The primary purpose of a blink is to protect the ocular surface and restore the transparent, uniform tear film that is required for uninterrupted vision. Increased blink rates, shortened blink intervals, and shifting blink patterns are thought to contribute considerably to the constellation of signs and symptoms that lead to poor visual performance in dry eye patients.
Blinking may act as a compensation for a defective and unstable tear film in dry eyes, exacerbating the deleterious effects on vision. Dry-eye patients regularly report ocular fatigue and poor visual performance as a result of their condition, and it's fascinating to study about the significance of changed blink states in both fatigue and dry eye.
Dry-eye patients appear to have a higher incidence of excessively long lid closures, and the inter blink intervals(IBIs) surrounding these long lid closures are only modified in dry-eye subjects.
It is observed that the mean total length of lid closure per kind of blink is the most clinically important end goal, with significant variations between dry eye and normal participants. The findings of 4.5 percent versus less than 1% of time with lids closed in dry-eye and normal people, respectively, point to the deleterious effects of dry eye on everyday activities and visual function, which have been well documented in many quality of life studies. This end point more accurately reflects dry-eye patients' greater need to "refresh" the tear film during visual tasking than a basic blink rate or inter blink interval (IBI), which ignores the mean total length of lid closure.
Dry-eye patients have their eyes closed for longer than normal people when their lids are closed for whatever reason, which could explain why their vision is compromised.
When IBI is used instead of blink rate, a significant quantity of information is disclosed for a given sample of blinks. The IBI series includes numerous endpoints characterising a subject's blink frequency, whereas the blink rate is a single measurement. The IBI is shown to be considerably shorter in dry eye patients completing a visual task. Studies have shown average IBI in normal eyes was 5.97 seconds against 2.56 seconds in dry eye cases.
Since dry eye is related with increased blink rates and shorter interblink intervals, ocular surface stress might also result in an increase in anomalous events such microsleeps and nonblink closures, or longer blinks.
Extended blinks tend to be longer in duration, IBIs are considerably longer after an extended blink, and blinks longer than one second occur nearly exclusively in patients with dry eye. Furthermore, regardless of dry eye state, the ratio of post-extended to pre-extended blink IBI increases as the duration of a blink increases.
The field of blink analysis is ever evolving as new devices like OSDx add more data to the armamentarium of the dry eye specialist.