BLOG: GP lenses still a good choice for mild, moderate keratoconus
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Most individuals with keratoconus rely on specialty contact lenses for best corrected vision.
While some with a mild presentation may function well with soft contact lenses, many with moderate to advanced keratoconus may require custom lenses made from a gas-permeable (GP) plastic material.
The field of specialty contact lenses has grown tremendously over the last decade, with significant attention given to scleral lenses. The rate of scleral lens fittings by eye care practitioners has been increasing since 2011 (Woods et al.), and scientific research on scleral lenses has also increased during the same period (Povedano-Montero et al.).
While few papers were written on scleral lenses until 2007, there has been a steady increase in publications since then (Efron et al.). A recent study in 2020 evaluating 86 subjects over a 5-year period even affirmed the long-term safety and efficacy of scleral lenses in the visual rehabilitation for keratoconus patients (Fuller et al.).
It is easy to understand why scleral lenses have become a popular contact lens option for keratoconus patients; they provide good comfort, stability and vision. These lenses vault over the cornea and do not rub on the ectatic corneal tissue, which also happens to be highly innervated.
The larger lens diameter also decreases movement on the ocular surface and limits friction with the inner eyelids; the customization of lens design with trial lenses, profilometry and impression molding techniques can lead to precise fits. Also, with the ability to incorporate front surface astigmatic correction, decentered optics and higher-order aberration control, vision correction can be excellent.
So, why would anyone still prescribe GP contact lenses? These lenses rub on the sensitive corneal tissue, decenter from the cornea frequently, contribute to corneal molding, pop out easily with extreme eye movements and feel like broken glass when dust gets in the eye.
Simply put, GP lenses work great for the right patient. In patients with mild to moderate keratoconus, GP lenses should be presented as an option. A well-centered or lid-attached fit, with good alignment and movement, can provide excellent comfort and vision.
These lenses are smaller and easier to apply and remove. Unlike scleral lenses that require saline fluid to fill the reservoir and careful balance for application, GP lenses can be placed directly on the cornea with one finger. The cost for these lenses and their maintenance are considerably less than scleral lenses and may be more affordable for some patients.
While scleral lenses may seem like a “sexier” option, more and more scleral lens-related challenges and complications are being reported, including conjunctival prolapse, epithelial bogging, midday fogging, limbal bearing and hypoxia (Walker et al.). Training time for lens handling and care can be extensive in office, and specialized cleaning and saline products can be challenging to find.
A study published in 2020 evaluated the satisfaction and care burden in keratoconus patients with either corneal GP or scleral lenses (Shorter et al.). Results from the electronic survey-based study found that scleral lens wearers had greater satisfaction with vision and comfort, but both groups reported issues with cloudy or foggy vision and contact lens discomfort.
Although GP wearers reported more problems with lens movement or loss, they had fewer difficulties with halos and lens handling compared with scleral lens wearers. GP wearers also reported less annual out-of-pocket costs compared to scleral lens wearers.
No contact lens modality is perfect, and each type has its pros and cons. It is our job as optometrists to determine the best modality for each individual patient, considering their disease presentation, occupation and lifestyle.
In addition, we must also remember to monitor for progressive keratoconus and consider corneal cross-linking when indicated, as good acuity in specialty contact lenses may mask progressive signs.
Although GP lenses have not been in the spotlight recently, that does not mean that they are not a good option for the right keratoconus patient.
References:
- Efron N, et al. Cont Lens Anterior Eye. 2021;doi:10.1016/j.clae.2021.101447.
- Fuller DG, et al. Optom Vis Sci. 2020;doi:10.1097/OPX.0000000000001578.
- Lim L, et al. Eye (Lond). 2020;doi:10.1038/s41433-020-1065-z
- Moschos MM, et al. Open Ophthalmol J. 2017;doi:10.2174/1874364101711010241.
- Ortiz-Toquero S, et al. Curr Opin Ophthalmol. 2021;doi:10.1097/ICU.0000000000000728.
- Povedano-Montero FJ, et al. Eye Contact Lens. 2018;doi:10.1097/ICL.0000000000000478.
- Saraç Ö, et al. Cont Lens Anterior Eye. 2019;doi:10.1016/j.clae.2019.02.013.
- Schornack MM. Eye Contact Lens. 2015;doi:10.1097/ICL.0000000000000083.
- Shorter E, et al. Optom Vis Sci. 2020;doi:10.1097/OPX.0000000000001565.
- Walker MK, et al. Cont Lens Anterior Eye. 2016;doi:10.1016/j.clae.2015.08.003.
- Woods CA, et al. Clin Exp Optom. 2020;doi:10.1111/cxo.13105.
For more information:
Gloria B Chiu, OD, FAAO, FSLS, is an associate professor of clinical ophthalmology at the USC Roski Eye Institute, department of ophthalmology, Keck School of Medicine, Los Angeles.
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