Vertical location of the corneal light reflex in strabismus photography

Objective: To improve the clinical documentation of strabismus by mathematically predicting and clinically verifying the location of a fixation target that produces a vertically centered corneal light reflex (first Purkinje image) in clinical photographs of the eye using a standard photographic flash unit. Materials and Methods: Mathematical modeling of the corneal light reflex during clinical photography was based on the schematic eye. Clinical photographs were taken using a range of fixation targets located between the center of the camera lens and the center of the flash. Image quality was also assessed subjectively. Results: Optimum vertical centration of the corneal light reflex was predicted and produced when the fixation target was located one fifth of the distance from the center of the flash to the center of the camera lens. Placement of the flash below, rather than above, the camera lens provided more uniform illumination of the patient's eyes and face. Decreasing the distance between the camera lens and the flash minimized the severity of these artifacts. Conclusions: A poorly positioned corneal light reflex makes it difficult to identify the fixing eye in photographs of patients with strabismus, especially when vertical strabismus is present. Adoption of the aforementioned protocol will reproduce the appearance of coaxially viewed corneal light reflexes and provide much-needed standardization for strabismus case presentation.