Instrument myopia*

Abstract

The basis for instrument myopia, the tendency to accommodate inappropriately while viewing through an optical instrument, was investigated in three experiments. The first demonstrated that the distance of a peripheral surround, analogous to a field stop, influences accommodation but that the magnitude of the effect cannot account for instrument myopia. The second experiment re-examined the hypothesis that perceived distance can affect accommodation. The data indicate that perceived distance is unlikely to influence accommodation and does not provide an explanation of instrument myopia. The last experiment tested the hypothesis that instrument myopia is a manifestation of the return of accommodation to an intermediate state of rest or equilibrium in the absence of an adequate stimulus for accommodation. Implications of the intermediate-resting-state hypothesis are discussed.

The visual accommodation response during concurrent mental activity

“…Even so, these instrument myopia responses appear to be larger in the presence of a 3.0-D peripheral target than in the presence of a O.O-D target. These results are consistent with the previous findings of Hennessy (1975) and Hennessy et al (1976).…”

“…If accommodation shifts are to be observed as a function of concurrent mental tasks, then it seems worthwhile to consider the dark focus, or the intermediate resting position of accommodation, first proposed by Cogan (1937) and later discussed and expanded upon by Hennessy (1975), Leibowitz and Owens (1975), Malmstrom and Randle (1976), Owens (1979), and Schober (1954). Under the constraints of this hypothesis, it is proposed that the dark focus is a behavioral null between the sympathetic and parasympathetic systems.…”

A subjective refraction-based assessment of image quality metric

“…All considered IQMs have achieved high correlations between the subjective and objective measures of vision quality for the mean spherical refractive power vector component (r 2 > 0.95). All of them also showed a significant level of intercept of up to 0.62 D indicating the so-called "instrument myopia" [22]. This is a common problem in wavefront sensors that do not have an open field-view in which the subject's level of accommodation (focusing) is not fully controlled.…”

Clinical evaluation of patient tolerance to autorefractor prescriptions

“…This is analogous to instrument myopia. 11 These problems in controlling accommodation are compounded by the fact that there are no facilities to binocular balance with autorefractors, which currently measure monocular refraction and have no provision for the assessment of the binocular status of the eyes. Although accommodation is a major problem, variability in autorefractor measurements is not con-Autorefractor evaluation Strang, Gray, Winn and Pugh fined to the pre-presbyopic population.…”