55 *Correspondence and reprint requests to: Kostas N. Fountas, 840 Pine St. Suite 880, Macon, GA 31201. E-mail: knfountasmd@excite.com Introduction Historical Evolution The size and morphology of the pupils have long been noted by physi- cians. Archimedes was among the first to record observations of the size and symmetry of pupils in humans, and Galileo is believed to have been the first to attempt to accurately calculate pupil diameters by using an entopic methodology (1) . Numerous studies of pupillary size, shape, and the speed of pupillary constriction have since been published. Wilson, in his pioneering Clinical Implications of Quantitative Infrared Pupillometry in Neurosurgical Patients Kostas N. Fountas, 1, * Eftychia Z. Kapsalaki, 2 Theofilos G. Machinis, 1 Angel N. Boev, 1 Joe S. Robinson III, 1 and E. Christopher Troup 1 1 Departments of Neurosurgery and 2 Neuroradiology, Medical Center of Central Georgia, Mercer University School of Medicine, Macon, GA study a century ago, introduced the term “pupil correctopia” and established a re- lationship between abnormally shaped pupils and mesencephalic lesions (2) . Similarly, years later, Fisher reported on the association of oval or football-shaped pupils with intracranial catastrophes (3) . More recently, Marshall et al. established a relationship between pupil morphol- ogy and intracranial pressure (ICP) in their study (4) , and Taylor et al. (5) reported in their clinical study that pupillary changes can reveal subtle ICP changes in a timely fashion. Take Notice Technology Abstract Pupillometry has been widely employed in the evaluation of a large number of pathological conditions, including intracranial pathology. The recent introduction of a portable, user-friendly, infrared pupillometer (ForSite, NeurOptics Inc., Irvine, CA) has enabled the accurate and reproducible measurement of several pupillary parameters, such as maximum and minimum apertures, constriction and dilation velocities, and latency period. It should be noted that various clinical conditions, especially neurological and ocular diseases, as well as numerous medications, may interfere with the measurements. Furthermore, a number of physiological parameters, such as the intensity of retinal illumination, the level of patient’s alertness, the intensity of ambient light, as well as the time of day that the examination is performed may alter the obtained values. The potential implications of pupillometry in the clinical assessment of neurosurgical patients, including its complex relationship to intracranial pressure changes, mandate the undertaking of prospective clinical studies validating the clinical significance of this noninvasive, diagnostic modality. Key Words: Anisocoria; constriction velocity; infrared pupillometry; intracranial pressure; latency period. ( Neurocrit. Care 2006;05:55–60) Neurocritical Care Copyright © 2006 Humana Press Inc. All rights of any nature whatsoever are reserved. ISSN 1541-6933/06/5:55–60 ISSN 1556-0961 (Online) DOI: 10.1385/Neurocrit. Care 2006;05:55–60