Hull, C.

Huntjens, B.

Mihic, K.

English

City Research Online

              City, University of London Institutional RepositoryCitation: Huntjens, B. ORCID: 0000-0002-4864-0723, Mihic, K. and Hull, C. ORCID: 0000-0002-2205-4443 (2020). Difference in corneal asphericity and sagittal height between emmetropes and myopes. Investigative Ophthalmology & Visual Science, 61(7), 4748.. This is the published version of the paper. This version of the publication may differ from the final published version. Permanent repository link:  https://openaccess.city.ac.uk/id/eprint/24938/Link to published version: Copyright and reuse: City Research Online aims to make research outputs of City, University of London available to a wider audience. Copyright and Moral Rights remain with the author(s) and/or copyright holders. URLs from City Research Online may be freely distributed and linked to.City Research Online:            http://openaccess.city.ac.uk/            publications@city.ac.ukCity Research OnlineOPEN ACCESSARVO Annual Meeting Abstract  |   June 2020Difference in corneal asphericity andsagittal height between emmetropesand myopesByki Huntjens; Kristina Mihic; Chris C Hull  Author Affiliations & NotesInvestigative Ophthalmology & Visual Science June 2020, Vol.61, 4748. doi:AbstractPurpose : Corneal shape and sagittal height play an important role in thesuccessful fitting of large diameter gas permeable contact lenses. The purpose ofthis study is to evaluate anterior corneal surface asphericity and sagittal heightdifference related to refractive error.Methods : Topography data from the right eye of 90 participants (mean age 21.1± 3.2 years) were grouped according to their refractive error (mean sphericalequivalent MSE −1.31 ± 1.77 D, corneal astigmatism ≤ -2.00 D). Three groupsincluded 43 emmetropes (range MSE -0.50 to +0.50 D); 26 low myopes (-0.75 D to-3.00D) and 20 moderate myopes (-3.25D to -6.00D). The Medmont E300topographer was used to collect 4 repeated measures of radius of curvature andasphericity (Q-values in flatter and steeper meridians) over a 9.35 mm chord.Difference in sagittal height (ΔSag) between both meridians was calculated overthe same chord.Results : The average radius of curvature of the anterior corneal surface was 7.76± 0.20mm for emmetropes, 7.78 ± 0.27mm for low myopes and 7.71 ± 0.35mmfor moderate myopes (P=0.66). Corneal astigmatism amount and direction didnot vary between the groups (P>0.05). Low myopes had a significantly smallercorneal asphericity (Q -0.39 ± 0.15) compared to emmetropes (-0.52 ± 0.19) andmoderate myopes (-0.52 ± 0.17; P=0.009) for the flat meridian only. Sag did notvary significantly between the three groups in either flat (P=0.61) or steepmeridians (P=0.65). The percentage of participants with ΔSag >40 µm was lowerin low myopes (17%) compared to emmetropes (48%) and moderate myopes(35%), although this difference was not statistically significant (P=0.15). There wasa weak but significant correlation between Q-values and ΔSag (r=-0.22, P=0.041).Conclusions : Moderate myopes showed significantly more corneal flatteningtowards the periphery compared to low myopes over a chord similar to thediameter of an orthokeratology lens. This could not be explained by the amountof corneal astigmatism or its direction. Even though corneal astigmatism was low,the relatively high percentage of ΔSag >40 µm in the moderate myopic groupindicates the potential clinical need for a toric orthokeratology lens. Furtherinvestigation is required to understand the effect of peripheral topography databeyond the 7mm chord in patients requiring large diameter contact lenses.This is a 2020 ARVO Annual Meeting abstract.This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Difference in corneal asphericity and sagittal height between emmetropes and myopes

https://openaccess.city.ac.uk/id/eprint/24938/3/Difference%20in%20corneal%20asphericity%20and%20sagittal%20height%20between%20emmetropes%20and%20myopes%20_%20IOVS%20_%20ARVO%20Journals.pdf

Difference in corneal asphericity and sagittal height between emmetropes and myopes

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