Myopia — When the Eye Focuses Light Too Early
Short placeholder: nearsightedness blurs distant objects from excess focusing power.
- 6–14: Typical onset age (Short placeholder note)
- ~30%: Global prevalence (Short placeholder note)
- −0.25 to −20D: Correction range (Short placeholder note)
- Concave: Lens type (Short placeholder note)
Why light converges before the retina
Short placeholder: elongated eyeball or steep cornea over-bends incoming light.
Hyperopia — When the Eye Focuses Light Too Late
Short placeholder: farsightedness blurs near objects from insufficient focusing power.
- Any age: Typical onset age (Short placeholder note)
- ~25%: Global prevalence (Short placeholder note)
- +0.25 to +10D: Correction range (Short placeholder note)
- Convex: Lens type (Short placeholder note)
Why light converges beyond the retina
Short placeholder: shortened eyeball or flat cornea under-bends incoming light.
Astigmatism — Two Focal Lines Instead of One Point
Short placeholder: an irregular cornea shape bends light unevenly across axes.
- Corneal curvature: Typical cause (Short placeholder note)
- ~30–40%: Global prevalence (Short placeholder note)
- Cylindrical: Correction type (Short placeholder note)
- With myopia/hyperopia: Common pairing (Short placeholder note)
Why light splits into two focal lines
Short placeholder: unequal corneal meridians create separate focal distances.
Combined Refractive Error Patterns
Short placeholder: myopia, hyperopia, and astigmatism can overlap in one eye.
- Myopic astigmatism: Common combo (Short placeholder note)
- Common in adults: Prevalence (Short placeholder note)
- Refraction test: Diagnosis tool (Short placeholder note)
- Sphero-cylindrical: Correction (Short placeholder note)
How multiple errors combine in one eye
Short placeholder: sphere and cylinder components are measured and summed.
Corresponding Lens Correction Types
Short placeholder: each refractive error is matched to a specific lens design.
- Concave (−): Myopia lens (Short placeholder note)
- Convex (+): Hyperopia lens (Short placeholder note)
- Cylindrical: Astigmatism lens (Short placeholder note)
- Sphero-cylindrical: Combined lens (Short placeholder note)
Matching lens shape to the underlying error
Short placeholder: lens curvature redirects rays back onto the retina.
Short placeholder: correct diagnosis of each error type guides precise lens choice.