How to perform retinoscopy for astigmatism
Nov 18, 2025
Source: Cainiu Health
Dr. Zhou Xiaofeng
Introduction
Astigmatism retinoscopy generally involves several steps: proper preparation before retinoscopy, determining an initial working distance, observing the movement of reflexes along different meridians, identifying the astigmatic axis, and adjusting lenses to determine the astigmatic refractive power. Prior to retinoscopy, the patient should wear appropriate corrective lenses (if available), the lighting in the examination room should be adjusted to a soft and dim level, and the retinoscope's light must be clearly projected onto the patient's fundus.
Astigmatism retinoscopy generally involves several steps: preparation before retinoscopy, determining the initial working distance, observing shadow movements in different meridians, identifying the astigmatic axis, and adjusting lenses to determine astigmatism diopter. The detailed process is as follows:
1. Preparation before retinoscopy: Before performing retinoscopy, ensure the subject wears appropriate corrective glasses (if any). Adjust the lighting in the examination room to be dim and soft so that the retinoscope's light can clearly project onto the subject’s retina. Have the subject fixate on a distant stationary target to prevent random eye movement and maintain a relaxed ocular state.
2. Determining the initial retinoscopy distance: The examiner typically stands at a fixed distance of 1 meter or 0.67 meters in front of the subject. This distance must be calibrated beforehand, and any subsequent calculation of refractive error should account for this distance to ensure accuracy and avoid misjudgment due to distance discrepancies.
3. Observing shadow movement in different meridians: Holding the retinoscope, the examiner projects light into the subject’s pupil area and slowly rotates the instrument to observe the characteristics of shadow movement along various meridians—horizontal, vertical, and oblique directions such as 45° and 135°. In individuals with astigmatism, differences in speed, brightness, and direction of shadow movement across meridians serve as key indicators for diagnosing astigmatism.
4. Determining the astigmatic axis: Based on observed differences in shadow movement among meridians, identify the astigmatic axis. When the shadow movement in one meridian reaches neutrality (i.e., no motion or at the borderline between with-and-against movement), that meridian corresponds to one of the principal meridians of astigmatism. The other principal meridian lies perpendicular to it, allowing precise determination and marking of the astigmatic axis.
5. Adjusting lenses to determine astigmatism magnitude: Along the determined astigmatic axis, gradually add cylindrical lenses of varying powers while observing changes in shadow movement until neutrality is achieved in all meridians. The power of the added cylindrical lens represents the subject’s astigmatic correction. Combined with spherical lens findings, this yields a complete refractive prescription.
Astigmatism retinoscopy should be performed by a trained optometrist. After retinoscopy, it is recommended to verify the results using a phoropter. If there is a discrepancy between objective retinoscopy findings and subjective visual experience, timely communication with the optometrist is essential to ensure accurate eyeglass prescriptions.
