Pupil size is critical for optimal performance of presbyopic contact lenses. Although the effect of luminance is well known, little information is available regarding other contributing factors such ...as aging and refractive status.
The cohort population comprised 304 patients (127 male, 177 female) aged 18 to 78 years. Pupils were photographed at three controlled luminance levels 250, 50, and 2.5 cd/m using an infra-red macro video camera. Measurements of pupil diameter were conducted after transforming pixel values to linear values in millimeters.
Luminance was the most influential factor with pupil diameter increasing with decreased luminance (p < 0.001, all comparisons). Age was also found to be a significant factor with a smaller diameter in the older groups, but overall the difference was only significant between the pre-presbyopes and the established presbyopes (p = 0.017). Pupil diameter decreased significantly with increasing age, the effect being most marked at low luminance (<0.001). The smallest pupil diameters were measured for hyperopes and the largest for myopes and although refractive error was not a significant factor alone, there was a significant interaction between luminance and refractive error with the greatest differences in pupil diameter between myopes and emmetropes at low luminance (p < 0.001). Pupil diameter changes modeled by multilinear regression (p < 0.001) identified age, luminance, best sphere refraction, and refractive error as significant factors accounting for just over 70% of the average variation in pupil diameter.
Both age and refractive status were found to affect pupil size with larger pupils measured for younger patients and myopes. Designs for multifocal contact lens corrections should take both age and refractive status into consideration; a faster progression from distance to near corrections across the optical zone of the lens is expected to be required for established presbyopes and hyperopes than it is for early presbyopes, myopes, and emmetropes.
To compare the optical zone centration accuracy between myopic eyes treated with small incision lenticule extraction (SMILE) and LASIK.
Retrospective analysis of 100 consecutive eyes treated with ...SMILE (the SMILE group) with the corneal fixation-based centration VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) and a matched group of 100 eyes treated with LASIK (the LASIK group) with VisuMax flap creation and eye tracker-based centration MEL 90 excimer laser (Carl Zeiss Meditec) ablation. In SMILE, the corneal vertex of the coaxially fixating eye was aligned with the vertex of the curved contact glass. In LASIK, the treatment was centered on the coaxially sighted corneal light reflex (first Purkinje image). A tangential (instantaneous) curvature preoperative to postoperative difference map was generated for each eye. A fixed grid and set of concentric circles were superimposed on the difference map to measure the offset between the optical zone center and corneal vertex (0,0), and vector analysis was used for comparative analysis at 3 months postoperatively.
Mean centration offset was 0.20 ± 0.11 mm for the SMILE group and 0.17 ± 0.10 mm for the LASIK group, with no statistically significant difference between groups (P >.05). In the SMILE group, the optical zone was centered within 0.1 mm of the corneal vertex in 17% of eyes, within 0.2 mm in 55% of eyes, within 0.3 mm in 81% of eyes, and within 0.4 mm in 96% of eyes. In the LASIK group, the optical zone was centered within 0.1 mm of the corneal vertex in 24% of eyes, within 0.2 mm in 62% of eyes, within 0.3 mm in 92% of eyes, and within 0.4 mm in 98% of eyes. There was no systematic directional decentration in either group.
Optical zone centration accuracy was no different between SMILE and LASIK with the MEL 90 laser.
To illustrate the hypothesis that epithelial thickness profile maps could be used as an adjunctive tool to improve the sensitivity and specificity of keratoconus screening by presenting a case series ...of examples.
The Artemis very high-frequency digital ultrasound arc-scanner was used to obtain epithelial thickness profiles in addition to a comprehensive ophthalmic examination to screen for keratoconus. Five case examples are presented; a normal eye, an eye with advanced keratoconus, and three cases where a diagnosis of keratoconus was uncertain based only on the ophthalmic examination.
The epithelial thickness profile in the normal eye was slightly thinner superiorly, consistent with that previously described for a normal population. The keratoconic eye demonstrated an epithelial doughnut pattern of epithelial thinning over the cone surrounded by an annulus of epithelial thickening. In case 1, an epithelial doughnut pattern confirmed the presence of keratoconus in an eye with an abnormal front surface topography. In case 2, the absence of an epithelial doughnut pattern excluded a diagnosis of keratoconus in a patient with an abnormal front surface topography. In case 3, the presence of an epithelial doughnut pattern coincident with an eccentric posterior elevation best-fit sphere indicated a diagnosis of keratoconus. The epithelium appeared to have compensated for the stromal surface cone, resulting in an apparently normal front surface topography.
An epithelial doughnut pattern appears to indicate the presence of an underlying stromal cone; the lack of an epithelial doughnut pattern would indicate that an abnormal topography was not due to keratoconus. In very early keratoconus, epithelial compensation can mask the presence of an underlying cone on front surface topography, ie, a diagnosis of keratoconus might be missed.
To report the visual and refractive outcomes of small incision lenticule extraction for low myopia using the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany).
A retrospective analysis of ...120 consecutive small incision lenticule extraction procedures was performed for low myopia. Inclusion criteria were preoperative spherical equivalent refraction up to -3.50 diopters (D), cylinder up to 1.50 D, and corrected distance visual acuity of 20/20 or better. Outcomes analysis was performed for all eyes with 1-year follow-up according to the Standard Graphs for Reporting Refractive Surgery, and also including mesopic contrast sensitivity.
One-year data were available for 110 eyes (92%). Preoperatively, mean spherical equivalent refraction was -2.61 ± 0.54 D (range: -1.03 to -3.50 D) and mean cylinder was 0.55 ± 0.38 D (range: 0.00 to 1.50 D). Postoperatively, mean spherical equivalent refraction was -0.05 ± 0.36 D (range: -0.94 to +1.25 D) and mean cylinder was ± 0.50 D in 84% and ± 1.00 D in 99% of eyes. Uncorrected distance visual acuity was 20/20 or better in 96% of eyes and 20/25 or better in 100% of eyes. One line of corrected distance visual acuity was lost in 9%, but no eyes lost two or more lines. There was an initial overcorrection in mean spherical equivalent refraction on day 1 (+0.37 D) as expected, which regressed to +0.10 D at 1 month and -0.05 D at 3 months, after which stability was reached (mean spherical equivalent refraction was -0.05 D at 1 year). Contrast sensitivity at 1 year was slightly increased at 3, 6, 12, and 18 cycles per degree (P < .05).
Small incision lenticule extraction for low myopia was found to be safe and effective with outcomes similar to those previously reported for LASIK.
To describe endokeratophakia in which a small incision lenticule extraction (SMILE) lenticule from a myopic patient is implanted into a recipient eye through a small incision to correct hyperopia.
A ...23-year-old aphakic woman presented following cataract surgery to remove a childhood congenital cataract with hyperopia of +12.00 -1.50 × 155, corrected distance visual acuity of counting fingers, and exotropia. A SMILE procedure using the VisuMax femto-second laser (Carl Zeiss Meditec, Jena, Germany) was performed on a donor patient with high myopia and the extracted lenticule was stored (power -10.50 diopter sphere, optical zone 5.75 mm, central lenticule thickness 127 μm). In the recipient eye, a pocket lamellar incision was created using the VisuMax SMILE software. The upper interface was separated and the donor lenticule was inserted through the small incision.
One year postoperatively, retinoscopy refraction was +7.50 -3.00 × 150, a spherical equivalent refraction reduction of 5.25 diopters. Mean keratometric power increased by 2.91 diopters. The posterior surface elevation changed significantly with a central bulge into the anterior chamber. Central corneal thickness by Pentacam (Oculus Optikgeräte, Wetzlar, Germany) increased by 121 μm. Central lenticule thickness was 130 μm and central epithelial thickness was 43 μm measured by RTVue OCT (Optovue Inc., Fremont, CA). The cornea remained clear over the 1-year postoperative period.
Endokeratophakia appears to be a viable procedure for correcting hyperopia on the cornea by implantation of an extracted myopic SMILE lenticule from a donor patient. However, posterior surface changes and epithelial remodeling resulted in only 50% of the intended correction. No adverse side effects were observed following implantation of donor tissue for 1 year.
To longitudinally follow epithelial thickness profile changes after myopic LASIK for 1 year to determine when and how epithelial changes occur and when epithelial stability is reached.
Epithelial ...thickness was measured with Artemis very high-frequency digital ultrasound (ArcScan Inc) across the central 10-mm corneal diameter in 11 eyes before and 1 day, and 1, 3, 6, and 12 months after myopic femtosecond LASIK. For each consecutive pair of time points, maps of the mean change in epithelial thickness and paired t test P value were plotted.
Mean preoperative spherical equivalent refraction was -3.34 ± 1.51 diopters (D) (range: -1.50 to -5.13 D). Overnight, there was a central 5-mm zone of epithelial thickening (0.5 to 1.5 μm, P<.05) surrounded by epithelial thinning (4 to 6 μm, P<.05) extending to the 8-mm zone. Between 1 day and 1 month, the epithelium thickened within the 7-mm zone by up to 5 μm (P<.05) in a lenticular pattern with greater thickening centrally and progressively less thickening centrifugally. Between 1 and 3 months, the epithelium continued to thicken in the central 7-mm zone by approximately 1 μm (P<.05). No change in epithelial thickness occurred after 3 months (P>.05).
A lenticular change occurred in the epithelial thickness profile, with more thickening centrally than paracentrally; 22% of the total increase in central thickness occurred overnight, 58% between 1 day and 1 month, and 20% between 1 and 3 months, with stability between 3 and 12 months. The lenticular epithelial changes contribute to the observed myopic shift after myopic LASIK during the first 3 months.
To assess the effectiveness of a keratoconus-detection algorithm derived from Artemis very high-frequency (VHF) digital ultrasound (ArcScan Inc., Morrison, CO) epithelial thickness maps in the fellow ...eye from a series of patients with unilateral keratoconus.
The study included 10 patients with moderate to advanced keratoconus in one eye but a clinically and algorithmically topographically normal fellow eye. VHF digital ultrasound epithelial thickness data were acquired and a previously developed classification model was applied for identification of keratoconus to the clinically normal fellow eyes. Pentacam (Oculus Optikgeräte, Wetzlar, Germany) Belin-Ambrósio Enhanced Ectasia Display "D" score (BAD-D) data (5 of 10 eyes), and Orbscan (Bausch & Lomb, Rochester, NY) SCORE data (9 of 10 eyes) were also evaluated.
Five of the 10 fellow eyes were classified as keratoconic by the VHF digital ultrasound epithelium model. Five of 9 fellow eyes were classified as keratoconic by the SCORE model. For the 5 fellow eyes with Pentacam and VHF digital ultrasound data, one was classified as keratoconic by the VHF digital ultrasound model, one (different) eye by a combined VHF digital ultrasound and Pentacam model, and none by BAD-D alone.
Under the assumption that keratoconus is a bilateral but asymmetric disease, half of the 'normal' fellow eyes could be found to have keratoconus using epithelial thickness maps. The Orbscan SCORE or the combination of topographic BAD-D criteria with epithelial maps did not perform better.
To compare measurements of corneal epithelial thickness using optical coherence tomography (OCT) and very high-frequency digital ultrasound (VHFDU).
Retrospective analysis of 189 virgin corneas and ...175 post-laser refractive surgery (LRS) corneas that had corneal epithelial thickness measurement with RTVue Fourier-domain OCT (Optovue, Inc., Fremont, CA) (tear film included) and Artemis VHFDU (ArcScan Inc., Morrison, CO) (tear film excluded). Averages were calculated for the central 2-mm diameter zone and for two further concentric annuli of 1.5- and 0.5-mm width, each divided into eight sectors. Agreement was analyzed by mean difference (OCT - VHFDU), 95% limits of agreement (LoA) (1.96 standard deviation of the difference), and Bland-Altman analysis.
In virgin epithelium, mean central thickness was 53.4 ± 3.20 µm (range: 46 to 62 µm) with OCT and 54.1 ± 2.96 µm (range: 48 to 61 µm) with VHFDU; OCT measured thinnest in 70% with a mean difference of -0.71 µm (95% LoA of ± 3.94 µm, P < .001). In post-LRS epithelium, mean central thickness was 57.9 ± 6.08 µm (range: 42 to 77 µm) with OCT and 60.5 ± 6.47 µm (range: 42 to 79 µm) with VHFDU; OCT measured thinnest in 88%, with a mean difference of -2.48 µm (95% LoA of ± 5.33 µm, P < .001). A larger difference between methods was more common with thicker epithelium.
Corneal epithelial thickness measurements using OCT were found to be slightly thinner than for VHFDU. In contrast to VHFDU, OCT measurement includes the tear film, so the true difference is probably approximately 4 µm more than reported. The difference was greatest inferiorly and higher for post-LRS eyes and in thicker epithelium.
To evaluate the accuracy of the lenticule thickness readout for small incision lenticule extraction (SMILE) with the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany).
Artemis very ...high-frequency digital ultrasound (ArcScan, Inc., Morrison, CO) measurements were obtained before and 3 months after SMILE in 70 eyes of 37 patients. The Artemis measured lenticule thickness was calculated as the maximum difference in stromal thickness before and after treatment. Comparative statistics and linear regression analysis were performed between the VisuMax readout lenticule thickness and Artemis measured maximum stromal change. Central epithelial thickness was measured and a similar analysis was performed using corneal thickness. Variability of the data were compared to ablation depths for a matched group of eyes from a previously published LASIK population treated with the MEL80 excimer laser (Carl Zeiss Meditec).
The mean maximum myopic meridian treated was -7.81 ± 2.33 diopters (range: -2.25 to -12.50 diopters). On average, the VisuMax readout lenticule depth was 8.2 ± 8.0 μm thicker (range: -8 to +29 μm) than the Artemis measured stromal change (P < .001). On average, central epithelial thickness was 15.0 ± 5.2 μm thicker (range: 5 to 30 μm) after the procedure. The VisuMax readout lenticule thickness was 23.2 ± 10.9 μm thicker (range: +5 to +49 μm) than the Artemis measured corneal thickness change. The R(2) of 0.868 for the SMILE group was higher than 0.738 for the LASIK group (P = .015).
The accuracy of SMILE lenticule thickness was found to be higher than actual measured stromal thickness change; however, predictability for SMILE lenticule thickness appeared higher than predictability for excimer laser ablation depth. The VisuMax readout lenticule depth was found to be 8 μm thicker than the achieved stromal change. This can be partly explained by alignment errors between preoperative and postoperative scans. However, this appears to show some biomechanical changes occur after SMILE.
To evaluate the accuracy and reproducibility of cap thickness for small incision lenticule extraction (SMILE) with the VisuMax femtosecond laser (Carl Zeiss Meditec, Inc., Jena, Germany).
Artemis ...very high-frequency digital ultrasound (ArcScan Inc., Morrison, CO) measurements were obtained before and 3 months after SMILE in 70 eyes of 37 patients with intended cap thickness between 80 and 140 μm. True cap thickness at the time of creation was calculated as the addition of the preoperative epithelial thickness and the postoperative stromal component of the flap and mapped for the central 5-mm diameter zone. Cap thickness accuracy was calculated as the difference between the mean and intended cap thickness. Reproducibility was evaluated as the cap thickness standard deviation between eyes. Accuracy and reproducibility of cap thickness were calculated for all eyes and grouped by intended cap thickness. Within-eye variation in cap thickness was calculated as the standard deviation of all data within the central 5-mm diameter zone.
Mean cap thickness accuracy was between -2.3 and 6.5 μm and was -0.7 μm centrally (range: -11 to +14 μm), including all eyes. Cap thickness reproducibility was 6 μm or less for the majority of the central 5-mm diameter zone and was 4.4 μm centrally. Cap thickness accuracy and reproducibility were similar for different intended cap thicknesses. Average within-eye variation in cap thickness was 4.3 μm.
SMILE cap thickness using the VisuMax femtosecond laser was found to be accurate and reproducible across the central 5-mm diameter zone for intended cap thicknesses over the range of 80 to 140 μm.
PDF
