Investigating the Usefulness of Fundus Autofluorescence in Retinitis Pigmentosa

Hyperautofluorescent Ring Pattern in Retinitis Pigmentosa: Clinical Implications and Modifications Over Time

Purpose

The purpose of this study was to investigate the relation among hyperautofluorescent ring patterns, visual acuity (VA), and optical coherence tomography (OCT) features in patients with retinitis pigmentosa (RP), and to describe its modifications over time.

Methods

This was a retrospective, longitudinal, and observational study. Clinical and imaging data from the first and last available visits of patients with a clinical diagnosis of RP were reviewed. The ellipsoid zone (EZ) width was measured on OCT acquisitions. Short-wavelength autofluorescence (SW-AF) images were classified based on the hyperautofluorescent ring pattern as absent, regular, and irregular, and their modifications over the follow-up were described. The VA, EZ width, and progression rate were compared among the three groups.

Results

One hundred eight eyes from 54 subjects were included in the study. The hyperautofluorescent ring was not present in 28 eyes (25.9%), appeared regular in 45 eyes (41.7%), and had an irregular pattern in 35 eyes (32.4%). The three groups differed in terms of age, VA, and EZ width (all P < 0.05). Additionally, the absence of a hyperautofluorescent ring indicated a faster rate of progression (P < 0.001). Throughout the follow-up period, 17 eyes (15.7%) experienced a change in the AF pattern, with irregular rings being more commonly affected.

Conclusions

The hyperautofluorescent ring is a useful tool to frame patients based on their EZ width and VA. We described its possible modifications over time, the knowledge of which can aid clinicians in the interpretation of imaging finding changes of their patients.

Morphological and functional involvement of the inner retina in retinitis pigmentosa

BACKGROUND

To investigate the morphological retinal parameters associated with retinal sensitivity status in retinitis pigmentosa (RP) through a quantitative multimodal imaging approach.

METHODS

The study was designed as an observational, prospective case series, including RP patients and healthy controls. Multimodal imaging included fundus autofluorescence (FAF), structural optical coherence tomography (OCT), OCT angiography (OCTA) and microperimetry (MP). The follow-up lasted 12 months. For each imaging modality, we performed an overall quantitative analysis and a detailed investigation based on the ETDRS-9 sectors grid. Quantitative parameters included the thickness of each retinal and choroidal layer, vessel density (VD), choriocapillaris porosity (CCP), FAF intensity and MP retinal sensitivity.

RESULTS

We included 40 eyes (40 patients) affected by RP and 40 healthy eyes (40 controls). Mean baseline BCVA was 0.14 ± 0.18 LogMAR, with 0.18 ± 0.24 LogMAR after 1-year of follow-up. RP eyes showed statistically significant alterations of retinal and choroidal layers on the ETDRS-9 sectors grid, significant reduction of VD values and MP retinal sensitivity, and significantly higher CCP than controls. The inner retinal layers proved closely associated with the functional integrity of the posterior pole. In addition, our ROC analysis provided quantitative cutoffs connected significantly with a high probability of observing a partial sparing of MP retinal sensitivity.

CONCLUSIONS

The inner retinal layers are closely associated with the functional integrity of the posterior pole in RP. FAF intensity reduction may be interpreted as lipofuscin metabolism impairment inducing increased phototoxic distress for retinal structures. Vascular involvement contributes to the morpho-functional deterioration of the macular region in RP.

Estimation of Visual Function Using Deep Learning From Ultra-Widefield Fundus Images of Eyes With Retinitis Pigmentosa

Importance

There is no widespread effective treatment to halt the progression of retinitis pigmentosa. Consequently, adequate assessment and estimation of residual visual function are important clinically.

Objective

To examine whether deep learning can accurately estimate the visual function of patients with retinitis pigmentosa by using ultra-widefield fundus images obtained on concurrent visits.

Design, Setting, and Participants

Data for this multicenter, retrospective, cross-sectional study were collected between January 1, 2012, and December 31, 2018. This study included 695 consecutive patients with retinitis pigmentosa who were examined at 5 institutions. Each of the 3 types of input images-ultra-widefield pseudocolor images, ultra-widefield fundus autofluorescence images, and both ultra-widefield pseudocolor and fundus autofluorescence images-was paired with 1 of the 31 types of ensemble models constructed from 5 deep learning models (Visual Geometry Group-16, Residual Network-50, InceptionV3, DenseNet121, and EfficientNetB0). We used 848, 212, and 214 images for the training, validation, and testing data, respectively. All data from 1 institution were used for the independent testing data. Data analysis was performed from June 7, 2021, to December 5, 2022.

Main Outcomes and Measures

The mean deviation on the Humphrey field analyzer, central retinal sensitivity, and best-corrected visual acuity were estimated. The image type-ensemble model combination that yielded the smallest mean absolute error was defined as the model with the best estimation accuracy. After removal of the bias of including both eyes with the generalized linear mixed model, correlations between the actual values of the testing data and the estimated values by the best accuracy model were examined by calculating standardized regression coefficients and P values.

Results

The study included 1274 eyes of 695 patients. A total of 385 patients were female (55.4%), and the mean (SD) age was 53.9 (17.2) years. Among the 3 types of images, the model using ultra-widefield fundus autofluorescence images alone provided the best estimation accuracy for mean deviation, central sensitivity, and visual acuity. Standardized regression coefficients were 0.684 (95% CI, 0.567-0.802) for the mean deviation estimation, 0.697 (95% CI, 0.590-0.804) for the central sensitivity estimation, and 0.309 (95% CI, 0.187-0.430) for the visual acuity estimation (all P < .001).

Conclusions and Relevance

Results of this study suggest that the visual function estimation in patients with retinitis pigmentosa from ultra-widefield fundus autofluorescence images using deep learning might help assess disease progression objectively. Findings also suggest that deep learning models might monitor the progression of retinitis pigmentosa efficiently during follow-up.

Outer retinal degeneration in a non-human primate model using temporary intravitreal tamponade with N-methyl-N-nitrosourea in cynomolgus monkeys

Objective:The main objective of this study was to induce and evaluate drug-dose-dependent outer retinal degeneration in cynomolgus monkeys by application of N-methyl-N-nitrosourea (MNU).Approach:Intravitreal temporary tamponade induced outer retinal degeneration with MNU solutions (2-3 mg ml^-1) after vitrectomy in five cynomolgus monkeys. Optical coherence tomography (OCT), fundus autofluorescence (FAF), full-field electroretinography (ffERG), and visual evoked potentials (VEP) were performed at baseline and weeks 2, 6, and 12 postoperatively. At week 12, OCT angiography, histology, and immunohistochemistry were performed.Main results:Outer retinal degeneration was observed in four monkeys, especially in the peripheral retina. Anatomical and functional changes occurred at week 2 and persisted until week 12. FAF images showed hypoautofluorescence dots, similar to AF patterns seen in human retinitis pigmentosa. Hyperautofluorescent lesions in the pericentral area were also observed, which corresponded to the loss of the ellipsoid zone on OCT images. OCT revealed thinning of the outer retinal layer adding to the loss of the ellipsoid zone outside the vascular arcade. Histological findings confirmed that the abovementioned changes resulted from a gradual loss of photoreceptors from the perifovea to the peripheral retina. In contrast, the inner retina, including ganglion cell layers, was preserved. Functionally, a decrease or extinction of scotopic ffERGs was observed, which indicated rod-dominant loss. Nevertheless, VEPs were relatively preserved.Significance:Therefore, we can conclude that temporary exposure to intravitreal MNU tamponade after vitrectomy induces rod-dominant outer retinal degeneration in cynomolgus monkeys, especially in the peripheral retina.

Predicting retinal sensitivity using optical coherence tomography parameters in central serous chorioretinopathy

PURPOSE

To predict changes in retinal sensitivity using optical coherence tomography (OCT) in eyes with central serous chorioretinopathy (CSC).

METHODS

Twenty-three eyes in 23 patients with CSC were enrolled. Retinal sensitivity was measured twice using microperimetry in all the examined eyes. Spectral domain OCT measurements were simultaneously conducted. The relationship between retinal sensitivity and the thicknesses of (i) the retinal nerve fiber layer plus the ganglion cell layer (RNFL + GCL), (ii) the inner nuclear layer (INL), (iii) the outer nuclear layer (ONL), and (iv) the serous retinal detachment height (SRDH) were investigated in a point-wise manner. The associations between the change in retinal sensitivity and the OCT parameters at baseline were also investigated.

RESULTS

The mean age of the participants was 49.8 ± 10.7 years. The mean SRDH was significantly lower (p < 0.001), and the mean retinal sensitivity (p < 0.001) was significantly higher at the second examination, compared with the first; however, the logMAR visual acuity (VA) did not differ significantly between the two examinations (p = 0.063). The logMAR VA was associated with retinal sensitivity at both the first and second examinations (p < 0.001). The retinal sensitivity at the second examination was significantly correlated with the retinal sensitivity, RNFL + GCL, INL, ONL, and SRDH at the first examination and with the improvement in SRDH.

CONCLUSIONS

Retinal sensitivity was associated with the retinal structure in eyes with CSC; these parameters could be useful for predicting the change in visual function prior to treatment.

A Prediction Method of Visual Field Sensitivity Using Fundus Autofluorescence Images in Patients With Retinitis Pigmentosa

Purpose

The purpose of this study was to investigate the association between fundus autofluorescence (FAF) and visual field (VF) sensitivities in eyes with retinitis pigmentosa (RP). We also investigated the model we developed to predict VF sensitivity using the FAF ring and its prediction accuracy.

Methods

The training dataset consisted of 51 eyes of 28 patients, and the testing dataset consisted of 42 eyes of 25 patients with RP. VF and FAF measurements were conducted using the Humphrey Field Analyzer (HFA) 10-2 test and Optos. The HFA 10-2 test was divided into three sectors according to the association with the FAF (IN, ON, and OUT). Moreover, concentric curves were drawn at 1-degree intervals outside the FAF ring and OUT was divided into six sectors (from OUT1 to OUT6 toward the periphery). Finally, the total deviation (TD) value was predicted using age and visual acuity (VA) in the whole field, and each of the eight sectors was compared.

Results

The TD value decreased significantly from IN, ON, and then toward OUT6. The absolute prediction error with the FAF ring (average, 7.6 dB) was significantly smaller than that without the FAF ring (average, 8.7 dB). The absolute prediction error with the FAF ring was significantly smaller in the central areas (IN, 4.4 dB and ON, 5.3 dB) than those in the peripheral areas (OUT1-6, 6.8-9.1 dB).

Conclusions

VF sensitivity decreases in association with the FAF ring. We developed a model to predict 10-2 VF sensitivity values using the FAF ring, which enabled us to predict 10-2 TD values.

Repeatability of binarization thresholding methods for optical coherence tomography angiography image quantification

Binarization is a critical step in analysis of retinal optical coherence tomography angiography (OCTA) images, but the repeatability of metrics produced from various binarization methods has not been fully assessed. This study set out to examine the repeatability of OCTA quantification metrics produced using different binarization thresholding methods, all of which have been applied in previous studies, across multiple devices and plexuses. Successive 3 × 3 mm foveal OCTA images of 13 healthy eyes were obtained on three different devices. For each image, contrast adjustments, 3 image processing techniques (linear registration, histogram normalization, and contrast-limited adaptive histogram equalization), and 11 binarization thresholding methods were independently applied. Vessel area density (VAD) and vessel length were calculated for retinal vascular images. Choriocapillaris (CC) images were quantified for VAD and flow deficit metrics. Repeatability, measured using the intra-class correlation coefficient, was inconsistent and generally not high (ICC < 0.8) across binarization thresholds, devices, and plexuses. In retinal vascular images, local thresholds tended to incorrectly binarize the foveal avascular zone as white (i.e., wrongly indicating flow). No image processing technique analyzed consistently resulted in highly repeatable metrics. Across contrast changes, retinal vascular images showed the lowest repeatability and CC images showed the highest.

Reviewing the Role of Ultra-Widefield Imaging in Inherited Retinal Dystrophies

Inherited retinal dystrophies (IRD) are a heterogeneous group of rare chronic disorders caused by genetically determined degeneration of photoreceptors and retinal pigment epithelium cells. Ultra-widefield (UWF) imaging is a useful diagnostic tool for evaluating retinal integrity in IRD, including Stargardt disease, retinitis pigmentosa, cone dystrophies, and Best vitelliform dystrophy. Color or pseudocolor and fundus autofluorescence images obtained with UWF provide previously unavailable information on the retinal periphery, which correlates well with visual field measurement or electroretinogram. Despite unavoidable artifacts of the UWF device, the feasibility of investigations in infants and in patients with poor fixation makes UWF imaging a precious resource in the diagnostic armamentarium for IRD.

A Novel Method for the Objective Identification of Hyperautofluorescent Ring in Retinitis Pigmentosa Using Binarization Processing

PURPOSE

To assess precision and accuracy of a new objective algorithm using binarization in a software for identifying the hyperautofluorescent ring (AF ring) in retinitis pigmentosa (RP) compared with subjective visual inspection.

METHODS

Ultra-widefield AF images were obtained from 23 eyes of 13 patients with retinitis pigmentosa (RP). We defined the borders of the AF rings using semiautomatic binarization algorithm in Fiji software. We compared the degree of precision (intra- and interrater agreements) of this algorithm and that of subjective visual inspection (freehand method) using Jaccard indices (JIs). To compare the classification performance (whether 68 points of Humphrey Field Analyzer is classified as inside, on, or outside AF rings), we calculated percent agreement and weighted kappa statistic between the two methods. The relationship between the distance from the AF ring and retinal sensitivities was also investigated.

RESULTS

The binarization method showed significantly higher JIs than the freehand method (for interrater: 0.94-0.95 vs. 0.73-0.78, respectively, P = 0.002; for intrarater: 0.95 vs. 0.68-0.71, respectively, P = 0.005). Percent agreement for classification between the two methods were 0.94 and weighted kappa statistic was 0.94 (P < 0.001). The retinal sensitivities decreased significantly and eccentrically from 2° inside to 3° outside the AF ring.

CONCLUSIONS

Defining the AF ring in RP using the binarization algorithm showed significantly higher precision and the same degree of accuracy compared with visual inspection.

TRANSLATION RELEVANCE

This novel method may enable quantitative analysis of the AF ring, an indicator of retinal function in RP.