A presumed reflex by which upward gaze induces relaxation of accommodation, a way to overcome instrument myopia.
This hypothesized reflex relates the vertical direction of gaze to the amount of tension exerted by the ciliary muscle. Based on simple observations the following is assumed. When looking downwards a tendency for closer focusing (near searching) exists even without a specific visual stimulus, whereas looking up favors a more relaxed state of the accommodative mechanism. This reflex is much weaker than accommodation induced by visual stimuli but may have potential practical implications with regards to automated objective ocular refraction devices. When using such instruments it is crucial to eliminate entirely all accommodation. The inability to achieve such relaxation has prevented automated devices from completely replacing all manual and subjective techniques in ophthalmology practice. If the reflex is empirically proven to exist, then by performing objective examinations while the patient's gaze is directed up, more precise measurements may be achieved. An additional benefit can be derived from comparing upward versus forward gaze measurements. Even a small difference can imply that accommodation has been triggered, so that ultimately this screening method enables identification of the accommodators sub-group and reciprocally approving the accuracy of the non-accommodators sub-group results.
Blumenthal
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D000065:Accommodation, Ocular / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D009216:Myopia / Q000209:etiology; D009801:Oculomotor Muscles / Q000502:physiology; D012018:Reflex / Q000502:physiology*; D012029:Refraction, Ocular