This study conducted a retrospective analysis of multiple risk factors associated with dERM based on the data obtained from fundus screenings of hospitalized diabetes patients. In dERM group, we observed an elevation in SII, coupled with a reduction in Alb levels. Especially concerning the SII, which was significantly associated with an increased hazard of dERM (OR = 3.919 [95%CI 1.591–9.654]).
SII is calculated from blood cell count of neutrophils, lymphocytes and platelets and has been regarded as a predictive and prognostic marker in various diseases, such as multiple malignancies[23], autoimmune disorders[24; 25] and cardiovascular diseases et.al[26]. Previous research has substantiated the correlation between SII and OCT biomarkers, such as DME, HRF and subretinal fluid in DR patients[15; 27; 28]. Taking a step further, the present study revealed that dERM as an ILM-vitreoretinal interface lesion is closely associated with SII. There is also a weak positive correlation between HRF and SII. HRF is related to the activation and aggregation of microglia, which rapidly subsides or appears in anti VEGF therapy, indicating active inflammation of the retina[29]. Alb not only reflects the nutritional metabolism status of the body, but also participates in the regulation of inflammation as a negative inflammatory indicator[30; 31]. But there was no significant correlation with the occurrence of dERM in regression analysis. Reviewing the data, it can be found that the mean of serum albumin in both groups is lower than the normal reference value. In regression analysis, using 40g/L as a cut-off value for binary variable conversion may underestimate the role of Alb in dERM. These results suggested that the dERM pathogenesis is also related to systemic inflammation, not confined to the regional retina inflammation response.
In addition, our study showed that patients with higher ACR levels face over four-fold increased risk of developing dERM. Spearman correlation analysis revealed ACR are also associated with IRC and HRF. ACR is the ratio of microalbumin to creatinine in urine, which is commonly considered as a marker of systemic endothelial dysfunction and a predictor of diabetes complications, such as diabetic nephropathy and DR[32]. Both diabetic nephropathy and DR are two most important microangiopathic complications in DM, and they seem to progress in a parallel manner. From the perspective of OCT biomarkers, this study supported the above opinion, it may deepen our understanding of overall cognition of diabetic complications.
This study found that the macular volume coefficients of the dERM group was significantly higher than that of the control group, reflecting the significant change in macular morphology caused by dERM. Its potential mechanism may attribute to the contraction of the fibrous membrane, causing traction in the macular area and macular edema. The greater macular volume coefficients, especially CMT, usually indicated the poorer visual acuity[33; 34].
We did not observe any association between dERM or any OCT biomarkers and BMI, HbA1c, insulin use rate, hypertension, dyslipidemia, and hyperuricemia in this study, which may be related to the small sample size of this study, and the study subjects were all hospitalized patients, with some admission bias. Of course, HbA1c only reflects the blood glucose level for 2–3 months. The research on the correlation between chronic hyperglycemia and the occurrence of complications of diabetes may need more long-term monitoring indicators. In addition, in DM patients, BMI alone may underestimate the obesity rate[35]. Later research should include such comprehensive indicators as waist circumference and waist hip ratio.
However, this study has certain limitations. Firstly, this study is a single center retrospective study that did not follow up on the visual prognosis of dERM patients, and the sample size is small; Secondly, the study subjects were all hospitalized patients and poor eyes were selected for inclusion in the study, which may have admission bias and selection bias; Finally, different researchers also have a certain degree of subjectivity in determining OCT biomarkers. In future research, it is necessary to further expand the sample size and introduce a more objective and intelligent OCT biomarker interpretation system to further elucidate the relationship between dERM and other OCT biomarkers and systemic inflammation.
To conclude, higher SII and ACR are closely related to dERM among hospitalized DM patients, which emphasizes the importance of systemic inflammatory and endothelial dysfunction in dERM occurrence. It also supports an inflammatory origin of the OCT biomarkers like HRF and IRC.