Fig. 24. Enhancement of hyperopia by raising the sleeve. Enhancement is one technique that combines changing in the illuminating system with properties of the viewing system. In hyperopic eyes, it is possible to narrow the beam on the retina sufficiently so that its borders can be seen despite the magnification (cross-hatched) of the viewing system. The amount that the sleeve is moved and the width of the facial intercept permit estimation of the amount of hyperopia. Moreover, meridional comparison is the basis for detection of hyperopic astigmatism.