MYOPIA (“Shortsightedness”)

WHAT IS MYOPIA?

When light rays from a distant object (6 m or further away) come into focus in front of the retina of an unaccommodated eye, we say that the eye is myopic, or that the person has myopia.

In Figure 12.8 you can see that the parallel light rays from a distant object come to a sharp focus before they reach the retina. The light rays are diverging when they reach the retina.This means that the unaided distance vision will be blurred.

Figure 1: The focal point in a relaxed myopic eye is in front of the retina

CAUSES OF MYOPIA

Myopia may be caused by:

• an eye that is longer than average (this is called axial myopia)
• a cornea and/or a crystalline lens that is curved too much and, therefore, too strong in power (this is called refractive myopia).

SYMPTOMS OF UNCORRECTED MYOPIA

Myopia is often called “shortsightedness”. The reason for this is that a person with myopia will have near vision that is better than their distance vision, no matter what age they are.People with myopia (also called myopes) usually complain of blurry distance vision, or say that they cannot recognise people who are far away. They may tell you, or you may notice, that they see better when they almost close their eyes (“screw up” or “squint” their eyes). Myopic people often find that their vision seems worse at night or in dim light.

CORRECTION OF MYOPIA

Concave (or “minus”) spherical lenses correct myopia.