Hyperopia Health Article

Definition

Hyperopia (farsightedness) is an eye condition in which incoming rays of light reach the retina before they converge into a focused image.

Description

When light passes through the lens and cornea of the eye, its velocity decreases. The surfaces of the lens and cornea are not perpendicular to the incoming light, so the direction of the light changes. The greater the curvature of the lens system, the greater the change in the direction of the light.

When parallel light rays pass through the lens system of the eye, they are bent so they converge at a point some distance behind the lens. With perfect vision, this point of convergence where the light rays are focused lies on the retina. Hyperopia is the condition in which the point of

focus of parallel light rays from an object lies behind the retina. This condition exists when the eyeball depth is too short for the curvature of its lens system.

There is a connection between the focusing of the lens of the eye (accommodation) and convergence of the eyes (the two eyes turning in to look at a close object). A good example is during reading, when the lens accommodates to make the close-up material clear and the eyes turn in to look at the print and keep it from doubling. Because of this connection between accommodation and convergence, if the lens needs to accommodate and focus for distance (to bring the image back onto the retina), the eyes may appear to turn in.

Causes & symptoms

Babies are generally born slightly hyperopic, but this symptom tends to decrease with age. There is normal variation in eyeball length and curvature of the lens and cornea, and some combinations of these variables give rise to eyes in which the cornea is too flat for the distance between the cornea and the retina. If the hyperopia is not too severe, the lens may be able to accommodate and bring the image back onto the retina. This accomodation results in clear distance vision, but the constant focusing could cause headaches or eyestrain. If the lens cannot accommodate for the full extent of the hyperopia, the distant image is blurry. If the eyes are focused for distance and the person is looking at a nearby object, the lens needs to accommodate further. This need may result in blurry nearby objects or headaches during close work.

Symptoms depend on the degree of hyperopia. Some individuals may have no symptoms, while others have blurry near vision and clear distance vision, and those with the most severe cases have blurry near and distance vision. Headaches and eyestrain may also occur, particularly when doing close work. An eye turned in (esotropia) may be a result of hyperopia, particularly in children. A turned eye could also signal a more serious problem, so a physician should be consulted.