Two types of lipid-containing eye drops, Artelac and Cationorm, were used for two separate groups of participants. We chose to use Artelac and Cationorm in this study because these two eye drops were the most commonly used and available lipid-containing eye drops in Singapore at that time. The choice of Cationorm or Artelac eye drops in participants was random and not based on any clinical decision.
The examination of the right eye of participants in the study was a monocular one. Before the instillation of eye drops, the baseline LLT was measured using the LipiView machine. One drop of the eye drops was then instilled into the participant's right eye and the LLT of participants was measured 1, 5, and 15 minutes after instillation of the eye drop. We chose our time points based on a preliminary study involving testing a separate and smaller group of participants (n = 3) with Artelac where the timeline for measurements was 0, 1, 15, 20, 45, and 60 minutes. From this study, we observed that there was no further significant change in LLT after 15 minutes. We added the 5-minute time point in our study because there were significant differences between the LLT of both the baseline LLT of <60 nm and >60 nm groups of participants from our pilot study. Therefore, the following time points were chosen: 0, 1, 5, and 15 minutes, with 15 minutes as our last study time point.
Participants had to take note of the precautions such as no rubbing of eyes and no blinking forcefully. This is because deliberate, forceful blinking was found to significantly increase the LLT of the tear film. The magnitude of increase was found to be correlated with the baseline LLT values; individuals with baseline LLT values of 75 to 150 nm demonstrated a mean increase in LLT of 33 nm after forceful blinking, whereas subjects with baseline LLT values of ≤60 nm experienced a mean increase of 19 nm. Forceful blinks increased the LLT by >15 nm owing to expression of meibum from meibomian gland dysfunction.
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