Efekan Coskunseven

Contralateral eye study of corneal collagen cross-linking with riboflavin and UVA irradiation in patients with keratoconus

PURPOSE To assess the progression of keratoconus in patients treated with collagen cross-linking with riboflavin and ultraviolet A (UVA) irradiation. METHODS Thirty-eight eyes of 19 patients with progressive keratoconus were enrolled in a prospective comparative study. Average follow-up was 9 +/- 2 months (range: 5 to 12 months). The worse eye was treated with collagen cross-linking, and the fellow eye served as the control. Corneal epithelium was mechanically removed. Riboflavin 0.1% solution in dextran T-500 20% solution was applied every 2 to 3 minutes for 30 minutes throughout the irradiation. Ultraviolet A irradiation (370 nm) was performed using a commercially available UVA lamp for 30 minutes. RESULTS The group treated with collagen crosslinking demonstrated a mean decrease (less myopic) in spherical equivalent refraction and cylinder of 1.03 +/- 2.22 diopters (D) (range: -5.25 to +3.75 D) and 1.04 +/- 1.44 D (range: -2.00 to +4.00 D), respectively (P < .01), and an increase in uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA) of 0.06 +/- 0.05 (range: 0.00 to 0.20) and 0.10 +/- 0.14 (range: -0.10 to 0.34), respectively (P < .01). The maximal curvature decreased by 1.57 +/- 1.14 D (range: 0.00 to 3.90 D), and intraocular pressure increased by 2 +/- 2 mmHg (range: -1 to 6 mmHg), which was statistically significant. No statistical difference was noted regarding central corneal thickness (P = .06) and endothelial cell count (P = .07). The untreated group showed no statistical difference for any of the clinical parameters, apart from UCVA and BSCVA, which decreased by 0.08 +/- 0.12 (range: -0.40 to 0.10) and 0.06 +/- 0.09 (range: -0.20 to 0.10), respectively (P < .01). CONCLUSIONS Riboflavin/UVA collagen cross-linking appears to be efficacious in inhibiting the progression of keratoconus by reducing the corneal curvature, spherical equivalent refraction, and refractive cylinder in eyes with progressive keratoconus at average 9-month follow-up.

Effect of treatment sequence in combined intrastromal corneal rings and corneal collagen crosslinking for keratoconus.

PURPOSE: To compare 2 sequences of combined intrastromal corneal ring segment (ICRS) implantation and ultraviolet/riboflavin–mediated corneal collagen crosslinking (CXL) in progressive keratoconus. SETTING: Dunya Eye Hospital, Istanbul, Turkey. METHODS: In this prospective comparative randomized consecutive study, CXL was followed by ICRS implantation (Group 1) or ICRS implantation was followed by CXL (Group 2). Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, spherical equivalent (SE), manifest cylinder (cylinder), and mean keratometry (K) were compared preoperatively and postoperatively. RESULTS: The mean interval between treatments was 7 months ± 2 (SD) (mean follow‐up, 13 ± 1 months). The mean UDVA and CDVA improved in both groups (UDVA: 0.07 ± 0.09 to 0.25 ± 0.12, Group 1, and 0.11 ± 0.09 to 0.32 ± 0.21, Group 2; CDVA: 0.24 ± 0.11 to 0.41 ± 0.20 and 0.22 ± 0.16 to 0.55 ± 0.2, respectively). The mean SE, cylinder, and mean K values decreased in both groups (SE: −7.13 ± 3.34 D to −2.98 ± 2.33 D, Group 1, and −7.05 ± 5.54 D to −2.81 ± 4.08 D, Group 2; cylinder: −4.38 ± 2.03 D to −2.62 ± 1.93 D and −4.68 ± 2.60 D to −2.20 ± 1.67 D, respectively; mean K: 52.47 ± 4.01 D to 48.31 ± 3.65 D and 52.06 ± 4.93 D to 48.08 ± 4.13 D, respectively). Overall, there was more improvement in CDVA, SE, and mean K in Group 2 than in Group 1. CONCLUSION: Implantation of ICRS followed by CXL resulted in greater improvement of keratoconus.

Refractive and Aberrometric Outcomes of Intracorneal Ring Segments for Keratoconus: Mechanical versus Femtosecond-assisted Procedures

OBJECTIVE To compare visual, refractive, and corneal aberrometric outcomes in keratoconic eyes implanted with intracorneal ring segments (ICRS) implantation using either a mechanical or a femtosecond laser-assisted procedure. DESIGN Retrospective, consecutive case series. PARTICIPANTS A total of 146 consecutive eyes of 106 patients with the diagnosis of keratoconus (68 unilateral and 39 bilateral) were included. Two groups were created according to the surgical technique used for corneal tunnelization: Mechanical group (mechanical tunnelization, 63 eyes) and Femtosecond group (femtosecond laser-assisted tunnelization, 83 eyes). Intracorneal ring segments implantation was indicated because of the existence of reduced best spectacle-corrected visual acuity (BSCVA) or contact lens intolerance. METHODS Intracorneal ring segments implantations were performed by 6 surgeons following the same protocol except for the incision location. A total of 55 eyes were implanted with Intacs (Addition Technology, Inc, Fremont, CA) and 8 eyes were implanted with KeraRings (Mediphacos, Belo Horizonte, Brazil) in the Mechanical group, and 25 eyes were implanted with Intacs and 58 eyes were implanted with KeraRings in the Femtosecond group. Mean follow-up was 10.66+/-8.20 months, ranging from 1 month to 24 months. MAIN OUTCOME MEASURES Uncorrected visual acuity (UCVA), BSCVA, refraction, keratometry, and root mean square (RMS) for different kinds of corneal aberrations. RESULTS By reporting only for statistically significant changes, UCVA improved in both groups at 6 months (P< or =0.02) and BSCVA improved in the Femtosecond group (P<0.01). The refraction improved in both groups at 6 months (P< or =0.02). The cornea on average was flatter in both groups at 6 months (P<0.01). Root mean square astigmatism was reduced in the Femtosecond group (P = 0.03), but there was an increase in some higher-order aberrations (P = 0.03). Significant differences were found between the 2 groups for eyes implanted with Intacs for primary spherical aberration, coma, and other higher-order aberrations, favoring the Femtosecond group (P< or =0.01). A significant negative correlation was found between the preoperative corneal aberrations and the postoperative BSCVA in the Mechanical group (r>0.63, P< or =0.04). CONCLUSIONS Intracorneal ring segments implantation using both mechanical and femtosecond laser-assisted procedures provide similar visual and refractive outcomes. A more limited aberrometric correction is observed for eyes with mechanical implantation. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Intraoperative Pachymetric Measurements during Corneal Collagen Cross-Linking with Riboflavin and Ultraviolet A Irradiation

OBJECTIVE To study central corneal pachymetric variations during corneal collagen cross-linking (CXL) treatment with the use of riboflavin and ultraviolet A irradiation (UVA). DESIGN Prospective, noncomparative, interventional clinical study. PARTICIPANTS Fifteen keratoconic patients (19 eyes) were enrolled. METHODS All patients underwent riboflavin-UVA-induced corneal CXL. Intraoperative central corneal thickness (CCT) measurements using ultrasound pachymetry were performed during the procedure. Measurements were obtained after epithelial removal, after riboflavin drop instillation, and every 5 minutes (6 interval times) during UVA irradiation (30 minutes). MAIN OUTCOME MEASURES Central corneal thickness measurements. RESULTS Mean patient age was 26.9+/-6.5 years (range, 17-40 years). Ten were male and 5 were female. Mean preoperative CCT was 458.5+/-21.5 microm (range, 427-494 microm; 95% confidence interval [CI], 448-467 microm) and 415.7+/-20.6 microm (range, 400-468 microm; 95% CI, 406-426 microm) before and after epithelial removal, respectively. There was a statistically significant decrease (mean, 75 microm) of CCT between the epithelial removal interval (415.7+/-20.6 microm; range, 400-468 microm) and at the end of riboflavin solution instillation (340.7+/-22.9 microm; range, 292-386 microm; P<0.001). There was no statistically significant change in CCT during irradiation (P>0.05). There was no statistically significant difference between preoperative and 1-month postoperative endothelial cell count (preoperative, 2780+/-197 to 1-month postoperative, 2713+/-116; P = 0.14). No intraoperative, early postoperative, or late postoperative complications were observed in this patient series. CONCLUSIONS During corneal CXL with the use of riboflavin and UVA irradiation, a statistically significant decrease of CCT was demonstrated.

Complications of intrastromal corneal ring segment implantation using a femtosecond laser for channel creation: a survey of 850 eyes with keratoconus

Acta Ophthalmol. 2011: 89: 54–57

Corneal collagen cross-linking

Corneal collagen cross-linking (CXL) with riboflavin and ultraviolet-A (UVA) is a new technique of corneal tissue strengthening by using riboflavin as a photosensitizer and UVA to increase the formation of intra and interfibrillar covalent bonds by photosensitized oxidation. Keratocyte apoptosis in the anterior segment of the corneal stroma all the way down to a depth of about 300 microns has been described and a demarcation line between the treated and untreated cornea has been clearly shown. It is important to ensure that the cytotoxic threshold for the endothelium has not been exceeded by strictly respecting the minimal corneal thickness. Confocal microscopy studies show that repopulation of keratocytes is already visible 1 month after the treatment, reaching its pre-operative quantity and quality in terms of functional morphology within 6 months after the treatment. The major indication for the use of CXL is to inhibit the progression of corneal ectasias, such as keratoconus and pellucid marginal degeneration. CXL may also be effective in the treatment and prophylaxis of iatrogenic keratectasia, resulting from excessively aggressive photoablation. This treatment has also been used to treat infectious corneal ulcers with apparent favorable results. Combination with other treatments, such as intracorneal ring segment implantation, limited topography-guided photoablation and conductive keratoplasty have been used with different levels of success.

Posterior Linear Stromal Haze Formation after Simultaneous Photorefractive Keratectomy followed by Corneal Collagen Cross-linking

PURPOSE To report the development of posterior linear stromal haze after simultaneous photorefractive keratectomy (PRK) followed by corneal collagen cross-linking (CXL). METHODS Combined simultaneous customized PRK followed by corneal collagen cross-linking was performed in 23 patients (28 eyes) with keratoconus. Corneas were examined biomicroscopically and by means of confocal microscopy before surgery and 1, 3, 6, 9, and 12 months after surgery. RESULTS Posterior linear stromal haze was observed clinically (slit lamp biomicroscopy) one month after surgery in 13 of 28 eyes (46.42%). No corneal edema or anterior haze formation was evident. Confocal microscopy revealed in those 13 eyes a hyperreflective area at the level of the posterior stroma 1 month after combined treatment. Both slit lamp examination and corneal confocal microscopy follow-up demonstrated a gradual anterior movement and a decrease in reflectance of this finding. At 12 months this posterior linear stromal haze, despite its anterior movement and decreased density, did not completely disappear at slit lamp and confocal microscopy analysis. CONCLUSIONS Posterior linear stromal haze formation may appear after simultaneous PRK followed by CXL in patients with keratoconus. This finding seems to gradually become less dense and slowly moves toward the anterior stroma.

Topography-guided Transepithelial PRK After Intracorneal Ring Segments Implantation and Corneal Collagen CXL in a Three-Step Procedure for Keratoconus

PURPOSE To present the results of topography-guided transepithelial photorefractive keratectomy (PRK) after intracorneal ring segments implantation followed by corneal collagen cross-linking (CXL) for keratoconus. METHODS In this prospective case series, 10 patients (16 eyes) with progressive keratoconus were included. All patients underwent topography-guided transepithelial PRK after Keraring intracorneal ring segments (Mediphacos Ltda) implantation, followed by CXL treatment. The follow-up period was 6 months after the last procedure for all patients. Time interval between both intracorneal ring segments implantation and CXL and between CXL and topography-guided transepithelial PRK was 6 months. RESULTS LogMAR mean uncorrected distance visual acuity and mean corrected distance visual acuity were significantly improved (P<.05) from 1.14±0.36 and 0.75±0.24 preoperatively to 0.25±0.13 and 0.13±0.06 after the completion of the three-step procedure, respectively. Mean spherical equivalent refraction was significantly reduced (P<.05) from -5.66±5.63 diopters (D) preoperatively to -0.98±2.21 D after the three-step procedure. Mean steep and flat keratometry values were significantly reduced (P<.05) from 54.65±5.80 D and 47.80±3.97 D preoperatively to 45.99±3.12 D and 44.69±3.19 D after the three-step procedure, respectively. CONCLUSIONS Combined topography-guided transepithelial PRK with intracorneal ring segments implantation and CXL in a three-step procedure seems to be an effective, promising treatment sequence offering patients a functional visual acuity and ceasing progression of the ectatic disorder. A longer follow-up and larger case series are necessary to thoroughly evaluate safety, stability, and efficacy of this innovative procedure.

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.

Customized pachymetric guided epithelial debridement for corneal collagen cross linking

BackroundWe describe a modified method for deepitheliazation prior to corneal cross linking (CXL). The technique may overcome the current corneal pachymetric limitation parameter (over 400 microns) that is necessary for the safety of the procedure without affecting the overall benefits.MethodsIn a series of two patients, with inferior topographic steepening and regional thinning (less than 400 microns corresponding to the area of corneal steepening), CXL after customized epithelial removal was performed.ResultsThere were no intra- or postoperative adverse events seen by the nine month follow up examination. Stabilization of the corneal ectasia was observed up to nine months post-costumized pachymetric-guided epithelial removal.ConclusionThe technique of customized pachymetric-guided epithelial removal is easy to perform and may overcome the limitations of the preoperative corneal pachymetry expanding the application of the procedure in patients with regional corneal thinning.