Unilateral high myopia: optical components, associated factors, and visual outcomes

Abstract

Aim: To elucidate the optical basis for unilateral high myopia and to identify the factors associated with its development.

Methods: Medical records of 48 children (aged 4 months to 17 years; mean age 6.8 years) with unilateral high myopia (5 dioptres or more) seen consecutively by the author during a 15 year period were reviewed. 45 (94%) of the 48 patients had unilateral axial myopia.

Results: The mean refractive difference between paired eyes was 9.4 (SD 3.6) dioptres and the more myopic eye was on average 3.3 (1.8) mm longer than the less myopic eye. All but three of the patients had an ocular disorder associated with reduced acuity, central nervous system abnormality, or family history of high myopia.

Conclusion: Clinical conditions associated with unilateral high myopia can be identified in the majority of patients and often account for the associated visual impairment.

Figure 1

Refractions in dioptres for 42 patients with unilateral high myopia. Hyperopic refractions are represented by unsigned values and myopic refractions by minus (–) values.

Figure 2

Total axial length (TAL) values in 42 patients with unilateral high myopia. For each pair of eyes the circle represents the total axial length of the more myopic eye and the square represents the total axial length of the less myopic eye. The mean total axial length values for normal subjects (middle curve) and upper and lower 95% confidence bands (outer curves) are shown for comparison.

Figure 3

The refractive difference between the more myopic eye and less myopic eye in dioptres is compared with the difference in their total axial length in millimetres.

Figure 4

Visual acuity of the more myopic eye is compared with the visual acuity of the less myopic eye in 40 patients. Visual acuity is expressed as the logarithm of the maximal angle of resolution (logMAR). Acuities of 20/2000 or less were arbitrarily assigned log MAR values of 2.0. The diagonal line represents the total distribution of interocularly identical acuities. Note that single circles located on the x-axis at the value 2, and on the y-axis at 0.1 and 0.4 represent two pair of patients with identical acuities.

Figure 5

Fundus photographs of an 8 year old boy with unilateral high myopia due to segmental optic nerve hypoplasia left eye. Note that the inferotemporal portion of the left optic disc is truncated and separated from the adjacent pigment epithelium by a crescent of peripapillary tissue.

Figure 6

Algorithm for diagnostic evaluation of the patient with unilateral high myopia which is based on axial length measurements, clinical findings, and relevant history.