Astigmatism Recognizing the presence of astigmatism When you

Astigmatism

Recognizing the presence of astigmatism When you begin retinoscopy on an eye, you will know that there is astigmatism present in the following situations: 1. Streaking one meridian gives you with-motion or againstmotion, and streaking the meridian 90° degrees away gives you a neutral reflex. 2. Streaking one meridian gives you against-motion, and streaking the meridian 90 degrees away gives you withmotion. 3. Streaking one meridian gives you with-motion (or againstmotion) with a wide streak reflex, and streaking the meridian 90 degrees away gives you the same motion but with a narrower streak reflex.

Recognizing the presence of astigmatism narrower streak reflex a wide streak reflex

Neutralizing of astigmatism - The great majority of refraction are cases either without astigmatism (spherical refractive error) or with regular astigmatism (cylindrical refractive error in which the principal are perpendicular to each other). - The minority of refractions consist of irregular astigmatism (in which the principle meridian are not perpendicular to each other).

Neutralizing of astigmatism - In spherical errors the retinoscopy will shows a neutral point which the same in all meridians, the result is no movement in all meridians using the same lenses. - The initial examination with in astigmatism the situation is not quite. Retinoscope is always exploratory to determine the direction of the movement of the red reflex. - The observer starts with vertical then with horizontal movement and lenses are inserted to determine the neutral point in each meridian separately. - If this is not so (corresponding) then the reflex may alter its plane of movement indicating the presence of astigmatism which is oblique. - In this case the examiner must again explore different planes of external movement of his light until it corresponds to those of red reflex.