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A. Ohlendorf, F. Schaeffel; Diurnal Variations of Binocular Refractive State and Effects of Temporary Monocular Positive Lens Wear, as Measured With a High Resolving Infrared Photoretinoscope. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3926.
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© ARVO (1962-2015); The Authors (2016-present)
It is difficult to relate a particular visual experience to myopia development in humans because of the long integration times involved. Experiments in animal models have shown that the choroid can thicken or thin, depending on the sign of imposed defocus. Therefore, we have measured changes in choroidal thickness in humans after defined changes in visual experience. In human eyes, diurnal fluctuations in axial length were found in the range of 46µm (Read et al., 2008), which is equivalent to 0.12D. By comparing the refraction of the right and the left eyes with high resolution, following treatment of one eye with a plus lens, interocular differences in choroidal thickness should become detectable.
To achieve sufficient resolution, an automated infrared photorefractor was programmed in Visual C++ to measure both eyes continuously at 25 Hz sampling rate at a very long distance of 3.5 m. Standard deviations of the refractions were less than 0.1 D. Refractions were measured in four near-emmetropic young adult subjects (28 ± 1.8 years) every hour from 9:30 am until 5:30 pm, over a period of three days. From 2:30 pm to 4:30 pm, the subjects wore a +4 D lens in front of their right eye. Accommodation was not controlled during the treatment.
(1) Three subjects showed a small myopic shift in refraction over the first half of the day, with a maximum of 0.19 D, although, one subject reached his most myopic refraction in the evening. (2) On average, the treatment of the right eye with +4D lenses for 2 hours did not have an effect on the difference in interocular refraction. (3) One subject was studied in more detail with the lenses in place for 1, 2 or 3 hours. There was a significant hyperopic shift in refraction in both eyes in the case of 2 and 3 hours of lens wear, but no differences in refraction were induced between both eyes.
Diurnal drifts towards a more myopic refraction at noon have previously been described (Stone et al., 2004). That monocular treatment with positive lenses did not induce any monocular hyperopic shift (as expected from choroidal thickening) is disappointing since the technique would have resolved it. Other modifications of visual experience in one eye may be more effective to induce monocular changes in choriodal thickness.
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