Condition guides
Common refractive eye conditions
Plain-language educational overviews of focusing conditions people often search about. These pages explain concepts — they do not diagnose or recommend treatment for an individual.
Featured tools
Interactive educational tools related to this topic.
Vision Simulator
Illustrative simulations of blur, astigmatic distortion, glare, and contrast reduction for learning only.
Visual Acuity Test
Educational on-screen eye chart to explore Snellen-style acuity lines — not a clinical examination.
Astigmatism Test
An educational astigmatism dial/line pattern to explore uneven blur — not a clinical cylinder measurement.
Prescription Decoder
Paste or enter OD/OS sphere, cylinder, axis, ADD, prism, and PD to get plain-English educational explanations.
Common refractive conditions
Educational overviews of myopia, hyperopia, astigmatism, and presbyopia.
Myopia (Nearsightedness)
Myopia (nearsightedness) is a refractive error where distance detail is softer while near work may still look relatively clear. NEI and AOA education explain optics, symptoms, and the need for professional refraction—not DIY power guessing.
Hyperopia (Farsightedness)
Hyperopia (farsightedness) is a refractive error where the eye must exert extra focusing effort for clarity, especially at near. Young people may hide it; adults often notice near strain sooner. NEI education emphasizes professional diagnosis.
Astigmatism
Astigmatism is a refractive error often related to toric (unequal) curvature that focuses light differently in different meridians. Cylinder and axis on a prescription describe the correcting lens—not a scar grade.
Presbyopia
Presbyopia is the age-related decline in near focusing amplitude that commonly becomes noticeable in the 40s. It is not the same as myopia or hyperopia, though it can combine with them on a prescription via an ADD.