Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Comparative Study
. 2019 Sep;67(9):1410-1416.
doi: 10.4103/ijo.IJO_1538_18.

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

Sara Ortiz-Toquero  1 , Guadalupe Rodriguez  1 , Victoria de Juan  2 , Raul Martin  3
Affiliations
Comparative Study

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

Sara Ortiz-Toquero et al. Indian J Ophthalmol. 2019 Sep.

Abstract

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.

Keywords: Contact lens; fitting; gas permeable; guidelines; keratoconus.

PubMed Disclaimer

Conflict of interest statement

None

Figures

Figure 1
Figure 1
Agreement between the BOZR proposed by each guideline and the final BOZR fitted. Guideline #10 exhibiting better agreement with lower LoA
Figure 2
Figure 2
Cumulative percentages of the differences between the BOZR proposed by each guideline and the final BOZR fitted
Figure 3
Figure 3
Success rate of the GP guideline fitting (difference between the BOZR of the diagnostic lens proposed with the final BOZR prescribed was ≤0.05 mm) according to Amsler–Krumeich classifications
See this image and copyright information in PMC

References

    1. Barnett M, Mannis MJ. Contact lenses in the management of keratoconus. Cornea. 2011;30:1510–6. - PubMed
    1. Downie LE, Lindsay RG. Contact lens management of keratoconus. Clin Exp Optom. 2015;98:299–311. - PubMed
    1. American Optometric Association. Optometric Clinical Practice Guideline: Care of the Contact Lens Patient. 2006. [Accessed November 4, 2017]. Available from: http://http://www.aoa.org/documents/optometrists/CPG-19.pdf .
    1. Ortiz-Toquero S, Perez S, Rodriguez G, de Juan V, Mayo-Iscar A, Martin R. The influence of the refractive correction on the vision-related quality of life in keratoconus patients. Qual Life Res. 2016;25:1043–51. - PubMed
    1. Romero-Jiménez M, Santodomingo-Rubido J, Wolffsohn JS. Keratoconus: A review. Cont. Lens Anterior Eye. 2010;33:157–66. - PubMed

Publication types