Optometry & Visual Performance 261 Volume 13 | Issue 4 | December 2025 Article • Effect of Forward Neck Posture on Ocular Accommodation Mitali Rane, MS • Southern California College of Optometry at Marshall B. Ketchum University • Fullerton, California Lawrence R. Stark, PhD • Southern California College of Optometry at Marshall B. Ketchum . University • Fullerton, California ABSTRACT Background: While many studies have shown an effect of accommodation on neck muscle activity, none have studied the causal effect of neck posture on accommodation. In addition, some Postural Restoration Institute (PRI) physical therapists believe that neck posture can influence subjective refraction. Methods: Twenty-four young adult subjects (19– 35 years) participated. Subjects adopted a neutral or forward neck posture while viewing a letter chart binocularly at 3 m during 2-minute sessions. Accommodation was recorded in the right and left eyes using a Grand Seiko WAM 5500 open-view autorefractor. Digital photographs of neck posture were taken before and after each trial to calculate the craniovertebral angle. Results: Any accommodative differences due to neck posture or between eyes were minimal and statistically non-significant. Analysis of craniovertebral angle demonstrated a significant difference between the neutral and forward postures, but no effect of before or after the trial, and no significant interaction of these two factors. Additionally, the accommodation change from neutral to forward head posture was not greater for those subjects who could bend their necks more than the others. Introduction This study examines the possible correlations between neck posture and accommodation. This study is designed to determine whether adopting a forward neck posture or a neutral neck posture leads directly to changes in accommodation. Previous studies have demonstrated a correlation between the level of accommodation and neck-muscle activity.1–13 Individuals with a higher accommodative response tend to have higher trapezius muscle activity.2,7 Visually demanding tasks may increase trapezius muscle tension, leading to musculoskeletal complaints in the neck and shoulder region.7,12 This is due to the visually demanding tasks leading to an increase in ciliary muscle contraction,1,2,4–7,9-11,13 especially during continuous eye-hand coordination.13 A strong and significant correlation has been found between the level of ciliary muscle contraction force and that of trapezius muscle activity during near tasks.13 It has also been theorized that visual load induces eye discomfort.6 Visual load is simulated by visually demanding near work; for example, by having a subject view through negative-powered lenses. However, most studies in this area have investigated only the causal effect of accommodation load or near work on neck muscle physiology. Research on the reciprocal actions between ciliary muscles and neck muscles is needed.8,14 Specifically, Mitali Rane, MS Fullerton, California Pursuing MS in Communication Sciences and Disorders at Emerson College BS Biology, University of North Carolina at Greensboro, 2013 MS Vision Science, Marshall B. Ketchum University, 2022 Conclusions: There was no significant effect of a forward neck posture on accommodation in our study. The individual change in craniovertebral angle between postures did not predict the observed changes in accommodation. These data do not support the PRI hypothesis that neck posture could affect subjective refraction. However, future studies could consider a longer duration for neck posture, and they could document actual patient postures to determine whether these affect accommodation. Keywords: craniovertebral angle, neck posture, ocular accommodation, subjective refraction
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