Abstract: Artificial tears - how long they last vs effect on vision

This study looks at (more or less) how long artificial tears outlast the blurring they cause. For the types of drops studied, both are brief enough that I don't know why we should care that much....

Visual Effect and Residence Time of Artificial Tears in Dry Eye Subjects.

PURPOSE.:
The purpose of this investigation was to examine the relationship between the visual effect (VE) and residence time (RT) of artificial tears (ATs) in dry eye subjects.

METHODS.:
The VEs and RTs were measured after administration of 25 μl of an AT into the inferior fornix of 18 dry eye subjects. The VE was investigated by measuring contrast sensitivity before and after AT administration. The return to baseline sensitivity (RTBS) was taken as the time it took to return to within 1 SD of baseline contrast sensitivity. RT was measured using fluorescent formulations and a scanning fluorometer.

RESULTS.:
No correlation was found between RTBS and RT for a low viscosity (saline-F) and a medium viscosity AT (CMC-F; p > 0.05). There was a moderate correlation for a higher viscosity AT (PEG-F; p = 0.03). For all solutions, RT was significantly longer than RTBS (p < 0.001). There was a significant difference in RTBS between saline-F and PEG-F (p = 0.002) but not between saline-F and CMC-F (p = 0.87). There was a significant difference in RT between saline-F and both PEG-F and CMC-F (p < 0.001 and p = 0.018, respectively).

CONCLUSIONS.:
No correlation was found between RTBS and RT for saline-F or CMC-F (moderate correlation for PEG-F). These ATs are present on the eye for a significantly longer time than their adverse affect on vision. An ideal AT would result in minimal if any initial blur on instillation while remaining in the eye for an extended period of time.

Optom Vis Sci. 2011 Apr 28. [Epub ahead of print]
Hall JQ Jr, Ridder WH 3rd, Nguyen AL, Paugh JR.
*BS, BA †OD, PhD, FAAO ‡PhD Southern California College of Optometry, Fullerton, California (JQH, WHR, JRP), and California State University, Fullerton, California (ALN).