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Visual acuity degradation resulting from dispersion in polycarbonate
L D Hampton1, N Roth, J R Meyer-Arendt
1Pacific University College of Optometry, Forest Grove, OR 97116.
Journal of the American Optometric Association
|October 1, 1991
Summary
Polycarbonate spectacle lenses cause significant visual blur due to optical dispersion. This effect, measurable with prisms, is greater than with CR39 material and impacts visual acuity.
Area of Science:
- Optometry
- Materials Science
- Ophthalmic Optics
Background:
- Polycarbonate is a common material for spectacle lenses due to its impact resistance.
- Optical dispersion, a property of materials, can affect image quality by causing chromatic aberration and blur.
- Previous comparisons of polycarbonate with other lens materials like CR39 have not fully quantified the impact of dispersion on visual acuity.
Purpose of the Study:
- To quantify the visual blur induced by optical dispersion in polycarbonate spectacle lenses.
- To compare the blurring effect of polycarbonate with CR39 material.
- To provide a tool for clinicians to predict blur in polycarbonate lenses.
Main Methods:
- Visual acuity (VA) was measured in 40 eyes using a series of prisms.
- Prisms of varying powers (up to 16 prism diopters) were incorporated into polycarbonate lenses.
- The reduction in VA was recorded and analyzed as a function of prismatic power.
Main Results:
- Mean unaided VA of 20/13 decreased to 20/31 through 16 prism diopters of polycarbonate.
- The reduction in visual acuity showed a linear relationship with prismatic power.
- Polycarbonate induced significantly more blur than CR39 material.
Conclusions:
- The optical dispersion in polycarbonate significantly degrades visual acuity.
- The blurring effect of polycarbonate is substantial and must be considered in spectacle lens selection.
- A graphical tool is available to help clinicians predict the degree of blur associated with specific polycarbonate lenses.