Principles of Flexure With The Boston Envision Lens.

The majority of corneas flatten from apex to the periphery with differing ecentricity. The central area of the cornea tends to be of low ecentricity in the range of approximately 0.3, but the mid-periphery begins to flatten at a rate of apporximately 0.7. Not all corneas are the same however, some corneas are actually steeper in the mid-periphery than in the center apical region. This is however is rare. The concept of the Boston Envision lens is to match the posterior surface of the RGP lens to the geometry of the cornea, specifically multiple
ecentricities. This should provide the patient with a better physical fit and the practioner with a more forgiving fit. This explains the concept of the Boston Envision lens. Flexure is
infuenced by three main factors: corneal topography; lens thickness; and physical characteristics of the material. Fitting relationship of the lens to the cornea, and eye lid tension also influence the amount of flexure. This explains the concept of flexure as studied in this report. The purpose of this study is to show the amount of flexure possible and the type of flexure that occurs with a standard Boston Envision lens as measured by over refraction, and over K's.