To evaluate the short-term changes in Schirmer I test (ST) after pars plana vitrectomy and to compare the results between 23 gauge and 20 gauge vitrectomy surgeries.

In this prospective, non-randomized, comparative study, 42 patients who underwent pars plana vitrectomy for posterior segment diseases were included. The choice of sclerotomy gauge was on surgeons` discretion. ST values were recorded before and one and 3 months after vitrectomy.

Twenty patients in 23 gauge and 22 patients in 20 gauge group with a mean age of 59.9±13.5 years were included. The mean preoperative ST values decreased significantly in both groups at 1 and 3 months after surgery (all P<0.01). In the fellow eyes, the ST values were the same, at baseline and during the follow up (P>0.05). At 3 months visit, 15 eyes (35.7%) had abnormal ST measurements. There was no statistically significant difference in the changes in ST measurements between the two groups at one month (P=0.7), however, 3 months after surgery, the mean decrease in ST measurements was significantly higher in 20 gauge group (P=0.03). At 3 months, 4 eyes in the 23 gauge group (20%) and 11 eyes in the 20 gauge group (50%) had abnormal ST measurements (P=0.05).

Although both 20 and 23-gauge vitrectomy decrease the ST measurements postoperatively, the value is less affected by 23 gauge vitrectomy.