Ten years of disposable contact lenses — a review of benefits and risks

Design of a questionnaire for detecting contact lens discomfort: the Contact Lens Discomfort Index

Clinical relevance: Questionnaires can provide unique information regarding the status of a condition from the perspective of the patient. Contact lens (CL) discomfort (CLD) is a condition subjectively reported by CL users; thus, updated and reliable questionnaires are needed.Background: The objective of this study was to design a new questionnaire for identifying CLD, based on the currently established CLD definition considered in the Tear Film and Ocular Surface CLD Workshop.Methods: A survey to characterise CL wearers was created and administered. Some items of the survey were selected by a focus group and analysed using a Rasch model to develop a questionnaire to identify CLD. Unidimensionality was checked applying principal components analysis. To build a plausible CLD classification (symptomatic vs asymptomatic), an unsupervised cluster analysis was used. Gower's general similarity coefficient, the partitioning around medoids algorithm, and the silhouette width were calculated. The reliability of the questionnaire was assessed using the intraclass correlation coefficient and Cohen's kappa coefficient. A study was performed to compare this questionnaire with the Contact Lens Dry Eye Questionnaire (CLDEQ)-8.Results: The 31-item survey was completed by 1104 volunteers, and the posterior analysis resulted in a 9-item questionnaire, the Contact Lens Discomfort Index (CLDI). It showed a good fit with the model (mean square infit and outfit values range was 0.76-1.10), and good unidimensionality (eigenvalues ≤ 1.3). The CLDI score range was 0-18 and the cut-off score for identifying CLD was 8. The intraclass correlation coefficient was 0.88 (95% confidence interval, 0.75-0.94), and kappa was 0.67 (95% confidence interval, 0.41-0.93). Comparison of the CLDI with the CLDEQ-8 in a sample of 58 CL wearers showed that 70.7% were classified equally by both questionnaires.Conclusions: The CLDI is a well-structured instrument, with acceptable psychometric properties, making it a valid and reliable tool to measure CL-related symptoms.

The elution of poly (vinyl alcohol) from a contact lens: The realization of a time release moisturizing agent/artificial tear

The use of a contact lens as a polymeric delivery vehicle is presented. Specifically, the elution of nonfunctionalized poly (vinyl alcohol) (PVA) from nelfilcon A hydrogel lenses is presented as a model of delivering polymeric active agents to the eye. High molecular weight nonfunctionalized PVA is added to the lens matrix for later release into the tears. This is made possible by photo crosslinking a macromer species in lieu of monomeric polymerization. Consistent near zero order release of 0.062% (wt/wt) was demonstrated in vitro over a 20-h period. The result is a new contact lens device based on the slow release of PVA. In vivo results demonstrate that this product improves the wearing comfort of this type of contact lens and acts as a model basis for drug delivery.

Contact lens induced keratitis associated with contact lens wear

PURPOSE

To evaluate clinical characteristics, risk factors, management and outcome of contact lens induced keratitis (CLIK) associated with contact lens wear.

METHODS

The study comprised all consecutive patients presenting with contact lens related presumed microbial keratitis during a 12-month period at our department. Detailed demographic data, type of contact lens, duration of lens wear, wearing schedule and lens hygiene were derived from a self-administered questionnaire. Severity of ulcer, corneal scrapings, treatment and final outcome were evaluated.

RESULTS

27 patients with CLIK, some of which may have been sterile peripheral infiltrates, due to contact lens wear were detected. In the majority of the cases patients had used disposable soft contact lenses (89%) and most of them had a daily wearing schedule (78%). 51.8% patients cleaned their lenses regularly. 6 (22%) applied no disinfection since their lenses were disposable on removal. In 3 of our cases with CLIK, penetrating keratoplasty had to be performed.

CONCLUSION

Disposable contact lenses seem to have been a predisposing factor for contact lens induced keratitis also when used on a daily wear schedule. Insufficient contact lens care products and/or manufacturing characteristics may be responsible for CLIK, which is also observed in otherwise compliant contact lens users. In 3 of our patients with CLIK keratoplasty became necessary, indicating that contact lens induced keratitis may result in severe corneal complications.