Retinal dysfunction and refractive errors: an electrophysiological study of children

Abstract

Aims: To evaluate the relation between refractive error and electrophysiological retinal abnormalities in children referred for investigation of reduced vision.

Methods: The study group comprised 123 consecutive patients referred over a 14 month period from the paediatric service of Moorfields Eye Hospital for electrophysiological investigation of reduced vision. Subjects were divided into five refractive categories according to their spectacle correction: high myopia (< or = -6D), low myopia (>-6D and < or = -0.75D), emmetropia (>-0.75 and <1.5D), low hyperopia (> or = 1.5 and <6D), and high hyperopia (> or = 6D). Patients with a specific diagnosis at the time of electrophysiological testing were excluded. Only the first member of any one family was included if more than one sibling had been tested. All tests were performed to incorporate ISCEV standards, using gold foil corneal electrodes where possible. In younger patients skin electrodes and an abbreviated protocol were employed.

Results: The mean age of patients was 7.1 years with an overall incidence of abnormal electrophysiological findings of 29.3%. The incidence of abnormality was higher in high ametropes (13/25, 52%) compared to the other groups (23/98, 23.5%). This difference was statistically significant (chi2 test, p = 0.005). There was also a significant association between high astigmatism (>1.5D) and ERG abnormalities (18/35 with high astigmatism v 20/88 without, chi2 test, p = 0.002). There was no significant variation in frequency of abnormalities between low myopes, emmetropes, and low hyperopes. The rate of abnormalities was very similar in both high myopes (8/15) and high hyperopes (5/10).

Conclusions: High ametropia and astigmatism in children being investigated for poor vision are associated with a higher rate of retinal electrophysiological abnormalities. An increased rate of refractive errors in the presence of retinal pathology is consistent with the hypothesis that the retina is involved in the process of emmetropisation. Electrophysiological testing should be considered in cases of high ametropia in childhood to rule out associated retinal pathology.

Figure 1

Histogram showing the distribution of refractive errors in the tested subjects.

Figure 2

Histogram showing the distribution of ages of subjects tested (n = 123).

Figure 3

Variation of percentage of patients with an abnormal ERG by sex and refraction.

Figure 4

Scatter plot showing the spherical equivalent refractive error and age for subjects with normal electroretinogram findings (open symbols) and for subjects with abnormal electroretinogram findings (closed symbols).