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Rosa H. Lee, Amanda C. Kingston, Gary Richardson; Evaluation of Contact Lens Image Stability and Predicted logMAR Image Resolution as Lenses Dehydrate. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6110.
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© ARVO (1962-2015); The Authors (2016-present)
To use a novel optical bench technique to analyze the image stability and predicted logMAR retinal image resolution of 1 investigational and 3 commercially available daily disposable contact lenses as the lenses dehydrate.
Twenty -3.00D lenses of each product type (etafilcon A [AV Moist], narafilcon B, nelfilcon A, test lens) were analyzed on an optical imaging bench. The bench uses a model cornea that mimics the optics and physical dimensions of an average human eye, and relays the retinal plane image of a target (US Air Force) to a CCD camera. Multiple images were captured through each lens over time with a target at optical infinity. Each lens was blotted to remove excess packaging solution and conformed to a 7.8mm radius PMMA model cornea. Two drops of rewetting solution were used to simulate the tear film. Images were acquired every 10s, as the lens is dehydrating, up to 180s following application of the rewetting drops. A pattern-matching algorithm was used to calculate the predicted logMAR score of the images from each lens following normalization against the initial time zero image for each image series.
A one-way ANOVA showed a statistically significant difference (p<0.001) between the test lens compared to nelfilcon A, narafilcon B and etafilcon A, where the overall predicted mean logMAR scores were -0.009, 0.116, 0.136 and 0.182. For the time 0 images, there was a statistically significant difference between the test lens and nelfilcon A (p<0.03) with mean predicted logMAR scores of -0.11 and -0.05, respectively. For the time 10s images (shorter than blink rates associated with reading or computer use), there was a statistically significant difference between the test lens compared to nelfilcon A and etafilcon A (p<0.001) with mean predicted logMAR scores of -0.10, -0.02, -0.03, respectively.
This novel in-vitro method quantitates the predicted logMAR score based on optical image quality as lenses dehydrate. The test lenses exhibited better optical image quality than the 3 commercially available daily disposable lenses. The test lens showed a more consistent and slower reduction in predicted retinal image quality over time compared to narafilcon B and etafilcon A lenses. Within 10s, there was a predicted 4 letter difference between the test lens and nelfilcon A and a 3.5 letter difference for etafilcon A. Further research is needed to understand the clinical impact to visual stability.
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