Silicone Hydrogels - A First Choice Lens

Ted Hamilton

Ted Hamilton graduated with a Bachelor of Optometry from the University of New South Wales in 1980. From there he worked in private practice in the United Kingdom until 1990. In 1994 Ted returned to Australia and set up practice in central Sydney, specialising in contact lenses.

I have used silicone hydrogel lenses extensively in my practice since their first release into the Australian market. My practice is situated in the heart of the business district of central Sydney. It serves a younger demographic base of predominantly tertiary educated & well informed younger professionals. This group have a high uptake of contact lens wear and before the advent of high DK materials regularly manifested the all too common symptoms from wearing (and often overwearing) thin, high water/low DK materials for extended hours in low humidified offices doing constant close and/or PC work.

Chronic limbal hyperaemia was the norm rather than the exception, often with associated neovascularisation. Corneal desiccation manifesting in mild bouts of SPK was also extremely common along with low grade corneal oedema. The sensation of dryness & irritation would often go hand-in -hand with these findings and drop-out from constant wear to just part-time or weekend wear was high. This decision was often unilaterally made by the patient and frustratingly, when patients did come for advice on these findings, I could only concur with their actions & hopefully (rather than confidently) add the application of lubricating drops to their wearing regime to try and help ease their symptoms.

I initially saw the release of a silicone hydrogel lenses as a panacea to the myriad of patients with symptoms as detailed above.....and I was not disappointed! The majority of patients who switched to these lenses showed dramatic improvements in wearing time during working hours and marked diminishment in symptoms of dry-eye and general irritation. From a practitioner level I was amazed at the rapid regression of limbal redness and oedema in these patients. For those with marked limbal neovascularisation a regression of these vessels was often noted leaving ghost vessels in their place.

An extreme example of this was a 27 year old female professional who wore two-week high water low DK disposable lenses up to 16 hours a day seven days a week. She felt the red eyes and chronic dry-eye sensation she endured were a better option than her perceived negative appearance with -4.00 dioptre specs on & the distortion they induced to her vision in her office environment. Of a more critical nature were the presence of chronic low grade corneal oedema, apparently wrought from her over wearing the contact lenses, and the aggressive approach of superficial and deep limbal vessels toward a small but deep corneal scar (of unknown aetiology) approximately 3-4mm from the temporal limbus of her right eye . I had previously tried reducing her wearing time (to no avail) and attempted a refit with high DK RGP materials (unsuccessful due to discomfort) in order to reduce these manifestations.

A refit with silicone hydrogel lenses worn on a daily basis resulted in almost instantaneous symptomatic relief for her. More pleasing to this practitioner was the resolving of the oedema within 48 hours (with the lenses being worn) coupled with a marked decrease in limbal redness. After six months of regular daily wear with these lenses the superficial neovascularisation approaching the scar appeared to be regressing while the deeper vessels, while still present, were much less visible. After a year the superficial vessels had transformed to ghost vessels and the deeper vessels were subjectively less obvious.

Generally, for previous wearers the benefits of using silicone hydrogel lenses for extended wear were less of an issue and being able to wear lenses comfortably and for longer periods in a more traditional daytime & evening scenario were more important. These patients eventually tend toward irregular overnight wear but I find only a very small minority go on to regular extended wear.

Regrets? I've had a few.... Marginal (or worse) dry-eye will soon lead to reduced wearing time with these lenses. Inferior/central corneal staining is a typical manifestation and even aggresive use of lubricating drops does not generally fix the problem. Switching back to the phosphorylcholine powered Proclear lens from CooperVision will generally help these patients.

Superior epithelial arcurate lesions are a problem, particularly in Asian eyes. A switch from one silicone hydrogel to the other will sometimes help, but again, if the problem persists an about face back to thinner & more flexible materials will see the lesions resolve.

While not without their problems, silicone hydrogel lenses are an extremely useful lens to counter the long term effects of low DK contact lens wear. However, rather than just using them as a trouble shooting lens, I tend to use them as a lens of first choice. Why not avoid all the troubles in the first place!