Myopia and Hyperopia, are eye problems caused by a failure of the eyes to correctly focus. Myopia is nearsightedness while hyperopia is better known as farsightedness. They are refractive error conditions of the eye.

Refractive disorders of the eye

Refractive disorders occur when the eye fails to refract properly for focusing on the fovea of the retina. Theoretically, refraction means the bending of light but in medical terms, it refers to the method of measuring the strength of the lens needed.

Refraction occurs when light slows down when it travels from one medium to another of greater density. All the light particles slow down concurrently when light hits a flat surface at right angles. Hence, it continues to travel in a straight line.

However, if light hits a surface at an angle, the particles that first enter the new medium slow down first and the rest follow. This causes light to bend. So, when light passes from the air into the cornea (the two mediums have a huge difference in density) it refracts and then focuses onto the retina with the help of the lens of the eye. The eye needs to accommodate in order to refract light from various objects, angles and distances. Hence, the lens of the eye accordingly adjusts its power for focusing adaptability.

Hyperopia, also known as hypermetropia or farsightedness, occurs when the power of the eye is weaker and the eyeball is too small. Hence, the eye cannot focus properly on near objects, and in extreme cases, it cannot focus on objects at any distance. The eye needs to increase its power in order to focus the image (on the retina) of an object that moves towards it. In hyperopia since the eye power is less, the image is blur.

Clinical characteristics of hyperopia

Hyperopia is marked by blurring, asthenopia, adjusting problems, binocular errors, amblyopia and strabismus.

Correction of hyperopia

For adults with hyperopia the standard treatment is with ‘plus’ lenses, but surgery is also an option. LASIK is the most popular procedure for the correction of mild and moderate hyperopia. For severe cases, clear lens exchange in addition with intraocular lens implantation, remains the commonest line of treatment.

However, there are no established guidelines for the degree of hyperopic refractive error that requires prescriptions. Mild hyperopia is often not given a prescription, especially in children. This is because various researches have shown that the eyes is elastic and will adjust in order to offset for the existence of anisometropic refractive corrections. However, too much strain to adjust may result in the risk of cross-eyes or convergent squint in children.

Hyperopia when left untreated also carries a high risk of also developing glaucoma.