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Review
. 2016 Oct 14;113(41):693-702.
doi: 10.3238/arztebl.2016.0693.

Refractive errors

Ulrich Schiefer  1 , Christina Kraus, Peter Baumbach, Judith Ungewiß, Ralf Michels
Affiliations
Review

Refractive errors

Ulrich Schiefer et al. Dtsch Arztebl Int. .

Abstract

Background: All over the world, refractive errors are among the most frequently occuring treatable distur - bances of visual function. Ametropias have a prevalence of nearly 70% among adults in Germany and are thus of great epidemiologic and socio-economic relevance.

Methods: In the light of their own clinical experience, the authors review pertinent articles retrieved by a selective literature search employing the terms "ametropia, "anisometropia," "refraction," "visual acuity," and epidemiology."

Results: In 2011, only 31% of persons over age 16 in Germany did not use any kind of visual aid; 63.4% wore eyeglasses and 5.3% wore contact lenses. Refractive errors were the most common reason for consulting an ophthalmologist, accounting for 21.1% of all outpatient visits. A pinhole aperture (stenopeic slit) is a suitable instrument for the basic diagnostic evaluation of impaired visual function due to optical factors. Spherical refractive errors (myopia and hyperopia), cylindrical refractive errors (astigmatism), unequal refractive errors in the two eyes (anisometropia), and the typical optical disturbance of old age (presbyopia) cause specific functional limitations and can be detected by a physician who does not need to be an ophthalmologist.

Conclusion: Simple functional tests can be used in everyday clinical practice to determine quickly, easily, and safely whether the patient is suffering from a benign and easily correctable type of visual impairment, or whether there are other, more serious underlying causes.

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Figures

Figure 1
Figure 1
Pinhole aperture – principle and diagnostic relevance: Opacities or irregularities in the refractive media interfere (green lines) with the ideal image-forming process (solid green lines). Holding a pinhole aperture in front of the eye distinctly improves the image quality and thus the detection of the initially barely perceptible gap in the Landolt C (upper C on white background) by largely eliminating the “distracting” rays (dashed green lines), so that only axial and paraxial rays (red lines) reach the eye. However, masking out parts of the image reduces the retinal illumination—the visual impression is generally darker (lower C on dark background).
Figure 2
Figure 2
Pathogenesis of astigmatism in the form of non-rotationally symmetrical deformation of the refractive media. Left: Formation of a spherical image with rotationally symmetrical refractive media; Right: Schematic depiction of the pathogenesis of astigmatism in the form of non-rotationally symmetrical deformation of the refractive media. Instead of being spherical, the lens now forms an ellipsoid resembling a football, with two different radii of curvature. Instead of one focal point as on the left, there are now two focal lines. The more anterior horizontal focal line 1 corresponds with the vertical meridian (blue bow-shaped line) with a smaller radius of curvature and thus a principal plane with higher refractive power, while focal line 2 corresponds to the horizontal meridina (green bow-shaped line) with a larger radius of curvature and a principal plane with lower refractive power. This constellation is called “with-the-rule” astigmatism” (see also Figure 3, Supplementary Material and eFigure 5).
Figure 3
Figure 3
The frequency distribution of axis alignment of the corrective minus cylinder in a large population. The relative frequency of a given alignment of the axis is shown by the length of the radial lines and by the radii of the concentric arcs (from the smallest radius, corresponding to n = 200, to the largest, corresponding to n = 1200). A., Astigmatism; OD, right eye; OS, left eye
eFigure 1
eFigure 1
Landolt C: The optotype is contained in a square made up of 5x5 smaller squares of edge length e. The line width of the C and the breadth of the gap correspond to e. The gap can be situated in any of eight evenly spaced positions. The visual angle under which the gap is discernable specifies the visual acuity of the eye.
eFigure 2
eFigure 2
Illustration of emmetropia (normal vision, efigure 2a) and spherical ametropia: myopia (shortsightedness, efigure 2b), hyperopia (farsightedness, efigure 2c), with diagrams showing the path of the rays without and with optical correction
eFigure 3
eFigure 3
Distortion of the temporal margin of the orbit by minus and plus lenses of varying refractive power
eFigure 4
eFigure 4
Cylindrical ametropia and its optical correction
eFigure 5a–d
eFigure 5a–d
Classification and effect of astigmatism depending on the axis alignment of the corrective minus cylinder (or of the more anterior focal line) – illustrated using a standardized reading text (Radner chart). The photographs are intended to depict the visual impression; this always depends on which of the focal lines lies closer to the retina.
None
See this image and copyright information in PMC

Comment in

  • Some Additions.
    Schmidt D. Schmidt D. Dtsch Arztebl Int. 2017 Mar 17;114(11):195. doi: 10.3238/arztebl.2017.0195a. Dtsch Arztebl Int. 2017. PMID: 28382912 Free PMC article. No abstract available.
  • Caution Required in Cases With Vitreous Opacities.
    Barry JC. Barry JC. Dtsch Arztebl Int. 2017 Mar 17;114(11):195-196. doi: 10.3238/arztebl.2017.0195b. Dtsch Arztebl Int. 2017. PMID: 28382913 Free PMC article. No abstract available.

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