Accurate detection of subjective refraction is important to provide patients with the best visual quality. One of the factors affecting detection of subjective refraction is viewing distance. Lack of requirements for optometric office arrangement and required space dimensions leads to smaller optometric offices that provide shorter distance between the patient and the optotype chart. However, the effect of decreased viewing distance on detected subjective refraction remains unknown. The aim of this study was to evaluate the effect of viewing distance on the assessment of subjective refraction. Two types of subjective refraction of the dominant eye were determined in 45 participants at five viewing distances (6 m, 5 m, 4 m, 3 m, and 2.5 m): subjective refraction that ensured visual acuity 1.0 (in decimal units) and maximum subjective refraction that ensured the best corrected visual acuity. The results demonstrated that viewing distance significantly affected the outcome of subjective refraction detection; there were hyperopic shifts in all types of refractions that increased as the viewing distance decreased. To conclude, the most appropriate viewing distance for subjective refraction detection is 5 m or 6 m. If viewing distance is reduced to 4 m or less, a negative spherical lens of the corresponding proximity should be added to the obtained subjective refraction as it cannot be reliably stated that ocular accommodation is fully relaxed. Since this is not always achievable by 0.25 D steps, mirror systems should be used in smaller (3 m and closer viewing distances) optometric offices to provide more appropriate subjective refraction detection.
Babij, N. V., Kozyreva, А. А. and Zhukova, Е. А. 2017. Daily fluctuations in visual acuity at various distances among students at the Kirov State Medical University. Tendentsii Razvitiya Nauki i Obrazovaniya, 25(3), 30–31 (in Russian).
Chen, A.-H., Norazman, F. N. N. and Buari, N. H. 2012. Comparison of visual acuity estimates using three different letter charts under two ambient room illuminations. Indian J. Ophthalmol., 60(2), 101–104.
https://doi.org/10.4103/0301-4738.90489
Ciuffreda, K. J. 2006. Accommodation, the pupil, and presbyopia. In Borish’s Clinical Refraction. 2nd ed. (Benjamin, W. J., ed.), pp. 93–144, Butterworth-Heinemann, Oxford.
https://doi.org/10.1016/B978-0-7506-7524-6.50009-0
Goss, D. A. and Grosvenor, T. 1996. Reliability of refraction – a literature review. J. Am. Optom. Assoc., 67(10), 619–630.
Grosvenor, T. P. 2007. Primary Care Optometry. 5th ed. Butterworth-Heinemann/Elsevier, St. Louis, MO.
Hecht, S. 1928. The relation between visual acuity and illumination. J. Gen. Physiol., 11(3), 255–281.
https://doi.org/10.1085/jgp.11.3.255
Hofstetter, H. W. 1973. From 20/20 to 6/6 or 4/4? Am. J. Optom. Arch. Am. Acad. Optom., 50(3), 212–221.
https://doi.org/10.1097/00006324-197303000-00005
ISO 8596:2017 Ophthalmic Optics – Visual Acuity Testing – Standard and Clinical Optotypes and Their Presentation.
Johnson, C. A. 1976. Effects of luminance and stimulus distance on accommodation and visual resolution. J. Opt. Soc. Am., 66(2), 138–142.
https://doi.org/10.1364/JOSA.66.000138
Lee, E. M., Feis, A. E. and Clark, A. 2009. Effect of room illumination in computerized visual acuity (using smart system II). Optometry, 80(6), 316.
https://doi.org/10.1016/j.optm.2009.04.072
Ludvigh, E. 1941. Effect of reduced contrast on visual acuity as measured with Snellen test letters. Arch. Ophthalmol., 25(3), 469–474.
https://doi.org/10.1001/archopht.1941.00870090093009
Marin, G. and Meslin, D. 2020. Refraction: Patients are sensitive to increments smaller than a quarter diopter! Points de Vue: Int. Rev. Ophthalmic Opt., 1–4.
Marg, E. and Morgan, M. W. 1950. Further investigation of the pupillary near reflex; The effect of accommodation, fusional convergence and the proximity factor on pupillary diameter. Am. J. Optom. Arch. Am. Acad. Optom., 27(5), 217–225.
https://doi.org/10.1097/00006324-195005000-00001
Neroev, V. V., Tarutta, E. P., Arutyunyan, S. G., Khandzhyan, A. T. and Khodzhabekyan, N. V. 2017. Wavefront aberrations and accommodation in myopes and hyperopes. Vestnik Oftalmologii, 133(2), 5–9 (in Russian).
https://doi.org/10.17116/oftalma201713324-9
O’Leary, D. J. and Allen, P. M. 2001. Facility of accommodation in myopia. Ophthalmic Physiol. Opt., 21(5), 352–355.
https://doi.org/10.1046/j.1475-1313.2001.00597.x
Owens, D. A. and Wolf-Kelly, K. 1987. Near work, visual fatigue, and variations of oculomotor tonus. Investig. Ophthalmol. Vis. Sci., 28(4), 743–749.
Pandian, A., Sankaridurg, P. R., Naduvilath, T., O’Leary, D., Sweeney, D. F., Rose, K. and Mitchell, P. 2006. Accommodation facility in eyes with and without myopia. Investig. Ophthalmol. Vis. Sci., 47, 4725–4731.
https://doi.org/10.1167/iovs.05-1078
Perrigin, J., Perrigin, D. and Grosvenor, T. 1982. A comparison of clinical refractive data obtained by three examiners. Am. J. Optom. Physiol. Opt., 59(6), 515–519.
https://doi.org/10.1097/00006324-198206000-00012
Ricci, F., Cedrone, C. and Cerulli, L. 1998. Standardized measurement of visual acuity. Ophthalmic Epidemiol., 5(1), 41–53.
https://doi.org/10.1076/opep.5.1.41.1499
Rice, M. L., Leske, D. A., Smestad, C. E. and Holmes, J. M. 2008. Results of ocular dominance testing depend on assessment method. J AAPOS, 12(4), 365–369.
https://doi.org/10.1016/j.jaapos.2008.01.017
Rosenfield, M. and Ciuffreda, K. J. 1991. Effect of surround propinquity on the open-loop accommodative response. Investig. Ophthalmol. Vis. Sci., 32(1), 142–147.
Rosenfield, M., Ciuffreda, K. J. and Hung, G. K. 1991. The linearity of proximally induced accommodation and vergence. Investig. Ophthalmol. Vis. Sci., 32(11), 2985–2991.
Schwartz, J. T. and Ogle, K. N. 1959. The depth of focus of the eye. AMA Arch. Ophthalmol., 61(4), 578–588.
https://doi.org/10.1001/archopht.1959.00940090580013
Sloane, A. E., Dunphy, E. B., Emmons, W. V. and Gallagher, J. R. 1954. A comparison of refraction results on the same individuals. Am. J. Ophthalmol., 37(5), 696–699.
https://doi.org/10.1016/0002-9394(54)91221-0
Tidbury, L. P., Czanner, G. and Newsham, D. 2016. Fiat lux: the effect of illuminance on acuity testing. Graefes Arch. Clin. Exp. Ophthalmol., 254(6), 1091–1097.
https://doi.org/10.1007/s00417-016-3329-7
Visual Functions Committee. 1988. Visual acuity measurement standard. Ital. J. Ophthalmol., 2(1), 1–15.
Wang, B. and Ciuffreda, K. J. 2006. Depth-of-focus of the human eye: theory and clinical implications. Surv. Ophthalmol., 51(1), 75–85.
https://doi.org/10.1016/j.survophthal.2005.11.003
Woodhouse, J. M. 1975. The effect of pupil size on grating detection at various contrast levels. Vision Res., 15(6), 645–648.
https://doi.org/10.1016/0042-6989(75)90278-3
Wozniak, H., Kelly, M., Glover, S. and Moss, N. 1999. The effect of room illumination on visual acuity measurement. Aust. Orthopt. J., 34, 3–8.
