The commoner diseases of the eye : how to detect and how to treat them . Another Example of Poor Illumination. rays of light passing into the eye to come to afocus at two different points. It is divided intoregular and irregular. In irregular astigmatism the rays have dif-ferent foci in the same meridian. This is us- 14 COMMONER DISEASES OF THE EYE ually caused by irregularities of the corneal sur-face or changes in the lens substance. Cornealulcers, leaving scars and facets on healing, isthe common source of irregular Position of {he Head the Patient Must Assume in Un-corrected
The commoner diseases of the eye : how to detect and how to treat them . Another Example of Poor Illumination. rays of light passing into the eye to come to afocus at two different points. It is divided intoregular and irregular. In irregular astigmatism the rays have dif-ferent foci in the same meridian. This is us- 14 COMMONER DISEASES OF THE EYE ually caused by irregularities of the corneal sur-face or changes in the lens substance. Cornealulcers, leaving scars and facets on healing, isthe common source of irregular Position of {he Head the Patient Must Assume in Un-corrected Myopia. Vision is much impaired and can be very littleimproved by glasses. In regular astigmatism one principal me-ridian of the cornea has a greater curve thanthe other. These two principal meridians arealways at right angles to one another, the mend- THE NORMAL AND ABNORMAL EYE 10 ian of greater curvature being usually situatedin the vertical and that of less curvature in thehorizontal meridian. When this is the case theastigmatism is said to be with the rule; when
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