Geriatric optometry OCULAR HEALTH EXAMINATION rf.pdf

REFRACTION The older population experiences significant changes in refractive error.17 Commonly a shift toward more against-the- rule astigmatism occurs, and the spherical component of refraction shifts in the direct of hyperopia. The prevalence of oblique astigmatism and anisometropia increases. Ca...

REFRACTION The older population experiences significant changes in refractive error.17 Commonly a shift toward more against-the- rule astigmatism occurs, and the spherical component of refraction shifts in the direct of hyperopia. The prevalence of oblique astigmatism and anisometropia increases. Cataractous changes in the lens may precipitate rapid changes in refraction. Often an individual’s refractive status is changed substantially as a result of cataract surgery. Objective Refraction Retinoscopy can be more difficult in older patients because of small pupils and media irregularities and opacities. However, it remains an important technique and the examiner should make every effort to obtain a retinoscopic estimate of refractive error. When retinoscopy becomes unusually difficult, however, the clinician should be prepared to vary techniques. Moving to closer than usual observation distances or moving off axis may provide an “easier” retinoscopic reflex; Mehr and Freid25 described this as radical retinoscopy. If a useful retinoscopic reflection cannot be obtained with the standard procedures, the clinician should first move closer and thus reduce the working distance, perhaps to as close as 5 cm in search of a satisfactory reflex. This technique is useful with unsuspected high myopia. If moving closer still provides no useful retinoscopic reflection, high hyperopia could be responsible. Placing a high positively powered lens (e.g., +14.00 D) at the patient’s eye, beginning with a standard working distance and gradually reducing the distance, might enable the clinician to find a difficult retinal reflection in patients with high hyperopia. Of course, when the retinoscopic working distance is changed, an appropriate allowance must be made in estimating the power of the refractive correction. Furthermore, moving off axis may produce some inaccuracy in both the spherical and astigmatic components; thus this procedure is used only when axial viewing does not provide an adequate reflex. When substantial lenticular irregularities are present because of cortical or posterior subcapsular cataract, obtaining consistent or accurate results may be impossible because the apparent movement of the reflected light seems to be fragmented (moving in different directions or at different speeds). In these circumstances, a spot retinoscope is sometimes more useful than a streak retinoscope. Objective optometers or automated refractors depend on light being reflected from the retina. Again, the small pupils and media opacities commonly found in older patients often lead to less-reliable results. Sometimes no result at all can be obtained. Keratometry or keratography to estimate total astigmatism becomes more important when retinoscopy or objective optometer measurement fails. A record of corneal curvature can be useful in quantifying any future changes. Patients with low vision are often unable to make accurate judgments in subjective refraction procedures. Thus more than usual reliance on objective refraction results may be necessary.