Greg was a 33-year-old computer analyst who presented for examination—his complaints involved fluctuating and unsatisfactory vision while wearing toric soft lenses. His symptoms were present both at a distance and in front of the screen. He presented with a normal ocular health, with a trace of marginal posterior blepharitis, moderate hyperopia, and moderate with-the-rule astigmatism.

After deciding to fit this patient in a corneal GP lens, I was challenged by a student: Why didn’t I use a scleral lens?

We now fit scleral lenses in more than 30% of cases that require specialized lenses (Shorter et al, 2018). Scleral lenses offer all the advantages of a rigid lens in terms of quality of vision and comfort, without neglecting the beneficial aspects of treating marginal or established dry eye (Lipson, 2016). Does this mean that eyecare practitioners should forget about the other types of lenses that have served us well to date? This could mean depriving patients of devices that can, in more marginal cases, still present the optimal solution.

Let’s return to the case of Greg. The choice of the rigid corneal lens was based on a detailed analysis. Greg is hyperopic and astigmatic, which already limits the options for soft lenses. The fluctuating vision with these lenses can be related to multiple factors, with tear film instability (Harthan and Hom, 2017) or undue lens rotation upon blinking (Davis and Eiden, 2013) at the top of the list of potential causes.

In this patient’s case, the reason was quite different.

This patient’s cornea was flatter than average, his corneal diameter was larger (12.1mm), and he had 6mm pupils (versus a 4.5mm optic zone)—all of which contributed to his visual discomfort with soft toric lenses. The sagittal height of his eyes was quite impossible to match with commercial soft toric lenses (Michaud et al, 2018). In addition, his corneal astigmatism was higher than his refractive astigmatism (–3.50D versus –2.25D corneal).

This case represents the ideal scenario for prescribing a rigid back-toric lens (Bennett and Henry, 2019). This option is easy to fit (empirically) (Michaud et al, 2009) and provides a stable visual acuity in 99% of the cases. On the other hand, the reservoir of a scleral lens would have compensated for the corneal astigmatism, but residual astigmatism would have had to be compensated for by a front toric design, which is more complicated, requiring consult with the lab (Potter, 2012).

Eyecare practitioners should always focus on the simplest options first, changing one parameter at a time when the case requires a more complex approach. Otherwise, it is easy to get lost.

There remains the question of comfort, which cannot be denied, especially during the initial lens wear. This discomfort is due to the corneal surface nerves, which quickly become desensitized, but especially to the lens-to-lid interaction (Efron et al, 2013). A lid attachment fit approach (minus carrier), and designing a larger diameter lens, associated with reduced movement, will provide comfortable wear after a few days. The choice of materials (wetting angle, modulus) and surface treatments can also be helpful.

And what about custom soft lenses? Usually reserved for irregular corneas, these lenses can also be an alternative for high astigmatism, especially when a larger diameter lens (14.8mm to 15mm) is needed to vault over the sag height of the eye (Lampa, 2020). The only limitation, as in Greg’s case, is their reduced oxygen permeability, due to the material they are made of but more so due to their increased thickness. In the case of a high convex lens, this is not a good idea.

At the end of my answer to the student, I simply concluded that not everything is purely black or white with contact lenses. We are very fortunate to have multiple shades of gray in our hands to meet our patients’ needs. The only limitation that exists is our own hesitations to make full use of all the tools we have on hand. We don’t have to choose; we have to learn to use them all for the benefit of our patients. CLS

REFERENCES

1. Shorter E, Harthan J, Nau CB, et al. Scleral Lenses in the Management of Corneal Irregularity and Ocular Surface Disease. Eye Contact Lens. 2018 Nov;44:372-378.
2. Lipson MJ. When to Opt for Scleral Lenses. Rev Cornea Contact Lens. 2016 Nov. Available at reviewofcontactlenses.com/article/when-to-opt-for-scleral-lenses . Accessed Aug. 24, 2022.
3. Harthan JS, Hom MM. It’s All About the Tear Film. Rev Cornea Contact Lens. 2017 May. Available at reviewofcontactlenses.com/article/rccl0517-its-all-about-the-tear-film . Accessed Aug. 24, 2022.
4. Davis R, Eiden SB. Problem Solving Soft Toric Contact Lenses. Contact Lens Spectrum. 2013 Feb;28:28-32.
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6. Bennett ES, Henry VA. Clinical Manual of Contact Lenses. 5th edition. Philadelphia, Wolters-Kluwer, 2019.
7. Michaud L, Barriault C, Dionne A, Karwatsky P. Empirical fitting of soft or rigid gas-permeable contact lenses for the correction of moderate to severe refractive astigmatism: a comparative study. Optometry. 2009 Jul;80:375-383.
8. Potter RT. Toric and Multifocal Scleral Lens Options. Contact Lens Spectrum. 2012 Feb;27:34-39.
9. Efron N. Jones L. Bron AJ, et al; members of the TFOS International Workshop on Contact Lens Discomfort. The TFOS International Workshop on Contact Lens Discomfort: report of the contact lens interactions with the ocular surface and adnexa subcommittee. Invest Ophthalmol Vis Sci. 2013 Oct;54:TFOS98-TFOS122.
10. Lampa M. Custom Versus Standard Soft Lenses: What to Use When. Contact Lens Spectrum, 2020 Nov;35:22-25.