 Strengths are generally prescribed in quarter-diopter steps (0.25 D) because most people cannot generally distinguish between smaller increments (e.g., eighth-diopter steps / 0.125 D).The use of improper corrective lenses may not be helpful and can even exacerbate binocular vision disorders.Eyecare professionals (optometrists and ophthalmologists) are trained to determine the specific corrective lenses that will provide the clearest, most comfortable and most efficient vision, avoiding double vision and maximizing binocularity.