In our last issue, I discussed how the material properties, including oxygen permeability, surface chemistry, hardness/modulus, and specific gravity, of rigid gas permeable (RGP) lenses may influence lens selection (Material Properties of RGPs).
In this month’s column, I present specific cases that highlight the considerations of these material properties.
Case 1: Over the rainbow
A 75-year-old female RGP wearer presented complaining of seeing “rainbows” around lights upon contact lens removal, starting about seven months prior to this visit.
The new patient had no significant ocular or systemic health history other than hyperlipidemia for which she took 20 mg of atorvastatin (Lipitor, Viatris).
She said her typical wearing time was 12 to 14 hours per day. At this appointment, she was at her seventh hour of wear.
She wore + 6.00 D spherical lenses bilaterally, and her best contact lens-corrected distance vision was 20/25 OU due to mild nuclear lens changes. The patient had no retinal pathology.
Corneal topography revealed simKs of 42.50 x 180/43.25 bilaterally, without irregularity, and an interpalpebral fit and movement of 1.5 mm upon blinking. Both lens surfaces were clean.
Ocular surface evaluation revealed a tear breakup time of nine seconds in both eyes without significant corneal or conjunctival staining. Indirect illumination slit lamp evaluation showed mild central corneal edema in both eyes.
Upon contacting the patient’s prior doctor, I learned her lenses were manufactured from a low-Dk material. As a result, I refit the patient in a higher-Dk material to optimize oxygen delivery to her corneas.
At a two-week follow-up visit at eight hours of wear, the patient reported complete resolution of the “rainbows.” Additionally, her corneas were without residual edema.
Pro tip. To optimize physiology in high-plus lenses, choose a high-Dk material.
Case 2: Out of the Fog
A 53-year-old female patient presented complaining of bilateral lens “fogging” of her multifocal RGPs.
The patient’s -4.00 D aspheric center-distance lenses were six months old, and she denied having changed any of her personal care products. The patient used a multipurpose cleaning and storage lens care product. Slit lamp examination revealed poor anterior surface wetting of both lenses. Visual acuity after cleaning was 20/20 in each eye. Internal ocular health was found to be excellent upon dilation.
Exam revealed mild meibomian gland dysfunction for which I prescribed lid hygiene, heat, gland expression, and unpreserved tear supplements.
To solve the “fogging” issue, which I attributed to lens surface non-wetting, I replaced her ultra-high-Dk lenses with a fresh pair that included a lens coating designed to mimic natural tears, and I switched her to a peroxide-based lens care system.
She returned three weeks later with continued lens “fogging,” so I re-ordered her lenses in a lower-Dk material that has a lower wetting angle, again with that coating.
At her two-week follow-up visit, the patient happily reported “the fog had lifted.”
Pro tip. Choosing lower-Dk materials that have lower wetting angles can help remedy lens surface fogging and or/deposition.
Choosing Wisely
With careful contact lens material selection, we can successfully optimize vision, comfort, and ocular health in our RGP lens wearers. OM
