Sophia I. Panagopoulou

Induced optical aberrations following formation of a laser in situ keratomileusis flap

Purpose: To determine how refractive error, visual acuity, and high‐order aberrations (3rd‐ and 4th‐order) are affected by the formation of a lamellar corneal flap during laser in situ keratomileusis (LASIK). Setting: University refractive surgery center. Methods: The effect of lamellar corneal flap formation was analyzed in 15 myopic eyes (mean preoperative refraction −4.72 diopters [D] [range −1.25 to −7.25 D]). The flap was created using a 2‐step procedure: (1) a nasally hinged lamellar corneal flap was created; (2) the flap was lifted and stromal ablation performed 2 months after the flap was made. A Hartmann‐Shack aberrometer was used to measure the aberrations. Results: There was no significant change in the refractive error (spherical equivalent pre‐flap −4.72 ± 1.99 D and post‐flap −4.62 ± 1.99 D [P = .28]) or visual acuity (pre‐flap uncorrected visual acuity [UCVA] 0.07 and best corrected visual acuity [BCVA] 0.96; post‐flap UCVA 0.08 and BCVA 0.95 [P = .16 and P = .33, respectively]). A statistically significant increase in total higher‐order wavefront aberrations was observed following flap formation (root mean square pre‐flap 0.344 ± 0.125 and post‐flap 0.440 ± 0.221 [P = .04]). Conclusion: Flap formation during LASIK can modify the eyes existing natural higher‐order aberrations (especially spherical and coma‐like aberrations along the axis of the flaps hinge), while visual acuity and refractive error remain unaffected.

Corneal Collagen Cross-linking With Riboflavin and Ultraviolet-A Irradiation in Patients With Thin Corneas

PURPOSE To report the outcomes after corneal collagen cross-linking (CXL) treatment with riboflavin and ultraviolet-A (UVA) irradiation in patients with thin corneas (minimum corneal thickness less than 400 μm after epithelial removal and before riboflavin instillation). DESIGN Prospective case series. METHODS Twelve patients (14 eyes, with minimum corneal thickness less than 400 μm after epithelial removal) were included in the study. All patients underwent riboflavin-UVA-induced CXL using the standard CXL (Dresden) protocol. Uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) (decimal scale), manifest refraction (diopters, D), and topography were evaluated at baseline and at 1, 3, 6, and 12 months follow-up. Images of the endothelium were acquired with a modified confocal scanning laser ophthalmoscope. RESULTS No intraoperative or postoperative complications were observed in this patient series. Mean minimum preoperative corneal thickness at the apex of the cone after epithelial removal and before riboflavin instillation was 373.92 ± 22.92 μm (range 340-399 μm). UDVA and CDVA improved from 0.25 ± 0.15 and 0.40 ± 0.20 to 0.27 ± 0.17 and 0.49 ± 0.20 respectively at the last follow-up examination. There was a reduction of the mean keratometry readings from 51.99 ± 5.57 D to 49.33 ± 4.82 D at the last follow-up. A significant decrease of endothelial cell density was observed (preoperative: 2733 ± 180 cells/mm(2) [range 2467-3016], last follow-up visit: 2441 ± 400 cells/mm(2) [range 1448-2920], P < .01). CONCLUSIONS CXL in thin corneas with minimum corneal thickness less than 400 μm after epithelial removal seems to result in a significant endothelial cell density decrease postoperatively. This finding was not related to other intraoperative or postoperative complications.

Combined transepithelial phototherapeutic keratectomy and corneal collagen cross-linking for progressive keratoconus.

PURPOSE To compare the outcomes of corneal collagen cross-linking (CXL) for the treatment of progressive keratoconus using 2 different techniques for epithelial removal: transepithelial phototherapeutic keratectomy (t-PTK) versus mechanical epithelial debridement. DESIGN Prospective, comparative, interventional case series. PARTICIPANTS Thirty-four patients (38 eyes) with progressive keratoconus were enrolled. METHODS All patients underwent uneventful CXL treatment. Sixteen patients (19 eyes) underwent epithelial removal using t-PTK (group 1) and 18 patients (19 eyes) underwent mechanical epithelial debridement using a rotating brush (group 2) during CXL treatment. Visual and refractive outcomes were evaluated along with corneal confocal microscopy findings preoperatively and at 1, 3, 6, and 12 months postoperatively. MAIN OUTCOME MEASURES Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, and keratometry readings. RESULTS No intraoperative or postoperative complications were observed in any of the patients. In group 1, logarithm of the minimum angle of resolution mean UDVA and mean CDVA improved from 0.99 ± 0.71 and 0.30 ± 0.26 preoperatively to 0.63 ± 0.42 (P = 0.02) and 0.19 ± 0.18 (P = 0.008) at 12 months postoperatively, respectively. In group 2, neither mean UDVA nor mean CDVA demonstrated a significant improvement at 12 months postoperatively (P>0.05). In group 1, mean corneal astigmatism improved from -5.84 ± 3.80 diopters (D) preoperatively to -4.31 ± 2.90 D (P = 0.015) at the last follow-up, whereas in group 2 there was no significant difference at the same postoperative interval (P>0.05). No endothelial cell density alterations were observed throughout the follow-up period for both groups (P>0.05). CONCLUSIONS Epithelial removal using t-PTK during CXL results in better visual and refractive outcomes in comparison with mechanical epithelial debridement.

Eleven-year follow-up of laser in situ keratomileusis.

PURPOSE: To report the long‐term (11‐year) outcomes (stability and complications) of laser in situ keratomileusis (LASIK) in patients with high myopia. SETTING: University refractive surgery center. METHODS: Seven patients (4 with bilateral treatment and 3 with unilateral treatment) who had myopic LASIK and completed 11 years of follow‐up were included in the study. RESULTS: The mean age of the 2 men and 5 women was 41.7 years ± 6.5 (SD) (range 34 to 50 years). The mean follow‐up was 140.18 ± 6.70 months (range 132 to 150 months). At 11 years, the spherical equivalent error was statistically significantly reduced, from a mean of −12.96 ± 3.17 diopters (D) (range −19.00 to −10.00 D) before LASIK to a mean of −1.14 ± 1.67 D (range −4.25 to 1.00 D) after (P<.001). Predictability of postoperative refraction 6 months and 11 years after LASIK showed that 6 eyes (55%) were within ±1.00 D of intended correction. No late postoperative complications occurred. Five patients (8 eyes, 73%) were satisfied with the final outcome. CONCLUSIONS: Laser in situ keratomileusis was moderately predictable in the correction of high degrees of myopia. After the sixth postoperative month, refractive and topographic stability were obtained. No long‐term sight‐threatening complications occurred during the follow‐up period.

Wavefront Customized Ablations With the WASCA Asclepion Workstation

PURPOSE WASCA (Wavefront Aberration Supported Cornea Ablation) is a method for wavefront-guided ablation. This new method records all existing eye aberrations with the Asclepion Wavefront Aberrometer and calculates the customized pattern for laser correction. We measured the low and high order aberrations of eyes before and after PRK and LASIK, as well as before and after flap creation. METHODS The Asclepion Shack-Hartmann aberrometer was used to measure wavefront aberrations. Preoperative and postoperative measurements were made following both PRK and LASIK performed with conventional software, modified Aberration-free Profile (AFA) software, and specially designed WASCA software. Surgery was performed with the Meditec MEL-70 G-scan excimer laser. Additionally, measurements were made before and after flap creation only (10 eyes). RESULTS There was a significant difference between preoperative and 1-month postoperative high order aberrations, with notable increases following conventional PRK and LASIK and less increase following modified AFA PRK and LASIK. Flap creation only changed the higher order aberrations slightly, and caused a shift toward hyperopia. In the eyes that received WASCA correction with PRK or LASIK, at 3 months postoperative the high order aberrations averaged an increase of 1.3 times for PRK and 1.8 times for LASIK. Both the AFA and WASCA treatments demonstrated improved outcomes in comparison to conventional PRK and LASIK. CONCLUSION Wavefront mapping of the eye and wavefront-guided ablation with the Asclepion Aberrometer can be used for optimizing the results and fine-tuning visual performance after laser vision correction. WASCA PRK appeared to result in better outcomes than WASCA LASIK.

Visual Outcomes and Safety of a Small Diameter Intrastromal Refractive Inlay for the Corneal Compensation of Presbyopia

PURPOSE To investigate the outcomes and safety of an intrastromal refractive inlay (Invue Lens, Biovision AG) for the corneal compensation of presbyopia. METHODS This prospective, noncomparative, interventional clinical study comprised 45 emmetropic presbyopes with a mean age of 52.3 ± 3.3 years (range: 47 to 58 years). The refractive inlay was inserted in the non-dominant eye within a corneal pocket that was created using a mechanical microkeratome. Last follow-up was 12 months in all patients and examinations were scheduled at 1 week and 1, 3, 6, and 12 months after surgery. Visual, wavefront, contrast sensitivity, and topographic outcomes as well as structural corneal alteration were evaluated. RESULTS Twelve months after surgery, uncorrected near visual acuity was 20/32 or better in 98% of operated eyes and binocularly, whereas uncorrected distance visual acuity was 20/40 or better in 93% of operated eyes and 20/25 or better in all patients binocularly. Three patients lost one line of corrected distance visual acuity in the operated eye. Overall, higher order aberrations were increased and contrast sensitivity was decreased in the operated eye. No tissue alterations were found using corneal confocal microscopy. No intra- or postoperative complications occurred. CONCLUSIONS The intracorneal refractive inlay (Invue Lens) seems to be an effective surgical method for the corneal compensation of presbyopia in emmetropes aged between 45 and 60 years.

Laser in situ keratomileusis intraoperative complications using one type of microkeratome.

OBJECTIVE To identify the incidence and refractive outcome of intraoperative laser in situ keratomileusis (LASIK) complications using one type of microkeratome. DESIGN Retrospective noncomparative case series. PARTICIPANTS Three hundred thirty-four consecutive myopic LASIK patients (September 1997 to November 1998) operated on by one surgeon. INTERVENTION Myopic LASIK surgeries were performed with the Mediate Mel 60 Aesculap Meditec Laser system. MAIN OUTCOME MEASURES Preoperative and 1-year postoperative spherical equivalent, best spectacle-corrected visual acuity (BSVA), and corneal anatomic features (as obtained from videokeratography) were recorded, as was the incidence of intraoperative complications. RESULTS Forty-eight (14%) eyes had keratome-related complications. Thirty-seven (77%) eyes were immediately treated; the remaining eyes were treated on a later date. One year after treatment, 13% of the immediately treated complicated eyes maintained the preoperative BSVA; 24% had a 1-line loss; 2.7% had a greater loss of BSVA. CONCLUSIONS Microkeratome-related complications may result in loss of BSVA. The complication of an irregular flap had the poorest refractive outcome in this series of eyes. We did not find any statistically significant relationship between corneal anatomic factors and keratome-related complications in this series.

Principles of ray tracing aberrometry.

PURPOSE Of all transforms of an eye, aberrations are significant when higher visual acuity is to be achieved. Ray tracing aberrometry developed by the Institute of Biomedical Engineering (Kiev) and first tested at the Vardinoyannion Eye Institute of Crete is a promising technique for eye refraction aberration and refraction mapping. METHODS The technique uses measurement of the position of a thin laser beam projected onto the retina. The beam is directed into the eye parallel to the visual axis. Each entrance point provides its own projection on the retina. A set of entrance points forms a set of projections. From these data, a refraction map is reconstructed as well as a point spread function of the eye. The total time of scanning over the whole aperture of the eye is within 10 to 20 ms and depends on the number of test points at the eye entrance, as well as on the number of independent measurements in each point. Configuration of the scanning pattern can be chosen by the operator. It may contain 60 to 400 points, each checked 1 to 5 times. RESULTS Preliminary studies showed high reproducibility of results. Twenty pseudophakic eyes were subjected to 30 consecutive measurements each. Ninety-five percent of all measured values were within +/-0.20 D of declination from the mean. CONCLUSIONS Ray tracing aberrometry is a flexible technology for eye investigation. It can be adapted to any laser technique of vision correction Its further development should be oriented on laser-linked applications of the refraction driven refractive surgery.

Management of post laser in situ keratomileusis ectasia with simultaneous topography guided photorefractive keratectomy and collagen cross-linking.

A thirty-nine year old man was referred to our institute due to progressive decreased visual acuity five years after bilateral Laser in situ Keratomileusis (LASIK). Topography revealed signs of post – LASIK ectasia. Patients’ left eye was treated with simultaneous Topography Guided Photorefractive Keratectomy (PRK) followed by Corneal Collagen Cross Linking (CXL). Twelve months after the combined procedure both uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) showed significant improvement while topographic findings revealed an improvement of the astigmatic pattern. All higher order aberrations showed a significant decrease twelve months postoperatively. Combined topography guided PRK and corneal cross linking could represent an alternative treatment for post – LASIK ectasia.We consider a set of nine polycyclic conjugated hydrocarbons, which includes at one extreme benzene, the prototype of aromatic compounds, and at the other extreme cyclooctatetraene, a well-known nonaromatic compound, while the remaining seven compounds illustrate molecules of decreasing degree of aromaticity. Using the model of conjugated circuits for calculations of ring currents, we report on variations in the -electron ring currents in these molecules with the decrease of their degree of aromaticity. This contribution is a hybrid of original scientific paper and a review, and if viewed as provocative, it is so by design.

Phakic refractive lens implantation in high myopic patients ☆: One-year results

Purpose: To evaluate the efficacy and safety of implantation of a new posterior chamber phakic refractive lens (PRL, Ciba Vision Surgical) in highly myopic eyes. Setting: Department of Ophthalmology, Medical School, University of Crete, Vardinoyannion Eye Institute of Crete, Crete, Greece. Methods: Thirty‐four myopic eyes of 19 patients were treated for high myopia with implantation of a silicone PRL in the posterior chamber. Mean patient age was 29.0 years ± 7.9 (SD) (range 18 to 44 years). Manifest refraction in spherical equivalent (MR), uncorrected (UCVA) and best corrected (BCVA) visual acuity (decimal scale), intraocular pressure, higher‐order aberrations (root‐mean‐square [RMS] wavefront error measured with a Shack‐Hartmann wavefront sensor WASCA analyzer [Carl Zeiss, Meditec]), possible complications, and subjective symptoms were evaluated. Results: Phakic refractive lenses were successfully implanted in all eyes. Mean follow‐up was 17.17 ± 3.76 months (range 12 to 24 months). There was a statistically significant reduction in the MR (from −14.70 D ± 2.65 D [range −20.75 D to −10.50 D] to −0.61 D ± 0.89 D [range −2.25 D to 1.00 D]) (P<.001). Twenty‐seven (79%) and 15 eyes (44%) were within ±1.00 D and ±0.50 D of target refraction, respectively. Mean UCVA significantly improved (from counting fingers to 0.62 ± 0.28 (range 0.08 to 1.20) (P<.001). Mean BCVA also improved from 0.70 ± 0.24 (range 0.10 to 1.00) to 0.85 ± 0.24 (range 0.10 to 1.20) (P<0.001). Overall, there was a mean increase in BCVA of 1.5 ± 1.5 lines (range loss of 2 lines to gain of 5 lines). There was no statistically significant difference in higher‐order aberrations after PRL implantation (pre‐PRL RMS: 0.18 &mgr;m ± 0.08 &mgr;m [range 0.09 &mgr;m to 0.38 &mgr;m]; post‐PRL RMS: 0.21 &mgr;m ± 0.08 &mgr;m; [range 0.05 &mgr;m to 0.38 &mgr;m]) (P = .12). Conclusion: The PRL showed encouraging results in treating high myopia. Additional patients and longer follow‐up period are needed to detect the long‐term efficacy and safety of this refractive lens.