Nazli Demirkaya

Retinal neurodegeneration may precede microvascular changes characteristic of diabetic retinopathy in diabetes mellitus

Significance Diabetic retinopathy (DR), a primary cause of blindness, is characterized by microvascular abnormalities. Recent evidence suggests that retinal diabetic neuropathy (RDN) also occurs in people with diabetes, but little is known about the temporal relationship between DR and RDN. This longitudinal study in people with diabetes with no or minimal DR shows that RDN precedes signs of microvasculopathy and that RDN is progressive and independent of glycated hemoglobin, age, and sex. This finding was further confirmed in human donor eyes and in two experimental mouse models of diabetes. The results suggest that RDN is not ischemic in origin and represent a shift in our understanding of the pathophysiology of this complication of diabetes that potentially affects vision in all people with diabetes mellitus. Diabetic retinopathy (DR) has long been recognized as a microvasculopathy, but retinal diabetic neuropathy (RDN), characterized by inner retinal neurodegeneration, also occurs in people with diabetes mellitus (DM). We report that in 45 people with DM and no to minimal DR there was significant, progressive loss of the nerve fiber layer (NFL) (0.25 μm/y) and the ganglion cell (GC)/inner plexiform layer (0.29 μm/y) on optical coherence tomography analysis (OCT) over a 4-y period, independent of glycated hemoglobin, age, and sex. The NFL was significantly thinner (17.3 μm) in the eyes of six donors with DM than in the eyes of six similarly aged control donors (30.4 μm), although retinal capillary density did not differ in the two groups. We confirmed significant, progressive inner retinal thinning in streptozotocin-induced “type 1” and B6.BKS(D)-Leprdb/J “type 2” diabetic mouse models on OCT; immunohistochemistry in type 1 mice showed GC loss but no difference in pericyte density or acellular capillaries. The results suggest that RDN may precede the established clinical and morphometric vascular changes caused by DM and represent a paradigm shift in our understanding of ocular diabetic complications.

Effect of age on individual retinal layer thickness in normal eyes as measured with spectral-domain optical coherence tomography.

PURPOSE To determine the effect of age on the thickness of individual retinal layers, measured with spectral-domain optical coherence tomography (SD-OCT), in a population of healthy Caucasians. METHODS One hundred and twenty subjects with an age ranging between 18 and 81 years were examined with SD-OCT. Mean layer thickness was calculated for seven retinal layers, in the fovea (region 1 of the 9 Early Treatment Diabetic Retinopathy Study [ETDRS] regions); in the pericentral ring (ETDRS regions 2 to 5); and the peripheral ring (ETDRS regions 6 to 9) following automated segmentation using the Iowa Reference Algorithm. In addition, mean peripapillary retinal nerve fiber layer (RNFL) thickness was measured. The partial correlation test was performed on each layer to determine the effect of age on layer thickness, while correcting for spherical equivalent, sex, and Topcon image quality factor as confounders, followed by Bonferroni corrections to adjust for multiple testing. RESULTS The thickness of the peripapillary RNFL (R = -0.332; P < 0.001); pericentral ganglion cell layer (R = -0.354, P < 0.001); peripheral inner plexiform layer (R = -0.328, P < 0.001); and foveal outer segment layer (R = -0.381, P < 0.001) decreased significantly with increasing age. Foveal RPE thickness (R = 0.467, P < 0.001) increased significantly with increasing age; other layers showed no significant differences with age. CONCLUSIONS Several macular layers and the peripapillary RNFL thickness showed significant changes correlated with age. This should be taken into consideration when analyzing macular layers and the peripapillary RNFL in SD-OCT studies of retinal diseases and glaucoma.

Retinal Structure and Function in Perinatally HIV-Infected and cART-Treated Children: A Matched Case-Control Study.

PURPOSE Subtle structural and functional neuroretinal changes have been described in human immunodeficiency virus (HIV)-infected adults without retinitis treated with combination antiretroviral therapy (cART). However, studies on this subject in HIV-infected children are scarce. This study aimed to assess the presence of (neuro)retinal functional and structural differences between a group of perinatally HIV-infected children on cART and age-, sex-, ethnicity-, and socioeconomically matched healthy controls. METHODS All participants underwent an extensive ophthalmological examination, including functional tests as well as optical coherence tomography, to measure individual retinal layer thicknesses. Multivariable mixed linear regression models were used to assess possible associations between HIV status (and other HIV-related parameters) and ocular parameters, while accounting for the inclusion of both eyes and several known confounders. RESULTS Thirty-three HIV-infected children (median age 13.7 years [interquartile range (IQR), 12.2-15.8], median CD4+ T-cell count 760 cells/mm3, 82% with an undetectable HIV viral load [VL]), and 36 controls (median age 12.1 years [IQR, 11.5-15.8]) were included. Contrast sensitivity (CS) was significantly lower in the HIV-infected group (1.74 vs. 1.76 logCS; P = 0.006). The patients had a significantly thinner foveal thickness (-11.2 μm, P = 0.012), which was associated with a higher peak HIV VL (-10.3 μm per log copy/mL, P = 0.016). CONCLUSIONS In this study, we found a decrease in foveal thickness in HIV-infected children, which was associated with a higher peak VL. Longitudinal studies are warranted to confirm our findings and to determine the course and clinical consequences of these foveal changes.

The Eye as a Window to the Brain: Neuroretinal Thickness Is Associated With Microstructural White Matter Injury in HIV-Infected Children

PURPOSE Despite combination antiretroviral therapy (cART), perinatal HIV-infection can cause decreased gray and white matter volume, microstructural white matter injury, and retinal structural abnormalities. As neuroretinal tissue is directly connected to the brain, these deficits may have a shared pathogenesis. We aimed to assess associations between neuroretinal thickness and cerebral injury in cART-treated perinatally HIV-infected children and healthy controls. METHODS This cross-sectional observational study included 29 cART-treated perinatally HIV-infected children and 35 matched healthy controls. All participants underwent 3.0 Tesla magnetic resonance imaging (MRI), determining gray and white matter volumes from T1-weighted sequences, and white matter diffusivity using diffusion tensor imaging (DTI). Regional individual and total neuroretinal layer thickness was quantified using spectral-domain optical coherence tomography. We explored associations between retinal and cerebral parameters using multivariable linear regression analysis. RESULTS In HIV-infected children, lower foveal and pericentral neuroretinal thickness was associated with damaged white matter microstructure, in terms of lower fractional anisotropy and higher mean and radial diffusivity. In healthy controls only, neuroretinal thickness was associated with gray and white matter volume. CONCLUSIONS Decreased neuroretinal thickness is associated with microstructural white matter injury, but not with lower cerebral volume in HIV-infected children. This suggests that HIV-induced retinal thinning and microstructural white matter injury may share a common pathogenesis, and longitudinal assessment of neuroretinal alterations in parallel with MRI and neuroinflammatory markers may further our insight into the pathogenesis of HIV-induced cerebral injury in children.

Inflammatory and Neuronal Biomarkers Associated With Retinal Thinning in Pediatric HIV

Purpose The pathophysiology of neuroretinal thinning in children with human immunodeficiency virus (HIV) is poorly understood. The current study aimed to assess whether neuroretinal thinning in clinically stable perinatally HIV-infected children was associated with biomarkers of immune activation, inflammation, and neuronal damage. Methods Inflammation-associated and neuronal damage markers were measured in blood and cerebrospinal fluid (CSF) of HIV-infected children aged 8 to 18 years. Using mixed-effects regression analyses, we assessed associations between these biomarkers and neuroretinal layer thickness, as measured with spectral-domain optical coherence tomography. Results Thirty-two HIV-infected children (median age 13.6 years, 50% male) were included. Blood plasma levels of interleukin-6, monocyte chemoattractant protein-1, and soluble intercellular adhesion molecule-1 were inversely correlated with foveal inner plexiform layer thickness (coef = -4.40, P < 0.001; coef = -9.67, P = 0.047; coef = -10.48, P = 0.042, respectively). Plasma interleukin-6 was inversely correlated with foveal ganglion cell layer thickness (coef = -2.49, P = 0.010). Total Tau levels in CSF were inversely correlated with outer nuclear layer and inner segments thickness (foveal: coef = -19.3, P = 0.029; pericentral: coef = -18.09, P = 0.006) and pericentral total retinal thickness (coef = -28.2, P = 0.017). Conclusions Neuroretinal thinning was associated with inflammation-associated and neuronal injury biomarkers in a cohort of antiretroviral therapy-treated perinatally HIV-infected children. These findings suggest that ongoing immune activation, inflammation, and neuronal injury occur in parallel with retinal thinning in pediatric HIV.