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R. E. Payor, G. Schmid; The Effect of Pupils Size on the Measurement of Peripheral Refraction Using the SureSightTM Autorefractor. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3328. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Clinical interest in the measurement of peripheral refraction is based on recent theories on the role of the peripheral retina in emmetropization and conversely refractive error development. While central subjective refraction, autorefraction and aberrometry are well understood adapting these methods to peripheral refraction raises new questions.
In this case we tested the Welch Allen® SureSightTM portable autorefractor and varied pupil size from habitual (mean of 3.7mm) to dilated (greater than 6.0mm) to test the effect of pupil size on the central and peripheral measurements. Central and in 10 degree steps peripheral refractions were measured in nasal, temporal, superior and inferior meridians until the ‘cylinder’ value exceeded the 3.00DC limit for the instrument. For total of 16 subjects the undilated central and peripheral autorefractions were compared with the corresponding dilated pupil measurements.
Using the held-held portable design of the SureSightTM autorefractor it was easy to measure central and peripheral refractions in any (not just the primary) meridian out to the measuring limit of the instrument. Marked asymmetry of the peripheral refraction was seen between the nasal and temporal (more peripheral change) meridians while superior and inferior were similar and closer to the temporal refractions. Hyperopic shift of the peripheral relative to the central refraction ranged for less than 0.50D to greater than 2.50D in these 3 meridians. The mean change in sphere equivalent peripheral refraction with pupil dilation was less than 0.25D which is within the SureSightTM measurement repeatability.
The SureSightTM autorefractor can be used like a clinical retinoscope to measure within 10 degrees of the visual axis while the patient fixates a distant target to control accommodation. Peripheral measurements can be made by moving away from the direction of gaze up to 30 to 50 degrees nasally and 20 to 40 degrees temporally, superiorally and inferiorally. The instrument measurement is robust over a range of pupil sizes from less than 4.0mm to greater than 6.0mm.
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