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]. 2021Jan.14 [cited 2021Apr.22];5(1):e1-e8. Available from: http://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

References

1. Johns L. and Barnett M. Contemporary Scleral Lenses: Theory and Application. Bentham eBooks; 2017.
2. van der Worp E, et al. Modern scleral contact lenses: A review. Cont Lens Anterior Eye 2014;37(4):240–50.
3. Goldberg JB. RGP contact lens adherence: Flexure or tear film thinning—Can we define the cause? Internat Contact Lens Clinic 1994;21(1):26–29.
4. Lin MC and Snyder C. Flexure and residual flexure with RGP lenses. Contact Lens Ant Eye 1999;26(1):5–9.
5. Corzine JC and Klein SA. Factors determining rigid contact lens flexure. Optom Vis Sci 1997;74(8):639–45.
6. Jedlicka J. Solving scleral lens complications. C.L. Spectrum 2012; 27(October):40–44.
7. Vincent SJ, et al. The influence of centre thickness on miniscleral lens flexure. Cont Lens Anterior Eye 2019;42(1):63–69.
8. Schornack M, Nau C, and Brown W. Estimation of refractive power of scleral lens/fluid reservoir optical systems in non-parallel scleral lens fits. in Poster presented at: Global Specialty Lens Symposium 2014.
9. Bray C, et al., Change in over-refraction after scleral lens settling on average corneas. Ophthalmic Physiol Opt 2017; 37(4):467–72.
10. Ramdass S, Rosen C, and Norman C. Clinical Analysis of Scleral Lenses on Regular Cornea, in Global Specialty Lens Symposium. 2016: Las Vegas.
11. Vincent SJ and Fadel D. Optical considerations for scleral contact lenses: A review. Cont Lens Anterior Eye 2019.
12. Hastings GD, et al. Comparison of wavefront-guided and best conventional scleral lenses after habituation in eyes with corneal ectasia. Optom Vis Sci 2019;96(4):238–47.
13. Michaud L, et al. Predicting estimates of oxygen transmissibility for scleral lenses. Cont Lens Anterior Eye 2012;35(6):266–71.
14. Vincent SJ, Alonso-Caneiro D, and Collins MJ. The temporal dynamics of miniscleral contact lenses: Central corneal clearance and centration. Cont Lens Anterior Eye 2018;41(2):162–68.
15. Courey C and Michaud L. Variation of clearance considering viscosity of the solution used in the reservoir and following scleral lens wear over time. Cont Lens Anterior Eye 2017;40(4):260–66.
16. Collins MJ, et al, Flexure of thin rigid contact lenses. Cont Lens Anterior Eye 2001;24(2):59–64.
17. Phillips AJ and Stone J Contact Lenses Third ed. London, UK: Butterworths; 1989.
18. Sorbara L, Fonn D and MacNeill K. Effect of rigid gas permeable lens flexure on vision. Optom Vis Sci 1992;69(12):953–8.
19. Choi J, et al. Changes of ocular higher order aberration in on- and off-eye of rigid gas permeable contact lenses. Optom Vis Sci, 2007;84(1):42–51.
20. Chen M and Yoon G. Posterior corneal aberrations and their compensation effects on anterior corneal aberrations in keratoconic eyes. Invest Ophthalmol Vis Sci 2008;49(12):5645–52.
21. Hashemi H, et al. Pentacam top indices for diagnosing subclinical and definite keratoconus. J Curr Ophthalmol 2016;28(1):21–6.
22. Barnett M and Fadel D. Scleral Lenses: The Benefits of Toric Landing Zones. C.L. Spectrum 2017;32(November):36–41.
23. Sabesan R, et al., Wavefront-guided scleral lens prosthetic device for keratoconus. Optometry and vision science : official publication of the American Academy of Optometry 2013;90(4):314–323.
24. Nave R. Coma. 2019; Available at: http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/coma.html accessed 2019-10-25