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Shiva Mehravaran, Hassan Hashemi, Kazem Amanzadeh, Mohammad Seyedian, Hojjat Zeraati, Cynthia J Roberts, Renato Ambrósio, Md Rahman, Riccardo Vinciguerra, Paolo Vinciguerra, Soheila Asgari; Single point versus zonal maximum keratometry in the assessment of CXL efficacy. Invest. Ophthalmol. Vis. Sci. 2020;61(9):PB0071.
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To compare the safety and efficacy of an accelerated cross-linking (CXL) protocol (9mW/cm2, 10 minutes) with standard CXL (3mW/cm2, 30 minutes) in patients with keratoconus (KC) and Down Syndrome (DS) using single point maximum keratometry (Kmax) and zonal-Kmax.
In this non-inferiority contralateral randomized clinical trial based on good clinical practice principles, 27 DS patients (age range: 10 to 20 years) with bilateral progressive KC who were identified over an 18-month monitoring period were enrolled in the study and completed follow-up exams for one year. Fellow eyes were randomly allocated to the accelerated or standard CXL groups. Zonal Kmax was defined as the average keratometry in the 3mm zone surrounding the point of maximum keratometry, as measured with Pentacam. Vision and refraction tests, ophthalmic examinations, and corneal tomography were done at baseline and at 6 and 12 months after the procedure. The main outcome measure was an inter-group difference of ≤1.0 diopter (D) in Kmax. Failure was defined as ≥1.0D increase in Kmax, ≥1.0D increase in astigmatism, or ≥2.0% reduction in minimum corneal thickness.
The mean age of the sample was 15.71±2.40 years. At one year, mean changes in single point Kmax in the accelerated and standard CXL groups were +0.61±1.02D and -0.46±1.25D, and failure rates based on this index were 32.1% and 11.1%, respectively. In the subgroup of failed cases, single point Kmax at baseline was 51.33±3.90D and 54.90±0.01D in the accelerated and standard CXL groups, respectively. Mean changes in zonal Kmax in the accelerated and standard CXL groups were +0.27±0.90D and -0.27 ±0.82D, and failure rates based on this index were 22.2% and 0.0%, respectively. In the subgroup of failed cases in the accelerated CXL group zonal Kmax at baseline was 48.90±3.12D.
Based on results with zonal Kmax, in pediatric DS patients with Kmax around 50.0D, the accelerated protocol could halt disease progression and be an alternative for standard CXL. Based on single point Kmax, however, the accelerated protocol is not as effective as standard CXL for cases with Kmax ≤50D.
This is a 2020 Imaging in the Eye Conference abstract.
Kamx = single point of greates curvature. Zonal Kmax = average of a specified region of greatest curvature.
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