Although the eye behind may be healthy, the astigmatic corneal surface is not symmetrical, causing horizontal focusing to be different from vertical focusing. Corrective lenses made to compensate for the specific irregularities of the eye solve the problem in most instances. This disorder is an inflammation of the margins of the eyelids, causing redness, swelling, severe itching , and scaly skin not unlike dandruff . Occasionally the roots, or follicles, of the eyelashes also become involved. In that case the eyelashes themselves become caked with flakes or crusts of dried material.
Adolescents are especially prone to blepharitis, as they are to dandruff.
The condition can sometimes be cleared up with repeated treatments of warm water but more often it takes the attention of a physician and a regimen of prescription eye medication to treat successfully. There are several forms of color blindness, the popular term for any abnormality that causes an individual to see colors differently or less distinctly than normal. The deficiencies are variable and differ markedly in severity. Daltonism is an inherited disorder that is usually sex-linked, with the majority of individuals afflicted being male, although women may carry the gene recessively and pass it on to their male children. The underlying cause of each form of color blindness is traceable to a defect in the light-sensitive cone cells of the retina, which under normal circumstances respond selectively to red, green, or blue colors.