Often we receive the question from our customers if there is any difference between the prism foils we offer on our website and the 3M prism foils. To answer this question we are glad that researchers from the University of Sheffield have published this article.
Aim of this study was to determine any differences in visual acuity (VA) and contrast sensitivity (CS) between 3M Fresnel prisms and Trusetal prisms foils.
Which method was used to compare the prism foils?
For this study sixteen participants (mean age 20 years) with normal VA and CS participated. The effect of 5D, 10D, 20D and 30D prism strengths on monocular VA and CS was assessed using a Bailey-Lovie logMAR vision chart and Pelli-Robson chart, respectively. Measurements were carried out for both 3M Fresnel prisms and Trusetal prism foils. A comparison of the physical properties of the two prism types was made.
Conclusion of the study
The conclusion is that the 3M Fresnel and Trusetal prism foils are very similar and there is very little or no difference between both prism foils in terms of how they affect visual acuity and CS at low to moderate strengths. However, with a prism strength of 30D a significantly better VA can be achieved with a Trusetal prism foil than with a 3M Fresnel prism. This gives valuable evidence that there is a significant benefit for the patient if a Trusetal prism foil is used when a high-strength prism is required as part of their treatment plan. Despite this benefit of the Trusetal prism foils in terms of VA, practical considerations must also be taken into account. Trusetal prism foils are thicker and caused more problems in relation to fitting them and securing them to the lens.