Cone photoreceptor recovery after experimental detachment and reattachment: an immunocytochemical, morphological, and electrophysiological study

Histological changes in retinal detachment: A systematic review for the clinician

Although there have been numerous innovations in the management of retinal detachment (RD) over the past decades, there is still limited understanding of the pathophysiological processes that take place before and after repair. Summarizing key concepts using animal studies may allow for a better assessment of common pre- and postoperative microstructural abnormalities in RD. We performed a systematic literature review on Ovid MEDLINE, EMBASE, and Cochrane Controlled Register of Trials from January 1968 to January 2022, searching animal or human studies reporting retinal histologic changes following primary or induced RD. Thirty-two studies were included. Main cellular events were summarized: photoceptor apoptosis occurs as early as 12 hours after RD and, although most cells survive, there is extensive remodeling. Outer segments progressively degenerate, while inner segments are reorganized. Rod and cone opsins are redistributed, and rod axons retract while cones undergo changes in shape. Second- and third-order neurons rearrange their dendritic processes, and Müller cells become hypertrophic, growing into the subretinal space. Finally, retinal pigment epithelium cells undergo a change in their morphology. Acknowledging critical morphologic changes following RD is crucial in understanding why anatomical and functional outcomes can vary. Insights from histological studies, together with high-resolution imaging, may be key in identifying novel biomarkers in RD.

The quantitative evaluation of retinal layers after resolution of subretinal fluid in acute central serous chorioretinopathy

PURPOSE

To evaluate the average retinal layer thicknesses in eyes with unilateral acute central serous chorioretinopathy (CSC) (with subretinal fluid (SRF)) and after complete resolution of SRF in these eyes and to compare the results with those obtained in healthy eyes.

METHODS

Fifty-four eyes of 27 patients with unilateral acute CSC (CSC in active phase) who had complete resolution of SRF and 25 eyes of 25 healthy control subjects enrolled in this retrospective study. The average thicknesses of the retinal layers were measured by segmentation analysis of optical coherence tomography at baseline and 6 months after complete resolution of SRF.

RESULTS

The mean outer nuclear layer (ONL) thickness was significantly lower in eyes with CSC than in fellow eyes (p < 0.001). The mean ONL thickness was increased after resolution of SRF, but still low compared to unaffected fellow eye and the increment was not statistically significant (p > 0.05). There were significant strong inverse correlations between visual acuity and ONL thicknesses at baseline and 6 months after complete resolution of SRF (p < 0.001, r = - 0.810; p < 0.001, r = - 0.705, respectively).

CONCLUSION

ONL thickness was thinned in cases with acute CSC, and although there was some increment in ONL thickness 6 months after complete resolution of SRF, it was still thinner compared to unaffected fellow eyes.

Reflectance adaptive optics findings in a patient with Vogt-Koyanagi-Harada disease

Purpose

To describe the reflectance adaptive optics scanning laser ophthalmoscopy (AOSLO) findings in different stages of Vogt-Koyanagi-Harada (VKH) disease and correlate them to visual gain post treatment. Confocal (cAOSLO) and non-confocal split-detector AOSLO (sdAOSLO) were used to assess longitudinally the status of the photoreceptors in a patient with VKH managed on corticosteroid and immunomodulatory therapy.

Observation

A 32-year-old Japanese American female presented with a 2-week history of blurred vision in both eyes (OU) and worsening headache previously diagnosed as a case of VKH and treated with high dose oral prednisone. At the time of presentation, though vision was improving, and frank serous retinal detachments were absent, spectral domain optical coherence tomography (SD-OCT) showed presence of residual subretinal fluid with disruption of the photoreceptor inner segments and outer segments (IS/OS) involving OU. The photoreceptor mosaic at the foveal center appeared very sparse with large areas devoid of visible photoreceptors on cAOSLO, in agreement with the SD-OCT data. sdAOSLO imaging over the same location shows a higher number of contiguous photoreceptors. After imaging, the patient was started on mycophenolate mofetil as steroid-sparing long-term therapy. Three months later, visual acuity improved to 20/20 OU, and SD-OCT showed almost complete resolution of subretinal fluid with significant improvement of the IS/OS SD-OCT signal, OU. cAOSLO imaging revealed a contiguous photoreceptor mosaic without gaps and of normal appearance.

Conclusions and Importance

VKH patients may demonstrate transient photoreceptor abnormalities on SD-OCT and cAOSLO imaging. sdAOSLO imaging revealed intact photoreceptor segments in areas that appeared as voids on cAOSLO, which later showed structural recovery on SD-OCT and cAOSLO. Therefore, sdAOSLO may predict potential for improvement in patients wherein there appears to be photoreceptor loss in cAOSLO and/or SD-OCT.

The Relationship Between Choroidal and Photoreceptor Layer Thickness With Visual Acuity in Highly Myopic Eyes

Purpose

The aim of this study was to evaluate the choroidal and photoreceptor thickness in highly myopic eyes and its correlation with visual acuity.

Methods

This is a cross-sectional, observational study involving 57 eyes of 57 highly myopic subjects [spherical equivalent ≥ –6 diopters (D) or axial length ≥ 26 mm] seen in a tertiary institutional center. Eyes with any clinical evidence of maculopathy or amblyopia were excluded. All subjects underwent a refraction assessment, visual acuity, axial length measurement using the IOL Master, and full ocular assessment. Eyes were imaged using Spectralis Optical Coherence Tomography by one experienced operator. Two independent investigators manually measured subfoveal choroidal thickness (SFCT) and foveal photoreceptor thickness (FPT).

Results

The mean SFCT was 195.88 ± 87.63 μm (range: 32–373) and mean FPT was 96.68 ± 11.23 μm (range: 67–100), after correction for ocular magnification. The best corrected visual acuity (BCVA) in LogMAR was negatively correlated with SFCT (r = –0.510, p = 0.001) and FPT (r = –0.397, p = 0.002) and positively correlated with age (r = 0.418, p = 0.001) and axial length (r = 0.551, p = 0.001). Multiple linear regression analysis showed that age, axial length, and corrected FPT were significant risk factors for poorer BCVA (p = 0.021, &lt; 0.001, and 0.02, respectively).

Conclusion

FPT, age, and axial length are significant moderate predictive factors for poorer visual acuity in highly myopic eyes without myopic maculopathy. Thinner SFCT does not translate into poorer vision.

Factors Associated With the Presence of Foveal Bulge in Eyes With Resolved Diabetic Macular Edema

Purpose: To evaluate factors associated with the presence of foveal bulge (FB) in resolved diabetic macular edema (DME) eyes.

Methods: A total of 165 eyes with complete integrity of ellipsoid zone (EZ) at the fovea and resolved DME were divided into two groups according to the presence of FB at 6 months after intravitreal injection of ranibizumab treatment. Best-corrected visual acuity (BCVA), central foveal thickness (CFT), outer nuclear layer (ONL) thickness, height of serous retinal detachment (SRD) and non-SRD, and inner segment (IS) and outer segment (OS) lengths of the two groups were measured and compared at baseline and each follow-up. The correlations between the presence of FB and pre- and post-treatment factors were determined by logistic regression analysis.

Results: At baseline, BCVA was significantly better, and CFT and incidence and height of SRD were significantly lower in the FB (+) group (all P < 0.05). At 6 months, FB was present in 65 (39.39%) eyes. Post-treatment BCVA was significantly better and OS length was significantly longer in the FB (+) group at 6 months (all P < 0.05). Multivariate analysis identified younger age, better BCVA, and lower CFT before treatment as significant predictors of the existence of FB at 6 months (all P < 0.05). At 6 months, better BCVA and longer OS length were significantly correlated with the existence of FB (all P < 0.05).

Conclusions: Factors associated with the presence of FB after the resolution of DME include younger age, better baseline BCVA and lower baseline CFT, and better post-treatment BCVA and longer post-treatment OS length.

Differential Effects of Experimental Retinal Detachment on S- and M/L-Cones in Rats

Retinal detachment is a vision-threatening condition, which occurs when the neurosensory retina is separated from its blood supply. The main purpose of this study was to examine the effect of experimental retinal detachment in rats on cone photoreceptors. Retinal detachment was induced in the eyes of rats via subretinal injection of sodium hyaluronate. Experimental detachment caused a rapid, sustained loss of short (S)- and medium/long (M/L)-wavelength cone opsins. Importantly, S-opsin⁺ cones were affected earlier than M/L-opsin⁺ cones and were affected to a greater extent than M/L-opsin⁺ cones throughout the duration of detachment. In comparison, to cone opsins, reductions in other cone markers-peanut agglutinin PNA and cone arrestin-were substantially less marked. These data suggest that loss of cone opsins does not reflect cone degeneration and may rather indicate prolonged downregulation of specific proteins in affected cones. This conclusion is supported by the lack of TUNEL⁺- cone arrestin⁺ double-labelled cells at the time point of greatest rod photoreceptor cell death, together with the partial recovery of cone arrestin⁺ cell numbers over time. Analysis of retinas that had naturally re-attached reinforced the deduction that few cones die following detachment, but also highlighted that prolonged detachment leads to deconstruction of cone segments that may not be readily reversible. Survival and functional recovery of cones following surgery for retinal detachment is vital for successful recovery of vision. The data suggest that experimental detachment in rats may offer a useful approach to model the response of S-cones to retinal detachment in humans.

Retinal electrophysiological changes related to early versus late silicone oil removal

PURPOSE

To compare between the effect of early (3 months) and late (6 months) silicone removal on the electroretinogram records.

METHODS

Thirty-four eyes with complex primary rhegmatogenous macula off retinal detachment undergone vitrectomy. Silicone oil was removed after 3 months in group I and after 6 months in group II. Scotopic and photopic ERGs, pattern electroretinogram (PERG) and multifocal ERG (mfERG) and best-corrected visual acuity (BCVA) were recorded for all eyes RESULTS: Preoperative mean best corrected visual acuity (BCVA) measured was 0.93 ± 0.05 in group I and 0.9 ± 0.08 in group II. One month after silicone removal, mean BCVA was 0.20 ± 0.04 and 0.18 ± 0.02 in groups I and II respectively. Before silicone oil removal the electroretinographic a- and b-waves were greatly reduced in both groups with no significant difference between them. One month after removal of silicone oil, the electroretinographic a- and b-waves increased in both groups with no significant difference between the two groups (p = 0.46 and 0.23 respectively).

CONCLUSION

The amplitudes of the ERGs increase after removal of silicone oil tamponade with no difference between early (3 months) and late (6 months) removal.

MULTIFOCAL ELECTRORETINOGRAPHY AND SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY IN MACULA-OFF RHEGMATOGENOUS RETINAL DETACHMENT: A Prospective Cohort Study

PURPOSE

To analyze the temporal trends in structural changes using spectral-domain optical coherence tomography and functional changes using multifocal electroretinogram after rhegmatogenous retinal detachment surgery.

METHODS

This prospective cohort study enrolled 69 patients with macula-off rhegmatogenous retinal detachment who underwent successful surgery. Early Treatment Diabetic Retinopathy Study visual acuity, multifocal electroretinogram evaluation of the central 5°, and spectral-domain optical coherence tomography were recorded at 1, 3, 6, and 12 months (M) after surgery. The fellow eye served as the control group for multifocal electroretinogram parameters.

RESULTS

Between M1 and M12, visual acuity improved from 64 to 75 letters (P = 0.001) and implicit time of N1 decreased from 27.8 to 25.2 milliseconds (P = 0.001), whereas the other parameters did not vary significantly. Amplitude and implicit time values did not reach normal values at M12. Alterations of the ellipsoid zone and the external limiting membrane decreased over time (P = 0.001). P1 implicit time correlated independently with the alteration of the external limiting membrane (P = 0.007).

CONCLUSION

Foveal wave amplitudes remain lower than normal values after successful surgery of rhegmatogenous retinal detachment, whereas anatomical improvement was found for outer retinal abnormalities and subretinal edema fluid. Retinal recovery improves N1 implicit time over time. Disruption of external limiting membrane seems to be predictive of increased P1 implicit time.

Clinical Perspective: Treating RPE65-Associated Retinal Dystrophy

Until recently, there was no approved treatment for a retinal degenerative disease. Subretinal injection of a recombinant adeno-associated virus (AAV) delivering the normal copy of the human RPE65 cDNA led to reversal of blindness first in animal models and then in humans. This led to the first US Food and Drug Administration (FDA)-approved gene therapy product for a genetic disease, voretigene neparvovec-rzyl (Luxturna). Luxturna was then approved by the European Medicines Association and is now available in the US through Spark Therapeutics and worldwide through Novartis. Not only has treatment with Luxturna changed the lives of people previously destined to live a life of blindness, but it has fueled interest in developing additional gene therapy reagents targeting numerous other genetic forms of inherited retinal disease. This review describes many of the considerations for administration of Luxturna and describes how lessons from experience with Luxturna could lead to additional gene-based treatments of blindness.

Effects of different tamponade materials on macular segmentation after retinal detachment repair

PURPOSE

This study used spectral domain-optical coherence tomography (SD-OCT) to evaluate individual retinal layer thickness in eyes with macula-off rhegmatogenous retinal detachment (RRD) treated with silicone oil (SiO) or gas endotamponades.

STUDY DESIGN

This was a retrospective, interventional, comparative study.

METHODS

The study included 86 eyes of 43 patients who were divided into 3 groups according to endotamponades: SiO, perfluoropropane (C3F8), and sulfur hexafluoride (SF6). The affected eyes were compared with the fellow eyes of the same patient via SD-OCT automated segmentation analysis. Patients with a follow-up of at least 6 months were included in the final analysis. Macular segmentation including 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), retinal pigment epithelium (RPE), inner retinal layers (IRLs), and outer retinal layers (ORLs) was analyzed.

RESULTS

In the SiO group, the mean thickness of each retinal layer including the RNFL, GCL, IPL, ONL, and IRLs within a 1-mm ETDRS subfield of the affected eyes was significantly lower than that of the fellow eyes (P = 0.036, P = 0.028, P = 0.003, P < 0.001, P = 0.013, respectively). There was no significant difference in the C3F8 and SF6 groups (all P > 0.05). The difference between the ONL and IRLs in the SiO-treated eyes differed significantly from that of the gas groups (P = 0.001 and P = 0.045, respectively) The difference in the GCL thickness of the affected eyes and healthy eyes showed a significant correlation with postoperative BCVA changes in the SiO, C3F8, and SF6 groups (P = 0.041, P = 0.048, and P = 0.045, respectively).

CONCLUSION

The findings of our study show that endotamponades used in RRD surgery may have different effects on retinal layers. In addition, SiO may cause undesirable effects on the retinal layers.

Electroretinogram of the Cone-Dominant Thirteen-Lined Ground Squirrel during Euthermia and Hibernation in Comparison with the Rod-Dominant Brown Norway Rat

Purpose

The majority of small animal species used in research are nocturnal, with retinae that are anatomically and functionally dissimilar from humans, complicating their use as disease models. Herein we characterize the retinal structure and electrophysiological function of the diurnal, cone-dominant 13-lined ground squirrel (13-LGS) retina during euthermia and in hibernation.

Methods

Full-field electroretinography (ERG) was performed in 13-LGS and Brown Norway (BN) rat models to establish baseline values for retinal function in each species, including following intravitreal injection of pharmacologic agents to selectively block the contributions of ON- and OFF-bipolar cells. The effect of hibernation-associated retinal remodeling on electrophysiological function was assessed in 13-LGS during torpor and emergence, with correlative histology performed using transmission electron microscopy.

Results

Under light-adapted conditions, the a-, b-, and d-wave amplitude of the 13-LGS was significantly greater than that of the BN rat. Retinal function was absent in the 13-LGS during hibernation and correlated to widespread disruption of photoreceptor and RPE structure. Remarkably, both retinal function and structure recovered rapidly on emergence from hibernation, with ERG responses reaching normal amplitude within 6 hours.

Conclusions

ERG responses for both BN rats and 13-LGS reflect the relative proportions of cone photoreceptors present within the retinae, indicating that the cone-dominant 13-LGS may be a potentially useful model for studying human central retinal function and disease. That retinal remodeling and restoration of electrophysiological function occurs rapidly on emergence from hibernation implies the 13-LGS may also be a useful tool for studying aspects of retinal physiology and recovery from injury.

Pemafibrate Protects Against Retinal Dysfunction in a Murine Model of Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the leading causes of blindness globally. Retinal neuronal abnormalities occur in the early stage in DR. Therefore, maintaining retinal neuronal activity in DR may prevent vision loss. Previously, pemafibrate, a novel selective peroxisome proliferator-activated receptor alpha modulator, was suggested as a promising drug in hypertriglyceridemia. However, the role of pemafibrate remains obscure in DR. Therefore, we aimed to unravel systemic and retinal changes by pemafibrate in diabetes. Adult mice were intraperitoneally injected with streptozotocin (STZ) to induce diabetes. After STZ injection, diet supplemented with pemafibrate was given to STZ-induced diabetic mice for 12 weeks. During the experiment period, body weight and blood glucose levels were examined. Electroretinography was performed to check the retinal neural function. After sacrifice, the retina, liver, and blood samples were subjected to molecular analyses. We found pemafibrate mildly improved blood glucose level as well as lipid metabolism, boosted liver function, increased serum fibroblast growth factor21 level, restored retinal functional deficits, and increased retinal synaptophysin protein expression in STZ-induced diabetic mice. Our present data suggest a promising pemafibrate therapy for the prevention of early DR by improving systemic metabolism and protecting retinal function.

Ground squirrel - A cool model for a bright vision

The great evolutionary biologist, Theodosius Dobzhansky, once said, "Nothing in biology makes sense except in the light of evolution." Vision, no doubt, is a poster child for the work of evolution. If it has not already been said, I would humbly add that "Nothing in biology makes sense except in the context of metabolism." Marrying these two thoughts together, when one chooses an animal model for vision research, the ground squirrel jumps out immediately for its unique cone dominant retina, which has evolved for its diurnal lifestyle, and for hibernation-an adaptation to unique metabolic challenges encountered during its winter sojourn.

Macular Ganglion Cell Layer Thickness after Macula-Off Rhegmatogenous Retinal Detachment Repair: Scleral Buckling versus Pars Plana Vitrectomy

(1) Background: We evaluated macular ganglion cell layer–inner plexiform layer (GCL-IPL) thickness in patients with primary macula-off rhegmatogenous retinal detachment (RRD) treated with scleral buckling (SB) or pars plana vitrectomy (PPV) using spectral domain optical coherence tomography (SD-OCT). (2) Methods: In this retrospective, observational study, we reviewed the medical records of patients undergoing SB or PPV surgery for macula-off RRD. SD-OCT was performed at three and 12 months after surgery. The central and parafoveal GCL-IPL thicknesses in treated eyes were compared with those of healthy fellow eyes. OCT measurements between the SB and PPV group were also compared using the analysis of covariance. (3) Results: Seventy-one eyes of 71 patients with a mean age of 61.2 ± 11.7 years were included. The parafoveal GCL-IPL thickness of the PPV group was significantly reduced, with respect to fellow eyes, at three and 12 months (p < 0.01). After adjusting for age, axial length, spherical equivalent, RD extent, preoperative intraretinal cysts, duration of symptoms and postoperative IOP, the parafoveal GCL-IPL thickness in the PPV group was significantly reduced with respect to the SB group, both at three and 12 months (F = 11.45, p = 0.001 and F = 12.37, p = 0.001, respectively). (4) Conclusions: In conclusion, the GCL-IPL is reduced in thickness in eyes with macula-off RRD treated with vitrectomy and is significantly thinner compared to eyes undergoing scleral buckling surgery.

Disruption in murine Eml1 perturbs retinal lamination during early development

During mammalian development, establishing functional neural networks in stratified tissues of the mammalian central nervous system depends upon the proper migration and positioning of neurons, a process known as lamination. In particular, the pseudostratified neuroepithelia of the retina and cerebrocortical ventricular zones provide a platform for progenitor cell proliferation and migration. Lamination defects in these tissues lead to mispositioned neurons, disrupted neuronal connections, and abnormal function. The molecular mechanisms necessary for proper lamination in these tissues are incompletely understood. Here, we identified a nonsense mutation in the Eml1 gene in a novel murine model, tvrm360, displaying subcortical heterotopia, hydrocephalus and disorganization of retinal architecture. In the retina, Eml1 disruption caused abnormal positioning of photoreceptor cell nuclei early in development. Upon maturation, these ectopic photoreceptors possessed cilia and formed synapses but failed to produce robust outer segments, implying a late defect in photoreceptor differentiation secondary to mislocalization. In addition, abnormal positioning of Müller cell bodies and bipolar cells was evident throughout the inner neuroblastic layer. Basal displacement of mitotic nuclei in the retinal neuroepithelium was observed in tvrm360 mice at postnatal day 0. The abnormal positioning of retinal progenitor cells at birth and ectopic presence of photoreceptors and secondary neurons upon maturation suggest that EML1 functions early in eye development and is crucial for proper retinal lamination during cellular proliferation and development.

Restoration of Foveal Bulge after Resolution of Diabetic Macular Edema with Coexisting Serous Retinal Detachment

PURPOSE

To evaluate the impact of restoration of foveal bulge (FB) in optical coherence tomography (OCT) images on visual acuity after resolution of diabetic macular edema with coexisting serous retinal detachment (SRD-DME).

METHODS

A total of 52 eyes with resolved SRD-DME and an intact ellipsoid zone at the central fovea were included. All eyes underwent best-corrected visual acuity (BCVA) examination and OCT scanning at baseline and follow-up visits (1, 3, and 6 months). The eyes were divided into two groups according to the presence of FB at 6 months. BCVA, central foveal thickness (CFT), height of SRD (SRDH), outer nuclear layer (ONL) thickness, photoreceptor inner segment (PIS), and outer segment (POS) length were compared between the two groups.

RESULTS

A FB was found in 25 of 52 (48%) eyes at 6 months. The FB (+) group had lower SRDH at baseline, and better BCVA, longer POS length at 6 months (all P < 0.05). There was no significant difference in the CFT, ONL thickness, and PIS length at 6 months between the two groups (all P > 0.05). More eyes in the FB (+) group had complete SRD resolution at 1 month (P = 0.009) and 3 months (P = 0.012). Eyes with complete SRD resolution at 1 month (P = 0.009) or 3 months (P = 0.012) were more likely to have a FB at 6 months.

CONCLUSIONS

The Presence of the FB is associated with better BCVA after resolution of SRD-DME. Eyes with lower baseline SRDH or faster SRD resolution are more likely to have a FB at 6 months.

Electroretinographic recordings with skin electrodes to assess effects of vitrectomy with gas tamponade on eyes with rhegmatogenous retinal detachment

The purpose of this study was to evaluate the retinal function by electroretinograms (ERGs) recorded with the RETeval system using skin electrodes after pars plana vitrectomy (PPV) with gas tamponade in eyes with a rhegmatogeneous retinal detachment (RRD). Flicker ERGs were recorded from 17 eyes with an RRD before (baseline), within 2 weeks after the PPV when the size of the tamponade gas was approximately one-half of the vitreous cavity (P1), and when the gas had been completely absorbed (P2). The amplitudes of the flicker ERGs at each phase were compared to that at the baseline. The median (25th, 75th percentile) of the amplitude was 10.0 µV (5.5, 13.0 µV) at the baseline, 11.7 µV at P1 (7.8, 14.8 µV; P = 0.003), and 17.1 µV at P2 (11.7 23.3 μV; P < 0.001). The ratio of the amplitudes in the affected eye to that in the fellow eye at the baseline and at each phase was calculated, and the ratio of the amplitudes at P1 and P2 were significantly and positively correlated (P = 0.723, P = 0.001; Spearman's rank correlation coefficient). We conclude that recordings the flicker ERGs with skin electrodes can be used to assess the physiology of eyes even with the vitreous cavity half-filled with the gas used to tamponade the retina.

Diurnal rodents as pertinent animal models of human retinal physiology and pathology

This presentation will survey the retinal architecture, advantages, and limitations of several lesser-known rodent species that provide a useful diurnal complement to rats and mice. These diurnal rodents also possess unusually cone-rich photoreceptor mosaics that facilitate the study of cone cells and pathways. Species to be presented include principally the Sudanian Unstriped Grass Rat and Nile Rat (Arvicanthis spp.), the Fat Sand Rat (Psammomys obesus), the degu (Octodon degus) and the 13-lined ground squirrel (Ictidomys tridecemlineatus). The retina and optic nerve in several of these species demonstrate unusual resilience in the face of neuronal injury, itself an interesting phenomenon with potential translational value.

Influence of submacular fluid on recovery of retinal function and structure after successful rhegmatogenous retinal reattachment

Purpose

To determine the influence of residual submacular fluid (SMF) on the recovery of function and structure of the retina after successful rhegmatogenous retinal detachment (RRD) reattachment.

Methods

We reviewed the medical records of all patients who had undergone successful RRD repair by scleral buckling (SB) surgery or by pars plana vitrectomy (PPV) from March 2011 to August 2014. Spectral-domain optical coherence tomographic images of the macular regions were used at 1, 2, 3, 6, 9, and 12 months following the surgery. The best-corrected visual acuities (BCVA) were evaluated at the same times.

Results

The eyes with a macula-off RRD that were treated by SB surgery had a significant higher incidence of residual SMF (52%) than those treated by PPV (6.8%; P <0.001). Nevertheless, the postoperative BCVA was significantly improved in the eyes that had undergone SB surgery (P = 0.007). The postoperative BCVAs were not significantly different between the groups in which the SMF was absorbed (12 eyes) and not absorbed (13 eyes) within 1 month after the SB surgery. The photoreceptor outer segment length and the presence of a foveal bulge were not significantly different between these two groups at 12 months. Multiple regression analyses showed that the presence of a foveal bulge (β = 0.531, P = 0.001) and the duration of the retinal detachment before surgery (β = 0.465, P = 0.002) but not the duration of the SMF were independent factors significantly correlated with the final BCVA.

Conclusions

These results suggest that the postoperative residual SMF does not significantly disrupt the functional and structural recovery of eyes with macula-off RRD treated by SB surgery.

Electroretinograms recorded with skin electrodes in silicone oil-filled eyes

Purpose

To assess the physiology of the retina by electroretinography (ERG) with skin electrodes in eyes that had undergone vitrectomy with silicone oil (SO) tamponade.

Design

Retrospective case series.

Method

ERGs were recorded from eleven eyes with complex vitreoretinal disorders and from the normal fellow eyes. The affected eyes underwent pars plana vitrectomy (PPV) with SO tamponade. ERGs were recorded before and after the SO was removed. The amplitudes and implicit times of the a- and b-waves of the affected eyes were compared to those of the normal fellow eyes. In addition, the ratios of the amplitudes of the b-waves of the affected eyes to those of the fellow eyes were compared before and after the SO was removed.

Results

ERGs were recordable from 7 eyes (63.6%) before the SO was removed and 11 eyes (100%) after the SO was removed. The a- and b-wave amplitudes were significantly smaller in the affected eyes than those of the fellow eyes at the baseline. The b-wave amplitude before the removal of the SO was significantly and positively correlated with that after the SO removal. The ratios of the b-waves of the affected/normal fellow eye significantly increased after the SO was removed.

Conclusion

The results indicate that ERGs picked up by skin electrode can be used to assess the physiology of the retina in eyes with a SO tamponade. The amplitude of the b-waves of the ERGs in silicone-filled eyes can be used to predict the amplitude after the silicone is removed.

Correlation between preoperative factors and final visual acuity after successful rhegmatogenous retinal reattachment

We evaluated the preoperative optical coherence tomographic (OCT) findings in eyes with macula-off rhegmatogenous retinal detachment (RRD) and determined the factors that were significantly correlated with the postoperative best-corrected visual acuity (BCVA). The length of the preoperative photoreceptors was defined as the distance between the external limiting membrane (ELM) and the outer end of the outer segments of the photoreceptors in the OCT images. The mean length of the photoreceptors was 102.8 ± 28.7 µm with a range of 20 to 159 µm in eyes with RRD. The length of the preoperative photoreceptors was not significantly correlated with the preoperative BCVA but it was significantly correlated with the postoperative BCVA (r = -0.353, P = 0.003). Multivariate regression analyses revealed that the length of the photoreceptors (β = -0.388, P = 0.001) and the preoperative BCVA (β = 0.274, P = 0.021) were the only independent factors that were significantly associated with the postoperative BCVA. The length of the preoperative photoreceptors was significantly correlated with the postoperative photoreceptor length (r = 0.486, P < 0.001). Longer preoperative photoreceptors were significantly correlated with longer postoperative photoreceptors and better BCVA after successful reattachment. These results suggest that the preoperative length of the photoreceptors can be good factor to use for predicting the final BCVA following successful reattachment of macula-off RRD.

Recovery of macular cone photoreceptors in Vogt-Koyanagi-Harada disease

PURPOSE

Our purpose was to study changes in macular cone photoreceptors in Vogt-Koyanagi-Harada (VKH) disease patients after high-dose corticosteroid treatment using an adaptive optics (AO) fundus camera.

METHODS

We retrospectively analyzed 16 eyes of eight patients with new-onset acute VKH disease that were studied retrospectively. After serous retinal detachment (SRD) had resolved, AO images were obtained using the rtx1™ AO fundus camera over a 12-month course. Cone counting was performed in the nasal, temporal, superior and inferior areas of the macula 0.75 mm from the foveal center. A control group of 30 eyes of 30 healthy subjects was established for comparison.

RESULTS

In the eyes with VKH disease, the mean cone densities 0.75 mm from the foveal center were 11,847 at baseline (resolution of SRD), and 15,218, 16,684 and 17,686 cones/mm², at 3, 6, and 12 months later, respectively. The mean cone densities at 3, 6, and 12 months were significantly increased compared to those of baseline (p = 0.007, p < 0.001, and p < 0.001, respectively); however, they were significantly lower than that of the healthy control eyes (p < 0.001). The mean cone densities at areas with a previous presence of cystoid spaces were significantly lower than those without cystoid spaces at the baseline, and at 3, 6, and 12 months (p < 0.001, p = 0.007, p < 0.001, and p = 0.008, respectively).

CONCLUSIONS

Cone densities were gradually increased after the resolution of SRD in the eyes of VKH disease patients. The presence of cystoid spaces might be a marker of severe damage to cone photoreceptors.

Evaluation of tolerance to lentiviral LV-RPE65 gene therapy vector after subretinal delivery in non-human primates

Several approaches have been developed for gene therapy in RPE65-related Leber congenital amaurosis. To date, strategies that have reached the clinical stages rely on adeno-associated viral vectors and two of them documented limited long-term effect. We have developed a lentiviral-based strategy of RPE65 gene transfer that efficiently restored protein expression and cone function in RPE65-deficient mice. In this study, we evaluated the ocular and systemic tolerances of this lentiviral-based therapy (LV-RPE65) on healthy nonhuman primates (NHPs), without adjuvant systemic anti-inflammatory prophylaxis. For the first time, we describe the early kinetics of retinal detachment at 2, 4, and 7 days after subretinal injection using multimodal imaging in 5 NHPs. We revealed prolonged reattachment times in LV-RPE65-injected eyes compared to vehicle-injected eyes. Low- (n = 2) and high-dose (n = 2) LV-RPE65-injected eyes presented a reduction of the outer nuclear and photoreceptor outer segment layer thickness in the macula, that was more pronounced than in vehicle-injected eyes (n = 4). All LV-RPE65-injected eyes showed an initial perivascular reaction that resolved spontaneously within 14 days. Despite foveal structural changes, full-field electroretinography indicated that the overall retinal function was preserved over time and immunohistochemistry identified no difference in glial, microglial, or leucocyte ocular activation between low-dose, high-dose, and vehicle-injected eyes. Moreover, LV-RPE65-injected animals did not show signs of vector shedding or extraocular targeting, confirming the safe ocular restriction of the vector. Our results evidence a limited ocular tolerance to LV-RPE65 after subretinal injection without adjuvant anti-inflammatory prophylaxis, with complications linked to this route of administration necessitating to block this transient inflammatory event.

Perioperative factors that are significantly correlated with final visual acuity in eyes after successful rhegmatogenous retinal detachment surgery

Purpose

To determine the perioperative factors that are significantly correlated with the final visual acuity following reattachment of a macula-off rhegmatogenous retinal detachment (RRD) by vitrectomy.

Methods

Twenty-nine eyes of 29 patients with a successfully reattached RRD by vitrectomy were retrospectively analyzed. Spectral-domain optical coherence tomographic images of the macular regions were used to measure the thicknesses of the retinal layers and the integrity of the microstructures of the photoreceptors at 2 weeks, 1, 2, 3, 6, 9, and 12 months following the vitrectomy. The best-corrected visual acuities (BCVA) were evaluated at the same times.

Results

The improvement of the BCVA from the preoperative BCVA to that at postoperative Week 2 (-0.67 ± 0.69 logMAR units) was the largest change between adjacent observation periods for the entire study duration. It was significantly greater than the improvement between Week 2 and Month 12 (-0.32 ± 0.22 logMAR units; P<0.001). The thickness of the ellipsoid zone (EZ)-retinal pigment epithelium (RPE) increased significantly with time (P<0.001). The final BCVA was significantly correlated with the BCVA at Week 2 (r = 0.61, P<0.001), the EZ-RPE thickness at Week 2 (r = -0.40, P = 0.035), the integrity of the external limiting membrane (ELM) (r = -0.61, P = 0.003), and an intact EZ (r = -0.66, P = 0.001) at Week 2. Multiple stepwise regression analyses of the final BCVA showed that the BCVA at Week 2 (P = 0.017) and the integrity of the EZ at Week 2 (P = 0.006) were independent predictors of the final BCVA.

Conclusions

The significantly better BCVA and presence of an intact EZ at 2 weeks following vitrectomy and their significant correlations with the BCVA at Month 12 indicate that these perioperative values can be used to predict the BCVA at Month 12 after a reattachment of macula-off RRD following vitrectomy.

Regeneration of Photoreceptor Outer Segments After Scleral Buckling Surgery for Rhegmatogenous Retinal Detachment

PURPOSE

To investigate the regeneration of the cone outer segments in eyes after surgery for fovea-off rhegmatogenous retinal detachment with an adaptive optics (AO) fundus camera and to correlate these findings with the findings of optical coherence tomography (OCT).

DESIGN

Retrospective, observational case series.

METHODS

Medical charts of 21 eyes of 21 patients who had undergone surgery for fovea-off rhegmatogenous retinal detachment were retrospectively studied. Cone mosaic images were obtained with an AO fundus camera. Cone packing density at 2 degrees from the fovea within the previously detached area was measured 6 and 12 months after surgery. Retinal thicknesses between the interdigitation zone and the retinal pigment epithelium (IZ-RPE) and between the ellipsoid zone and the retinal pigment epithelium (EZ-RPE) were measured in OCT images.

RESULTS

Cone density 12 months after surgery was significantly increased from that at 6 months (P = .001), but was still significantly lower than that of normal fellow eyes (P < .001). IZ-RPE and EZ-RPE thickness significantly increased from 6 to 12 months (P = .045, P = .033, respectively), and these values were not significantly different from those of normal fellow eyes. Multivariate analysis showed that cone density at 12 months was significantly associated with IZ-RPE thickness (P = .002), and increases in cone packing density were significantly associated with increases in IZ-RPE thickness (P = .001).

CONCLUSIONS

Recovery of cone packing density measured by AO was associated with structural recovery of the outer retina observed in OCT, suggesting regeneration of the photoreceptor outer segment after surgery.

Noninvasive imaging of the thirteen-lined ground squirrel photoreceptor mosaic

Ground squirrels are an increasingly important model for studying visual processing, retinal circuitry, and cone photoreceptor function. Here, we demonstrate that the photoreceptor mosaic can be longitudinally imaged noninvasively in the 13-lined ground squirrel (Ictidomys tridecemlineatus) using confocal and nonconfocal split-detection adaptive optics scanning ophthalmoscopy using 790 nm light. Photoreceptor density, spacing, and Voronoi analysis are consistent with that of the human cone mosaic. The high imaging success rate and consistent image quality in this study reinforce the ground squirrel as a practical model to aid drug discovery and testing through longitudinal imaging on the cellular scale.

Non-image Forming Light Detection by Melanopsin, Rhodopsin, and Long-Middlewave (L/W) Cone Opsin in the Subterranean Blind Mole Rat, Spalax Ehrenbergi: Immunohistochemical Characterization, Distribution, and Connectivity

The blind mole rat, Spalax ehrenbergi, can, despite severely degenerated eyes covered by fur, entrain to the daily light/dark cycle and adapt to seasonal changes due to an intact circadian timing system. The present study demonstrates that the Spalax retina contains a photoreceptor layer, an outer nuclear layer (ONL), an outer plexiform layer (OPL), an inner nuclear layer (INL), an inner plexiform layer (IPL), and a ganglion cell layer (GCL). By immunohistochemistry, the number of melanopsin (mRGCs) and non-melanopsin bearing retinal ganglion cells was analyzed in detail. Using the ganglion cell marker RNA-binding protein with multiple splicing (RBPMS) it was shown that the Spalax eye contains 890 ± 62 RGCs. Of these, 87% (752 ± 40) contain melanopsin (cell density 788 melanopsin RGCs/mm²). The remaining RGCs were shown to co-store Brn3a and calretinin. The melanopsin cells were located mainly in the GCL with projections forming two dendritic plexuses located in the inner part of the IPL and in the OPL. Few melanopsin dendrites were also found in the ONL. The Spalax retina is rich in rhodopsin and long/middle wave (L/M) cone opsin bearing photoreceptor cells. By using Ctbp2 as a marker for ribbon synapses, both rods and L/M cone ribbons containing pedicles in the OPL were found in close apposition with melanopsin dendrites in the outer plexus suggesting direct synaptic contact. A subset of cone bipolar cells and all photoreceptor cells contain recoverin while a subset of bipolar and amacrine cells contain calretinin. The calretinin expressing amacrine cells seemed to form synaptic contacts with rhodopsin containing photoreceptor cells in the OPL and contacts with melanopsin cell bodies and dendrites in the IPL. The study demonstrates the complex retinal circuitry used by the Spalax to detect light, and provides evidence for both melanopsin and non-melanopsin projecting pathways to the brain.

Astrocyte structural reactivity and plasticity in models of retinal detachment

Although retinal neurodegenerative conditions such as age-related macular degeneration, glaucoma, diabetic retinopathy, retinitis pigmentosa, and retinal detachment have different etiologies and pathological characteristics, they also have many responses in common at the cellular level, including neural and glial remodeling. Structural changes in Müller cells, the large radial glia of the retina in retinal disease and injury have been well described, that of the retinal astrocytes remains less so. Using modern imaging technology to describe the structural remodeling of retinal astrocytes after retinal detachment is the focus of this paper. We present both a review of critical literature as well as novel work focusing on the responses of astrocytes following rhegmatogenous and serous retinal detachment. The mouse presents a convenient model system in which to study astrocyte reactivity since the Mϋller cell response is muted in comparison to other species thereby allowing better visualization of the astrocytes. We also show data from rat, cat, squirrel, and human retina demonstrating similarities and differences across species. Our data from immunolabeling and dye-filling experiments demonstrate previously undescribed morphological characteristics of normal astrocytes and changes induced by detachment. Astrocytes not only upregulate GFAP, but structurally remodel, becoming increasingly irregular in appearance, and often penetrating deep into neural retina. Understanding these responses, their consequences, and what drives them may prove to be an important component in improving visual outcome in a variety of therapeutic situations. Our data further supports the concept that astrocytes are important players in the retina's overall response to injury and disease.

Seasonal and post-trauma remodeling in cone-dominant ground squirrel retina

With a photoreceptor mosaic containing ∼85% cones, the ground squirrel is one of the richest known mammalian sources of these important retinal cells. It also has a visual ecology much like the human's. While the ground squirrel retina is understandably prominent in the cone biochemistry, physiology, and circuitry literature, far less is known about the remodeling potential of its retinal pigment epithelium, neurons, macroglia, or microglia. This review aims to summarize the data from ground squirrel retina to this point in time, and to relate them to data from other brain areas where appropriate. We begin with a survey of the ground squirrel visual system, making comparisons with traditional rodent models and with human. Because this animal's status as a hibernator often goes unnoticed in the vision literature, we then present a brief primer on hibernation biology. Next we review what is known about ground squirrel retinal remodeling concurrent with deep torpor and with rapid recovery upon re-warming. Notable here is rapidly-reversible, temperature-dependent structural plasticity of cone ribbon synapses, as well as pre- and post-synaptic plasticity throughout diverse brain regions. It is not yet clear if retinal cell types other than cones engage in torpor-associated synaptic remodeling. We end with the small but intriguing literature on the ground squirrel retina's remodeling responses to insult by retinal detachment. Notable for widespread loss of (cone) photoreceptors, there is surprisingly little remodeling of the RPE or Müller cells. Microglial activation appears minimal, and remodeling of surviving second- and third-order neurons seems absent, but both require further study. In contrast, traumatic brain injury in the ground squirrel elicits typical macroglial and microglial responses. Overall, the data to date strongly suggest a heretofore unrecognized, natural checkpoint between retinal deafferentiation and RPE and Müller cell remodeling events. As we continue to discover them, the unique ways by which ground squirrel retina responds to hibernation or injury may be adaptable to therapeutic use.

Cell-Based Therapy for Degenerative Retinal Disease

Stem cell-derived retinal pigment epithelium (RPE) and photoreceptors (PRs) have restored vision in preclinical models of human retinal degenerative disease. This review discusses characteristics of stem cell therapy in the eye and the challenges to clinical implementation that are being confronted today. Based on encouraging results from Phase I/II trials, the first Phase II clinical trials of stem cell-derived RPE transplantation are underway. PR transplant experiments have demonstrated restoration of visual function in preclinical models of retinitis pigmentosa and macular degeneration, but also indicate that no single approach is likely to succeed in overcoming PR loss in all cases. A greater understanding of the mechanisms controlling synapse formation as well as the immunoreactivity of transplanted retinal cells is urgently needed.

Analytical platforms in vitreoretinal proteomics

Current proteomic technologies can effectively be used to study the proteins of the vitreous body and retina in health and disease. The use of appropriate samples, analytical platform and bioinformatic method are essential factors to consider when undertaking such studies. Certain proteins may hinder the detection and evaluation of more relevant proteins associated with pathological processes if not carefully considered, particularly in the sample preparation and data analysis stages. The utilization of more than one quantification technique and database search program to expand the level of proteome coverage and analysis will help to generate more robust and worthwhile results. This review discusses important aspects of sample processing and the use of label and label-free quantitative proteomics strategies applied to the vitreous and retina.

Strain difference in photoreceptor cell death after retinal detachment in mice

PURPOSE

To evaluate the potential for mouse genetic background to effect photoreceptor cell death in response to experimental retinal detachment (RD).

METHODS

Retinal detachment was induced in three inbred mouse strains (C57BL/6, BALB/c, and B6129SF2) by subretinal injection of sodium hyaluronate. A time course of photoreceptor cell death was assessed by TUNEL assay. Total photoreceptor cell death was analyzed through comparing the outer nuclear layer (ONL)/inner nuclear layer (INL) ratio 7 days post RD. Western blot analysis or quantitative real-time PCR (qPCR) were performed to assess cell death signaling, expression of endogenous neurotrophin, and levels of apoptosis inhibitors 24 hours after RD. Inflammatory cytokine secretion and inflammatory cell infiltration were quantified by ELISA and immunostaining, respectively.

RESULTS

The peak of photoreceptor cell death after RD was at 24 hours in all strains. Photoreceptor cell death as well as monocyte chemoattractant protein 1 and interleukin 6 secretion at 24 hours after RD was the highest in BALB/c, followed in order of magnitude by C57BL/6 and B6129SF2. Conversely, nerve growth factor expression and ONL/INL ratio were the lowest in BALB/c. Apoptosis signaling was higher in C57BL/6, whereas necroptosis signaling was higher in C57BL/6 and BALB/c. Autophagic signaling was higher in BALB/c. X-linked inhibitor of apoptosis (XIAP) and survivin protein levels were lower in C57BL/6 and BALB/c, respectively. Macrophage/microglia infiltration was higher in C57BL/6 and BALB/c at 24 hours after RD.

CONCLUSIONS

Photoreceptor cell death after RD was significantly different among the three strains, suggesting the presence of genetic factors that affect photoreceptor cell death after RD.

Photoreceptor impairment and restoration on optical coherence tomographic image

With recent development of spectral-domain optical coherence tomography (SD-OCT), the pathological changes of retina can be observed in much greater detail. SD-OCT clearly delineates three highly reflective lines in the outer retina, which are external limiting membrane (ELM), photoreceptor inner and outer segment (IS/OS) junction, and cone outer segment tips (COST) in order from inside. These lines can serve as hallmarks for the evaluation of photoreceptor condition. In retinitis pigmentosa (RP) leading to photoreceptor degeneration, the ELM, IS/OS, and COST lines are shortened with the progression of the disease. In addition, shortening of the ELM, IS/OS and COST lines is significantly associated with each other. The line length is longest in the ELM, followed by the IS/OS, and COST, suggesting that retinal layer becomes disorganized first at the COST, followed by the IS/OS and finally the ELM. This finding is consistent with the previous report that the earliest histopathological change in RP is a shortening of the photoreceptor outer segments. On the other hand, retinal layer becomes restored first at the ELM, followed by the IS/OS and finally the COST after macular hole surgery. There may be a directionality of photoreceptor impairment or restoration on optical coherence tomographic image.

A chick model of retinal detachment: cone rich and novel

BACKGROUND

Development of retinal detachment models in small animals can be difficult and expensive. Here we create and characterize a novel, cone-rich retinal detachment (RD) model in the chick.

METHODOLOGY/PRINCIPAL FINDINGS

Retinal detachments were created in chicks between postnatal days 7 and 21 by subretinal injections of either saline (SA) or hyaluronic acid (HA). Injections were performed through a dilated pupil with observation via surgical microscope, using the fellow eye as a control. Immunohistochemical analyses were performed at days 1, 3, 7, 10 and 14 after retinal detachment to evaluate the cellular responses of photoreceptors, Müller glia, microglia and nonastrocytic inner retinal glia (NIRG). Cell proliferation was detected with bromodeoxyuridine (BrdU)-incorporation and by the expression of proliferating cell nuclear antigen (PCNA). Cell death was detected with terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). As in mammalian models of RD, there is shortening of photoreceptor outer segments and mis-trafficking of photoreceptor opsins in areas of RD. Photoreceptor cell death was maximal 1 day after RD, but continued until 14 days after RD. Müller glia up-regulated glial fibriliary acidic protein (GFAP), proliferated, showed interkinetic nuclear migration, and migrated to the subretinal space in areas of detachment. Microglia became reactive; they up-regulated CD45, acquired amoeboid morphology, and migrated toward outer retina in areas of RD. Reactive NIRG cells accumulated in detached areas.

CONCLUSIONS/SIGNIFICANCE

Subretinal injections of SA or HA in the chick eye successfully produced retinal detachments and cellular responses similar to those seen in standard mammalian models. Given the relatively large eye size, and considering the low cost, the chick model of RD offers advantages for high-throughput studies.

Neuronal and glial alterations in complex long-term rhegmatogenous retinal detachment

PURPOSE

To explore neuronal and glial alterations in eyes with complex long-term rhegmatogenous retinal detachment (RRD).

METHODS

Morphological analysis was performed on eight retinal specimens derived from patients treated with peripheral retinectomy for RRD complicated by retinal shortening or retinal thinning. All eyes had undergone previous surgeries including silicone oil tamponade, and had a median total detachment time of 2.5 months (range 2-12). Specimens were examined with hematoxylin and eosin staining and immunohistochemistry directed against activated Müller cells, ganglion cells, rod bipolar cells, and photoreceptors.

RESULTS

Retinal specimens displayed severe loss of photoreceptor and rod bipolar cells. Remaining neuronal cells exhibited disorganized perikarya and neurites with disruption of the normal retinal lamination. Müller cell activation was evident in all specimens with subretinal and epiretinal hypertrophy present in tissue derived from shortened retinal detachments.

CONCLUSION

Long-term RRD leads to retinal remodeling characterized by loss of first and second order retinal neurons, disruption of the entire retinal lamination and gliosis. The severity of histopathological changes indicates that anatomical as well as functional recovery of the involved retina is precarious. The findings may be important when devising surgical strategies to avoid permanent retinal detachment.

The effect of subretinal viscoelastics on the porcine retinal function

The functional consequence of long-term retinal detachment in the porcine model is examined by multifocal electroretinography (mfERG). Retinal detachment (RD) in humans leaves permanent visual impairment, despite anatomical successful reattachment surgery. To improve treatment, adjuvant pharmaceutical therapy is needed, and can only be tested in a suitable animal model. The porcine model is promising and the mfERG is well validated in this model. RD was induced in 18 pigs by vitrectomy and healon injection of various concentrations. Preoperatively and 6 weeks postoperatively eight animals were examined by mfERG. The major component P1 was analyzed statistically. Indirect ophthalmoscopy and bilateral color fundus photography (FP) were performed. Selected animals underwent high-resolution optical coherence tomography (OCT). Examination by ophthalmoscopy and FP showed that the RDs remained detached for the 6 weeks of follow-up. The P1 amplitude of the mfERG did not differ significantly between the detached areas, the surrounding attached areas, and the healthy eye (p = 0.25). Similarly, P1 implicit time did not differ between the areas (p = 0.85). The lack of functional consequences of long-term RD makes the porcine model unsuitable for examining adjuvant pharmaceutical RD treatment. Future studies should focus on foveated primates.

The photoreceptor layer as a prognostic factor for visual acuity in the secondary epiretinal membrane after retinal detachment surgery: imaging analysis by spectral-domain optical coherence tomography

PURPOSE

To study the prognostic factors that influence best-corrected visual acuity (BCVA) outcome in patients with secondary epiretinal membrane (ERM) after retinal detachment surgery.

DESIGN

Retrospective case series.

METHODS

Forty-two patients with ERM were divided into macula-on and macula-off groups based on the macular status before retinal detachment surgery and were studied using the same spectral-domain optical coherence tomography device. Several variables, including the integrity of the external limiting membrane (ELM), the status of the photoreceptor inner segment/outer segment (IS/OS) junction line, and central foveal thickness were evaluated in 17 treated and 25 untreated patients. Linear regression analysis was used to determine the best combination of all variables affecting BCVA.

RESULTS

Final BCVA was significantly better in macula-on and macula-off eyes with intact ELMs and IS/OS junction lines (0.35 ± 0.18 logarithm of the minimal angle of resolution [logMAR] and 0.51 ± 0.17 logMAR, respectively) than in macula-off eyes with disrupted or absent ELMs and IS/OS junction lines (0.83 ± 0.17 logMAR and 1.04 ± 0.05 logMAR, respectively; P < .001, analysis of variance). Final BCVA also was better in the treated group than in the controls (0.55 ± 0.31 logMAR and 0.73 ± 0.26 logMAR, respectively; P = .05, t test). ELM and IS/OS junction line integrity were the main variables significantly affecting the final BCVA outcome (β = 0.42; P = .006, linear regression analysis). Disruption of the ELM and IS/OS junction line was observed in 21 of the 42 cases studied.

CONCLUSIONS

ERM secondary to retinal detachment surgery is accompanied by a high incidence (50%) of IS/OS junction line and ELM disruption. Among the variables studied, the condition of the IS/OS junction layer and the ELM are the main factors that predict final BCVA after ERM peeling.

Factors influencing the visual acuity of chronic central serous chorioretinopathy

PURPOSE

To investigate correlated factors on final visual acuity in conjunction with fluorescein angiography (FA) and optical coherence tomography (OCT) findings of chronic central serous chorioretinopathy (CSCR).

METHODS

Twenty-four patients (36 eyes) with typical findings of chronic CSCR based on medical records, FA and OCT results were enrolled in this study. We investigated demographic findings, initial and final visual acuity (VA), and some typical findings of FA including the type of leakage pattern, the existence of a gravitational tract and an abnormal hyperfluorescent area centered on the fovea. We also investigated OCT findings to examine serous retinal detachment, outer photoreceptor layer (OPRL) preservation, continuity of the inner segment (IS) and the outer segment (OS) of the photoreceptor layer in case of macular attachment, and other typical findings. The converted logarithm of the minimum angle of resolution VA was used to investigate the statistical correlation with these FA and OCT findings.

RESULTS

An abnormal hyperfluorescent area within 1 macular photocoagulation study disc area on FA and cystoid degeneration on OCT were correlated with poor final VA of less than 20 / 40. However, the preserved OPRL and the continuity of IS / OS junction were correlated with a good final VA of 0.5 or more.

CONCLUSIONS

These specific findings could be associated with recurrent or persistent subretinal fluid and could be important parameters of decision for treatment.

Angiotensin II type 1 receptor signaling contributes to synaptophysin degradation and neuronal dysfunction in the diabetic retina

OBJECTIVE

Pathogenic mechanisms underlying diabetes-induced retinal dysfunction are not fully understood. The aim of the present study was to show the relationship of the renin-angiotensin system (RAS) with the synaptic vesicle protein synaptophysin and neuronal activity in the diabetic retina.

RESEARCH DESIGN AND METHODS

C57BL/6 mice with streptozotocin-induced diabetes were treated with the angiotensin II type 1 receptor (AT1R) blocker telimsartan or valsartan, and retinal function was analyzed by electroretinography. Retinal production of the RAS components and phosphorylation of ERK (extracellular-signal regulated kinase) were examined by immunoblotting. Retinal mRNA and protein levels of synaptophysin were measured by quantitative RT-PCR and immunoblot analyses, respectively. In vitro, synaptophysin levels were also evaluated using angiotensin II-stimulated PC12D neuronal cells cultured with or without the inhibition of ERK signaling or the ubiquitin-proteasome system (UPS).

RESULTS

Induction of diabetes led to a significant increase in retinal production of angiotensin II and AT1R together with ERK activation in the downstream of AT1R. AT1R blockade significantly reversed diabetes-induced electroretinography changes and reduction of synaptophysin protein, but not mRNA, levels in the diabetic retina. In agreement with the AT1R-mediated posttranscriptional downregulation of synaptophysin in vivo, in vitro application of angiotensin II to PC12D neuronal cells caused the UPS-mediated degradation of synaptophysin protein via AT1R, which proved to be induced by ERK activation.

CONCLUSIONS

These data indicate the first molecular evidence of the RAS-induced synaptophysin degradation and neuronal dysfunction in the diabetic retina, suggesting the possibility of the AT1R blockade as a novel neuroprotective treatment for diabetic retinopathy.