Validity of Optical Coherence Tomography as a Diagnostic Method for Diabetic Retinopathy and Diabetic Macular Edema

Abstract

To validate optical coherence tomography (OCT) for the diagnosis of referable retinopathy (severe, very severe or proliferative retinopathy, and macular edema) in diabetic patients.We performed a cross-sectional observational study. A random sample was analyzed comprising 136 eyes of diabetic patients referred to the hospital in Elche (Spain) with suspected referable retinopathy between October 2012 and June 2013. Primary variable: Referable retinopathy measured by ophthalmological examination of the retina. OCT data included: central foveal thickness, presence of intraretinal fluid, and fundus photographs. The receiver operating characteristic (ROC) curve was calculated to determine the minimum thickness value with a positive likelihood ratio >10. To determine the validity of OCT, the following diagnostic test was defined: Positive: if the patient had at least 1 of these criteria: foveal thickness greater than the point obtained on the previously defined ROC curve, intraretinal fluid, abnormal fundus photographs; Negative: none of the above criteria. Sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios, and Kappa statistic were determined.Of the 136 eyes, 48 had referable retinopathy (35.3%, 95% confidence interval [CI]: 27.3–43.3). The minimum thickness value with a positive likelihood ratio >10 was 275 μm. The diagnostic test constructed showed: sensitivity, 91.67% (95% CI: 79.13–97.30); specificity, 93.18% (95% CI: 85.19–97.20); positive predictive value, 88.00% (95% CI: 75.00–95.03); negative predictive value, 95.35% (95% CI: 87.87–98.50); positive likelihood ratio, 13.44 (95% CI: 6.18–29.24); negative likelihood ratio, 0.09 (95% CI: 0.03–0.23). The Kappa value was 0.84 (95% CI: 0.75–0.94, P < 0.001.This study constructed a diagnostic test for referable diabetic retinopathy with type A evidence. Nevertheless, studies are needed to determine the validity of this test in the general diabetic population.

External validation of cut-off points for foveal thickness taking into account the intraretinal fluid using optical coherence tomography to diagnose diabetic macular oedema

“…A random day was selected each week and all patients who attended that day and wanted to participate in the study were recruited. Patients were excluded if they had any of the following ( Azrak et al, 2015a ; Azrak et al, 2015b ): cataract surgery in the last three months, laser treatment in the macular area or panphotocoagulation, dementia, treatment with intravitreal anti-angiogenic drugs, vitreoretinal surgery, high myopia or other macular conditions. The justification for these criteria is that they are conditions which can alter the anatomy of the macula.…”

“…These examinations were carried out by an expert retinal ophthalmologist ( Anonymous, 1985 ; Kinyoun et al, 1989 ). Through the analysis of the images obtained using these techniques, the ophthalmologist was able to confirm the presence of diabetic macular oedema, according to the following definition: the presence of hard exudates or retinal thickening located 500 µm from the fovea ( Azrak et al, 2015a ; Azrak et al, 2015b ).…”

“…To perform the indicated measurement, an area of 6 mm in diameter was used, where the centre was the fovea, to thus obtain an area of 1,000 central microns for the assessment. To measure the presence of intraretinal fluid (cysts or hyporeflective spaces), the ophthalmologist examined the horizontal OCT image of the retina (B-Scan) ( Azrak et al, 2015a ; Azrak et al, 2015b ; Hernández-Martínez et al, 2015 ).…”

“…Our sample size was 134 eyes. To estimate whether this sample was sufficient to validate the diagnostic test, we computed the specificity estimation using the following parameters: expected specificity value of 89% ( Hernández-Martínez et al, 2015 ), prevalence of macular oedema in referred patients of 30.6% ( Azrak et al, 2015a ; Azrak et al, 2015b ) and Type I error of 5%. With these parameters, a precision of 6.36% was obtained, which was satisfactory for our objective.…”

Ratiometric analysis of optical coherence tomography–measured in vivo retinal layer thicknesses for the detection of early diabetic retinopathy

“…Thinning of the NFL to IPL in obese mice [21] , and ganglion cell-inner plexiform layer (GCIPL) in resolved DME eyes compared to no DME eyes [22] , have also been reported as predictive markers for diabetic changes. In a recent study, a diagnostic test for referable DR based on central foveal thickness from OCT images was proposed to confirm or rule out the disease [23] . Moreover, significant reductions were also observed in the GC- IPL and RNFL thickness values in patient groups with both no-DR and mild non-proliferative DR (type-2 DM) compared with HC [24] .…”