Blurring Strength & Aberrometric Changes Following Corneal Cross-linking (CxL) and CxL Combined With Photorefractive Keratectomy (PRK) in Keratoconus
|Keratoconus||Procedure: Corneal Collagen Cross-Linking (CxL) Procedure: Corneal Collagen Cross-Linking combined with t-PRK|
|Study Design:||Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: Open Label
Primary Purpose: Treatment
|Official Title:||Blurring Strength & Aberrometric Changes Following Corneal Cross-linking (CxL) and CXL Combined With Photorefractive Keratectomy (PRK) in Keratoconus.|
- Higher order corneal aberations [ Time Frame: 1 year postoperatively ]
|Study Start Date:||September 2010|
|Study Completion Date:||January 2012|
|Primary Completion Date:||December 2011 (Final data collection date for primary outcome measure)|
Experimental: CxL group
Volunteers of this group received CxL treatment.
Procedure: Corneal Collagen Cross-Linking (CxL)
The same surgical procedure was applied to all keratoconus patients that included: Instillation of proparacaine hydrochloride 0.5% drops for topical anaesthesia, application of a sponge saturated with 10% alcohol to the central cornea for 30 seconds and subsequent de-epithelialization by means of a hockey knife. Following de-epithelialization, a mixture of 0.1% riboflavin in 20% Dextran solution was instilled to the cornea for 30 minutes (2 drops every 2 minutes) prior to the irradiation, until the stroma was completely penetrated and aqueous was stained yellow. The UVA radiation source was UV-XTM Zurich, . Instillation of riboflavin drops (1 drop every 2 minutes) was continued during irradiation, as well, in order to sustain the necessary concentration of the riboflavin. Moreover, balanced salt solution (BSS) was applied every 6 minutes to moisten the cornea.
Experimental: tCxL group
Volunteers of this group received CxL combined with t-PRK treatment
Procedure: Corneal Collagen Cross-Linking combined with t-PRK
For tCxL group, the topo-guided PRK preceded the CXL. The epithelium was mechanically removed with a hockey knife and ablation was performed in a 9.0 mm zone with a maximal intended ablation depth of 50μm. No adjuvant Mitomycin-C was applied in any case. For the photorefractive ablation we used the Allegretto Wave 200 Hz (1.0071-1-0.81/1.208 software/ WaveLight AG, Erlangen, Germany) with the T-CAT ablation profile.
The Pentacam Classic (Oculus Optikgerate GmbH, Heidelberg, Germany, software version 1.14r04) was used for the sake of the study.32 patients with keratoconus were included in the study. Of them, 19 patients underwent CxL treatment (CxL group), while the rest 13 patients underwent CxL combined with t-PRK (tCxL) [tCxL group]. If both eyes were eligible, only one eye was enrolled in the study.Regarding Scheimpflug camera (Pentacam Classic, Oculus Optikgerate GmbH, Heidelberg, Germany, software version 1.14r04 ) measurements, acceptable maps had at least 10.0mm of corneal coverage. Moreover, images with extrapolated data in the central 9.0mm zone were excluded.
For both anterior and posterior corneal surfaces, Pentacam-derived HOAs parameters for both pupil diameters of 4mm and 6mm were calculated, as well as the HOA root mean square (RMS)values. Pentacam-derived HOA measurements were obtained one day prior to treatment and then one year post-op.The impact of the surgical technique (either CXL or tCXL) on spherocylindrical error was evaluated by power vector analysis as described before. Furthermore, manifest refractions comprising of sphere (S), cylinder (C) and axis (φ), were converted into three dioptric powers (M, J0 and J45). Moreover, we calculated the overall blurring strength (B) of the spherocylindrical error by measuring the length of the produced vector.
Please refer to this study by its ClinicalTrials.gov identifier: NCT01527721
|Eye Institute of Thrace (EIT)|