Eye Defect and its Correction: Hypermetropia or Far-sightedness

Hypermetropia (Hyperopia), also known as farsightedness, is a common vision defect where a person can see distant objects clearly, but nearby objects appear blurry. This occurs because light rays focus behind the retina instead of directly on it. It is common in newborn babies due to small eyeball size but often corrects itself as the eyeball grows.

Farsightedness

Hypermetropia occurs due to structural abnormalities in the eye that prevent proper light focusing.

Structural Causes:

• Shortened eyeball → Light focuses behind the retina, causing blurred vision.
• Flattened cornea or lens → Reduces the converging power of the eye, preventing proper focus.
• Increased focal length of the eye lens → Leads to improper light convergence.
• Stiffening of ciliary muscles → Reduces the ability of the eye to adjust its focus.

1. Simple Hypermetropia: It is the most common type. Includes axial hypermetropia (short eyeball) and curvature hypermetropia (flat cornea/lens).
2. Pathological Hypermetropia: It is caused by congenital (birth-related) or acquired conditions. Includes senile (age-related), positional, aphakic (absence of lens), and consecutive hypermetropia.
3. Functional Hypermetropia: Occurs due to third cranial nerve palsy or internal ophthalmoplegia, causing paralysis of accommodation.

Hypermetropia is categorised based on severity (lens power required for correction):

Symptoms of Hypermetropia:

• Blurred vision while focusing on close objects.
• Eye strain and fatigue while reading or working on screens.
• Headaches, particularly in the forehead region.
• Difficulty in adjusting focus, causing discomfort in switching from distant to near objects.
• Double vision in severe cases due to excessive eye strain.

A. Spectacles and Contact Lenses

• Convex lenses (positive power lenses) are used to converge incoming light rays before they reach the eye lens.
• The eye lens then further converges them, forming a sharp image on the retina.
• Glasses and contact lenses are the most common correction methods.

B. Surgical Treatments for Hypermetropia

1. Photorefractive Keratectomy (PRK): It removes a small portion of the cornea to improve refraction. May cause temporary corneal haze and astigmatism.
2. Laser Epithelial Keratomileusis (LASEK): It is similar to PRK but uses alcohol to loosen the corneal surface before reshaping it.
3. Laser-Assisted In Situ Keratomileusis (LASIK): It reshapes the cornea to correct the refractive error, eliminating the need for glasses or contact lenses.