Re: Putting vital stains in context

EDITOR: Professor Efron has written an excellent review of the properties of vital stains, their use and limitations in the assessment of the ocular surface. His very thorough review covers the aetiology of corneal staining, including the characteristics of solution-induced corneal stain (SICS) and the particular form of SICS known as preservative-associated transient hyperfluorescence (PATH). As detailed by Professor Efron, PATH is a transient form of SICS being a specific designation for sodium fluorescein staining, which results from wearing certain combinations of contact lens types and brands of storage solutions. Typically, it will dissipate within a few hours of lens insertion. Professor Efron’s conclusion that SICS, such as PATH, may be a benign phenomenon does not help clinicians manage their contact lens patients at aftercare visits. Even if some or all of any observed staining is PATH and even whether such staining is benign, how can a clinician know which part of the corneal stain observed is not related to PATH? Some or all of any observed stain may be clinically significant, whether PATH-related or not. Some degree of fluorescent staining of the cornea was observed in 79 per cent of 102 non-contact lens wearers examined on only one occasion. A study of 16 subjects over a two-week period by two practitioners found that the average duration of an episode of corneal fluorescent staining (median grade 0.5 using a zero to four scale) was for 1.2 ± 0.4 days. Usually, such a stain may be classed as ‘normal’. At contact lens aftercare examinations, a significant advantage of observing a stain, some or all of which may be classified as ‘normal’ and non-significant, is the platform it provides for discussing the possibility that the patient’s poor compliance with lens care may be related to the observed stain. Such discussion can be the basis for improving patient understanding of the possible consequences of using non-prescribed solutions, re-using solutions or ‘topping up’ instead of completely replacing them, not rubbing and rinsing prior to storage, extending lens use beyond recommended periods et cetera. This discussion and associated improved understanding of the possible consequences may result in a concomitant improvement in compliance and to that extent, the observation of staining will have been useful, even if the staining is not otherwise significant. Aftercare examinations of contact lens wearers require that the background noise provided by ‘normal’ staining, such as may be observed in non-contact lens wearers, is differentiated from any stain which is clinically significant for the contact lens wearer. A total of 98 hydrogel contact lens wearers were examined at three centres and the average fluorescent corneal staining grade observed was 0.5 (on a scale of zero to four). This average level is similar to that which is seen in non-contact lens wearers; however, one-third of the hydrogel lens wearers were found to have ‘notable’ staining, although that 1996 study precedes the more recent SICS phenomenon of PATH. Of course, ‘notable’ stain does not just depend on the area, location and intensity of staining, because other signs such as conjunctival hyperaemia as well as symptoms will often help make the differential diagnosis between notable and acceptable staining. Staining is frequently a symptomless phenomenon as is PATH in particular, at least in the short term. There does not appear to have been any examination of the long-term effects of prolonged exposure to day-to-day PATH, making it difficult to assume that it is benign. A practitioner examining a patient since the advent of PATH forms of SICS has increased chances of observing staining but reduced chances of successful differential diagnosis. For patients who are using lens/ solution combinations, which might induce PATH responses, not examining them within the first few hours of lens insertion, (by which time PATH should have dissipated) is not often practical. Similarly, asking a patient with staining to return in a few hours for re-examination to see if the suspected PATH stain persists or has dissipated is not efficient practice. Not prescribing lens/solution combinations which might induce PATH seems the more practical option, as one source of staining ‘noise’ and associated potential confusion will be avoided by this approach.