Introduction:
This study was aimed at analyzing, modeling, and comparing the risk factors of diabetic retinopathy (DR) among type 2 diabetes mellitus (DM) patients with and without metabolic syndrome (MS).

Material and methods:
A cross-sectional study from July 2017 to July 2019 was performed by tracing type 2 DM patients who received treatment at an out-patient clinic and a mydriatic examination by an ophthalmologist in a single institute in south Taiwan. A total of 802 patients without DR were recruited and divided into two groups based on whether they had MS for this study. We analyzed the impact of DR based on the potential and related factors of these two groups.

Results:
The sample consisted of 802 patients; 282 patients did not have MS, and 520 did. A comparison of the risk factors of DR among the patients with and without MS revealed that the level of glycated hemoglobin (HbA1c) was a co-risk factor of DR. However, female sex, betel quid chewing, family history of DM, and higher total cholesterol were found to be risk factors of DR among the patients who had MS. Betel quid chewing, especially, could exacerbate the disease condition of DM and elevate the risk of DR.

Conclusions:
Of those risk factors, betel quid chewing may be the main reason for DM deterioration and raised risk of DR. Hence, we recommend that the chewing of betel quid should be avoided to prevent DR.