This article was originally published in a sponsored newsletter.

With a multitude of toric lens options, it can be overwhelming to decide which diagnostic toric lens to select first. Fortunately, our understanding of the sagittal height of the ocular surface is improving with novel diagnostic instrumentation. However, we have more to understand about sagittal height values when fitting soft contact lenses in clinical practice.

A study by van der Worp et al. at Pacific University evaluated six distinct daily replacement toric and 11 reusable (both two-week and four-week) toric lens designs. Posterior sagittal height of the contact lens was quantified with a spectral domain OCT-based instrument (Optimec is830).¹ 

van der Worp and colleagues noted a wide range of contact lens sagittal height values for these toric lenses from 3,536 to 4,157 microns.¹ Even in contact lenses with identical base curves, the greatest difference was 345 microns in the toric lens group. In a single toric lens with two base curves, they noted a 377-micron variation. There were also distinct differences in contact lens sagittal height values and between lenses with the same base curve. Simply a base curve-only lens change can result in larger lens fit changes due to significant differences in sagittal height values. Overall, the study determined that the combination of both contact lens diameter and base curve affects contact lens sagittal height values.

The authors developed sagittal depth charts to guide our lens selection process for spherical and toric lenses in both daily replacement and reusable lens options.¹ Lenses towards the left side of the chart have a shallower sagittal depth while lenses towards the right side of the chart have a deeper sagittal depth. Additionally, lens modulus may influence the lens fit on-eye. 

When fitting toric lenses, we can measure horizontal visible iris diameter, vertical visible iris diameter, base curve, sagittal depth, and refractive error to improve our initial diagnostic lens selection as well as our toric lens fitting.

REFERENCES

van der Worp E, Lampa M, Kinoshita B, Fujimoto MJ, Coldrick BJ, Caroline P. Variation in sag values in daily disposable, reusable and toric soft contact lenses. Cont Lens Anterior Eye. 2021 Dec;44:101386.

Melissa Barnett, OD, FAAO, FSLS, s the director of optometry at the University of California, Davis in Davis, specializing in anterior segment disease and specialty contact lenses. She is the past president of the Scleral Lens Education Society. She is an advisor to and/or has received honoraria or travel expenses from AccuLens, Alcon, Allergan, Bausch + Lomb, Bruder, Contamac, CooperVision, Johnson & Johnson Vision, Ocusoft, ScienceBased Health, Shire, Tarsus, and Visus Therapeutics.