Epithelial thickness profile as a method to evaluate the effectiveness of collagen cross-linking treatment after corneal ectasia.

PURPOSE: To illustrate the hypothesis that epithelial thickness profile maps could be a useful adjunct to topography in monitoring patients after corneal collagen cross-linking (CXL) treatment. METHODS: Epithelial thickness profile in vivo was measured by Artemis very high-frequency (VHF) digital ultrasound scanning (ArcScan Inc) across the central 10-mm corneal diameter of a patient before collagen CXL for corneal ectasia after LASIK and at intervals up to 2 years later. Manifest refraction, corneal topography, and corneal front-surface aberrations were also monitored. Epithelial thickness changes were cross-correlated with corneal topography changes and corneal front-surface aberration changes. RESULTS: Corneal collagen CXL appeared effective in halting the progression of corneal ectasia. Manifest refraction showed a reduction in spherical equivalent over time after CXL in both eyes. Corneal topography demonstrated stable central keratometry in both eyes. Corneal wavefront aberrations demonstrated a reduction of higher order root-mean-square coma and spherical aberration in both eyes. The epithelial thickness profile was altered, with a slight reduction of the area of epithelial thinning and decreased peripheral thickening. This resulted in minimizing the difference between the thinnest and thickest epithelium and might indicate an improvement of the condition. There were no significant changes in minimum stromal and minimum corneal thicknesses. CONCLUSIONS: Epithelial thickness maps provide useful information for monitoring the progression of corneal ectasia after corneal collagen CXL, showing in this case, at least no further progression of the ectasia.

Epithelial, stromal, and corneal pachymetry changes during orthokeratology.

PURPOSE: To describe epithelial, stromal, and corneal thickness profile changes induced by orthokeratology treatment. METHODS: This is a case report of a mild myopic patient (OD -3.25/-0.50 x 172 and OS -3.25/-0.50 x 45) treated with orthokeratology lenses. The patient was assessed before treatment (following 2 weeks of no orthokeratology contact lens wear) and during treatment (after 30 consecutive nights of wearing orthokeratology lenses). Epithelial, stromal, and corneal thickness profile in vivo was measured by Artemis very high-frequency digital ultrasound scanning across the central 10 mm diameter of the cornea before and during orthokeratology treatment. Manifest refraction, contrast sensitivity, corneal topography, and corneal front surface aberrations were also measured before and during orthokeratology treatment. Thickness changes were correlated with corneal topography changes and corneal front surface aberrations changes. The effects of these changes on the patient's quality of vision were measured with manifest refraction and contrast sensitivity. RESULTS: Orthokeratology lenses effectively corrected the patient's myopic refraction. Corneal topography demonstrated typical central flattening and an annulus of mid-peripheral steepening in both the eyes. The epithelial thickness profile was altered, with up to 18 microm of central epithelial thinning and up to 16 microm of annular mid-peripheral epithelial thickening. There also appeared to be a degree of stromal changes, with central stromal thickening and mid-peripheral stromal thinning, in particular in the left eye. There was a large increase in higher order aberrations, in particular in the left eye. This was associated with a decrease in contrast sensitivity in both the eyes. CONCLUSIONS: Refractive changes during orthokeratology treatment are mainly induced by changes in epithelial thickness profile, while stromal changes may also contribute to a small extent.

LASIK for hyperopic astigmatism and presbyopia using micro-monovision with the Carl Zeiss Meditec MEL80 platform.

PURPOSE: To evaluate the monocular and binocular outcomes of LASIK for a micro-monovision protocol for the correction of hyperopic astigmatism and presbyopia. METHODS: A prospective non-comparative case series included 258 eyes of 129 consecutive patients with hyperopic astigmatism and presbyopia who were treated with LASIK-induced micro-monovision. The CRS-Master software was used to generate ablation profiles for the Carl Zeiss Meditec MEL80 excimer laser. The target refraction was piano for distance eyes (dominant eye) and between -1.00 and -1.50 diopters (D) for near eyes. Patients were followed for 1 year. RESULTS: Mean attempted spherical equivalent refraction (SE) correction was +2.54+/-1.16 D (range: +0.25 to +5.75 D). Mean attempted cylinder was -0.52+/-0.49 D (range: -0.00 to -3.25 D). Median age was 56 years (range: 44 to 66 years). Median follow-up was 12.5 months (range: 3.3 months [early retreatment] to 18.2 months). The retreatment rate was 22%. Outcome measures after all treatments were as follows. Mean deviation from the intended SE correction was +0.09+/-0.48 D, with 79% of eyes within +/-0.50 D and 95% within +/-1.00 D. The cylinder correction ratio was 1.23+/-0.63 and the error ratio was 0.67+/-0.65. Of the distance eyes, 86% achieved uncorrected visual acuity of 20/20 and 100% achieved 20/40. Binocularly, 95% of patients achieved 20/20 and 100% achieved 20/40. Eighty-one percent of patients could read J2 and 100% could read J5. Binocularly, 95% of patients achieved 20/20 and could read J5. No eyes lost 2 or more lines of best spectacle-corrected visual acuity. A statistically significant increase was noted in contrast sensitivity at 3 and 6 cycles per degree (cpd), with no reduction at 12 and 18 cpd. The average change in refraction between 3 months and 1 year was +0.11+/-0.36 D with a change of >1.00 D in 2.6% of eyes. CONCLUSIONS: This hyperopic micro-monovision protocol was a well-tolerated and effective procedure for treating patients with presbyopia in moderate to high hyperopia with corrections ranging up to +5.75 D. Contrast sensitivity was improved and the distance vision of near eyes was found to contribute positively to binocular distance vision compared to distance eyes monocularly.

Artemis very high-frequency digital ultrasound-guided repositioning of a free cap after laser in situ keratomileusis.

We present a patient in whom a symmetrically round free cap occurred during laser in situ keratomileusis (LASIK), and flap repositioning was performed without laser ablation. A loss of 3 lines of best spectacle-corrected visual acuity (BSCVA), monocular diplopia, and topographic irregular astigmatism confirmed that the free cap orientation was incorrect. Two subsequent free cap rotations based on refraction failed to realign the free cap into its original position. Artemis 3-dimensional very high-frequency digital ultrasound analysis found the thickness profiles of the free cap and bed to be irregular and mismatched. The rotation required for anatomic realignment was determined by digitally generating a "lock and key" superimposition of the free cap and stromal bed thickness profiles. After Artemis-guided free cap rotation, the eye regained preoperative BSCVA and symmetrical corneal topography with a +0.50 diopter change in spherical equivalent.

Direct residual stromal thickness measurement for assessing suitability for LASIK enhancement by Artemis 3D very high-frequency digital ultrasound arc scanning.

We present a patient scheduled for LASIK enhancement based on conventional residual stromal thickness (RST) prediction methods in whom direct measurement of the RST changed the management due to an unexpectedly low RST. The preoperative refraction was -6.00 -0.50 x 115 in the right eye and -6.00 -0.50 x 20 in the left eye. At 9 months, the refractions had regressed to -0.50 -0.50 x 150 and -0.75 -0.25 x 145, respectively. Predicted RST based on preoperative parameters was 283 microm in the right eye and 281 microm in the left eye, sufficient for the planned enhancement. Using the Artemis 3-dimensional very high-frequency digital ultrasound arc scanner, the minimum RST was directly measured as 277 microm in the right eye but only 212 microm in the left eye, which may have significantly increased the risk of iatrogenic ectasia yielding a predicted post-enhancement RST of 253 microm and 192 microm, respectively. The treatment plan was altered as a result of the thinner than predicted RST in the left eye; an enhancement was performed in the right eye only. A second Artemis examination after 22 months found the RST in the left eye to be stable.

Accuracy of the WASCA aberrometer refraction compared to manifest refraction in myopia.

PURPOSE: To evaluate the accuracy of myopic refraction by a single measurement using the Wavefront Supported Custom Ablation (WASCA) aberrometer (Carl Zeiss Meditec AG, Jena, Germany). METHODS: We retrospectively compared the refractive errors obtained by manifest refraction and wavefront refraction (WASCA) in 50 eyes of 25 consecutive myopic patients undergoing laser refractive surgery. The sphere ranged from -1.00 to -8.25 diopters (D) and cylinder from 0 to -3.75 D. WASCA measurements under cycloplegia were made and WASCA refractions calculated for a 6-mm analysis zone using the Seidel method within the WASCA. We used the manifest refraction as our best estimate of the true refractive error, therefore accuracy was defined as the difference between manifest refraction and that of the WASCA. Correlation coefficients and mean vector errors between manifest and WASCA refraction were calculated. RESULTS: High correlation was shown between manifest and WASCA refractions, with correlation coefficients (R2) of 0.97, 0.85, and 0.79 for M, J180, and J45, respectively. Mean power vector error (standard deviation) was 0.22 D (0.39), +0.03 D (0.21), and +0.03 D (0.13) for M, J180, and J45, respectively. Total dioptric power vector error was 0.43 D with 74% eyes within 0.50 D. CONCLUSIONS: When measuring normal myopic eyes, the concordance between manifest and WASCA refractions was found on average to be high; however, outlier measurements occurred.

A new night vision disturbances parameter and contrast sensitivity as indicators of success in wavefront-guided enhancement.

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 microm. The RAWS parameter (unit = microm2) 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 microm2 preoperatively and 276 microm2 postoperatively). For the night vision disturbances repair eye group, RAWS at presentation was 104% (563 microm2) above the respective postoperative RAWS control eyes. Following wavefront-guided repair, RAWS was decreased (P < .05) to only 49% (410 microm2) 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.