Prognosis
Astigmatism is a refractive condition with a relatively predictable course throughout life. A high degree of astigmatism in infants and toddlers is common, but in most cases the cornea flattens and astigmatism lessens later in childhood. The degree of astigmatism usually stabilises in adulthood and there are typically small degrees of astigmatism, mostly of a with-the-rule (WTR) type. After 40 years of age, the cornea tends to steepen again, more in the horizontal than the vertical meridian, and so a shift towards against-the-rule (ATR) astigmatism is observed.[24]
Regular astigmatism in children
Prognosis is good in most of these cases, as the degree of astigmatism is gradually reduced throughout early childhood. However, it is important to detect those who remain with high degrees of astigmatism and to prescribe correction to decrease the risk of amblyopia.[24]
Regular astigmatism in adults
In adult patients, the degree of astigmatism is usually stable and good visual acuity can be achieved by optic correction.
Keratoconus
Keratoconus usually affects one eye first and then the other eye becomes affected within a few years. Consequently, the first eye affected tends to develop a more advanced corneal distortion. Predicting the rate of progression for an individual patient is impossible. Some patients experience alternating periods of fast progression and stabilisation. According to one large study of keratoconic patients, >20% of the patients required corneal grafting at an average of 8.8 years from the time of diagnosis.[75]
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