation and primary treatment by multipoint (segmental) custom ablation for the correction of refractive errors and visual symptoms using the Nidek NAVEX platform. RESULTS: Twelve eyes showed resolution of visual symptoms following diagnosis and treatment with MCA using the NAVEX platform. No patient lost two or more lines of best spectacle-corrected visual acuity. The postoperative root mean square of higher order aberrations did not change in a predictable or reproducible fashion. CONCLUSION: Multipoint (segmental) custom ablation with the Nidek NAVEX system was safe and effective for correcting mixed myopic astigmatism and for resolving visual symptoms in selected refractive surgery candidates. Small changes in the root mean square of higher order aberration values were not always reflected in a patient's subjective assessment of vision quality.