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.

A preliminary study of silicone hydrogel lens material and care solution bioincompatibilities.

PURPOSE: The study purpose was to evaluate corneal barrier function and staining relative to potential bioincompatibilities. METHODS: This was a randomized double-masked study (n = 25 subjects). Three lens material-care solution combinations were tested: (1) lotrafilcon B/polyhexamethylene biguanide (PHMB)-based multipurpose (MPS) solution (MPS-1); (2) lotrafilcon B/polyquaternium-1 and myristamidopropyl dimethylamine-based solution (MPS-2); and (3) lotrafilcon B and another PHMB-based solution (MPS-3). Saline served as the control. New lenses were soaked in the preserved solutions or saline and then worn for 2 hours before corneal measurements. Barrier function was characterized by the fluorescein penetration rate, corneal amount, both measured with an objective scanning fluorometer. The dye penetration rate ratio, test to control; amount ratio, test to control, and corneal staining were evaluated. RESULTS: The mean rate ratios (± SD) for the combinations were 2.98 (± 3.04), 1.23 (± 1.01), and 1.83 (± 1.77) for MPS-1, MPS-2, and MPS-3 solutions, respectively. Significant ratio differences were found across regimens (P = 0.007); for MPS-1 compared with baseline (P = 0.031) and for MPS-1 compared with MPS-2 (P = 0.007). The statistical results for staining were similar. CONCLUSIONS: Use of an objective quantitative physiological method suggests that significant differences in lens solution bioincompatibilities occur that mirror corneal staining data relative to corneal compromise.

Contrast sensitivity and tear layer aberrometry in dry eye patients.

PURPOSE: Dry eye disease is a common condition that affects millions of people world wide. The common findings of dry eye disease are blurred vision and tear film instability. The purpose of this study was to determine if long-term use of artificial tears altered visual disturbances and tear film instability of dry eye patients. METHODS: Contrast sensitivity and optical aberrations were measured in 22 dry eye and 10 normal patients before and after daily use of artificial tears. The contrast sensitivity and optical aberrations were measured in response to the administration of a single drop of artificial tear placed in the eye. RESULTS: The short-term effect (i.e., a few minutes) of a single drop of artificial tear placed in the eye was a decrease in contrast sensitivity and an increase in optical aberrations. Long-term daily use of the artificial tears (i.e., up to 2 weeks) resulted in less of a short-term effect in dry eye patients. No long-term effect was observed for normal subjects. Both contrast sensitivity loss and optical aberrations decreased by 35% per week of artificial tear use for the dry eye patients suggesting that the changes in contrast sensitivity were the result of optical aberrations. CONCLUSIONS: The results suggest that the changes in contrast sensitivity with artificial tear administration were the result of optical aberrations. It appears that long-term use of artificial tears may normalize the tear layer of dry eye disease patients.