Abstract
Abstract: :
Purpose: Many factors such as environmental conditions, systemic medications, age, visual tasking and emotional state have shown to influence blink rate. Researchers have also determined that 73% of patients diagnosed with dry eye report ocular discomfort within 1 second of tear film break-up time. Since blinking is responsible for re-establishing a tear protected ocular surface, it is believed that the awareness that precedes ocular discomfort may be one of the driving factors in causing this physiological response. The purpose of this study was to investigate the relationship between blink rate and corneal sensitivity. Methods: Twenty-nine (29) subjects, 21 diagnosed with dry eye and 8 normals underwent examinations including a slit-lamp biomicroscopy evaluation, corneal sensitivity measurement and blink rate. Corneal sensitivity was determined with a Luneau Cochet Bonnet Aesthesiometer (model # 8305). Blink rate was measured with a digital micro-camera equipped with an infrared illuminator that tracks the diameter of a subject's pupil. This device was mounted to a headset and directed towards the eye so that complete blinks (defined as >95% decrease in pupil diameter) could be measured non-invasively. During the blink rate evaluation, subjects were isolated and completed a standard visual task. The inter-blink interval (IBI) or time between blinks was calculated from the blink rate measurements. Results: Subjects diagnosed with dry eye were grouped as having either Low Corneal Sensitivity (LCS) (defined as ≤ 4), n = 9 (mean = 2.55), or Normal Corneal Sensitivity (NCS) (defined as > 4), n = 12 (mean = 5.63). Mean IBI was 18.62 seconds in LCS eyes and 5.83 seconds in NCS eyes (p = 0.006). All normals had NCS, n = 8 (mean = 5.88). Mean IBI for this group was 10.58 seconds. Conclusions: The data shows that approximately 42% of the dry eye patients have reduced corneal sensitivity and that these patients blink less frequently than those with NCS. Further, dry eye patients with NCS blinked almost twice as frequently as normals. A possible explanation for this difference is that normals have a longer tear film break-up time, providing greater protection of the ocular surface during the IBI. Clearly, these findings have diagnostic and therapeutic relevance.
Keywords: cornea: tears/tear film/dry eye • cornea: clinical science • clinical (human) or epidemiologic studies: tre