Contact Lens Materials

contact lens materials
Contact Lens Materials for Babies

As I write this column, I'm awaiting my second child. While in the hospital, I know I'll do the same thing with my second child as I did with my first: Grab the ophthalmoscope and make sure that my baby doesn't have a cataract.

For those unfortunate few babies who do have a cataract, contact lenses fortunately are available to help them visually rehabilitate once they undergo cataract surgery in the first few weeks of life. Here, I reflect on some characteristics of babies that make them so special and how knowing those characteristics will help you fit them with contact lenses.

Babies are Resilient

Babies don't stay mad at us when we let them cry themselves to sleep, and they forget about mommy and daddy leaving them with a babysitter. Medically, they heal well and they heal quickly. In fact, you can fit contact lenses within a week of an infant's cataract surgery.

If our first lens doesn't work, we can try another. Multiple lens material options are available for babies. The Silsoft lens (Bausch & Lomb) is a pure silicone elastomer lens. It features a range of powers, three base curves and two diameters, although powers between +20.00D and +32.00D come in 3.00D steps.

GP materials are also an option, and they offer unlimited parameters. It takes skill to fit babies with GP lenses, and often I accompany the surgeon to the operating room and fit the lens prior to cataract removal, then I order the lens power empirically.

Lastly are low-Dk hydrogels. These lenses offer a decent selection of curvatures, powers and diameters, but they suffer in extremely low oxygen transmissibility in high plus powers.

Babies Sleep a Lot

Because babies' eyes are closed for about two-thirds of the day (if you're lucky!), you should use materials approved for extended wear. In fact, I typically recommend a three- to four-day extended wear schedule. This is one reason why I never fit low-Dk hydrogels on babies; corneal swell-ing will undoubtedly occur over time. The Silsoft lens has a Dk of 340, which makes it a tremendous material for overnight use.

GP lenses can also provide enough oxygen transmission for safe extended wear. My favorite materials are Menicon Z (Menicon Co., Ltd.), Fluoroperm 151 and HDS 100 (Paragon Vision Sciences) and Boston XO (B&L).

Babies Frequently Cry

Crying is a baby's way of telling us something is wrong, but babies quickly turn happy once we attend to their needs. Contact lens fitting for babies also has its ups and downs. Although the Silsoft lens has phenomenal material properties for oxygen transmission, comfort and stability on an infant's eye, lipid deposits can limit the life of the lens to only a few months. The hydrophobic material repels water and creates a non-wettable surface.

Silicone hydrogel lens manufacturers have tried to remedy this situation by combining hydrogel and silicone properties, often with a surface treatment to make the surface wettable. I look forward to the day when manufacturers allow custom orders in silicone hydrogel disposable materials for these tiny patients.

Dr. Szczotka-Flynn is an associate professor at Case Western Reserve University Dept. of Ophthalmology and is director of the Contact Lens
Service at University Hospitals of Cleveland.