Eye’s Center of Rotation Not Strongly Correlated With Axial Length

The position of the center of rotation (COR) of the eye does not depend on axial length, according to findings published in Ophthalmic and Physiological Optics.

Researchers used a custom-built eye tracker to measure COR in a cohort of patients. They measured axial length and evaluated horizontal and vertical eye movements in the right eyes of 59 patients (mean age: 36.6±9.1 years, 32 women, 27 men), completing each measurement 5 times without spectacle correction. A total of 31 participants were classified as myopes (spherical equivalent refractive error (SE) ≤-0.50 D), 18 as emmetropes (SE between -0.5 and +0.5 D) and 10 as hyperopes (SE >+0.50 D). 

Investigators found that mean COR for horizontal eye movements was approximately 15.3 mm behind the corneal apex, while the average COR for vertical eye movements was roughly 2.8 mm more anterior. The analysis revealed that horizontal COR was significantly correlated with axial length (R=0.28, P =.02), but not with spherical equivalent refractive error (R=0.39, P =.90). Likewise, the analysis also showed that vertical COR was significantly correlated with axial length (R =0.25, P =.03), but not with the spherical equivalent refractive error (R=0.17, P =.90). 

“While it might be expected that the COR is dependent on axial length, the correlation was not strong. Interestingly, the location of the COR was substantially different for horizontal and vertical eye movements which may relate to the flatter curvature of the eyeball in the vertical meridian, compared to the horizontal,” the investigators explain. They also stress how “knowledge of the position of the center of rotation is important for the optical design of spectacle lenses,” making it a crucial factor in the manufacturing of prescription eyewear. 

Study limitations include a small sample size and the omission of oblique movement measurements.

Disclosure: This research was supported by Carl Zeiss Vision International GmbH. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures. 

Reference

Ohlendorf A, Schaeffel F, Wahl S. Positions of the horizontal and vertical centre of rotation in eyes with different refractive errors. Ophthalmic Physiol Opt. Published online January 20, 2022. doi:10.1111/opo.12940