Myopia (short-sightedness) and hypermetropia (long-sightedness) are the two most common defects of vision. In myopia, the person can see nearby objects clearly but distant objects appear blurred. In hypermetropia, the person can see distant objects clearly but nearby objects appear blurred. Both are caused by defects in the shape of the eyeball or the lens and can be corrected using appropriate lenses. This guide covers the difference between the two conditions with a comparison table, causes, symptoms, correction methods, and frequently asked exam questions.
Myopia = short-sightedness — cannot see far objects clearly
Hypermetropia = long-sightedness — cannot see near objects clearly
Myopia: eyeball too long or lens too convex — image forms in front of retina
Hypermetropia: eyeball too short or lens too flat — image forms behind retina
Myopia corrected by concave (diverging) lens
Hypermetropia corrected by convex (converging) lens
Presbyopia = age-related loss of near vision — corrected by bifocal lenses
All three are defects of refraction in the eye
Feature | Myopia (Short-sightedness) | Hypermetropia (Long-sightedness) Also called | Near-sightedness | Far-sightedness Clear vision | Nearby objects | Distant objects Blurred vision | Distant objects | Nearby objects Cause | Eyeball too long / lens too convex | Eyeball too short / lens too flat Image formation | In front of the retina | Behind the retina Correction | Concave (diverging) lens | Convex (converging) lens Lens power | Negative (−) | Positive (+) Common in | Children and young adults | Older adults and children Eye shape | Elongated (oval) | Shorter than normal
Myopia (short-sightedness or near-sightedness) is a defect of vision in which a person can see nearby objects clearly but cannot see distant objects clearly.
Cause: • The eyeball is too long from front to back, OR • The eye lens is too thick or too convex • Result: parallel rays from distant objects converge in front of the retina instead of on it
Symptoms: • Difficulty reading a blackboard or screen from a distance • Squinting to see far objects • Headaches when trying to focus far
Correction: • A concave (diverging) lens is used • It diverges the incoming rays so they converge exactly on the retina • Lens power is negative (e.g., −1.5 D, −2.0 D)
Far point: • The far point of a normal eye is infinity • In a myopic eye, the far point is closer than infinity (e.g., 1 m, 2 m)
Hypermetropia (long-sightedness or far-sightedness) is a defect of vision in which a person can see distant objects clearly but cannot see nearby objects clearly.
Cause: • The eyeball is too short from front to back, OR • The eye lens is too thin or too flat • Result: rays from nearby objects converge behind the retina instead of on it
Symptoms: • Difficulty reading books or phone screens • Eyestrain or headaches when doing close work • Objects must be held at arm's length to see clearly
Correction: • A convex (converging) lens is used • It converges the incoming rays so they focus exactly on the retina • Lens power is positive (e.g., +1.5 D, +2.0 D)
Near point: • The near point of a normal adult eye is 25 cm • In a hypermetropic eye, the near point is farther than 25 cm
Presbyopia is an age-related defect of vision that typically develops after the age of 40. As we age, the ciliary muscles weaken and the lens loses its flexibility, making it harder to focus on nearby objects.
Key features: • Caused by reduced flexibility (elasticity) of the eye lens • A person with presbyopia finds it difficult to read fine print at normal distance • Both near and far vision may be affected • Corrected by bifocal lenses — lenses that have both concave (for far) and convex (for near) parts • A person can have both myopia and presbyopia simultaneously
Difference from hypermetropia: • Hypermetropia: structural defect (eyeball shape) — can occur at any age • Presbyopia: age-related, caused by loss of lens flexibility — develops after 40
Understanding defects requires knowing how the normal eye focuses:
• Light enters through the cornea and passes through the lens • The lens bends (refracts) light to focus it exactly on the retina • The retina converts the image to nerve signals sent to the brain • The ciliary muscles adjust the shape of the lens to focus near or far objects (accommodation) • For distant objects: ciliary muscles relax, lens becomes thin and flat • For nearby objects: ciliary muscles contract, lens becomes thick and convex
In myopia and hypermetropia, the image does not fall exactly on the retina: • Myopia: image falls in front of retina • Hypermetropia: image falls behind retina
The corrective lens shifts the effective focal point back onto the retina.
Myopia (short-sightedness): the person sees nearby objects clearly but distant objects are blurred. Caused by an eyeball that is too long or a lens that is too convex — the image forms in front of the retina. Corrected by concave (diverging) lenses with negative power. Hypermetropia (long-sightedness): the person sees distant objects clearly but nearby objects are blurred. Caused by an eyeball that is too short or a lens that is too flat — the image forms behind the retina. Corrected by convex (converging) lenses with positive power.
Myopia is corrected by a concave (diverging) lens. In a myopic eye, light converges in front of the retina. A concave lens diverges the incoming parallel rays before they enter the eye, effectively moving the focal point back to fall exactly on the retina. The power of the concave lens used is negative (e.g., −2.5 D). The lens essentially moves the far point back to infinity.
Hypermetropia is corrected by a convex (converging) lens. In a hypermetropic eye, light from nearby objects would converge behind the retina. A convex lens converges the rays before they enter the eye, effectively moving the focal point forward onto the retina. The power of the convex lens is positive (e.g., +1.5 D). The lens moves the near point closer, to the normal 25 cm.
Presbyopia is an age-related defect developing after age 40, caused by the loss of flexibility of the eye lens — the ciliary muscles weaken and the lens cannot thicken enough for near vision. Hypermetropia is a structural defect caused by a short eyeball or flat lens — it can occur at any age. Both cause difficulty in near vision, but they have different causes. Presbyopia is corrected by bifocal lenses.
Far point: the farthest point at which the eye can see clearly. For a normal eye, the far point is at infinity. For a myopic eye, the far point is closer (e.g., 1–2 metres). Near point: the closest point at which the eye can see clearly. For a normal adult eye, the near point is 25 cm. For a hypermetropic eye, the near point is farther than 25 cm. For a myopic eye, the near point is less than 25 cm.
Yes. As a person with myopia ages, they can also develop presbyopia (age-related near vision loss), effectively having difficulty at both near and far distances. In such cases, bifocal lenses are used — the upper part (concave) corrects distance vision and the lower part (convex) corrects near vision.
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