Abstract
Background/aimsSome aspects of visual performance worsen with increasing myopia. Whilst the underlying causes are not always clear, reduction in retinal image quality is often attributed to structural changes in the posterior myopic eye. Forward light scatter, originating principally from the cornea and lens, is known to produce veiling glare which subsequently reduces retinal image contrast. It is therefore of interest to investigate whether forward light scatter varies with refractive error.MethodsThirteen young-adult subjects (18–25 years), with mean spherical errors (MSE ± sd, D) RE, − 1.69 ± 2.02 (range 0.38 to − 4.75); LE, − 1.91 ± 1.94 (range 0.50 to − 4.63) underwent binocular assessment of forward light scatter using the AVOT light scatter test. Five glare annuli, with effective eccentricities ranging from 2 to 10°, were used to estimate parameters, k and n, which define the light scatter function of the eye. These were then used to calculate the area under the light scatter function (k′) and the total volume of light scatter (k″).ResultsSignificant correlation was found between increasing myopia and k′ values (RE, p < 0.05; r = 0.64; LE, p < 0.05, r = 0.66). Neither the ‘volume’ of light scatter (k″), the parameter, n, which controls the angular distribution of light scatter, or the straylight parameter constant, k, were significantly correlated with refractive error (p > 0.05 for both eyes). Axial length was also not correlated with any of the light scatter parameters measured.ConclusionThe preliminary data from this study provide evidence that some light scatter parameters may be correlated with refractive error. Further studies are needed to characterize how changes in the anterior media of the eye, and inclusion of a wider range of refractive errors, may affect forward light scatter.
Highlights
Some visual functions in myopes are often poorer when compared with emmetropes [1,2,3], even when refractive errors are fully corrected
The backscatter from the retina and, in particular, the deeper structures involving the retinal pigment epithelium can be quite significant in older individuals, but this light is less useful in decreasing the effective retinal image contrast because of the directional sensitivity of cones
We aim to investigate the effects of refractive error and axial length on a range of forward light scatter parameters
Summary
Some visual functions in myopes are often poorer when compared with emmetropes [1,2,3], even when refractive errors are fully corrected. Owing to the strong association between increasing myopia and axial length elongation, the impaired visual response is frequently attributed to structural and neural changes relating to the posterior region of the myopic eye. A less well studied cause of retinal image degradation is forward light scatter, known as retinal straylight. The forward light scatter within the retina is believed to be negligible by comparison. The backscatter from the retina and, in particular, the deeper structures involving the retinal pigment epithelium can be quite significant in older individuals, but this light is less useful in decreasing the effective retinal image contrast because of the directional sensitivity of cones. Significant deviations from normal cone alignment towards the centre of the pupil have, been reported in myopia [10]
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