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To investigate tear ferning (TF) test repeatability between sessions by observing changes in the tear fern pattern during the day.Twenty-three healthy young adults (15 men and 8 women), ranging in age from 20 to 32 years (mean±SD: 22.9±3.3 years) without signs or symptoms of dry eye disease, ocular disease, or contact lens wear were enrolled in the study. Schirmer I, tear break-up time (TBUT) test, and McMonnies questionnaire were used to screen volunteers. Schirmer I and TBUT tests were applied to both eyes in each subject. Four samples of tear fluid were collected from the right eye of each subject using glass capillaries at set intervals during a single day (9 AM, 11 AM, 2 PM, and 4 PM). The TF patterns obtained from samples were classified according to the Masmali TF grading scale to increments of 0.1.The median values obtained from the McMonnies, Schirmer, and TBUT tests were 4.0±2.0, 30.0±7.0 mm (OD), and 16.0±10.0 sec (OD), respectively. There were no statistically significant differences between the TF grades for tear samples collected at different times of the day (Wilks' Lambda, P=0.351). The majority (84.8%) of TF grades was between 0.0 and 1.5; the remaining 15.2% of subjects had TF between grades 1.6 and 1.9. The overall mean grade for the TF was 1.1±0.3. There were small insignificant correlations between TF grades and the McMonnies questionnaire (r=0.1.30) and TBUT (r=0.248) and a negligible correlation with Schirmer test (r=−0.046).The results found no significant differences within the TF for tear samples collected at different times of the day, suggesting that there is little diurnal variation evident.