A New Tool For Understanding Early Diabetic Retinal Disease

The incidence of cataract among persons living with diabetes (PwD) is twice that of the normal population, those 45-54 years having the highest incidence rate ratio. Thus, cataract surgeons are increasingly having to manage PwD to prevent visual impairment and blindness over the lifetime of PwD. Monitoring early damage to decide whom to treat with interventions like Fenofibrate could help. Thinning of inner retinal layers precedes classical vascular diabetic retinopathy (DR) but that can be masked by oedema. Functional changes that can be measured before any classical DR have been published, leading to the idea of Functional DR (DOI: 10.1016/j.survophthal.2024.11.010). Here we assess two new forms of rapid objective perimetry to manage PwD.

The studies were conducted in an ophthalmic research clinic that has developed the objectiveFIELD analyser (OFA) with Konan Medical USA. There are 37 publications on OFA, 9 on DR. A 2024 review of 44 functional and structural tests from 23 studies comparing diagnostic power to discriminate eyes of persons without diabetes from PwD without classical DR suggested that the OFA has by far the best diagnostic performance (DOI:10.1016/j.survophthal.2023.09.002).

A cohort of 16 PwD in a study comparing OFA results 10 years apart were also tested with two new OFA perimetry tests. Those tests take less than 90 seconds to assess both eyes concurrently. OFA uses cortically driven pupil responses to objectively determine sensitivity and response delay at each visual field location. The OFA has regulatory clearance in the USA, Japan, and Australia and so is widely available. The two tests were: a widefield test, W20, and a macular test M18. W20 tests 20 regions across the central ±30 deg. M18 examines 18 regions (±10 deg) that are based upon the OCT ETDRS grid devices making structure/function comparisons easy. Linear mixed effects models assessed effects of field location, DR severity, Age and Sex.

Models examining Total Deviations (TDs) at each location (differences from normative data) showed suppression of central sensitivity for W20 and M18 (-8.37 ± 0.98 dB and -13.04 ± 1.20 dB, respectively; both p < 0.0001), and independent significant loss as a function of DR severity. Response delays increased with DR severity. Results from Pattern Deviations (PDs), which remove constant offsets due to things like: cataract for sensitivity, and iris neuropathy for delay, showed significant per region delay effects. For W20 this included extra delays between 10.9 and 14.6 ms (all p < 0.027) for four middle to far retinal eccentricities. For M18 there were fewer significant regions, with extra delays up to 13.0 ms (p = 0.015).

Loss of sensitivity in the central visual field was accompanied by per-region increases in response delays at mid-to far-peripheral locations. This agrees with a previous report on 35 persons with Type 2 diabetes and less severe DR (DOI:10.3389/fendo.2023.1333826), where OFA also appeared to outperform Matrix and SWAP perimetry. A study of persons with mild off-axis diabetic macular oedema followed for an average of 27 months showed that regional changes in delay tracked changes in retinal thickness, whereas Matrix perimetry showed no changes (DOI:10.1371/journal.pone.0287319). Overall, OFA may prove to be a useful tool for assessing Functional DR to assist with treatment decisions and to modify behaviour of PwD who are prone to cataract.