Impairment of retinal adaptive circuitry in the myopic eye

Abstract

Previous studies have proposed that the inner retina is affected in myopes. This study aimed to investigate the changes in adaptive circuitry of the inner retina in myopia, using the global flash multifocal electroretinogram (global flash mfERG) with different levels of contrast (luminance modulation). Fifty-four myopes had global flash mfERG recorded with different contrasts. The direct component (DC) and the induced component (IC) of the mfERG response were pooled into six regions for analysis. The response amplitudes and implicit times at different contrasts were also analysed. Results showed that myopes had significant reduction in the paracentral DC amplitude for the 29% and 49% contrasts and in the paracentral IC amplitude at all contrasts measured. The peripheral IC amplitude for the 49% contrast was also reduced. No significant change was found in implicit time for either DC or IC response. Refractive error explained about 14% of the variance in DC and 16% of the variance in IC amplitude respectively; axial length could not account for additional variance in either paracentral DC or IC amplitudes in the hierarchical regression models used. We concluded that the paracentral retinal region in myopes showed signs of impaired retinal adaptation, suggesting a functional loss at the inner retinal layer. In addition, functions attributed to the outer retinal layer showed only small changes due to myopia.

Subclinical Decrease in Central Inner Retinal Activity Is Associated With Myopia Development in Children

“…This finding is consistent with the finding of Chen et al 22 that refractive error accounted for a greater proportion of the variability than axial length in mfERG responses in myopic adults. The studies of Ho et al 5,6 used a hierarchical regression model that evaluates the individual effect of both variables and these researchers also showed that refractive error contributed most of the reduction in ERG response in adults. In our study, we calculated the 1-year changes in refractive error (À0.55 6 0.53 D) and axial length (0.37 6 0.22 mm) of young children.…”

“…It has been reported that myopia in adults was associated with decreased nonlinear components of ERG responses, 1 multifocal ERG (mfERG) responses, 2,3 retinal adaptation response, 4 and inner retinal function. [5][6][7] Axial length was shown to be linearly related to ERG amplitudes, 8 first-order kernel, and the first slice of second-order kernel of mfERG responses. 9 The reduction in mfERG responses in myopic adults is believed to be due to the deterioration in retinal function associated with long-standing myopia.…”

Myopia Progression in Children Is Linked with Reduced Foveal mfERG Response

“…The multifocal electroretinogram (mfERG) measures retinal function of multiple loci simultaneously and can detect localized defects within the central retinal field. 6 Many authors [7][8][9][10] have also reported reduced and delayed mfERG responses in myopic adults, especially in the paracentral region. Interestingly, Luu and coworkers 11 have found that the mfERG response is affected by the magnitudes of myopia in adults but not in children, which implies that the effect of myopia on the retinal function is not the same between children and adults.…”

“…The paracentral retina has been shown to be affected in adult myopes. 9 The present study aimed to investigate the regional changes of retinal function in children during myopia progression. The global flash mfERG with different contrast stimulation was used to separate the inner and outer retinal activities to the mfERG response.…”

Is the peripheral retina an important site for myopic development? [Liu Y, Wildsoet C (2011) The effectof two-zone concentric bifocal spectacle lenses on refractive error development and eye growth in young chicks. Invest Ophthalmol Vis Sci 52(2):1078–1086]

“…Does the human eye have a particular zone of the retina which guides refractive development? Avery recent study from Ho and co-workers may provide some hints [4]. They applied the electroretinogram to study retinal function in myopic human eyes.…”