RECENTLY, A COLLEAGUE described an interesting patient. A 65-year-old male patient presented with the following glasses prescription and acuities:

The refraction upon examination revealed:

Keratometry displayed approximately 4.00D of against-the-rule corneal astigmatism in each eye. The eye examination revealed neither previous keratoplasty nor keratoconus. It appeared that this patient had an unfortunately high combination of corneal and lenticular astigmatism.

My colleague explained that this patient required him to “dig deep” and utilize the auxiliary cylinder lenses tucked away in his exam desk drawer. While these auxiliary lenses are not typically used every day, they are useful and easy to apply.

Most traditional phoropters have cylinder lenses that measure up to and including –6.00D of astigmatism. However, each auxiliary lens provides –2.00D of additional power, extending the range to –8.00D. Furthermore, the –0.12D auxiliary lens is available for astigmatism correction refinement if chosen (Figure 1). The auxiliary lens is inserted into the phoropter eye piece (Figure 2).

Ocular conditions such as post-keratoplasty, keratoconus, and pterygium may exhibit unusually high amounts of astigmatism, 6D to 10D in magnitude (Reddy et al, 2021). The need to measure astigmatism higher than –6.00D for such patients is apparent and perhaps more common than expected.

Improving a patient’s acuity from 20/40 to 20/25 can be life enhancing and life changing. Fully correcting high astigmatism may make it possible to obtain a driver’s license or read a medication label.

Eyecare practitioners recognize the importance of correcting astigmatism, because uncorrected astigmatism decreases patient vision-related quality of life and increases productivity losses for working-age adults (Zhang et al, 2022). Fortunately, there are an abundance of contact lens brands that correct high amounts of astigmatism, available in various materials and modalities (Contact Lens Spectrum, 2022).

So, the next time a patient has astigmatism exceeding the typical, know that a straightforward and helpful tool is readily available. You may want to dig around for those auxiliary lenses now, just so you will be ready. CLS

References

1. Reddy JK, Pooja CM, Prabhakar GV. High power custom toric intraocular lens for correcting high corneal astigmatism in post-keratoplasty and keratoconus patients with cataract. Indian J Ophthalmol. 2021 Jul;69:1766-1768.
2. Zhang J, Dhariwal M, Wu Y, Bullimore MA. Epidemiology and burden of astigmatism: a systematic literature review. Invest Ophthalmol Vis Sci. 2022 Jun;63:3538 – A0118.
3. 2022 Contact Lenses & Solutions Summary. Contact Lens Spectrum. 2022 Sep. Available at clspectrum.com/resources/class-pdfs/0922-class_final_hyperlinks . Accessed Jan. 15, 2023.