INFLUENCE OF THE SCLERAL LENS AND FLUID RESERVOIR THICKNESSES ON RESIDUAL ASTIGMATISM

Main Article Content

Langis Michaud
Gabriella Courey

Abstract

Purpose
This study aims to determine if lens or tear fluid reservoir thicknesses (LT/FRT) may influence the presence of residual astigmatism and participant’s visual acuity.


Methods
The study was a randomized, non-dispensing, prospective study. Empirically and randomly chosen participants were fitted with 4 combinations (350 and 250 um LT fitted with 250 and 350 um FRT) of 16 mm diameter scleral lenses, designed using a corneo-scleral profiler software (sMap 3D, Visionary Optics, US). Lenses haptics were kept spherical for all lenses. They were evaluated under a slit lamp, anterior segement OCT (objective fluid reservoir and lens thicknesses), topography over lenses and aberrometry, after 30 minutes of lens wear. Spherico-cylindrical refraction and logMar acuity were also assessed.


Results
Study population was composed of 24 participants aged 24.2 + 4.7 years old. Baseline refractive error was -2.3 + 1.6 D with -0.48 + 0.26 D of astigmatism. In vivo (OCT) lens A was 344.1 ± 15.4 um thick, fitted with a vault of 213.6 ± 42.4 um; Lens B was 346.2 ± 12.5/327.2 ± 44.8; Lens C was 260.3 ± 17.7/214.0 ± 40.6 um and Lens D was 262.2 ±13.2/330.8 ± 52.0 respectively. All lenses were found similarly decentered inferiorly by 0.10 to 0.15 um. BCVA was −0.32 + 0.08 (A), −0.21 + 0.10 (B), −0.28 + 0.08 (C), and −0.14 + 0.10 (D), compared to −0.25 + 0.08 (A), −0.11 + 0.10 (B), −0.23 + 0.06 (C), and −0.05 + 0.12 (D) when sphere only was compensated. Residual refractive astigmatism (RA = -0.50 to -0.75D) is found significantly higher based on the FRT (F=9.560; p=0.037) and not LT(F=0.429; p=0.522). There is no correlation be-tween RA and over-k readings (Lens A r=-0.078, p=0.773; Lens B r=−0.073, p=0.788; Lens C r=−0.345, p=0.171; Lend D r=0.019, p=0.944). Higher order aberrations, mostly vertical coma, were found clinically significant but not statistically different between lenses (A= 0.350 + 0.032; B=0.382 + 0.053, C=0.329 + 0.044 and D=0.385+ 0.062; p=0.776)


Conclusion
This study proves that low level of RA may be found when scleral lenses are fitted on normal corneas. Its occurrence is related to the presence of high-order aberrations and less likely to lens flexure.

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How to Cite
1.
Michaud L, Courey G. INFLUENCE OF THE SCLERAL LENS AND FLUID RESERVOIR THICKNESSES ON RESIDUAL ASTIGMATISM . JCLRS [Internet]. 2021 Jan. 14 [cited 2024 Oct. 5];5(1):e1-e8. Available from: https://jclrs.org/index.php/JCLRS/article/view/40
Section
Original Article
Author Biographies

Langis Michaud, Université de Montréal

Full professor- Université de MOntréal
Senior Optometrist
Contact Lens and Clinical researcher
Speaker for professional and public audiences
Teaching in optometry - ocular diseases
Expert on ad board committees
Legal expertise in contact lenses
Communication: radio and television on topics related to eye, vision, contact lenses, children vision development, etc.

Gabriella Courey , University of Montreal

Ecole d’optométrie de L’Université de Montréal

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