Developmental Hyperopia
Less is known about the epidemiology of hyperopia than that of myopia. There appears to be an increase in the prevalence of adult hyperopia with age that is separate from the development of nuclear sclerotic cataracts. Nuclear sclerosis is usually associated with a myopic shift. In Caucasians, the prevalence of hyperopia increases from about 20% among those in their 40s to about 60% among those in their 70s and 80s. In contrast to myopia, hyperopia has been associated with lower educational achievement.
Lee KE, Klein BE, Klein R. Changes in refractive error over a 5-year interval in the Beaver Dam Eye Study. Invest Ophthalmol Vis Sci. 1999;40(8):1645–1649.
Prevention of Refractive Errors
Over the years, many treatments have been proposed to prevent or slow the progression of myopia. Because accommodation is a postulated mechanism for the progression of myopia, optical correction through the use of bifocal or multifocal spectacles or the removal of distance spectacles when performing close work has been recommended to reduce the progression of myopia. Administration of atropine eyedrops also has long been proposed because it inhibits accommodation, which may exert forces on the eye that result in axial elongation. Use of a drug that lowers intraocular pressure has been suggested as an alternative pharmacologic intervention; this approach works presumably by reducing internal pressure on the eyewall. It has also been postulated that use of rigid contact lenses could slow the progression of myopia in children. Visual training purported to reduce myopia includes convergence exercises and those that incorporate changes in near–far focus. However, evidence reported in the peer-reviewed literature, including that from randomized clinical trials, is currently insufficient to support a recommendation for intervention using any of these proposed treatments.
The need to correct refractive errors depends on the patient’s symptoms and visual needs. Patients with low refractive errors may not require correction, and small changes in refractive corrections in asymptomatic patients are not generally recommended. Correction options include spectacles, contact lenses, or surgery. Various occupational and recreational requirements, as well as personal preferences, affect the specific choices for any individual patient.
Saw SM, Shih-Yen EC, Koh A, Tan D. Interventions to retard myopia progression in children: an evidence-based update. Ophthalmology. 2002;109(3):415–421.
Chapter Exercises
Questions
2.1. Using the reduced schematic eye and the concept of the nodal point, what is the retinal image height of an 18.mm 20/40 Snellen letter at a distance of 20 ft (6 m)?
a.0.5 mm
b.0.05 mm
c.1 mm
d.0.1 mm
e.0.01 mm
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2.2.The angle subtended by the 20/40 Snellen letter at a distance of 20 ft (6 m) is approximately
a.1 arcmin
b.2 arcmin
c.5 arcmin
d.10 arcmin
e.40 arcmin
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2.3. What is the relative size of target lights in a Goldmann perimeter (with a radius of 33 cm) relative to their corresponding retinal image?
a.same
b.5 times larger
c.10 times larger
d.20 times larger
e.15 times larger
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2.4.Which of the following statements is not true?
a.In emmetropia with accommodation relaxed, parallel light rays from infinity focus to a point on the retina.
b.In myopia with accommodation relaxed, parallel light rays from infinity focus to a point anterior to the retina, forming a blurred image on the retina.
c.In myopia with accommodation relaxed, light rays emanating from a point on the retina focus to a far point in front of the eye between optical infinity and the cornea.
d.In hyperopia with accommodation relaxed, parallel light rays from infinity focus on the far point posterior to the retina.
e.In hyperopia with accommodation relaxed, light rays emanating from a point on the retina are divergent as they exit the eye, appearing to have come from a virtual far point behind the eye.
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2.5.Which of the following statements is not true?
a.If the principal meridians of astigmatism have constant orientation and the amount of astigmatism is the same at every point across the pupil, the refractive condition is known as regular astigmatism.
b.With-the-rule astigmatism is more common in children.
c.In with-the-rule astigmatism, the vertical meridian is steepest, and a correcting plus cylinder should be used at or near axis 90°.
d.In against-the-rule astigmatism, the horizontal meridian is steepest, and a correcting minus cylinder should be used at or near axis 180°.
e.Oblique astigmatism is the term used to describe regular astigmatism in which the principal meridians do not lie at, or close to, 90° and 180°.
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2.6. A patient with myopic vision is wearing glasses that were prescribed incorrectly with an overminus of 1.00 D. When he wears them, his near point of accommodation is 20 cm. What is his amplitude of accommodation?
a.none
b.1.00 D
c.5.00 D
d.6.00 D
e.There is not enough information to solve this problem.
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