National Contact Lens Examiners (NCLE) Practice Exam

The prescription of -4.50 +1.00 x 75 indicates the presence of astigmatism. This notation describes a refractive error where the curvature of the cornea or lens differs in one direction compared to the other, resulting in blurred vision. The first part of the prescription, -4.50, represents the spherical component, indicating myopia (nearsightedness), but the second part, +1.00 x 75, introduces a cylindrical component with a specific axis (75 degrees). This cylindrical correction is solely for astigmatism, and it indicates the amount of lens power needed to correct the asymmetrical curvature of the eye. Astigmatism is diagnosed when there is a disparity in focusing ability at different meridians, requiring this dual correction of both spherical and cylindrical powers to achieve clear vision. Thus, the presence of both a negative spherical value and a positive cylindrical value clearly identifies this prescription as primarily associated with astigmatism.