Refractive Errors and Color Vision

Some eyes are either too long or too short and need help focusing light onto the retina. If an eye is too long, the light rays focus in front of the retina and the image is blurred; the person can move things closer to see better or can wear glasses. This condition is called nearsightedness (myopia). With farsightedness (hyperopia), the light focuses behind the retina because the eye is too short and causes a blurred image. Both conditions are corrected by glasses or contact lenses. Astigmatism, another common error in the eye's focusing abilities, is caused by unequal curvature of the front surface of the cornea. Corrective glasses are necessary if it

Figure 41-17 Accommodative esotropia and anisometropic amblyopia in 5-year-old patient who has unequal refractive errors between the two eyes as well as accommodative esotropia.
Figure 41-18 Accommodative esotropia in 3-year-old patient uncorrected (top) and corrected by hyperopic (farsighted) glasses (bottom). (From AAO. The Child's Eye.)

causes blurred vision or discomfort. Unless there is a marked amount of myopia (nearsightedness), hyperopia (farsightedness), or astigmatism, or a significant refractive difference between the eyes, eyeglasses can adequately compensate for these problems. Refractive errors requiring eyeglasses affect almost 20% of the pediatric population before full growth is attained.

Figure 41-19 Exotropia in 8-year-old patient with right exotropia.
Figure 41-20 Positive angle kappa, which appears similar to exotropia, in 8-year-old patient. Actually, this patient has retinopathy of prematurity, with bilateral dragged maculas.

Figure 41-21 Patient with diagnosis of Crouzon's syndrome presented with proptosis, amblyopia, and left exotropia.

Figure 41-22 Positive head tilt in 4-year-old child could indicate a vertical deviation, especially superior oblique palsy. (From AAO. The Child's Eye.)

Figure 41-21 Patient with diagnosis of Crouzon's syndrome presented with proptosis, amblyopia, and left exotropia.

Color vision defects rarely result in significant visual difficulties. About 8% of white males have some red-green color deficiency, whereas less than 1% of females are affected. In isolation, this defect rarely results in any real drawback to normal function, especially during childhood. Although the identification of such defects can be helpful in a classroom situation, emphasis should not be placed on these minor abnormalities at this age. Color vision testing is not required unless a retinal dystrophy or optic nerve disease is suspected, the family history is positive, or the family specifically requests it.

Figure 41-23 Ocular torticollis in 34-year-old patient. Note the abnormal head tilt.
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