Inputs and outputs of the lacrimal system: review of production and evaporative loss

Meta-analyses were carried out of studies of tear production (by fluorophotometry, tear turnover rate [TTR]) and evaporation (from capture of fluid loss from the eye). TTR was reduced in dry eye relative to normal at 9.26 ± 5.08%/min (0.54 ± 0.28 µl/min) vs 16.19 ± 5.1%/min (1.03 ± 0.39 µl/min); with values of 7.71 ± 1.02%/min (0.4 ± 0.10 µl/min) in aqueous deficiency dry eye (ADDE) and 11.95 ± 4.25%/min (0.71 ± 0.25 µl/min) in evaporative dry eye (EDE). Evaporation was increased in dry eye at 21.05 ± 13.96 × 10^-7g/cm²/s (0.21 ± 0.13 µl/min) vs 13.57 ± 6.52 × 10^-7g/cm²/s (0.14 ± 0.07 µl/min) in normals; with values of 17.91 ± 10.49 × 10^-7g/cm²/s (0.17 ± 0.1 µl/min) in ADDE and 25.34 ± 13.08 × 10^-7g/cm²/s (0.26 ± 0.16 µl/min) in EDE.