Myriam is one of the first patients whom I adapted to scleral lenses, so we have met on several occasions! And yet, entering the exam room recently, her mood was less joyful than usual. When asked how she was doing, she replied: “I can see nothing with these lenses! This has never happened before.”

At the mention of a potential total blindness, the gears in my brain went full speed: Is it retinal artery/vein occlusion, retinal detachment, stroke, something else? I decide to apply the famous test of my colleague Léo Breton, OD: I asked Myriam to close her eyes and to realize that now she was seeing nothing. Then, I told her to open her eyes and tell me what she was really seeing. The test was successful; her complaint was more about blurriness than a total loss of vision. On examination, visual acuity was well below what was recorded at lens delivery a few days earlier. On slit lamp exam, the lenses were almost completely hydrophobic, with their surfaces drying very quickly between blinks.

What Changed?

How can we determine what happened? First, review the prescribed lenses’ parameters. In this case, the lab’s working sheet was similar to what was ordered. In theory, that was not the problem. Next, check for a potential manufacturing defect, such as residue from the manufacturing processes, lens material altered by heat, etc. This would have manifested itself on delivery. Third, talk about lens care. Have there been any changes of solution, lack of cleaning with rubbing step, use of viscous topical products? In this case, Myriam was using the same products (H₂O₂, surfactant, and saline) and was being compliant.

Next are personal factors. Is she using hydrophobic makeup or a new mascara? Has she handled her lenses after using a hand cream? Again, no.

Finally, investigate eye health, in particular the presence of blepharitis or other signs associated with ocular surface disorders. Myriam has mild (grade 1) meibomian gland dysfunction (MGD) that is well managed with regular lid hygiene. So again, nothing seemed different from our existing clinical picture.

Eureka!

Without a logical explanation for the lens surface issues, I decided to compare the lenses delivered with those that had been ordered more than two years prior. First, the lens material was different. The supplied lenses are made of hexafocon A; the previous lenses were made of roflufocon D, a material with a reduced wetting angle (WA; 3º versus 38º). WA is an important factor that influences the accumulation of lens surface deposits and a patient’s comfort (Bourassa and Benjamin, 1989). Reduced WA means faster tear breakup time (TBUT), according to the study.

Second, the previous lenses had been automatically coated, which was obviously not the case with the last lenses delivered. An initial preliminary study showed that coating a lens with polyethylene glycol (PEG) improved symptoms in a population of dry eye patients wearing scleral lenses (Mickles et al, 2020). However, there is no other study reporting similar results in other populations (e.g., not experiencing severe dryness or ocular surface disorders). Therefore, I usually reserve PEG-based coatings for patients showing more severe conditions.

Also, based on my experience, the effectiveness of this treatment has a limited duration, as it erodes despite manufacturer-recommended cleaning procedures. However, it is possible to restore homeostasis of the ocular surface (with scleral lens wear and medication), which helps to lower the deposits generated. This then allows patients to remain comfortable despite erosion of the lens surface treatment over time.

For all patients who are experiencing surface deposits or wettability issues with their scleral lenses, we must therefore follow these three steps in order: 1) diagnose and control ocular surface disease, 2) select a material with the smallest possible WA, 3) apply a PEG treatment to lenses for those considered heavy depositors. And make sure to reorder the same lenses. Lesson learned! CLS

For references, please visit www.clspectrum.com/references and click on document #302.