30/10/2025
Types of Myopia (Nearsightedness) 👁️
Myopia is a refractive error in which near objects are seen clearly but distant objects appear blurred. It occurs when light rays focus in front of the retina instead of directly on it.
There are several types of myopia, classified based on cause, degree, and progression:
🔹 1. Simple Myopia
Most common type
Occurs due to a slightly longer eyeball or excessive curvature of the cornea.
Usually develops in childhood or adolescence.
Vision improves with glasses or contact lenses.
Degree: < -6.00 diopters
🩺 Example: School-going children who need glasses for distance vision.
🔹 2. Pathological (Degenerative or Malignant) Myopia
A progressive and severe form.
Associated with excessive elongation of the eyeball and degenerative changes in the retina, choroid, or sclera.
May cause retinal detachment, macular degeneration, or choroidal neovascularization.
Degree: Often > -6.00 diopters
🩺 Seen in: Adults and sometimes inherited genetically.
🔹 3. Axial Myopia
Caused by increased axial length (longer eyeball).
The most frequent anatomical cause of myopia.
Correctable with concave (minus) lenses.
🔹 4. Curvatural Myopia
Caused by increased curvature of the cornea or lens, leading to excessive refractive power.
Seen in conditions like keratoconus or post-corneal surgery.
🔹 5. Index Myopia
Due to changes in the refractive index of the lens, usually from aging or cataract formation.
Common in nuclear sclerosis (a type of cataract).
🔹 6. Induced or Pseudomyopia
Temporary myopia caused by overuse of accommodation (near work) or spasm of the ciliary muscle.
Vision may return to normal after rest or cycloplegia.
🩺 Example: Students after prolonged screen or study time.
🔹 7. Nocturnal (Night) Myopia
Blurred distance vision in dim light, due to dilated pupil and accommodative errors in low illumination.
🔹 8. Secondary Myopia
Caused by underlying ocular or systemic disease, such as:
Diabetes mellitus
Nuclear cataract
Certain drugs (e.g., sulfonamides, acetazolamide)
