Farsightedness

Signs and symptoms

In young patients, mild hypermetropia may produce no symptoms. Common signs include blurry vision, frontal or frontotemporal headaches, eye strain, and tired eyes, especially after close work in the evening.

Difficulty with binocular vision and depth perception can occur. Rare complications include strabismus and amblyopia; severe hyperopia in children may cause double vision from over-focusing. Hypermetropic adults with short axial length have a higher risk of primary angle closure glaucoma, warranting routine gonioscopy.

Causes

Simple hypermetropia, the most common form, results from normal biological variations in eyeball development. Causes are classified as axial (short axial length, as in nanophthalmos), curvatural (flatter cornea or lens curvature, as in microcornea or cornea plana), index (age-related cortical sclerosis, diabetes, or certain cataracts), positional (posterior dislocation of lens or IOL from trauma), consecutive (surgical overcorrection of myopia or undercorrection in cataract surgery), functional (paralysis of accommodation from internal ophthalmoplegia or CN III palsy), and absence of lens (congenital or acquired aphakia). About 1 mm decrease in axial length causes 3 diopters of hypermetropia; about 1 mm increase in radius of curvature causes 6 diopters.

Diagnosis

Diagnosis is made through objective refraction using a retinoscope or automated refractor, and subjective examination with trial lenses in a trial frame or phoropter. Ancillary slit lamp testing examines the cornea, conjunctiva, anterior chamber, and iris. In severe congenital hyperopia, the brain cannot merge blurred images from each eye, risking one eye becoming dominant and the brain blocking the non-dominant eye. Hyperopia is classified clinically as simple (biological diversity), pathological (disease, trauma, abnormal development), or functional (accommodative paralysis).

Severity categories are low (≤ +2.00 D), moderate (> +2.00 D to +5.00 D), and high (> +5.00 D). Accommodative status divides hyperopia into total (after cycloplegic relaxation), latent (corrected by ciliary tone, about 1 diopter), and manifest (not corrected by ciliary tone), which further splits into facultative (corrected by patient's accommodation) and absolute (causing distance blur). Total hyperopia equals latent plus manifest hyperopia.

Treatment

The simplest treatment is corrective lenses—eyeglasses with convex lenses or contact lenses. Surgical options include laser procedures: PRK (removes minimal corneal surface, with risks of regression, astigmatism, and corneal haze), LASIK (reshapes cornea, corrects up to +6 diopters, contraindicated in lupus and rheumatoid arthritis), LASEK (uses alcohol to loosen corneal surface), Epi-LASIK (uses epikeratome, no alcohol), and LTK (non-destructive, uses THC:YAG laser). IOL implantation corrects aphakia (high hypermetropia from absent lens) and refractive lens exchange replaces the natural lens; phakic IOLs can correct up to +20 diopters without removing the crystalline lens.