Vardhaman P. Kankariya

Femtosecond laser technology in corneal refractive surgery: a review.

PURPOSE To discuss current applications and advantages of femtosecond laser technology over traditional manual techniques and related unique complications in corneal refractive surgical procedures, including LASIK flap creation, intracorneal ring segment implantation, astigmatic keratotomy, presbyopic treatments, and intrastromal lenticule procedures. METHODS Literature review. RESULTS From its first clinical use in 2001 for LASIK flap creation, femtosecond lasers have steadily made a place as the dominant flap-making technology worldwide. Newer applications are being evaluated and are increasing in their frequency of use. CONCLUSIONS Femtosecond laser technology is rapidly becoming a heavily utilized tool in corneal refractive surgical procedures due to its reproducibility, safety, precision, and versatility.

Correlation of the Corneal Collagen Cross-Linking Demarcation Line Using Confocal Microscopy and Anterior Segment Optical Coherence Tomography in Keratoconic Patients

PURPOSE To evaluate and compare the depth of the corneal stromal demarcation line after corneal collagen cross-linking (CXL) using 2 different methods: confocal microscopy and anterior segment optical coherence tomography (AS OCT). DESIGN Prospective, comparative, interventional case series. METHODS Seventeen patients (18 eyes) with progressive keratoconus were enrolled. All patients underwent uneventful CXL treatment according to the Dresden protocol. One month after surgery, corneal stromal demarcation line depth was measured in all patients by 2 independent observers using confocal microscopy and AS OCT. RESULTS Mean corneal stromal demarcation line depth measured using confocal microscopy by the first observer was 306.22 ± 51.54 μm (range, 245 to 417 μm) and that measured by the second observer was 303.5 ± 46.98 μm (range, 240 to 390 μm). The same measurements using AS OCT were 300.67 ± 41.56 μm (range, 240 to 385 μm) and 295.72 ± 41.01 μm (range, 228 to 380 μm) for the first and second observer, respectively. Pairwise comparisons did not reveal any statistically significant difference between confocal microscopy and AS OCT measurements for both observers (P = .3219 for the first observer and P = .1731 for the second observer). CONCLUSIONS Both confocal microscopy and AS OCT have similar results in evaluating the depth of the corneal stromal demarcation line after CXL.

Long-term Follow-up of Corneal Collagen Cross-linking for Keratoconus — The Cretan Study

Purpose: The aim of this study was to present the long-term results of corneal collagen cross-linking (CXL) in patients with keratoconus. Methods: In this prospective, interventional case series, patients with progressive keratoconus underwent CXL treatment according to the Dresden protocol. Visual, refractive, and topographic outcomes along with endothelial cell density were evaluated preoperatively and at 1, 2, 3, 4, and 5 years postoperatively. Results: Twenty-one patients (25 eyes) were enrolled. The mean follow-up was 43.7 ± 12.2 (range, 24–60) months. Logarithm of the minimum angle of resolution (logMAR) mean uncorrected visual acuity and the mean best spectacle-corrected visual acuity improved significantly from 0.92 ± 0.54 and 0.29 ± 0.21 preoperatively to 0.63 ± 0.41 (P = 0.010) and 0.18 ± 0.18 (P = 0.011), respectively, at the last follow-up. Mean steep and mean flat keratometry readings reduced significantly from 52.53 ± 6.95 diopters (D) and 48.11 ± 5.98 D preoperatively to 49.10 ± 4.50 D (P < 0.001) and 45.58 ± 3.81 D (P = 0.001), respectively, at the last follow-up. The mean endothelial cell density was 2708 ± 302 cells per square millimeter preoperatively and did not change significantly (P > 0.05) at any postoperative interval (2593 ± 258 cells/mm2 at the last follow-up; P = 0.149). Conclusions: CXL seems to be effective and safe in halting progression of keratoconus over a long-term follow-up period up to 5 years postoperatively.

Evaluation of the corneal collagen cross-linking demarcation line profile using anterior segment optical coherence tomography.

Purpose: To evaluate the depth of the stromal demarcation line after corneal collagen cross-linking (CXL) using anterior segment optical coherence tomography. Methods: In this prospective, interventional case series, 23 patients (27 eyes) with progressive keratoconus were enrolled. All patients underwent uneventful CXL treatment. Corneal stromal demarcation line depth was measured centrally, 3 mm temporally, and 3 mm nasally by 2 independent observers using anterior segment optical coherence tomography at 1 month postoperatively in all patients. Results: Mean depth of the corneal stromal demarcation line measured by the first observer was 310.67 ± 31.04 &mgr;m (range, 258–364 &mgr;m) centrally, 212.07 ± 24.5 &mgr;m (range, 178–279 &mgr;m) nasally, and 218.04 ± 21.91 &mgr;m (range, 191–261 &mgr;m) temporally. Mean depth of the corneal stromal demarcation line measured by the second observer was 308.78 ± 29 &mgr;m (range, 262–381 &mgr;m) centrally, 211.04 ± 23.93 &mgr;m (range, 180–277 &mgr;m) nasally, and 217.22 ± 25.51 &mgr;m (range, 179–271 &mgr;m) temporally. There was a statistically significant difference (P < 0.001) between central and both nasal and temporal depths of the corneal stromal demarcation line (paired samples t test) for both observers. There was no statistically significant difference between nasal and temporal corneal stromal demarcation line depths (paired samples t test, P > 0.05) for each observer. Conclusions: Mean depth of the corneal stromal demarcation line after CXL treatment is greater centrally in comparison with nasal and temporal depths.

Management of pediatric keratoconus - evolving role of corneal collagen cross-linking: an update.

Pediatric keratoconus demonstrates several distinctive management issues in comparison with adult keratoconus with respect to under-diagnosis, poor compliance and modifications in treatment patterns. The major concerns comprise of the accelerated progression of the disease in the pediatric age group and management of co-morbidities such as vernal keratoconjuntivitis. Visual impairment in pediatric patients may affect social and educational development and overall negatively impact their quality of life. The treatment algorithm between adults and pediatric keratoconus has been similar; comprising mainly of visual rehabilitation with spectacles, contacts lenses (soft or rigid) and keratoplasty (lamellar or penetrating) depending on the stage of the disease. There is a paradigm shift in the management of keratoconus, a new treatment modality, corneal collagen crosslinking (CXL), has been utilized in adult keratoconic patients halting the progression of the disease. CXL has been utilized for over a 10 year period and based on the evidence of efficacy and safety in the adult population; this treatment has been recently utilized in management of pediatric keratoconus. This article will present an update about current management of pediatric keratoconus with special focus on CXL in this age group.

Safety of high-intensity corneal collagen crosslinking

Purpose To evaluate the safety of a new high‐intensity corneal collagen crosslinking (CXL) treatment protocol for keratoconus. Setting Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece. Design Prospective interventional case series. Methods Patients with progressive keratoconus had CXL using a new treatment protocol with 9 mW/cm2 irradiance for duration of 10 minutes. The rate of reepithelialization, endothelial cell density (ECD), corrected distance visual acuity (CDVA), and steep and flat keratometry (K) values were evaluated preoperatively and 3 months postoperatively. Results Nine patients (10 eyes) were enrolled. No intraoperative or early postoperative complications were observed in any patient. The ECD did not change significantly 3 months postoperatively (P=.169). The CDVA improved from 0.19 logMAR ± 0.20 (SD) preoperatively to 0.10 ± 0.16 logMAR 3 months postoperatively; however, the improvement did not attain significance (P=.141). No eye lost lines of CDVA. The mean steep K readings decreased significantly from 48.04 ± 2.57 diopters (D) preoperatively to 46.51 ± 2.81 D 3 months postoperatively (P=.047); the mean flat K readings did not change significantly postoperatively (P=.285). Conclusions Corneal collagen crosslinking at 9 mW/cm2 irradiance for 10 minutes did not cause significant changes in ECD or intraoperative or early postoperative complications. None patient lost a line of CDVA 3 months after the procedure. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Long-term results of combined transepithelial phototherapeutic keratectomy and corneal collagen crosslinking for keratoconus: Cretan protocol

Purpose To present the long‐term results of combined transepithelial phototherapeutic keratectomy (PTK) and corneal collagen crosslinking (CXL) for keratoconus. Setting Vardinoyiannion Eye Institute of Crete, University of Crete, Heraklion, Crete, Greece. Design Prospective case series. Methods Patients with progressive keratoconus had combined transepithelial PTK and CXL (Cretan protocol). Visual and refractive outcomes and the endothelial cell density (ECD) were evaluated preoperatively and postoperatively. Results Twenty patients (23 eyes) were enrolled; postoperatively 23 eyes were evaluated at 1 and 2 years, 11 at 3 years, and 7 at 4 years. The mean follow‐up was 33.83 months ± 10.82 (SD) (range 24 to 56 months). No intraoperative or postoperative complications occurred. The mean uncorrected distance visual acuity improved significantly from 0.99 ± 0.57 logMAR preoperatively to 0.61 ± 0.36 logMAR at the last follow‐up (P < .001) and the mean corrected distance visual acuity, from 0.27 ± 0.24 logMAR to 0.17 ± 0.14 logMAR (P = .018), respectively. The mean steep and mean flat keratometry readings decreased significantly from 53.39 ± 7.14 diopters (D) and 47.17 ± 4.87 D, respectively, preoperatively to 49.99 ± 4.36 D (P < .001) and 45.47 ± 2.95 D (P = .002), respectively, at the last follow‐up. The mean corneal astigmatism improved significantly from −6.27 ± 4.19 D preoperatively to −4.52 ± 2.80 D (P < .001) at the last follow‐up. No significant ECD alterations occurred (P > .05). Conclusion Combined transepithelial PTK and CXL was effective and safe in keratoconic patients over a long‐term follow‐up. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Comparative study of stromal bed of LASIK flaps created with femtosecond lasers (IntraLase FS150, WaveLight FS200) and mechanical microkeratome

Background/aim To compare stromal bed smoothness in LASIK flaps created with two different femtosecond lasers (IntraLase FS150 and WaveLight FS200) and a mechanical microkeratome (MMK) (Carriazo-Pendular microkeratome). Methods Sixty freshly enucleated porcine eyes were used for the study. Twenty flaps were created and constitute each of the following three groups: IntraLase FS150 (IFS group), WaveLight FS200 (WFS group) and MMK (MMK group). In each of the three groups, 10 flaps were created with intended thickness of 110 μm and another 10 flaps with 130 μm. Images were assessed with light microscopy and scanning electron microscopy. Qualitative surface roughness grading of the images was performed by five masked observers and statistical comparisons of scores were made between groups. Results The results of qualitative surface roughness grading demonstrated that there was no significant difference between the two femtosecond (FS) lasers when comparing the subgroups with the same flap thickness (p>0.05 in both comparisons, Mann–Whitney U test). In addition, there was no statistically significant difference (p>0.05) in each flap maker group between different thickness subgroups. However, the scores of the FS laser subgroups were significantly better than the scores of the MMK subgroups with corresponding flap thicknesses (p<0.05, Mann–Whitney U test). Conclusions Our study demonstrates that the IntraLase FS150 and the WaveLight FS200 had a similar performance and provided flaps with smooth surfaces. In comparison to the MMK, the studied femtosecond laser systems had a superior performance in terms of smoothness.

Effect of Corneal Collagen Cross-Linking on Corneal Innervation, Corneal Sensitivity, and Tear Function of Patients with Keratoconus

PURPOSE To evaluate the effect of corneal collagen cross-linking (CXL) on corneal innervation, corneal sensitivity, and tear function in patients with keratoconus. DESIGN Prospective, interventional case series. PARTICIPANTS Twenty-four patients with bilateral keratoconus (30 eyes) who presented to the Institute of Vision and Optics, University of Crete, from May 2008 to October 2008. METHODS Patients underwent CXL. Confocal microscopic analysis of corneal sub-basal nerve plexus (total nerve length per image), corneal sensitivity (assessed with the Cochet-Bonnet esthesiometer), basic tear secretion (assessed with Schirmers I test with anesthesia), and tear film stability (evaluated by means of tear film break-up time [TFBUT]) were assessed preoperatively and at 1, 3, 6, 9, 12, 18, and 24 months postoperatively. MAIN OUTCOME MEASURES Comparisons between preoperative and each postoperative value of total nerve length per image, corneal sensitivity, Schirmers I test results, and TFBUT. RESULTS Total nerve length per image and corneal sensitivity were significantly decreased until postoperative month 6 (for both parameters: P<0.05 paired-samples t test at 1, 3, and 6 months postoperatively). Total nerve length per image tended to increase up to 2 years postoperatively, when it reached the preoperative level, but differences with the preoperative values after the sixth post-CXL month were insignificant. The results of Schirmers I test and TFBUT had no statistically significant difference at any time point. CONCLUSIONS A transient decrease in corneal innervation and corneal sensitivity can be observed up to 6 months after CXL. No significant effect of CXL could be detected on basic tear secretion and tear film stability in our group of patients. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Combined treatment with flap amputation, phototherapeutic keratectomy, and collagen crosslinking in severe intractable post-LASIK atypical mycobacterial infection with corneal melt.

A 23-year-old woman was referred for management of intractable post-laser in situ keratomileusis (LASIK) keratitis due to atypical mycobacteria in the left eye. Corrected distance visual acuity was 20/20 in the right eye and counting fingers at 3 meters in the left eye. Slitlamp examination revealed multiple infiltrates in the flap interface and severe corneal stromal melting with thinning. Despite maximum antibiotic therapy for 7 days, the keratitis continued to worsen. A penetrating keratoplasty (PKP) was scheduled. While waiting for a corneal graft, corneal collagen crosslinking (CXL) with riboflavin and ultraviolet-A was proposed as an alternative treatment. Flap amputation and limited phototherapeutic keratotomy (PTK) (10 μm) were also performed. One week postoperatively, all infiltrates and stromal edema had resolved. At 3 months, the uncorrected distance visual acuity improved to 20/35. Corneal crosslinking after flap amputation and limited PTK was an effective treatment for severe intractable post-LASIK keratitis with corneal melting and obviated PKP.