## Optical Correction of Myopia **Key Point:** Myopia (nearsightedness) requires a **concave (minus) lens** to diverge incoming light rays and shift the focal point posteriorly onto the retina. ### Mechanism of Correction In myopia: - The eye is too long or the cornea is too curved - Parallel light rays converge anterior to the retina - A concave lens diverges light rays before they enter the eye - This shifts the focal point backward onto the retinal plane ### Power Notation - Myopic correction is denoted with a **minus (−) sign** - Example: −2.00 D (2 diopters of myopic correction) - The stronger the myopia, the more negative the power required **High-Yield:** Remember the mnemonic **"M for Minus"** — Myopia corrected with Minus lens. ### Comparison of Refractive Corrections | Refractive Error | Lens Type | Power Sign | Light Path | |---|---|---|---| | Myopia | Concave | Minus (−) | Diverges rays | | Hypermetropia | Convex | Plus (+) | Converges rays | | Astigmatism | Cylindrical | Varies | Corrects meridional difference | | Presbyopia | Bifocal/Progressive | Plus (+) | Adds near vision power | **Clinical Pearl:** Myopic patients often complain of difficulty seeing distant objects but have clear near vision without accommodation. 
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