Impact of COVID-19 pandemic on the ocular surface

Table 1 Ocular surface parameters before lockdown (from August 2019 to March 2020 - group 1), after lockdown without mask mandate (from April 2020 to October 2020 - group 2), and after lockdown with mask mandate (from November 2020 to April 2021 - group 3)

Variables1	Group 1: Before lockdown (August 2019 to March 2020)	Group 2: After lockdown without mask mandate (April 2020 to October 2020)	P value: Group 1 vs group 2	Group 3: After lockdown with mask mandate (November 2020 to April 2021)	P value: Group 1 vs group 3	P value: Group 2 vs group 3
NIBUT, s	10.92 ± 4.87	9.53 ± 3.45	0.0303	11.56 ± 7.08	0.263	0.007
Blink rate, %	92.43 ± 17.52	91.78 ± 13.29	0.821	68.24 ± 19.67	< 0.0013	< 0.001
Lipid layer thickness, nm	49.44 ± 27.07	65 ± 23.91	0.0012	73.53 ± 25.60	< 0.0012	0.052
Loss area of the MG, %	8.68 ± 12.45	13.50 ± 16.06	0.0313	14.06 ± 14.23	< 0.0013	0.828
Tear meniscus height, mm	0.35 ± 0.19	0.32 ± 0.16	0.370	0.31 ± 0.18	0.0383	0.820
Tear osmolarity, mOsm/L	299.14 ± 13.23	308.25 ± 12.96	< 0.0013	311.30 ± 14.54	< 0.0013	0.218
Schirmer, mm	11.08 ± 6.55	10.48 ± 5.19	0.576	13.02 ± 7.54	0.0022	0.011

¹Values represent mean ± SD, except corneal staining was represented as percentage.

²Represents a statistically significant improvement compared to group 1.

³Represents a statistically significant worsening compared to group 1.

NIBUT: Non-invasive break-up time; MG: Meibomian glands.