- - - - - - SIGHT

At birth, sight is the least developed sense. A new-born baby can distinguish vague colours and shapes. It needs several months to recognise people or objects by sight.

Certain malfunctions become apparent very early: MYOPIA (short sight) means an overly convergent eye. A short-sighted person does not see distant objects clearly, but this can be corrected with divergent lenses. HYPERMETROPIA (long sight) means that the eye is insufficiently convergent, and the person does not see close objects clearly. Convergent lenses correct this anomaly.

Other defects appear with age: PRESBYOPIA involves loss of elasticity in the crystalline lens of the eye and causes a loss of close sight (To read the paper, a person has to hold it at arm’s length). This can be corrected with convex or progressive lenses (if distance sight also needs correction), or even contact lenses. With a CATARACT, the crystalline lens gradually becomes opaque. It can eventually cause eye fatigue after watching television, blurry vision or a need for extra light to see clearly. These MINOR PROBLEMS, sometimes troublesome in our daily lives, are usually correct with glasses or with an operation that has become almost benign. There are more serious conditions that are pathologies and require medical treatment. One such condition is GLAUCOMA, which is caracterised by ocular tension.