Corneal staining and subjective symptoms with multipurpose solutions as a function of time

Isabelle Jalbert, OD, PhD, FAAO Project Director, Vision Cooperative Research Centre, Sydney Australia Director of Clinical Research, Institute for Eye Research, Sydney Australia Visiting Lecturer, School of Optometry and Vision Science, University of New South Wales

Garofalo RJ, Dassanayake N, Carey C, Stein J, Stone R, David R
Eye & Contact Lens: 2005;31:166-74.

When silicone hydrogel lenses were first launched more than a decade ago, they were squarely aimed at capturing and growing the continuous wear market. Since, a much larger range of materials with varying oxygen transmissibilities, material properties and surface characteristics have become available to practitioners. Today, prescribing trends reveal that in many countries, silicone hydrogel lenses will be prescribed on a daily wear basis very frequently, representing a significant shift from the wear modality these materials were primarily used for. Because of this, it is important that the performance of these materials when used for re-usable daily wear be investigated, particularly in terms of their compatibility with the various lens care products available in today’s marketplace.

The feature article presents data on the corneal staining characteristics associated with wear of two hydrogel (alphafilcon A & etafilcon A) and one silicone hydrogel (lotrafilcon A) lens material used in combination with four different multipurpose lens care products. Three of the multipurpose solutions were PHMB-based (ReNu MultiPlus, SOLO-care PLUS and Complete MoisturePLUS) and the other was a polyquad-based system (OPTI-FREE Express). The major finding of the study was to confirm and demonstrate significantly increased staining when alphafilcon A hydrogel lenses were pre-soaked in PHMB-based lens care solutions. In contrast, both etafilcon A and lotrafilcon A lenses were generally associated with very little corneal staining. Note that lotrafilcon A lenses did show increased staining at one visit with one of the PHMB-based products.

Because this study compared three different PHMB-containing multipurpose solutions, it is a useful illustration of the possible differences in solution uptake and associated corneal response among seemingly identical solutions. Although the three multipurpose solutions were based on the same unique active ingredient, they differed in the formulation.

It is important to make the point that the results presented here from one lens type of each lens group is not necessarily representative of other lens types belonging to the same group. Most particularly, it is well known that silicone hydrogel materials have very different material and surface characteristics; the uptake and release of preservatives contained in multipurpose contact lens solutions may therefore vary between one lens silicone hydrogel lens type to the other. As the authors rightfully point out, it would be unwise to assume that the results reported in this paper for the lotrafilcon A material will be the same for the various other silicone hydrogel materials currently available.

Perhaps the most valuable learning from this study is the notion that solution-induced toxic staining has a time course. Regardless of the solution or lens type, staining typically tended to occur early on (1 to 2 hours following lens insertion). Based on this, practitioners may be well advised to attempt to examine daily wearing contact lens subjects in the early hours of the morning, at least for the initial visit following a new fit or a change of lens type or lens care system.

Some questions remain unanswered by this study. For example, whether a cumulative effect will be present if lenses are worn for more than one day so that a steady increase in solution uptake will occur after each overnight soak? One might also wonder, given the asymptomatic nature of this staining, whether the presence of solution-based staining warrants intervening? Indications as to whether this level of staining is potentially relevant to patients and practitioners are not available from this study and as such, the significance of toxic staining remains largely unknown.