Rear 4-min Schirmer test, a modified indicator of Schirmer test in diagnosing dry eye

This study aims to investigate the reliability and efficacy of rear 4-min Schirmer test, as a supplement indicator, in assessing tear secretion and diagnosing dry eye. 180 participants were enrolled in this study. Schirmer test I without anaesthesia was performed once on both eyes to determine the value of normal Schirmer test. The values of tear secretion were recorded at each minute. Other examinations included the following: the ocular surface disease index (OSDI), the standard patient evaluation of eye dryness (SPEED), fluorescein stain, tear film break-up time (BUT), and Meibomian gland (MG) secretion grading. The participants were divided into dry eye (DE) group and non-dry eye (ND) group. The values of the 2-min Schirmer test, rear 3-min Schirmer test, rear 4-min Schirmer test, and 5-min Schirmer test were 5.36 ± 4.63, 5.57 ± 2.11, 7.21 ± 4.13, and 10.93 ± 6.30, respectively, in the DE group. These indicators were 8.25 ± 6.80, 2.73 ± 2.31, 7.36 ± 3.42, and 11.84 ± 6.16, respectively, in the ND group. The rear 4-min Schirmer test had a significant correlation with OSDI and SPEED in the DE group (r =  - 0.242/ - 0.183) and in the ND group (r =  - 0.316/ - 0.373). Meanwhile, the rear 4-min Schirmer test had a stronger connection with fBUT (r = 0.159) and MG secretion (r =  - 0.162) in the DE group and also had higher accuracy in diagnosing severe DE and borderline DE. In conclusion, the rear 4-min Schirmer test may be a supplement indicator in assessing tear secretion and diagnosing DE.