REMINDERS ARE EFFECTIVE—they keep us informed and on time. Reminders can also be important when considering the correction of low amounts of astigmatism for our contact lens patients. Is this actually important and worthwhile?

PREVALENT CONDITION

Astigmatism is common. A recent study reported that the overall prevalence of astigmatism of ≥ –0.25DC in at least one eye was 87% (Luensmann et al, 2018). Perhaps more surprising, a large prevalence study reported that 47.4% of patients demonstrated astigmatism of ≥ 0.75D in at least one eye and 24.1% in both eyes (Young et al, 2011). Astigmatism in lower amounts is widespread. Are we correcting it or masking it?

In 2021, of the total soft lenses prescribed, 31% were for toric contact lenses in the U.S. and 32% worldwide (either one or two toric lenses prescribed) (Morgan et al, 2022). The prevalence of astigmatism appears to be greater than the correction for it. What would explain this?

Long-standing beliefs contributing to the non-correction of lower amounts of astigmatism may include perceptions of increased chair time, variable vision due to axis mislocation, restricted ranges of available toric parameters, and simplifying a bilateral contact lens fit when only one eye requires toric correction (Efron et al, 2011).

IMPORTANCE FOR PATIENTS

Does the correction of low amounts of astigmatism significantly help our patients? Recent research compared toric versus spherical soft lens correction for participants who had low amounts of refractive cylinder (approximately –1.00D) (Logan et al, 2020). With toric lenses, participants were able to read significantly smaller print size more comfortably on digital devices. The participants reported significantly improved satisfaction with toric lenses and 85% of participants preferred toric correction.

In other research involving the correction of low astigmatism, distance vision was significantly improved and eyestrain was reduced with toric versus spherical lenses (Chaudhry et al, 2021). Furthermore, equal lens comfort was reported and 79% preferred toric lenses.

Additionally, the correction of low astigmatism (approximately –1.00D) has been shown to significantly improve overall night driving performance (Black et al, 2019). Sign recognition, avoidance of road hazards, and recognition of pedestrians were all significantly improved for toric versus spherical lens wear.

RECENT UPDATES

Research shows us the benefits to our patients, but what about the efficiency for present day, time-pressed clinicians?

• Efficiency. Increased chair time is a concern for busy clinicians. A recent study compared fitting times of soft toric lenses versus soft spherical lenses for participants who had astigmatism (mean: –1.28D ± 0.36D) (Cox et al, 2018). The average fitting time for toric lenses was 10.2 ± 4.3 minutes versus 9.0 ± 6.5 minutes for the spherical lenses. Furthermore, the average number of contact lenses necessary for a successful fit was 1.2 ± 0.47 lenses for toric and 1.2 ± 0.46 lenses for spherical. The authors concluded that there was no significant difference between the two groups for fitting time or the number of contact lenses required.
• Plentiful Parameters. Currently in the U.S., there are more than 45 different soft toric contact lenses available from more than 10 manufacturers (Contact Lens Spectrum, 2022). Depending on the design, these soft toric lenses are replaced daily, biweekly, monthly, quarterly, semiannually, or annually. While parameters vary, some brands offer sphere powers from –20.00D to +20.00D with cylinder powers of –10.00D to –0.50D with axes in 1º steps. This impressive range of replacement modalities and lens parameters remind practitioners that numerous toric possibilities are available for low, middle, or high amounts of correction for patients today.

Innovations in toric lenses remind us that correction of low astigmatism is now more efficient and streamlined and more important than ever for patient vision and satisfaction. CLS

REFERENCES

1. Luensmann D, Schaeffer JL, Rumney NJ, Stanberry A, Walsh K, Jones L. Spectacle prescriptions review to determine prevalence of ametropia and coverage of frequent replacement soft toric contact lenses. Cont Lens Anterior Eye. 2018 Oct;41:412-420.
2. Young G, Sulley A, Hunt C. Prevalence of astigmatism in relation to soft contact lens fitting. Eye Contact Lens. 2011 Jan;37:20-25.
3. Morgan PB, Woods CA, Tranoudis IG, et al. International Contact Lens Prescribing In 2021. Contact Lens Spectrum. 2022 Jan;37:32-38.
4. Efron N, Morgan PB, Helland M, et al. Soft toric contact lens prescribing in different countries. Cont Lens Anterior Eye. 2011 Feb;34:36-38.
5. Logan AM, Datta A, Skidmore K, et al. Randomized Clinical Trial of Near Visual Performance with Digital Devices Using Spherical and Toric Contact Lenses. Optom Vis Sci. 2020 Jul;97:518-525.
6. Chaudhry M, Sah SP, Sharma IP, Mondal S. Does offering only the spherical contact lens trial to the low astigmats mislead the practitioners? Int J Ophthalmol. 2021 Aug;14:1281-1284.
7. Black AA, Wood JM, Colorado LH, Collins MJ. The impact of uncorrected astigmatism on night driving performance. Ophthalmic Physiol Opt. 2019 Sep;39:350-357.
8. Cox SM, Berntsen DA, Bickle KM, et al. Efficacy of Toric Contact Lenses in Fitting and Patient-Reported Outcomes in Contact Lens Wearers. Eye Contact Lens. 2018 Sep;44 Suppl 1:S296-S299.
9. 2022 Contact Lenses & Solutions Summary. Contact Lens Spectrum. 2022 Sep. Available atclspectrum.com/resources/class-pdfs/0922-class_final_hyperlinks . Accessed Jan. 3, 2023.