Outer Photoreceptor Research Articles

Large macular hole-Always a poor prognosis?

HintergrundAlter, präoperativer Visus und Makulaforamengröße gelten als prognostische Marker für das postoperative Ergebnis bei Patienten mit durchgreifendem Makulaforamen (MF).Ziel der ArbeitUm den postoperativen Verlauf nach i‑ILM Peeling (inverted-Flap ILM-Peeling) mit konventionellem ILM-Peeling (k-ILM) zu vergleichen, wurde eine retrospektive Beobachtungsstudie durchgeführt. Patienten mit i‑ILM Peeling hatten dabei präoperativ ein statistisch signifikant größeres Makulaforamen.Material und MethodenEs wurden 45 konsekutive Patienten mit durchgreifendem Makulaforamen (MF) in 2 Gruppen (i-ILM vs. k‑ILM) eingeteilt und auf Unterschiede im postoperativen Visus (BCVA) und der Netzhautmorphologie hin untersucht. Die Integrität der äußeren Netzhautschichten, äußere limitierende Membran (ELM), ellipsoide Zone (EZ) und äußere Photorezeptoraußensegmente (OS), wurde postoperativ mittels SD-OCT (Spectral-Domain-OCT) analysiert.ErgebnisseDie präoperative Apertur in der i‑ILM Gruppe war signifikant größer (i-ILM = 408,4 µm, SD = 157,5 µm; k‑ILM = 287,4 µm, SD = 104,9 µm; p = 0,01). Der Ausgangsvisus sowie der postoperative Visus nach 1 Monat waren in der Gruppe mit k‑ILM-Peeling signifikant besser (p = 0,03 und p = 0,001). Der postoperative Visus nach mindestens 6 Monaten zeigte keinen signifikanten Unterschied zwischen den beiden Gruppen (p = 0,24). Die ELM zeigte als erste der äußeren Netzhautschichten eine Re-Integrität in beiden Gruppen.SchlussfolgerungMithilfe der i‑ILM-Peeling-Technik erschien es in dieser konsekutiven Serie möglich zu sein, für Patienten mit großem durchgreifendem MF ein ähnliches postoperatives Visusergebnis zur erreichen wie für mittels k‑ILM-Peeling-Technik operierte Patienten mit kleinerem durchgreifendem MF.

Bilateral multiple serous retinal detachments after treatment with nivolumab: a case report

BackgroundImmune checkpoint inhibitors have recently been widely used for advanced cancers and are known to cause ocular complications. We herein report a case developing bilateral serous retinal detachments, without ocular inflammation, after starting nivolumab treatment.Case presentationA 73-year-old man was referred to our hospital, having become aware of metamorphopsia 2 months after starting nivolumab (anti-programmed cell death protein 1 monoclonal antibody) for malignant melanoma of the nasal cavity. The initial corrected visual acuity of the right eye was 20/20, and that of the left eye was 20/16. There were no inflammatory findings in the anterior segment or the vitreous. Vitelliform lesions were found in the macular area of both ocular fundi, consistent with serous retinal detachment and subretinal deposits. Swept source optical coherence tomography showed diffuse thickening of the outer photoreceptor segment and thickening of the choroid. Two months after the initial diagnosis, multiple vitelliform lesions were noted, and the fundus findings had worsened. Indocyanine green fluorescein angiography showed delayed inflow in the peripapillary and posterior pole regions in the early phase of imaging. Fundus autofluorescence showed hyperautofluorescence consistent with most of the vitelliform lesions on color fundus photography.ConclusionsNivolumab may have impaired the pumping and phagocytosis functions of retinal pigment epithelial cells, resulting in bilateral serous retinal detachments and thickening of the photoreceptor outer segment. This is the first case report, to our knowledge, describing multiple bilateral serous retinal detachments and outer segment thickening without inflammation in a patient treated with nivolumab.

Deregulation of neuro‐developmental genes and primary cilium cytoskeleton anomalies in iPSc‐derived retinal sheets from human syndromic ciliopathies

Modeling human developmental and degenerative diseases has been always logistically challenging in particular in the case of rare diseases where no exhaustive animal models are available. Generation of sustainable human disease models that allow in‐depth analysis of the molecular mechanism is one of the big challenges nowadays. Stem cell technology holds great potential in disease modeling and represents a new powerful tool for generating scalable and animal‐free models that can more accurately illustrate clinical phenotypes of complex human diseases. Ciliopathies are a group of heterogeneous genetic diseases affecting proteins involved in primary cilium structure and function. Syndromic ciliopathies have a broad spectrum of symptoms ranging from retinal degeneration to skeletal and neuro‐development anomalies, including polydactylism and mental retardation. Herein we describe the generation and molecular characterization of iPSC‐derived photoreceptor sheets from patients affected by ciliopathies. Photoreceptor sheets are characterized by a polarized, multi‐layered tissue expressing outer segment, connecting cilium, and nuclear photoreceptor markers. Ciliopathic photoreceptors displayed significant common alterations in the expression of hundreds of developmental genes. Moreover, they showed several anomalies in the formation and maintenance of cilia, the positioning of the mother centriole and the activation of a stress response to misfolded proteins. Furthermore, we observed genomic instabilities and accumulation of DNA damage in the photoreceptors progenitors of one of the patients. This study reveals how combining cell reprogramming and organogenesis technologies with nextgeneration sequencing enable the elucidation of molecular and cellular mechanisms involved in human ciliopathies. The same approach, combining photoreceptor sheet differentiation and wide genome expression profile could be applied to model many genetic, developmental and degenerative diseases affecting photoreceptors. These patient‐derived retinal sheets may be useful for elucidating the molecular mechanisms underlining these diseases, for drug screening of compounds with potential therapeutic effect and predicting drugs side effects.Support or Funding InformationStem Cell Network (SCN), Fondation de l’Hôpital Maisonneuve‐Rosemont (FHMR), Réseau de recherche en santé de la vision (RRSV), Université de Montréal (UdeM)

Yap1 is required for maintenance of adult RPE differentiation.

Nuclear YAP1 plays a critical role in regulation of stem cell proliferation, tissue regeneration, and organ size in many types of epithelia. Due to rapid turnover of most epithelial cell types, the cytoplasmic function of YAP1 in epithelial cells has not been well studied. The retinal pigment epithelium (RPE) is a highly polarized epithelial cell type maintained at a senescence state, and offers an ideal cell model to study the active role of YAP1 in maintenance of the adult epithelial phenotype. Here, we show that the cytoplasmic function of YAP1 is essential to maintain adult RPE differentiation. Knockout of Yap1 in the adult mouse RPE caused cell depolarization and tight junction breakdown, and led to inhibition of RPE65 expression, diminishment of RPE pigments, and retraction of microvilli and basal infoldings. These changes in RPE further prompted the loss of adjacent photoreceptor outer segments and photoreceptor death, which eventually led to decline of visual function in older mice between 6 and 12months of age. Furthermore, nuclear β-catenin and its activity were significantly increased in mutant RPE. These results suggest that YAP1 plays an important role in active inhibition of Wnt/β-catenin signaling, and is essential for downregulation of β-catenin nuclear activity and prevention of dedifferentiation of adult RPE.

Time course of bilateral microglial activation in a mouse model of laser-induced glaucoma

Microglial activation is associated with glaucoma. In the model of unilateral laser-induced ocular hypertension (OHT), the time point at which the inflammatory process peaks remains unknown. Different time points (1, 3, 5, 8, and 15 d) were compared to analyze signs of microglial activation both in OHT and contralateral eyes. In both eyes, microglial activation was detected in all retinal layers at all time points analyzed, including: i) increase in the cell number in the outer segment photoreceptor layer and plexiform layers (only in OHT eyes) from 3 d onward; ii) increase in soma size from 1 d onward; iii) retraction of the processes from 1 d in OHT eyes and 3 d in contralateral eyes; iv) increase in the area of the retina occupied by Iba-1+ cells in the nerve fiber layer/ganglion cell layer from 1 d onward; v) increase in the number of vertical processes from 1 d in contralateral eyes and 3 d in OHT eyes. In OHT eyes at 24 h and 15 d, most Iba-1+ cells were P2RY12+ and were down-regulated at 3 and 5 d. In both eyes, microglial activation was stronger at 3 and 5 d (inflammation peaked in this model). These time points could be useful to identify factors implicated in the inflammatory process.

Multistep peripherin-2/rds self-assembly drives membrane curvature for outer segment disk architecture and photoreceptor viability

Rod and cone photoreceptor outer segment (OS) structural integrity is essential for normal vision; disruptions contribute to a broad variety of retinal ciliopathies. OSs possess many hundreds of stacked membranous disks, which capture photons and scaffold the phototransduction cascade. Although the molecular basis of OS structure remains unresolved, recent studies suggest that the photoreceptor-specific tetraspanin, peripherin-2/rds (P/rds), may contribute to the highly curved rim domains at disk edges. Here, we demonstrate that tetrameric P/rds self-assembly is required for generating high-curvature membranes in cellulo, implicating the noncovalent tetramer as a minimal unit of function. P/rds activity was promoted by disulfide-mediated tetramer polymerization, which transformed localized regions of curvature into high-curvature tubules of extended lengths. Transmission electron microscopy visualization of P/rds purified from OS membranes revealed disulfide-linked tetramer chains up to 100 nm long, suggesting that chains maintain membrane curvature continuity over extended distances. We tested this idea in Xenopus laevis photoreceptors, and found that transgenic expression of nonchain-forming P/rds generated abundant high-curvature OS membranes, which were improperly but specifically organized as ectopic incisures and disk rims. These striking phenotypes demonstrate the importance of P/rds tetramer chain formation for the continuity of rim formation during disk morphogenesis. Overall, this study advances understanding of the normal structure and function of P/rds for OS architecture and biogenesis, and clarifies how pathogenic loss-of-function mutations in P/rds cause photoreceptor structural defects to trigger progressive retinal degenerations. It also introduces the possibility that other tetraspanins may generate or sense membrane curvature in support of diverse biological functions.

Comparison of Long-Term Automated Retinal Layer Segmentation Analysis of the Macula between Silicone Oil and Gas Tamponade after Vitrectomy for Rhegmatogenous Retinal Detachment

Purpose: To identify long-term changes in individual retinal layer thickness using automated retinal layer segmentation analysis on high-resolution spectral-domain optical coherence tomography (SD-OCT) scans of eyes with macula-off rhegmatogenous retinal detachment (RRD) treated with vitreoretinal surgery (VRS) and gas or silicone oil tamponade and having single-operation success. Methods: A total of 58 patients operated on by VRS for RRD and followed up for 12 months were imaged by SD-OCT. The patients with retinal diseases such as an epiretinal membrane or cystic macular edema in the operated and fellow eyes were excluded. The thicknesses of the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), photoreceptor layer, and retinal pigment epithelium were compared to those of the fellow eyes after the 12-month follow-up. Thickness changes in individual layers were quantitatively analyzed in the operated and fellow eyes and correlated with the type of tamponade used in the surgery. Results: Spectralis OCT automated segmentation software was used for the retinal layer analysis. There were 22 females and 36 males. Their mean age was 60.7 ± 11.2 years. The mean central macular thickness was 214.3 ± 29.5 µm in the operated and 229.7 ± 21.7 µm in the fellow eyes (p = 0.008). There was a statistically significant difference between the operated and the healthy fellow eyes in the following layers: the RNFL (p = 0.017), GCL (p = 0.02), INL (p = 0.005), and ONL (p = 0.008) in the central foveal area; the RNFL (p < 0.001), INL (p = 0.017), and ONL (p = 0.022) in the perifoveal ring; and the RNFL (p < 0.001), IPL (p = 0.042), INL (p = 0.001), and OPL (p = 0.001) in the peripheral ring. The logMAR best corrected visual acuities were 2.51 ± 0.68 and 2.69 ± 0.62 at baseline and 0.60 ± 0.38 and 0.50 ± 0.38 at month 12 in the silicone oil tamponade (n = 28) and the gas tamponade (n = 30) group (p = 0.52 and p = 0.21, respectively). The foveal GCL, OPL, and ONL and the perifoveal GCL and IPL were statistically significantly thinner in the silicone oil tamponade group (p = 0.01, p = 0.046, p = 0.024, p = 0.006, and p = 0.011, respectively). Conclusions: Significant changes were observed in the retinal layers after VRS for RRD. Individual retinal layers seem to be affected 1 year after VRS for RRD. The type of tamponade can influence the thickness of the retinal layers. The thickness of the retinal layers was significantly preserved in eyes treated with gas tamponade when compared to those treated with silicone oil tamponade in the long term. Further studies are needed to validate our results.

Non‐invasive, needle‐free drug delivery for treatment of retinal degeneration on Bardet‐Biedl syndrome

AbstractPurposeTo develop a non‐invasive drug delivery system based on superparamagnetic nanoparticles (NP) for the treatment of retinal degeneration on Bardet‐Biedl syndrome (BBS). The delivery system will be used to deliver two small molecules, valproic acid (VPA) and Guanabenz (GBZ).MethodsA mixture of two NP (one loaded with VPA and other with GBZ) was applied as eyedrops on 14‐days old mice with the use of a magnetic field. The treatment was assessed in both wild type and a mice model for BBS (Bbs12−/−). The effects of the treatment were evaluated 2 weeks post treatment at 1‐month‐old. Retinal structure and function were analysed using electroretinogram recordings (ERG), histology and transmission electron microscopy (TEM).ResultsIn vitro studies showed no important toxic effects in cell cultures for retinal pigmented epithelium (RPE1) and 661W (murine photoreceptor precursor) after treatment with unloaded NP. Scotopic and photopic ERG recordings showed no toxic effect of the NP on photoreceptor (PR) function. TEM analysis indicated the presence of the NP in the PR layer of the retina after eyedrop application. TEM images showed a decrease in Endoplasmic Reticulum (ER) dilatation. The treated group with loaded NP showed an increase in the thickness of the inner nuclear layer, outer nuclear layer, inner PR segment and outer PR segment.ConclusionsThese results highlight the potential for these NP for non‐invasive drug delivery to the retina. Both the presence of the NP and biological effect were shown in our mouse model. The VPA and GBZ combination has already shown decrease of cell death mediated by ER stress in the Bbs12−/− model. This is an unmet clinical need with no curative treatment for retinal ciliopathies. The possibility of delaying PR death would increase the therapeutic window of gene therapy potentially increasing its effectivity.

Ganglion cell layer thickening in well-controlled patients with type 1 diabetes: an early sign for diabetic retinopathy?

PurposeTo evaluate early changes in retinal layers using optical coherence tomography (OCT) in patients with long‐standing type 1 diabetes (DM1) receiving intensified insulin therapy.MethodsIn a cross‐sectional case–control study 150 patients with DM1 and 150 age‐ and sex‐matched healthy control participants underwent OCT imaging. Scans of both eyes were analysed for different layers (NFL, GCL (+IPL), INL, outer layer complex (OLC, including OPL, ONL and ELM) and photoreceptors (PR)) in all subfields of an ETDRS grid. All analyses were performed semi‐automatically using custom software by certified graders of the Vienna Reading Center. ANOVA models were used to compare the mean thickness of the layers between patients and controls.ResultsSix hundred eyes with 512 datapoints in 49 b‐scans in each OCT were analysed. Mean thickness in patients/controls was 31.35 μm/30.65 μm (NFL, p = 0.0347), 76.7 μm/73.15 μm (GCL, p ≤ 0.0001), 36.29 μm/37.13 μm (INL, p = 0.0116), 114.34 μm/112.02 μm (OLC, p < 0.0001) and 44.71 μm/44.69 μm (PR, p = 0.9401). When evaluating the ETDRS subfields separately for clinically meaningful hypotheses, a significant swelling of the GCL in patients could be found uniformly and a central swelling for the OLC, whereas the distribution of NFL and INL thickening suggests that their statistical significance was not clinically relevant.ConclusionThese preliminary results demonstrate that preclinical retinal changes in patients with long‐standing DM1 can be found by retinal layer evaluation. However, the changes are layer‐specific, with significant thickening of the GCL and less so of the OLC suggesting a role as an early sign for diffuse swelling and the evolution of DME even in well‐controlled diabetes.

Optical Coherence Tomography Findings After Childhood Lensectomy.

PurposeTo explore the impact of childhood lensectomy on posterior segment development.MethodsCross-sectional observational study at children's eye clinics at a tertiary referral center in London, UK. We included 45 children age 4 to 16 years with healthy eyes and 38 who had undergone lensectomy. We acquired posterior segment optical coherence tomography scans of both eyes. We used parametric and nonparametric tests in SPSS24 for the comparison of parameters between groups and within individuals; a P value less than 0.05 was considered significant. The main outcome measures were foveal pit depth and subfoveal choroidal thickness (CT). Secondary outcomes were inner and outer ring CT and photoreceptor layer parameters, macular and peripapillary retinal nerve fiber layer thickness.ResultsFoveal pit depth and subfoveal CT are significantly reduced in eyes that have undergone lensectomy compared with nonoperated eyes. Inner ring CT and outer ring CT are reduced. Foveal inner retinal layer thickness is increased. Mean inner retinal and outer nuclear layer thickness are not affected.ConclusionsChildhood lensectomy is associated with a reduction in developmental foveal pit deepening and lack of developmental thickening of the posterior choroid. Mechanical and optical disruption of foveal and subfoveal choroidal development may affect structural foveal development after childhood lensectomy.

The flicker Pupil Light Response (fPLR).

PurposeThe photoreceptor classes driving the flicker pupil light response (fPLR) to monochromatic sinusoidal temporal modulation are largely unknown. Here, we determine the photoreceptor inputs to the fPLR.MethodsThe 0.5-Hz fPLR was measured in healthy observers using a Maxwellian view (41° diameter) pupillometer at five narrowband wavelengths (short: 409 nm; intermediate: 462, 507, 530 nm; and long: 592 nm) over ∼10 log units of irradiance spanning scotopic to photopic levels (5.6 to 15.6 log quanta·cm−2·s−1; −6.9 to 3.6 log cd·m−2). The relative photoreceptor contributions to the fPLR were then derived from these amplitude-irradiance functions using a criterion fPLR.ResultsThe fPLR amplitude is small (≤ 3.9 ± 3.1%; mean ± SEM) below 8.0 log quanta·cm−2·s−1 then increases with retinal irradiance in accordance with a Hill function that asymptotes between 13.0 to 15.0 log quanta·cm−2·s−1 (wavelength dependent). The Hill slope is steepest for the intermediate wavelengths. Further increases in irradiance (>15.0 log quanta·cm−2·s−1) produce a distinct suppression of the fPLR for the intermediate wavelengths. The fPLR phase delay shows a linear decrease with increasing irradiance. The spectral sensitivity of the fPLR is dominated by inner retinal melanopsin ganglion cell and outer retinal rod photoreceptor inputs to the afferent pupil control pathway; the relative melanopsin : rhodopsin weighting decreases with the transition from photopic to scotopic lighting.ConclusionsThe fPLR can be used as a marker of melanopsin and rod interactions during the flicker stimulation and to quantify their contributions to the post-illumination pupil response (PIPR).Translational RelevanceThese irradiance and wavelength responses will be useful in standardizing the measurements of the fPLR using chromatic pupillometry.

Outer Retinal Layers' Thickness Changes in relation to Age and Choroidal Thickness in Normal Eyes.

Purpose To identify and correlate age-related changes in outer retinal layers' thickness and choroidal thickness (CT) in the normal eyes using spectral-domain optical coherence tomography (SD-OCT) and to investigate factors affecting these changes. Study Design Observational cross-sectional study. Subjects and Methods We studied 125 healthy Egyptians between 20 and 79 years old. Patients were divided into 3 groups: group 1 (20–40 years), group 2 (40–60 years), and group 3 (>60 years). All patients had full ophthalmic examination. SD-OCT was done to measure the 9 ETDRS macular grid sectors of retinal pigment epithelium and photoreceptor outer segment (RPE-OS), outer nuclear layer and photoreceptor inner segment (ONL-IS), and choroidal thickness (CT) (by enhanced depth imaging). Results RPE-OS was significantly thinner in group 3 than in the other 2 groups (central: P < 0.001). Moreover, the 3 groups were significantly different from each other regarding the CT (central: P < 0.001); significant thinning was noticed in the choroid with age. The 3 groups did not show significant difference concerning the ONL-IS thickness. RPE-OS and CT showed statistically significant negative correlation with age (central RPE-OS: r = −0 C.345, P < 0.001, and central CT: r = −0.725, P < 0.001) while ONL-IS showed statistically nonsignificant correlation with age (central ONL-IS: r = −0.08, P=0.376). Multiple regression analysis revealed that the most important determinant of central 1 mm RPE-OS thickness in this study was age (β = −0.087, P=0.010) rather than choroidal thinning (β = 0.001, P=0.879). Conclusion RPE-OS layer thickness shows significant thinning with increasing age, and with decrease in CT, however, age is the most determinant factor of this thinning.

Contributions of the Melanopsin-Expressing Ganglion Cells, Cones, and Rods to the Pupillary Light Response in Obstructive Sleep Apnea.

To investigate the impact of obstructive sleep apnea (OSA) on the contribution of inner and outer retinal photoreceptors to the pupillary light response (PLR). Ninety-three eyes from 27 patients with OSA and 25 healthy controls were tested. OSA severity was graded according to the apnea-hypopnea index. PLR was measured monocularly with an eye tracker in a Ganzfeld in response to 1-second blue (470 nm) and red (640 nm) flashes at -3, -2, -1, 0, 1, 2, and 2.4 log cd/m2. Peak pupil constriction amplitude, peak latency, and the postillumination pupil response were measured. The Cambridge Colour Test, standard automatic perimetry, spectral domain optical coherence tomography, polysomnography, and the Pittsburgh Sleep Quality Index were used. OSA patients have a significantly decreased peak pupil constriction amplitude for blue stimuli at -3, -2, -1, 1 log cd/m2 and at all red flash luminances (P < 0.050), revealing reduction of outer retina contributions to PLR. OSA patients showed reduced peak latency for blue (-2, 0, 2, 2.4 log cd/m2) and red stimuli (-2, 0 log cd/m2; P < 0.040). No significant difference was found in the melanopsin-mediated PLR. This study is the first to evaluate the inner and outer retinal contributions to PLR in OSA patients. The results showed that the outer retinal photoreceptor contributions to PLR were affected in moderate and severe OSA patients. In contrast, the inner retina contributions to PLR are preserved.

Role of TGF-Beta1/SMAD2/3 Pathway in Retinal Outer Deep Vascular Plexus and Photoreceptor Damage in Rat 50/10 Oxygen-Induced Retinopathy.

In retinopathy of prematurity (ROP), outer deep vascular plexus (oDVP) was the emerging field, and the mechanisms of photoreceptor dysfunction remained to be explored. ODVP and photoreceptors were related, with oDVP being part of the supplier of oxygen and nutrients to photoreceptors, while their possible relationship in ROP was not clear. TGF-beta1 has been reported indispensable in oDVP development and altered in ROP patients and animal models. We hypothesized that the TGF-beta1 alteration in rat 50/10 oxygen-induced retinopathy (OIR) model contributed to oDVP malformation and exerted consequent effects on photoreceptor development. We first explored the profile of oDVP development in rat after birth and compared the expression of TGF-beta1 and pSMAD2/3 in Normoxia and OIR groups. Afterwards, the inhibitor of the pathway, LY364947, was used to establish the OIR, OIR+LY364947, Normoxia, and Normoxia+LY364947 groups. The oDVP and photoreceptor were examined by Isolectin B4 staining, western-blot of CD31 and Rho, and electron microscopy. ODVP sprouted at postnatal day 10 (D10) and reached the edge of retina at D14. The TGF-beta1/SMAD2/3 pathway was compromised during the critical period of oDVP development. The inhibitor simulated the oDVP retardation, pericyte, and photoreceptor malformation in the Normoxia+LY364947 group and might further compromise the development of oDVP and photoreceptor in the OIR+LY364947 group. The inhibition of the TGF-beta1/SMAD2/3 pathway indicated its critical role in oDVP malformation and photoreceptor damage, suggesting a possible therapeutic target of ROP treatment.

Melanopsin and Cone Photoreceptor Inputs to the Afferent Pupil Light Response.

Background: Retinal photoreceptors provide the main stage in the mammalian eye for regulating the retinal illumination through changes in pupil diameter, with a small population of melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) forming the primary afferent pathway for this response. The purpose of this study is to determine how melanopsin interacts with the three cone photoreceptor classes in the human eye to modulate the light-adapted pupil response.Methods: We investigated the independent and combined contributions of the inner and outer retinal photoreceptor inputs to the afferent pupil pathway in participants with trichromatic color vision using a method to independently control the excitations of ipRGCs, cones and rods in the retina.Results: We show that melanopsin-directed stimuli cause a transient pupil constriction generated by cones in the shadow of retinal blood vessels; desensitizing these penumbral cone signals uncovers a signature melanopsin pupil response that includes a longer latency (292 ms) and slower time (4.1x) and velocity (7.7x) to constriction than for cone-directed stimuli, and which remains sustained post-stimulus offset. Compared to melanopsin-mediated pupil responses, the cone photoreceptor-initiated pupil responses are more transient with faster constriction latencies, higher velocities and a secondary constriction at light offset. The combined pupil responses reveal that melanopsin signals are additive with the cone signals.Conclusions: The visual system uses the L–, M–, and S–cone photoreceptor inputs to the afferent pupil pathway to accomplish the tonic modulations of pupil size to changes in image contrast. The inner retinal melanopsin-expressing ipRGCs mediate the longer-term, sustained pupil constriction to set the light-adapted pupil diameter during extended light exposures.

Melanopsin driven enhancement of cone-mediated visual processing

The precise control of visual sensitivity to variations in external lighting is critical for optimising human visual function in a changing environment. In photopic illumination, the cone photoreceptors and their post-receptoral pathways have a primary role in regulating these adjustments; it is not fully understood how a small population of melanopsin-expressing, intrinsically photosensitive retinal ganglion cells (ipRGCs) can interact with the three cone photoreceptor classes to modulate human visual function. Here we investigated interactions between these inner and outer retinal photoreceptor classes in participants with trichromatic colour vision under conditions that independently controlled the excitations of ipRGCs, cones and rods in the retina. In the peripheral retina, we show that interaction between melanopsin- and cone-directed signals affect conscious, image-forming vision. The interaction patterns are inconsistent with any potential effects arising from artefacts due to open-field and penumbral-cone contrasts, or rod intrusion. For cone signals mediated via each of the three primary visual pathways, melanopsin activation enhances contrast sensitivity. The contrast response functions indicate this enhancement is a more generalised facilitation effect that onsets at ∼9% melanopsin contrast. The implication for human vision is that the contrast sensitivity of cone-mediated visual processes can be modulated by the level of melanopsin excitation in the stimulus light.

Outer Retinal Structure and Function Deficits Contribute to Circadian Disruption in Patients With Type 2 Diabetes.

Light transmitted by retinal photoreceptors provides the input for circadian photoentrainment. In diabetes, there is a high prevalence of circadian and sleep disruption but the underlying causes are not well understood. Patients with diabetes can exhibit dysfunctional photoreceptors but their role in circadian health is not known. Here we quantify photoreceptor function and contributions to circadian health and sleep in patients with diabetes without diabetic retinopathy and healthy controls. Rod, cone, and melanopsin function was derived using chromatic pupillometry in 47 participants including 23 patients with type 2 diabetes and 24 age-matched healthy controls after an ophthalmic examination including retinal thickness assessment using optical coherence tomography. Circadian health was determined using dim light melatonin onset (DLMO) and sleep questionnaires; light exposure was measured using actigraphy. Compared with the control group, the patients with diabetes had a significantly earlier DLMO (1 hour) (P = 0.008), higher subjective sleep scores (P < 0.05), a reduction in pupil constriction amplitude for red stimuli (P = 0.039) and for the early postillumination pupil response (PIPR) for blue (P = 0.024) stimuli. There were no between-group differences in the light exposure pattern, activity levels, and intrinsic melanopsin-mediated PIPR amplitude (P > 0.05). A significant correlation was evident between outer retinal thickness and DLMO (r = -0.65, P = 0.03) and the pupil constriction amplitude (r = 0.63, P = 0.03); patients with thinner retina had earlier DLMO and lower pupil amplitudes. We infer that the observed changes in circadian function in patients with no diabetic retinopathy are due to structural and functional outer retinal rod photoreceptor deficits at early stage of diabetic eye disease.

Retinal structural-vascular-functional relationship using optical coherence tomography and optical coherence tomography \u2013 angiography in myopia

BackgroundTo examine the retinal structure–vascular-function relationship using optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) in myopia.MethodsThis was a prospective cross-sectional study comprising 86 eyes of 45 individuals with varying axial lengths and spherical equivalents and no posterior segment abnormalities. All eyes underwent optical coherence tomography with the Spectralis SD-OCT and OCTA with RTVue-XR Avanti; Optovue. Individual macular retinal layer thicknesses and flow areas and vessel densities were measured on OCT and OCTA, respectively. Linear correlations were made between the macular layer thicknesses, flow areas and vessel densities with axial length, spherical equivalent and visual acuity.ResultsThe participants’ mean ages were 33.34 ± 14.45 years, mean spherical equivalent refractions were − 7.17 ± 5.71 D and axial lengths were 25.95 ± 2.41 mm. There were significant positive correlations of foveal angle (r = 0.757, p = 0.001), inner retinal (r = 0.764, p = 0.001) and outer plexiform layer (r = 0.771, p = 0.001) thickness on OCT and vessel densities in deep capillary plexus (r = 0.313, p = 0.003) on OCTA with axial length and negative correlations with spherical equivalents and visual acuity. Significant negative correlations of outer nuclear layer (r = − 0.560, p = 0.03) and photoreceptor outer segment layer thickness (r = − 0.856, p < 0.001) were noted on OCT with axial length and positive correlations with spherical equivalents and visual acuity.ConclusionThe lateral retinal stretching in myopia could possibly explain the correlation between retinal layer thickness, vascular density and visual acuity in these eyes. Further research is required to investigate this.

Quantitative Assessment of Outer Retinal Layer and Photoreceptor Outer Segment Layer and Their Relation to Visual Acuity in Diabetic Macular Edema.

Purpose To compare outer retinal layer (ORL) thickness and photoreceptor outer segment (PROS) length between normal eyes and eyes with diabetic macular edema (DME), and also, to study the correlation between central macular thicknesses (CMT), ORL, and PROS length with best corrected visual acuity (BCVA) in DME. Methods 80 eyes were included in the study; they were divided into two groups, group Ι (40 normal eyes) and group ΙΙ (40 eyes) with DME. Complete ophthalmic examination and OCT were done for all eyes. Comparison between ORL and PROS was done between both groups; also, correlation between ORL thickness, PROS length, and CMT with BCVA in group ΙΙ was studied. Results CMT was greater in group ΙΙ than group Ι (392.70 ± 62.91 and 265.73 ± 17.17, respectively) (SS, p < 0.001). ORL thickness was statistically significantly greater in group Ι than group ΙΙ (104.80 ± 4.94, 93.68 ± 6.34, p < 0.001). Regarding PROS length, it was statistically significantly greater in group Ι than group ΙΙ (31.38 ± 3.4 and 26.65 ± 3.39, respectively, p < 0.001). There was moderate correlation between BCVA and ORL thickness (r = −0.440, p=0.004) and strong correlation between BCVA and PROS length in group ΙΙ (r = − 0.690, p < 0.001), while there was weak correlation between BCVA and CMT (r = 0.198, p=0.220). Conclusion Both ORL thickness and PROS length were greater in healthy normal eyes than eyes with DME. BCVA was correlated better with PROS length and ORL thickness than CMT.

Chromatic Pupillometry Methods for Assessing Photoreceptor Health in Retinal and Optic Nerve Diseases.

The pupillary light reflex is mediated by melanopsin-containing intrinsically-photosensitive retinal ganglion cells (ipRGCs), which also receive input from rods and cones. Melanopsin-dependent pupillary light responses are short-wavelength sensitive, have a higher threshold of activation, and are much slower to activate and de-activate compared with rod/cone-mediated responses. Given that rod/cone photoreceptors and melanopsin differ in their response properties, light stimuli can be designed to stimulate preferentially each of the different photoreceptor types, providing a read-out of their function. This has given rise to chromatic pupillometry methods that aim to assess the health of outer retinal photoreceptors and ipRGCs by measuring pupillary responses to blue or red light stimuli. Here, we review different types of chromatic pupillometry protocols that have been tested in patients with retinal or optic nerve disease, including approaches that use short-duration light exposures or continuous exposure to light. Across different protocols, patients with outer retinal disease (e.g., retinitis pigmentosa or Leber congenital amaurosis) show reduced or absent pupillary responses to dim blue-light stimuli used to assess rod function, and reduced responses to moderately-bright red-light stimuli used to assess cone function. By comparison, patients with optic nerve disease (e.g., glaucoma or ischemic optic neuropathy, but not mitochondrial disease) show impaired pupillary responses during continuous exposure to bright blue-light stimuli, and a reduced post-illumination pupillary response after light offset, used to assess melanopsin function. These proof-of-concept studies demonstrate that chromatic pupillometry methods can be used to assess damage to rod/cone photoreceptors and ipRGCs. In future studies, it will be important to determine whether chromatic pupillometry methods can be used for screening and early detection of retinal and optic nerve diseases. Such methods may also prove useful for objectively evaluating the degree of recovery to ipRGC function in blind patients who undergo gene therapy or other treatments to restore vision.