Gas permeable contact lens fitting in keratoconus: Comparison of different guidelines to back optic zone radius calculations

Autor: Sara Ortiz-Toquero, Guadalupe Rodriguez, Victoria de Juan, Raul Martin
Jazyk: angličtina
Rok vydání: 2019
Předmět:
Zdroj: Indian Journal of Ophthalmology, Vol 67, Iss 9, Pp 1410-1416 (2019)
Druh dokumentu: article
ISSN: 0301-4738
1998-3689
DOI: 10.4103/ijo.IJO_1538_18
Popis: Purpose: Compare the agreement between the finally fitted back optic zone radius (BOZR) of a spherical gas permeable (GP) contact lense (CL) with those proposed by different guidelines currently available to fit GP CLs in keratoconus. Methods: The BOZR fitted in 81 keratoconus eyes (46 patients) were recorded and compared with the BOZR calculated with ten different guidelines (identified after a literature review) proposed to calculate the first diagnostic lens BOZR to be fitted in keratoconus. Arithmetic and absolute mean difference between both BOZR were calculated (paired t-test). The success rate of each guideline (difference between both BOZR ≤0.05 mm) was calculated for different keratoconus stages (Amsler–Krumeich classification). Agreement between BOZR was evaluated using Bland-Altman analysis. Results: The BOZR proposed by all guidelines correlated with the final BOZR that was fitted (R2 > 0.71; P < 0.01). A statistically significant difference was found between the BOZR suggested by all guidelines and the BOZR that was prescribed (P < 0.05), except for three Guidelines (P ≥ 0.11). CALCULENS.com presented the best agreement (mean difference of 0.00 ± 0.12 mm), and 50.6% of cases showed ≤0.05 mm of difference with the BOZR that was fitted. However, the worst guideline showed an agreement of −0.38 ± 0.22 mm, and just 3.8% of cases had ≤0.05 mm of difference with the final fitted BOZR. Conclusion: BOZR calculated with most of the analyzed guidelines shows statistical differences with final fitted BOZR, suggesting a lack of clinical validation of these guidelines. The selection of the BOZR with CALCULENS.com could provide a better starting point for spherical GP CL fitting in keratoconus eyes.
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