When angle alpha modifies the visual aspect of an ocular deviation

Abstract

AbstractPurposeOcular optics relies on several specific axes and angles. Angle alpha is the angle between the optical and the visual axes while the angle kappa is formed by the pupillary and the visual axes. The literature reports a non‐null angle kappa range between 1,91° ± 0,14° and 5,73° ± 0,10° in the healthy population. There is a positive correlation between the both angles. High positive angles can be found in high hypermetropia or genetic disorders such as albinism and aniridia. In strabological practice, a high angle can modify the visual aspect of the strabismus. A failed strabismus screening and divergence between visual appearance and Prism Covert Test (PCT) measurement can result from the presence of a high angle. We aim to purpose a classification of the visual appearance of the strabismus according to the PCT and the angle alpha value.MethodsPatients were recruited in the ophthalmology department. For each patient, the best corrected visual acuity was performed. Monocular and binocular corneal light reflex was evaluated and the ocular deviation was measured by PCT. Monocular picture with flash was realized. The angle alpha was calculated using the algorithm developed in the department.ResultsWe report a case series of five patients (3 boys and 2 girls) exhibiting an esotropia. Age range was 5.5 to 19 years‐old (med = 15, sd = 5.77). Esotropia range was 8 to 90∆ (med = 30, sd = 32.27) and angle alpha range was 8.37° to 26.49° (med = 17.7, sd = 4.93). According to values of angle alpha and strabismus deviation, five categories of visual aspect can be defined.ConclusionsAccording to the angle value, a confusion between the visual aspect and the ocular deviation measurement can modify the diagnosis of strabismus. Five categories of visual aspect could be described. Then, the digital assessment of the angle alpha is a new tool which combined to the PCT, will help the practitioner to the correct evaluation of the ocular deviation and the strabismus screening.