taVNS device (Elmmedicare, EC100, Shenzhen, China) was used to apply stimulation for patients. Stimulation parameters comprised an electrical current of 1 mA at a frequency of 20 Hz, with a waveform width of 1 ms. Repurposed off-the-shelf devices were utilized for this purpose, with the stimulator generating single square-wave pulses lasting 1 ms each. Enhancing conductivity was achieved by wiping the ear with tap water. The electrodes were placed on the cymba conchae and concha around the affected ear, which is the region of rich vagus nerve branch distribution.

Drug: Hyaluronic acid eye drops Participants in both groups received hyaluronic acid eye drops (HYLO COMOD® eye drops, Ursapharm, Ltd., Germany) with the treatment of 3 times a day.

taVNS device were applied using the same stimulator, stimulation parameters and same sessions. However, the electrodes were placed on the antihelix around the affected ear, which is the region of few vagus nerve branch distribution. Drug: Hyaluronic acid eye drops Participants in both groups received hyaluronic acid eye drops (HYLO COMOD® eye drops, Ursapharm, Ltd., Germany) with the treatment of 3 times a day.

taVNS device (Elmmedicare, EC100, Shenzhen, China) was used to apply stimulation for patients.

Stimulation parameters comprised an electrical current of 1 mA at a frequency of 20 Hz, with a waveform width of 1 ms. Repurposed off-the-shelf devices were utilized for this purpose, with the stimulator generating single square-wave pulses lasting 1 ms each. Enhancing conductivity was achieved by wiping the ear with tap water. The electrodes were placed on the cymba conchae and concha around the affected ear, which is the region of rich vagus nerve branch distribution. Patients in control group were applied using the same stimulator, stimulation parameters and same sessions. However, the electrodes were placed on the antihelix around the affected ear, which is the region of few vagus nerve branch distribution.

Ocular Surface Disease Index (OSDI) questionnaire: The OSDI questionnaire is designed to assess the severity of symptoms and the impact of ocular surface diseases, such as dry eye disease, on a patient's quality of life.

Tear Breakup Time (TBUT): TBUT is a diagnostic test used to evaluate the stability of the tear film and diagnose dry eye disease. It measures the time it takes for dry spots to appear on the corneal surface after blinking while using a fluorescent dye. A shorter TBUT indicates less stable tear film, which is often associated with dry eye disease.