Subclinical Changes in Retinal Microstructure Found in Type 1 Diabetes

Subclinical retinal changes may include neurodegeneration that precedes overt microvascular alteration. Retinal neurons can be affected by oxidative stress, mitochondrial dysfunction and activation of proinflammatory and apoptotic pathways seen in response to hyperglycemia, even in the absence of vascular compromise. This image from the study shows subtle but notable changes in choroidal thickness in a type 1 diabetes with otherwise unremarkable findings. Photo: Kahraman HG, et al. BMC Ophthalmol. 2025;25:296. Click image to enlarge. Autoimmune conditions greatly affect the body’s response to, and output of, inflammation. While the effects of type 1 diabetes on the eyes have been extensively studied, Turkish researchers recently looked at choroidal, inflammatory and urine markers comprehensively to determine their relationship with the condition in the period before any diabetic retinopathy (DR) is present.Included in the investigation were 64 participants, of which 33 were type 1 diabetic patients and 31 were healthy controls who were age- and sex-matched. All participants underwent eye assessments and OCT angiography imaging, with retinal and choroidal parameters measured. Systemic markers measured included C-reactive protein, erythrocyte sedimentation rate, HbA1c, spot urine tests and a new marker this team calls systemic immune-inflammation index (SII). “The SII is calculated from the platelet, neutrophil and lymphocyte ratios and stands out as a comprehensive parameter that reflects not only inflammation but also the balance of the immune response,” they wrote in their paper for BMC Ophthalmology. Upon analysis, it was found that the diabetic patients had significantly higher SII and HbA1c values as well as higher spot microalbumin levels and albumin/creatinine ratios. Macular thickness, vascular density and foveal avascular zone all were found to not display significant difference between groups; however, mean retinal nerve fiber layer and perifoveal ganglion cell complex thicknesses were both lower in the diabetic patient group.SII was found to be strongly positively correlated with choroidal thickness and negatively correlated with parafoveal ganglion cell layer thickness; HbA1c was negatively correlated with mean vascular density, and no correlation was seen between SII and foveal avascular zone or vascular density. Mean vascular density was found to display significant correlation with both spot creatinine and spot microalbumin levels.In their paper, the team elaborated on the novelty of finding a strong association of SII and choroidal thickness in patients without DR. Choroidal thickening may be multifactorial and reflect early inflammatory involvement, they speculated. One potential reason for this observation is vascular dilation of choroidal vessels, leading to increased choroidal blood flow.The authors continue that the elevated SII seen was linked to inner retinal neurodegeneration, as reflected by ganglion cell complex thinning, and microvascular compromise, as reflected by reduced vessel density and an enlarged foveal avascular zone. This supports the idea that inflammation may contribute to parallel retinal neuronal and microvascular injury, and this correlation between SII and choroidal vascularity may show that SII influences microcirculation in the eye beyond just the retina. That is, all this seems to suggest SII acts as a systemic biomarker of neurovascular stress—in turn, linking systemic immune dysregulation to early subclinical changes both retinal and choroidal.Related to this, the authors posit that “this study highlights the potential of the SII as a biomarker for detecting early subclinical retinal and choroidal changes in T1DM patients before the onset of retinopathy. The observed correlations among spot urine tests, the SII and OCTA parameters support the role of systemic inflammation in the early microvascular alterations associated with diabetes.”In the future, they believe that “these findings may contribute to early diagnosis and novel preventive strategies in DR.” Click here for the journal source. Kahraman HG, Güven YZ, Akay F, Üzüm Y, Aysin M. New marker for the detection of pre-retinopathy in patients with type 1 diabetes mellitus: systemic immuno-inflammation index. BMC Ophthalmol. 2025;25:296.