You Can’t Do This with Sclerals—nor with Soft Lenses

And you should not do this with corneal GPs either. That said, this image shows a successful corneal GP lens wearer who has no complications and no unusual diagnosis. The case below explains why this is so remarkable.

History

This 37-year-old female patient has bilateral keratoconus. She is from another state in Brazil, and she first came to our clinic in 2010 after failing to adapt to GP lenses fitted elsewhere. In 2010, she was refit in our clinic with a specialty keratoconus corneal GP design, which she wore until 2015 when she returned for a refit.

At the visit in 2015, there were no complications; however, her lenses were old, with clear signs of deposits and wear. She was refit with a new pair of corneal GPs, and we reviewed GP lens wear and care requirements with the patient including how to clean and disinfect the lenses at the end of each day and how to reapply them at the beginning of each day.

A few weeks ago, the patient came to see us again after another five-year absence, still wearing the lenses fitted in 2015. We instructed her to not wear her lenses for three days before her appointment, as we do with every patient so that the tests are more accurate. The lens fit was still fine, there was no keratoconus progression even though she had given birth to her second child. We asked her how many hours a day she was wearing her lenses, and she informed us that she hardly ever removed them at all! She admitted to taking out her lenses approximately once a month when she feels some minor discomfort, then she cleans the lenses and reapplies them.

Corneal Biomicroscopy

Slit lamp observation showed a clear cornea, no signs of corneal or epithelial edema, and no signs of corneal scarring or keratitis with fluorescein evaluation. We have always ordered her lenses in a 100-Dk material, and the keratoconus design allows a good lacrimal distribution and tear exchange, which has contributed to preserving the corneal physiological health. Both lenses presented similar fluorescein patterns; the image at the top of the page shows the right lens on the eye, and Figure 2 shows the OS fit.

Until now, she had never revealed that she was wearing her lenses on an extended wear basis, although we had explained to her that the higher-Dk materials allowed for more consecutive hours of lens wear and for occasional overnight wear. Her visual acuity with the lenses was 20/15 J1 OD and OS.

The slit lamp optic section view shows no touch at the apex and the necessary aspheric periphery and edge lift that allows adequate tear exchange (Figures 3 and 4).

Figure 5 shows how calm the eyes are with these corneal GP lenses.

Specular Biomicroscopy

We decided to perform specular microscopy to evaluate the patient’s endothelial cells. The endothelial cell density count was at the inferior limit for her age, and there was some polymegathism and pleomorphism. Though both processes correlate with decreased corneal endothelial function, there is no direct relationship between the amount of pleomorphism and polymegathism, suggesting that there is a variable structure-function relationship. Contact lens-induced endotheliopathy in long-term contact lens wear is much more common in low-Dk lenses.¹

As the corneal endothelium is nonregenerative, contact lens-induced endotheliopathy persists even when lens wear is discontinued or when a higher-Dk material is prescribed. In this case, the patient has no history of blurred vision with her GPs, no fluctuating vision, no corneal edema, no dry eye symptoms, no photophobia, nor any other complaint. Figure 6 shows the specular microscopy of the patient.

Discussion

Despite the fact that advancing age may produce abnormal or asymmetric reduction in endothelial cell density, this patient had no significant reduction in hexagonally shaped cells.² She is almost 38 years old (December 2020), and she wears her corneal GPs continuously for approximately 30 days and removes them for only a few hours each month. We suspect that even with a 100-Dk material, lid closure during sleep hours is affecting the endothelium; however, we are unable to confirm this as the patient did not undergo specular biomicroscopy in 2015.

During the exam, Marcelo Bittencourt, MD, and I found that the cornea was clear, with no visible signs of problems; additionally, the patient had no complaints. We believe that the higher-Dk material, combined with a well-designed and finished GP lens that provides excellent tear exchange during waking hours, was crucial to minimize disruption of the corneal epithelial cell layer and to maintain an adequate barrier to infection at the ocular surface.³

There are some studies related to extended corneal GP lens wear.^4,5 Complications such lens binding, blepharoptosis, transient pupil size increases, and corneal staining were observed with GP lenses that had inadequate oxygen transmissibility, as were hypoxia-induced corneal changes such as microcysts and striae.⁴ One study of low- and mid-Dk GP continuous wear indicated that if GP materials of high oxygen transmissibility and better designs could be attained, the potential of corneal GP extended wear would appear promising.⁴

We take a conservative approach to GP lens fitting in our clinic, and we do not recommend extended wear of corneal GP lenses even when manufactured in higher-Dk materials. We tell patients that the material and lens design will help if for some reason they occasionally need to wear their lenses overnight. Yet, some patients will wear the lenses continuously despite our recommendations. For these patients, we suggest extended wear for one week and then to let the eyes rest for one day, but we’ve found that these patients tend to extend it to one month of continuous wear. If patients do not follow the advice that they are given, we have two options: 1) let the patients go because they represent a risk, bearing in mind that they will probably find another practitioner who will agree with them; and 2) work with patients by optimizing the fit, instructing them to immediately suspend lens wear if they develop symptoms such as hyperemia, photophobia, burning sensation, visual fluctuations, blurred vision, or rainbows around lights. Fortunately, we have not seen any of these findings in the few patients we have who wear their corneal GPs on a continuous basis.

Conclusion

Our clinic completed 50 years of specialty lens fitting at the beginning of 2020, and I started working there with my father in 1986. Over those years, we have had very few complications with corneal GP lenses in general, and no serious complications to the best of my knowledge. However, we are always concerned about patients who do not follow our instructions for a proper wear and care regimen.

The use of high-Dk materials is fundamental for patients who wear their corneal GP lenses on an extended wear basis, but again, much also depends on the design. It is crucial that the lens design offers a good distribution of the tear film to facilitate lacrimal exchange and also to not induce corneal binding.

The best approach with noncompliant patients is usually to retain them and to instruct them to report any symptoms that may develop and to suspend lens wear if something is not normal. Also, inform them about the importance of more frequent follow-up visits, and perform specular microscopy and ultrasound pachymetry from time to time to compare results, if possible in 12 to 18 months. The patient in this case lives in another state, so we always provide her with written instructions and have her sign an acknowledgement form.

References

1. Epstein D. What Specular Microscopy Reveals About Your Patients. Rev Cornea Contact Lens. 2019 Sep 15. Available at https://www.reviewofcontactlenses.com/article/what-specular-microscopy-reveals-about-your-patients . Accessed Nov. 25, 2020.
2. Thomas C. Use Specular Microscopy to Diagnose Corneal Disease. Rev Optom. 2009 Jun 15. Available at https://www.reviewofoptometry.com/article/use-specular-microscopy-to-diagnose-corneal-disease . Accessed Nov. 25, 2020.
3. Lin MC, Graham AD, Fusaro RE, Polse KA. Impact of rigid gas-permeable contact lens extended wear on corneal epithelial barrier function. Invest Ophthalmol Vis Sci. 2002 Apr;43:1019-1024.
4. Fonn D, Holden BA. Rigid gas-permeable vs. hydrogel contact lenses for extended wear. Am J Optom Physiol Opt. 1988 Jul;65:536-544.
5. Gleason W, Tanaka H, Albright RA, Cavanagh HD. A 1-year prospective clinical trial of menicon Z (tisilfocon A) rigid gas-permeable contact lenses worn on a 30-day continuous wear schedule. Eye Contact Lens. 2003 Jan;29:2-9.

Mr. Bastos is the director and clinical instructor of specialty contact lenses at the Instituto de Olhos Dr. Saul Bastos (IOSB) and is the director and specialty lens consultant of Ultralentes, a small laboratory specializing in GP and scleral lens designs in Porto Alegre, RS, Brazil.