Examining the visual health of bats can offer valuable insights into their overall well-being. The condition of wing membranes is essential for bats, supporting water balance and protecting against dehydration during hibernation. Assessing the visual state of bat wing membranes is crucial for tracking their health and identifying abnormalities or infections in the wild. However, conducting this assessment in the field poses practical challenges, potential biases, and increased handling time, which can stress the animals. To address these issues, we propose a new way of collecting data on wing condition of bats. This method involves capturing images of bats' wings in the field and subsequently performing a detailed visual examination of these photos using the open-access software ImageJ. It allows for a careful and thorough examination of the visual health state of the wings, collecting quantitative data on different abnormal structures and further scoring the wing damage index (WDI), providing a more accurate and comparable assessment. In addition, our protocol allows for a precise estimation of the wing surface area, a crucial but currently understudied morphological parameter.