Retinal Reflectivity Measurement for Cone Impairment Estimation and Visual Assessment After Diabetic Macular Edema Resolution (RECOVER-DME).

Purpose: Photoreceptor loss has been suspected of being involved in incomplete visual recovery after diabetic macular edema (DME) resolution. Recent studies have shown that cone density in the perifoveal area could be estimated by in vivo measurements of the outer retinal reflectivity on optical coherence tomography (OCT). The main objective of this study was to assess the photoreceptor layer reflectivity after DME resolution and to determine its relationship with final visual acuity (VA). Methods: In this cross-sectional case-control study, 77 eyes of 58 patients were divided into three groups: a first group (n = 34) encompassed eyes with resolved DME (R-DME), a second group (n = 24) corresponded to diabetic eyes without DME (no-DME), and a third group (n = 19) comprised a control group of nondiabetic healthy eyes. Outer retinal reflectivity was measured on volumetric spectral-domain (SD)-OCT scans acquired 3 months after DME resolution, from the photoreceptor ellipsoid zone (EZ) and the retinal pigment epithelium (RPE). Results: The mean DME duration was 26.5 ± 13.4 months in the R-DME group. EZ reflectivity was 19.8% lower (P < 0.0001) in this group compared to diabetic eyes without DME and 26.5% lower (P < 0.0001) than in nondiabetic control eyes. Reflectivity was 7.8% lower in the no-DME group compared to controls (P < 0.0001). RPE reflectivity was comparable among the three groups (P > 0.05). VA was significantly correlated with EZ reflectivity in diabetic patients (r2 = 0.57; P < 0.0001). Reflectivity tended to decrease with prolonged DME duration without reaching statistical significance (P = 0.10). Conclusions: DME significantly impacts the photoreceptor layer. This impairment can be estimated by measuring outer retinal reflectivity on OCT images after edema resorption. We also provide evidence that in diabetic eyes without a history of DME, there is early photoreceptor loss, or at least outer segment (OS) disorganization, in addition to the inner retinal degeneration reported previously. This suggests the neurodegenerative process in diabetes. This quantitative approach may help monitor neuroprotective strategies to rescue photoreceptor cells in diabetic eyes.

Quantitative analysis of photoreceptor layer reflectivity on en-face optical coherence tomography as an estimator of cone density.

BACKGROUND: To investigate whether outer retinal reflectivity on en-face Optical coherence tomography (OCT) can be considered as an estimator of cone density measured in the same area. METHODS: Forty-one points of comparisons were studied in 9 eyes (n = 6 patients) presenting maculopathies with various degrees of impairment of the photoreceptor layer. The inner segment ellipsoid zone (EZ), interdigitation zone (IZ), and retinal pigment epithelium (RPE) reflectivity were measured on coronal reconstruction of the photoreceptor layer using homemade dedicated software (Matlab, MathWorks Inc., Natick, USA). The cone metrics were measured in the same perifoveal region of interest using a high-resolution flood illumination adaptive optics camera. A semi-automatic cone counting method was adopted and all photoreceptor densities provided by the manufacturer's software were recounted manually by two experienced readers. RESULTS: Mean manual cone count was 21,522 ± 6700 (range, 5908-31,233 cells/mm2). Both EZ and IZ reflectivity values were closely correlated with cone density in the area studied (r2: 0.80 and 0.62, respectively; p < 0.0001). CONCLUSION: Outer retinal reflectivity on en-face optical coherence tomography correlates well with photoreceptor density. This cone density estimation method based on retinal reflectivity could have interesting applications in the exploration and management of maculopathies.

Functional homogenization of flower visitor communities with urbanization.

Land-use intensification and resulting habitat loss are put forward as the main causes of flower visitor decline. However, the impact of urbanization, the prime driver of land-use intensification in Europe, is poorly studied. In particular, our understanding of whether and how it affects the composition and functioning of flower visitor assemblages is scant, yet required to cope with increasing urbanization worldwide. Here, we use a nation-wide dataset of plant-flower visitor (Coleoptera, Diptera, Hymenoptera, Lepidoptera) interactions sampled by citizen scientists following a standardized protocol to assess macroecological changes in richness and composition of flower visitor communities with urbanization. We measured the community composition by quantifying the relative occurrence of generalist and specialist flower visitors based on their specialisation on flowering plant families. We show that urbanization is associated with reduced flower visitor richness and a shift in community composition toward generalist insects, indicating a modification of the functional composition of communities. These results suggest that urbanization affects not only the richness of flower visitor assemblages but may also cause their large-scale functional homogenization. Future research should focus on designing measures to reconcile urban development with flower visitor conservation.

Three-dimensional Printing of Optical Lenses and Ophthalmic Surgery: Challenges and Perspectives.

PURPOSE: To determine whether the historical Ridley lens could be reproduced with current three-dimensional lens printing technology. METHODS: A reproduction of the Ridley lens was printed using the Printoptical Technology (LUXeXceL Group BV, Kruiningen, Netherlands). Photographs and electron microscopy images were taken. Dimensions, weight, anterior and posterior surface radius of curvature, optical transmission, back optical power, and surface analysis using interferometry were obtained. RESULTS: The printed lens was 8.10 ± 0.01 mm in diameter, 2.50 ± 0.01 mm thick, and weighed 117 mg. The anterior radius of curvature was 14.63 ± 0.69 mm and the posterior radius of curvature was 10.88 ± 0.22 mm. The back focal length in air was 14.1 ± 0.4 mm. An average 75% transmission in the visible spectrum (400 to 700 nm) was achieved. Surface analysis showed significant surface roughness. CONCLUSIONS: The printed reproduction of the Ridley lens was far from current clinical standards, but had the properties of a biconvex lens.

Reflectivity of the outer retina on spectral-domain optical coherence tomography as a predictor of photoreceptor cone density.

PURPOSE: To investigate the relationship between outer retinal reflectivity on spectral-domain optical coherence tomography and cone density in the corresponding area. DESIGN: Prospective cross-sectional observational study. METHODS: In this institutional-based study, 20 eyes of 10 patients presenting maculopathies with various degrees of impairment of the photoreceptor layer (central serous chorioretinopathy, chronic central serous chorioretinopathy, maculopathy associated with hydroxychloroquine, and healthy eyes) were studied. Selection criteria were intended to ensure good image quality. Inner segment ellipsoid band reflectivity, global retinal reflectivity, and relative inner segment ellipsoid reflectivity (defined as the ratio of inner segment ellipsoid band reflectivity on overall retinal reflectivity) were measured on a longitudinal reflectance profile extracted from the spectral-domain optical coherence tomography B-scan. The cone metrics were measured in the same region of interest, located in the perifoveal area, using an adaptive optics retinal camera. RESULTS: Inner segment ellipsoid and relative ellipsoid reflectivity were closely correlated with cone density (Pearson r: 0.72 and 0.70, respectively, P < .01). CONCLUSION: Outer retinal reflectivity on the transversal optical coherence tomography scan can be correlated to adaptive optics in terms of photoreceptor density. This quantitative approach using optical coherence tomography images could have important implications in the management of maculopathies.

Assessment of parafoveal cone density in patients taking hydroxychloroquine in the absence of clinically documented retinal toxicity.

PURPOSE: To measure cone density in patients taking hydroxychloroquine (HCQ), with no clinical evidence of maculopathy. METHODS: Patients visiting for HCQ macular toxicity screening in the Besançon University Hospital Ophthalmology Department (France) were studied. They underwent routine examination including spectral-domain optical coherence tomography, fundus autofluorescence and multifocal electroretinogram to detect HCQ-induced retinal toxicity. Cone metrics (density, spacing and percentage of cones with six neighbours) were obtained using an adaptive optics camera (RTX1, Imagine Eyes, Orsay, France). The region of interest corresponded to a 0.3° × 0.3° square placed nasally and temporally at 2° of eccentricity from the fovea. RESULTS: Forty eyes of 23 patients were studied. The majority of the patients (21/23) were female. They were aged from 25 to 60 years (mean age ± SD: 40.1 years ± 10). The cumulative dose for HCQ ranged from 24 to 2160 g (777 ± 558 g). None of them displayed HCQ toxicity on screening tests. Bivariate analysis showed moderate cone loss with escalating doses of HCQ (linear regression, r² = 0.23, p = 0.018). Cone spacing also increased with increasing cumulative dose (r² = 0.17, p = 0.008). Cone packing remained unchanged (p > 0.05). Multivariate analysis showed that age and cumulative dose were additive and independent factors of cone dropout. CONCLUSIONS: In this pilot study, we observed moderate cone loss as HCQ cumulative doses increased. The early detection of parafoveal cone metric changes may represent the earliest sign of HCQ macular toxicity during screening.

Reliability of cone counts using an adaptive optics retinal camera.

BACKGROUND: To assess the reproducibility and repeatability of cone imaging in healthy human eyes, using the RTx-1 Adaptive Optics Retinal Camera and its proprietary cone-counting software. DESIGN: Single-centre, prospective study. PARTICIPANTS: Ten healthy adults. METHODS: Macular cones were imaged. Intrasession repeatability was assessed by comparing 10 consecutive acquisitions obtained by the same operator from each subject. For the intersession study, each subject was imaged five consecutive days. Interoperator reproducibility was also evaluated by comparing the images obtained from 10 different subjects by two independent operators. Finally, intergrader agreement was evaluated by comparing the cone counts measured by two masked graders. MAIN OUTCOME MEASURES: Mean cone density (cells/mm(2) ), spacing between cells (µm) and percentage of cones with six neighbours calculated on Voronoi diagrams were measured. Correlation coefficients, intraclass correlation coefficients, and coefficients of variation were calculated. RESULTS: Correlation coefficient and intraclass correlation coefficient were respectively 0.81 and 0.96 between operators, and 0.97 and 0.98 between the two graders. The intrasession and intersession coefficients of variation were under 7%. The percentage of cells with six neighbours and the spacing between cones varied in the same proportion (coefficients of variation ranged from 1.66 to 10.05%). CONCLUSIONS: Overall, the test-retest variability of RTx-1 and its software was good in normal human eyes. Further studies in the normal clinical setting are mandatory.

The whereabouts of flower visitors: contrasting land-use preferences revealed by a country-wide survey based on citizen science.

BACKGROUND: In the past decade, accumulating evidence of pollinator decline has raised concerns regarding the functioning of terrestrial ecosystems and the sustainability of crop production. Although land-use changes have been advanced as the major causes, the affinities of most wild pollinators with the main land-use types remain unknown. Filling this gap in our knowledge is a prerequisite to improving conservation and management programmes. METHODOLOGY/PRINCIPAL FINDINGS: We estimated the affinity of flower visitors with urban, agricultural and natural land-uses using data from a country-wide scale monitoring scheme based on citizen science (Spipoll). We tested whether the affinities differed among insect orders and according to insect frequency (frequent or infrequent). Our results indicate that the affinities with the three land-use types differed among insect orders. Apart from Hymenopterans, which appeared tolerant to the different land-uses, all flower visitors presented a negative affinity with urban areas and a positive affinity with agricultural and natural areas. Additionally, infrequent taxa displayed a lower affinity with urban areas and a higher affinity with natural areas than did frequent taxa. Within frequent taxa, Hymenoptera and Coleoptera included specialists of the three land-use types whereas Diptera and Lepidoptera contained specialists of all but urban areas. CONCLUSIONS/SIGNIFICANCE: Our approach allowed the first standardised evaluation of the affinity of flower visitors with the main land-use types across a broad taxonomical range and a wide geographic scope. Our results suggest that the most detrimental land-use change for flower visitor communities is urbanisation. Moreover, our findings highlight the fact that agricultural areas have the potential to host highly diverse pollinator communities. We suggest that policy makers should, therefore, focus on the implementation of pollinator-friendly practices in agricultural lands. This may be a win-win strategy, as both biodiversity and crop production may benefit from healthier communities of flower visitors in these areas.