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Introduction: Most young emmetrope eyes are far from ideal and have some degree of minor spherocylindrical error including also physiological astigmatism. Because of the changes in the shape of optical interfaces, pupil size, eyelid pressure, tear film, body posture, binocularity and accommodation astigmatism is considered as constantly dynamic phenomenon (Cheng et al, 2004). The purpose of this study was to evaluate and quantify changes in physiological astigmatism during accommodation. Method: Twenty young emmetropes with mean age 24 ± 4 years were selected for the study. Refraction and accommodative response were measured monocularly for dominant eye with an open-field infrared autorefractometer (Shin-Nippon, SRW-5000) at far (7 m) and near (30 cm). Each measurement consisted of approximately 130 dynamic data points collected during consecutive 2 min time. Results: Clinically and statistically significant increase in cylindrical power and change in cylindrical axis during accommodation (stimulus demand 3.33 D) was seen in 80 % of participants presenting average change of 0.22 ± 0.10 D for power and 37 ± 7° for axis (paired t-test: p = 0.001). Changes in a direction towards with-the-rule astigmatism was observed in 56 % of participants, while changes towards against-the-rule direction for 44 %. Results are only partially in an agreement with previous studies that has observed astigmatism changes during accommodation towards with-the-rule direction (Mohammadi et al, 2012; Tsukamoto et al, 2000). Our results suggest that direction of astigmatism change might be related to baseline astigmatism. For 75 % of participants changes occurred towards closest principal meridian. References Cheng, H., et al. (2004), A population study on changes in wave aberrations with accomodation, J Vis, 4 (4) 272-80; Seyed-Farzad Mohammadi, Maryam Tahvildari and Hadi Z-Mehrjardi (2012). Physiology of Astigmatism, Astigmatism - Optics, Physiology and Management, Dr. Michael Goggin; Tsukamoto, M., et al. (2000), Accommodation causes with-the-rule astigmatism in emmetropes, Optom Vis Sci, 77 (3), 150-5
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