Imaging system records ocular interface reflections in vivo

Pablo Artal and Juan Tabernero at the University of Murcia (Murcia, Spain) have built a prototype imaging system for recording reflections (called Purkinje images) from four ocular interfaces-air-cornea (PI), cornea-aqueous (PII), aqueous-lens (PIII), and lens-vitreous (PIV)-in vivo. The prototype imaging system contains a chin and forehead rest for the subject; a semicircular array of infrared LEDs to illuminate the eye; a telecentric camera objective and CCD camera to collect and record the reflections; an array of LEDs for the subject to fixate on; and other optical components.

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When an illumination source is aligned with principle line of sight in a well-aligned human eye, the reflection images align around a common center. PI and PII usually overlap due to small corneal thickness. PIII appears largest, and PIV appears inverted. The outermost circle, in the large image on the left of well-aligned reflections, traces the circumference of the pupil. The relative positioning of the Purkinje images changes, however, with misalignments, either among ocular surfaces or between the illumination source and the line of sight. The new instrument is expected to prove useful in basic studies of the eye and in clinical ophthalmology. Contact Pablo Artal at pablo@um.es.