Screening der diabetischen Retinopathie und Papillentopographie mit dem ?Retinal Thickness Analyzer? (RTA)

Application of non-mydriatic fundus photography-assisted telemedicine in diabetic retinopathy screening

BACKGROUND

Early screening and accurate staging of diabetic retinopathy (DR) can reduce blindness risk in type 2 diabetes patients. DR's complex pathogenesis involves many factors, making ophthalmologist screening alone insufficient for prevention and treatment. Often, endocrinologists are the first to see diabetic patients and thus should screen for retinopathy for early intervention.

AIM

To explore the efficacy of non-mydriatic fundus photography (NMFP)-enhanced telemedicine in assessing DR and its various stages.

METHODS

This retrospective study incorporated findings from an analysis of 93 diabetic patients, examining both NMFP-assisted telemedicine and fundus fluorescein angiography (FFA). It focused on assessing the concordance in DR detection between these two methodologies. Additionally, receiver operating characteristic (ROC) curves were generated to determine the optimal sensitivity and specificity of NMFP-assisted telemedicine, using FFA outcomes as the standard benchmark.

RESULTS

In the context of DR diagnosis and staging, the kappa coefficients for NMFP-assisted telemedicine and FFA were recorded at 0.775 and 0.689 respectively, indicating substantial intermethod agreement. Moreover, the NMFP-assisted telemedicine's predictive accuracy for positive FFA outcomes, as denoted by the area under the ROC curve, was remarkably high at 0.955, within a confidence interval of 0.914 to 0.995 and a statistically significant P-value of less than 0.001. This predictive model exhibited a specificity of 100%, a sensitivity of 90.9%, and a Youden index of 0.909.

CONCLUSION

NMFP-assisted telemedicine represents a pragmatic, objective, and precise modality for fundus examination, particularly applicable in the context of endocrinology inpatient care and primary healthcare settings for diabetic patients. Its implementation in these scenarios is of paramount significance, enhancing the clinical accuracy in the diagnosis and therapeutic management of DR. This methodology not only streamlines patient evaluation but also contributes substantially to the optimization of clinical outcomes in DR management.

Computer-aided diagnosis of diabetic retinopathy: a review

Diabetes mellitus may cause alterations in the retinal microvasculature leading to diabetic retinopathy. Unchecked, advanced diabetic retinopathy may lead to blindness. It can be tedious and time consuming to decipher subtle morphological changes in optic disk, microaneurysms, hemorrhage, blood vessels, macula, and exudates through manual inspection of fundus images. A computer aided diagnosis system can significantly reduce the burden on the ophthalmologists and may alleviate the inter and intra observer variability. This review discusses the available methods of various retinal feature extractions and automated analysis.

Algorithms for the automated detection of diabetic retinopathy using digital fundus images: a review

Diabetes is a chronic end organ disease that occurs when the pancreas does not secrete enough insulin or the body is unable to process it properly. Over time, diabetes affects the circulatory system, including that of the retina. Diabetic retinopathy is a medical condition where the retina is damaged because fluid leaks from blood vessels into the retina. Ophthalmologists recognize diabetic retinopathy based on features, such as blood vessel area, exudes, hemorrhages, microaneurysms and texture. In this paper we review algorithms used for the extraction of these features from digital fundus images. Furthermore, we discuss systems that use these features to classify individual fundus images. The classifications efficiency of different DR systems is discussed. Most of the reported systems are highly optimized with respect to the analyzed fundus images, therefore a generalization of individual results is difficult. However, this review shows that the classification results improved has improved recently, and it is getting closer to the classification capabilities of human ophthalmologists.

Topography of diabetic macular oedema compared with fluorescein angiography

PURPOSE

To compare the amount and pattern of fluorescein leakage in diabetic macular oedema with the retinal thickness maps obtained with the retinal thickness analyser (RTA) and optical coherence tomography (OCT).

METHODS

A consecutive series of 30 eyes from 30 patients with diabetic macular oedema was included. On fluorescein angiography (FA) the macula was analysed in 10 subfields as defined by the ETDRS. The amount and source of leakage for each field were determined. Retinal thickness was measured by OCT and RTA maps in each of the 10 fields and compared with the FA grading.

RESULTS

Foveal retinal thickness on OCT was most influenced by the overall FA leakage, which was the only significant covariate on multivariate analysis. The source and amount of leakage correlated significantly with the topography of retinal thickness in the four peripheral fields between 1500 microm and 3000 microm from the macular centre (r = 0.54, p = 0.002). The mean amount and source of leakage in those fields also showed the highest correlation with central macular thickness on OCT (r = 0.46, p = 0.01). Similar results were obtained by RTA when excluding ischaemic cases (r = 0.44, p = 0.04). For both instruments, FA leakage within the four central fields < 1500 microm did not correlate significantly with retinal thickness. Thickness by OCT and RTA were highly correlated with one another for central macular measurements (r = 0.73, p < 0.001), but correlated poorly in the peripheral fields. Overall, OCT measurements correlated more highly with FA.

CONCLUSIONS

Optical coherence tomography and RTA thickness measurements can be used to identify patients for further examination. Fluorescein angiography leakage in the outer ETDRS fields correlates best with central thickness and retinal thickness topography by OCT.

Age Effect on Retina and Optic Disc Normal Values

PURPOSE

To investigate retinal thickness and optic disc parameters by the Retinal Thickness Analyzer (RTA) glaucoma program in older normal subjects and to determine any age effect.

METHODS

Subjects over 40 years of age without any prior history of eye diseases were recruited. Only subjects completely normal on clinical ophthalmologic examination and on visual field testing by Humphrey Field Analyzer (HFA) using the SITA 24-2 program were included. A total of 74 eyes from 74 subjects with even age distribution over the decades were enrolled and underwent topographic measurements of the posterior pole and of the optic disc by RTA. The 'glaucoma full' program in software version 4.11B was applied.

RESULTS

Mean patient age was 59.9 +/- 10.3 years with a range from 40 to 80 years. The only parameter intraocular pressure (IOP) correlated with was retinal posterior pole asymmetry (r = 0.27, p = 0.02). IOP itself increased significantly with age (r = 0.341, p = 0.003). Mean defect and pattern standard deviation of the HFA did not correlate with any of the retinal or optic disc measurements. Increasing age correlated significantly with some of the morphologic measurements of the RTA: decreasing perifoveal minimum thickness (r = -0.258, p = 0.026), increased cup-to-disc area ratio (r = 0.302, p = 0.016) and increased cup area (r = 0.338 p = 0.007).

CONCLUSIONS

An age effect exists for some of the retina and optic disc measurements obtained by the RTA.

Repeatability and reproducibility of optic nerve head topography using the retinal thickness analyzer

OBJECTIVE

The objective was to determine the reproducibility and repeatability of topographic disk parameters with the retinal thickness analyzer (RTA).

METHODS

Thirty-nine eyes of 39 healthy subjects were included. Three observers performed three consecutive measurements of optic disk topography independently. Combined repeatability (intra-observer component of variability) and reproducibility (inter-observer component of variability, R and R) was assessed by variance component analysis.

RESULTS

Six topographic parameters (disk area, cup area, cup volume, mean cup depth, maximum depth, and cup shape measure) revealed an acceptable repeatability and reproducibility expressed as the percentage of the total measurement variability (range 17.6-28.4%). The average reproducibility and repeatability of all optic disk parameters measured using the RTA was not acceptable (combined R and R = 33.4%).

CONCLUSIONS

Repeatability and reproducibility of the optic disk topography analysis using the RTA reveals a high variation, and should, therefore, be interpreted carefully for glaucoma diagnosis and for monitoring the disease.