Optometry & Visual Performance 269 Volume 13 | Issue 4 | December 2025 produced a larger-than-expected and reproducible change in craniovertebral angle. Future research Dark focus Placing a subject in total darkness is a straightforward way of creating an optically stimulusfree environment that eliminates blur, vergence, and most proximal stimuli to accommodation. Darkness allows changes in autonomic balance, including those due to stress, to manifest.36 Unfortunately, our study could not include planned dark focus measures due to concerns about coronavirus transmission in the enclosed lab room. The dark focus could provide an alternative dependent variable since it is not constrained by ‘reflex’ accommodation. Body, head, and neck postures Overall, physical therapists recommend that a slight slouch is ideal and encouraged in one’s everyday posture. However, when conducting this study, the neutral posture did not involve any slouching and instead was conducted using a relatively straight, shoulders-back posture. Subjects may have adopted a “neutral” posture that was not optimally neutral. This posture, in turn, could have led to stress during the study, thus affecting the subject’s accommodation. Another potential source of discomfort for four of our subjects was wearing a trial frame. Several other postural variables considered by PRI physical therapists could be controlled or investigated. These include heel placement, peripheral vision between trials, and jaw posture. People adopt many body and neck postures during extended tasks in their daily occupations. Further studies could document actual occupational postures and then find whether the maintenance of such postures influences accommodation. These studies could address the coupling between accommodation and neck posture.8,14 For example, they could use electromyography to measure the load on the neck muscles and use validated surveys to document visual ergonomic symptoms.37,38 Head, back, and neck pain, and neck vibration therapy We excluded individuals with any significant head, neck, or back problems. In future studies, it would be interesting to find how posture interacts with these individuals’ accommodation and near work, as they might be sensitive to visual and postural changes. A difficulty with such research would be that some subjects might experience significant discomfort or pain from adopting uncomfortable neck or body postures during the sessions. Another area of research could be to extend Han and Lennerstrand’s approach15 to study vergence and accommodation in those patients who are receiving neck vibration as a therapy. Clinical significance A young patient’s forward neck posture during refraction, such as due to a poorly set up phoropter or autorefractor, will not affect the refraction finding. Similarly, their accommodation accuracy for distance tasks in daily life will not be influenced by an overly slouched, forward neck posture. Acknowledgments: We want to acknowledge Sangini Rane, PRC, PT for her assistance in obtaining PRI literature and the Postural Restoration Institute for providing PRI manuals and references. This study was presented at the American Academy of Optometry annual meeting in San Diego on 26–29 October, 2022. References 1. Rempel D, Willms K, Anshel J, Jaschinski W, Sheedy J. The effects of visual display distance on eye accommodation, head posture, and vision and neck symptoms. Hum Factors 2007;49(5):830-8. 2. Richter HO, Bänziger T, Abdi S, Forsman M. Stabilization of gaze: A relationship between ciliary muscle contraction and trapezius muscle activity. 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Eur J Appl Physiol 2015;115(7):1501-12. 10. Zetterberg C, Richter HO, Forsman M. Temporal co-variation between eye lens accommodation and trapezius muscle activity during a dynamic near-far visual task. Plos One 2015;10(5):e0126578. 11. Domkin D, Forsman M, Richter HO. Ciliary muscle contraction force and trapezius muscle activity during manual tracking of a moving visual target. J Electromyogr Kinesiol 2016;28:1938. 12. Zetterberg C, Forsman M, Richter HO. Neck/shoulder discomfort due to visually demanding experimental near work is influenced by previous neck pain, task duration, astigmatism, internal eye discomfort and accommodation.
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