The aim of this study was detect and compare the vitreous acidity and alkalinity (pH) in patients with diabetic retinopathy (DR) and idiopathic macular hole (IMH), and to explore the changes of pH in vitreous exposed to air and room temperature at 22℃.

Fifteen patients (15 eyes) with DR were admitted to the Ophthalmological Center of Affiliated Hospital of Weifang Medical College from May 2018 to December 2018 as DR group, and 16 patients (16 eyes) with IMH were admitted to the same period as IMH group. All patients underwent standard three-incision 23 G vitrectomy by the same surgeon. During the operation, 0.2-0.5 ml of undiluted and contaminated vitreous specimens in the middle of the vitreous cavity were collected and immediately transferred to the sterilization cup. The pH value was measured with a standard pH30A pen acidity meter, and was repeated after 5 min, 10 min, 15 min, 20 min, 25 min, 30 min and 60 min. In all the data, age and vitreous pH were expressed as mean (±s ). Independent sample t test was used to compare the differences between groups, and Fisher's exact probability method was used to compare the differences between groups. The difference was statistically significant with P<0.05.

The vitreous pH values of DR group and IMH group were (7.83±0.24) and (7.66±0.11) respectively. The vitreous pH value of DR group was significantly higher than that of IMH group (t=2.45, P<0.05). The pH value of DR group and IMH group increased significantly in a short time after vitreous body was exposed to room temperature and air in vitro, and gradually increased over time.

Vitreous bodies of DR patients and IMH patients were weakly alkaline. Among them, the vitreous pH value of DR patients was higher than that of IMH patients. After vitreous body was isolated, the pH value of all patients increased with the prolongation of exposure to air and room temperature for a certain period of time.