Spherical Aberration

This means that the refractive power of the lens varies according to the location at which the light ray strikes the lens.

refraction testing.

— Chromatic aberration.

Fig. 16.20 Chro matic aberration splits white light into its component spectral colors. Red is refracted least, and blue is refracted most.

Fig. 16.20 Chro matic aberration splits white light into its component spectral colors. Red is refracted least, and blue is refracted most.

Patients may report being able to see better when looking through a disk with a pinhole (a stenopeic aperture) than without it. This usually is a sign of an uncompensated refractive error in the eye.

The further peripherally the light ray strikes the lens, the more it will be refracted (Fig. 16.21). The iris intercepts a large share of these peripheral light rays. A narrow pupil will intercept a particularly large share of peripheral light rays, which improves the depth of field. Conversely, depth of field is significantly poorer when the pupil is dilated.

H Patients who have received mydriatic agents should refrain from driving.

H Patients who have received mydriatic agents should refrain from driving.

Stretch Marks

Stretch Marks

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