Parallelism as a novel marker for structural integrity of retinal layers in optical coherence tomographic images in eyes with epiretinal membrane

Insights into the underlying choroid in different stages of idiopathic epiretinal membranes after Viteromacular surgery

PURPOSE

The purpose of the study was to longitudinally investigate the correlation between choroidal morphologic and vascular parameters and postoperative visual outcome in different stages of idiopathic epiretinal membranes (iERMs).

METHODS

A prospective, observational, institutional case series of 102 consecutive patients diagnosed with unilateral iERMs were recruited at Peking University Third Hospital and were followed up for 12 months after surgical treatment with vitrectomy. Participants were classified into four stages according to current staging scheme. All eligible subjects underwent standardized imaging evaluation of choroidal parameters including subfoveal choroidal thickness (SFCT), choroidal vascularity index (CVI), and choroidal capillary perfusion (CCP) at baseline and each follow-up by enhanced depth optical coherence tomography (EDI-OCT) and OCT angiography (OCTA). Longitudinal follow-up of choroidal parameters over 12 months was analysed, and their correlations with best-corrected visual acuity (BCVA) were also assessed for predictive prognostic value.

RESULTS

CVI and CCP were significantly correlated with BCVA at each follow-up examination (all p < 0.05). However, SFCT exhibited no variation among different stages of iERMs at baseline (p = 0.981) or during follow-up (p = 0.520). The preoperative CVI correlated with 12-month postoperative BCVA (p < 0.001) and its predictive prognostic effect on BCVA was validated in multiple regression analysis (p = 0.006).

CONCLUSION

CVI varied among different stages of iERM and was significantly correlated with visual outcomes after the surgery. CVI could serve as a predictive prognostic marker in iERMs, which further indicates the underlying choroid should be taken into consideration in clinical evaluation of iERMs.

Preoperative ocular coherence tomographic prognosticators of visual acuity after idiopathic epiretinal membrane surgery

PURPOSE

To provide a current review of the evidence for the utility of preoperative ocular coherence tomography (OCT) parameters in prognosticating postoperative visual acuity and visual improvement after idiopathic epiretinal membrane surgery. To determine which OCT bio-markers are most useful in this regard and where future studies may apply more emphasis.

METHODS

An extensive search of the PubMed database was performed for studies investigating this relationship. Key search terms included: idiopathic, epiretinal membrane, surgery, peel, vitrectomy, vision, outcomes, visual acuity, ocular coherence tomography, central foveal thickness, foveal contour, foveal morphology, ectopic inner foveal layers, inner retinal layers, inner retinal irregularity index, outer retinal layers, ellipsoid zone, interdigitation zone, photoreceptor outer segment length, central bouquet abnormality, staging, choroidoscleral irregularity, ganglion cell and nerve fibre layers, inner and outer plexiform layers, inner and outer nuclear layers. Forty-nine peer-reviewed articles were included in this review. These consisted of 28 retrospective studies [1-3,13,16-18,20,23-29,32-36,38,40,42-47], 17 prospective studies[6-12,14,19,21,22,30,31,37,41,48,49], 2 reviews [4,39] and 2 systematic reviews [5,15].

CONCLUSION

The weight of literary evidence seems to support photoreceptor integrity as the most consistent OCT marker of better postoperative visual acuity. This includes analysis of ellipsoid and interdigitation zones as well as photoreceptor outer segment length. However, the newer OCT staging system proposed by Govetto et al. (2017) fulfils a need for a clinically useful and evidence-based OCT classification. It may be the way forward in prognosticating ERM surgical outcomes by preoperative stratification. There is insufficient evidence to suggest the other discussed parameters in this review as useful prognosticators of postoperative visual acuity.

Idiopathic Epiretinal Membranes: Visual Outcomes and Prognostic Factors

Objectives

To evaluate the associations between anatomical changes and visual outcomes in patients with idiopathic epiretinal membrane (ERM).

Materials and Methods

We performed a prospective study of 130 consecutive idiopathic ERM patients and report their visual outcomes and the factors associated with visual outcome and anatomical changes.

Results

Of 130 eyes of 130 patients, 87 eyes underwent surgery, while the remaining 43 eyes were observed. At 6-month follow-up, the best-corrected visual acuity (BCVA) increased in the whole population. Mean Early Treatment Diabetic Retinopathy Study letter score changed from 51 to 65 in the surgical group and from 67 to 68 in the non-surgical group. The surgical group had improvement in BCVA at all ERM stages and grades of disorganization of the retinal inner layers (DRIL) (p<0.01). In multivariable analysis of the surgical group, factors associated with BCVA of ETDRS 60 letters or more were no or mild DRIL and the absence of ellipsoid zone disruption at baseline (p=0.002 and p=0.034, respectively) and this statistically significant positive correlation was still maintained at 12-month follow-up.

Conclusion

Baseline DRIL grade and presence of ellipsoid zone disruption were the most informative prognostic factors in patients with idiopathic ERMs. Patients with severe DRIL and/or advanced ERMs had improved vision after ERM removal.

Significance of Hyperreflective Foci as an Optical Coherence Tomography Biomarker in Retinal Diseases: Characterization and Clinical Implications

Hyperreflective foci (HRF) is a term coined to depict hyperreflective dots or roundish lesions within retinal layers visualized through optical coherence tomography (OCT). Histopathological correlates of HRF are not univocal, spacing from migrating retinal pigment epithelium cells, lipid-laden macrophages, microglial cells, and extravasated proteinaceous or lipid material. Despite this, HRF can be considered OCT biomarkers for disease progression, treatment response, and prognosis in several retinal diseases, including diabetic macular edema, age-related macular degeneration (AMD), retinal vascular occlusions, and inherited retinal dystrophies. The structural features and topographic location of HRF guide the interpretation of their significance in different pathological conditions. The presence of HRF less than 30 μm with reflectivity comparable to the retinal nerve fiber layer in the absence of posterior shadowing in diabetic macular edema indicates an inflammatory phenotype with a better response to steroidal treatment. In AMD, HRF overlying drusen are associated with the development of macular neovascularization, while parafoveal drusen and HRF predispose to macular atrophy. Thus, HRF can be considered a key biomarker in several common retinal diseases. Their recognition and critical interpretation via multimodal imaging are vital to support clinical strategies and management.

Segmentation of Preretinal Space in Optical Coherence Tomography Images Using Deep Neural Networks

This paper proposes an efficient segmentation of the preretinal area between the inner limiting membrane (ILM) and posterior cortical vitreous (PCV) of the human eye in an image obtained with the use of optical coherence tomography (OCT). The research was carried out using a database of three-dimensional OCT imaging scans obtained with the Optovue RTVue XR Avanti device. Various types of neural networks (UNet, Attention UNet, ReLayNet, LFUNet) were tested for semantic segmentation, their effectiveness was assessed using the Dice coefficient and compared to the graph theory techniques. Improvement in segmentation efficiency was achieved through the use of relative distance maps. We also show that selecting a larger kernel size for convolutional layers can improve segmentation quality depending on the neural network model. In the case of PVC, we obtain the effectiveness reaching up to 96.35%. The proposed solution can be widely used to diagnose vitreomacular traction changes, which is not yet available in scientific or commercial OCT imaging solutions.

Clinical Update on Metamorphopsia: Epidemiology, Diagnosis and Imaging

Purpose: To discuss the pathophysiology of metamorphopsia, its characterisation using retinal imaging and methods of assessment of patient symptoms and visual function.Methods: A literature search of electronic databases was performedResults: Metamorphopsia has commonly been associated with vitreomacular interface disorders (such as epiretinal membrane) and has also regularly been noted in diseases of the retina and choroid, particularly age-related macular degeneration and central serous chorioretinopathy. Developments in optical coherence tomography retinal imaging have enabled improved imaging of the foveal microstructure and have led to the localisation of the pathophysiology of metamorphopsia within the retinal layers of the macula. Alteration of alignment of inner and outer retinal layers at various retinal loci has been identified using multimodal imaging in patients with metamorphopsia in a range of conditions. Although the Amsler Grid assessment of metamorphopsia is a useful clinical indicator, new emerging methods of metamorphopsia assessment with psychophysical tests such as M-CHARTS and preferential hyperacuity perimetry, have been developed.Conclusions: It appears that there is a complex relationship between visual acuity and metamorphopsia symptoms that vary between retinal conditions. Although metamorphopsia has traditionally been challenging to measure in the clinic, advances in technology promise more robust, easy-to-use tests. It is possible that home assessment of metamorphopsia, particularly in conditions such as age-related macular degeneration, may help to guide the need for further clinic evaluation and consideration of treatment.

Epiretinal membrane: A review

The prevalence of epiretinal membrane (ERM) is 7% to 11.8%, with increasing age being the most important risk factor. Although most ERM is idiopathic, common secondary causes include cataract surgery, retinal vascular disease, uveitis and retinal tears. The myofibroblastic pre-retinal cells are thought to transdifferentiate from glial and retinal pigment epithelial cells that reach the retinal surface via defects in the internal limiting membrane (ILM) or from the vitreous cavity. Grading schemes have evolved from clinical signs to ocular coherence tomography (OCT) based classification with associated features such as the cotton ball sign. Features predictive of better prognosis include absence of ectopic inner foveal layers, cystoid macular oedema, acquired vitelliform lesions and ellipsoid and cone outer segment termination defects. OCT-angiography shows reduced size of the foveal avascular zone. Vitrectomy with membrane peeling remains the mainstay of treatment for symptomatic ERMs. Additional ILM peeling reduces recurrence but is associated with anatomical changes including inner retinal dimpling.

The predictive value of ectopic inner retinal layer staging scheme for idiopathic epiretinal membrane: surgical results at 12 months

BACKGROUND/OBJECTIVES

To assess the effect of ectopic inner foveal layers (EIFL) based staging scheme, foveal avascular zone (FAZ) alterations and other microstructural optical coherence tomography (OCT) findings on visual function for patients undergoing idiopathic epiretinal membrane (iERM) surgery.

SUBJECTS/METHODS

In this retrospective study, patients who underwent 27 G pars plana vitrectomy (PPV) for idiopathic ERM with a minimum follow-up of 12 months were included. Preoperative and postoperative OCT scans, FAZ area measurements on en face OCT angiography images and mean retinal sensitivity (MRS) using microperimetry were recorded in all cases. The correlation of FAZ area, EIFL and other OCT parameters with preoperative and postoperative best-corrected visual acuity (BCVA) was analysed.

RESULTS

In all, 112 eyes of 112 patients were included. Visual acuity improvement was statistically significant in all four stages; however, differences between Stages 2, 3 and 4 ERMs remained significant (p < 0.05). The presence and thickness of the EIFL was associated with worse baseline (p = 0.013; p = 0.005, respectively) and final (p < 0.001 for both) BCVA. The presence of cystoid macular oedema was associated with worse BCVA at baseline (p = 0.027) and postoperative month-6 (p = 0.04). The mean FAZ area was significantly reduced in all stages of ERM compared with the fellow eyes (p < 0.05 for all). Postoperative retinal sensitivity improvement was statistically significant in Stage 1 and Stage 2.

CONCLUSION

The presence of EIFL is an independent predictor of worse postoperative BCVA. Accordingly, despite significant BCVA improvements in all stages of ERM, visual acuity gain remains limited in eyes with Stage 3 and Stage 4 ERM.

CORRELATIONS BETWEEN CHANGES IN PHOTORECEPTOR LAYER AND OTHER CLINICAL CHARACTERISTICS IN CENTRAL SEROUS CHORIORETINOPATHY

This study of 222 eyes with central serous chorioretinopathy demonstrates that morphologic changes in photoreceptor layer, visual acuity, decreasing foveal outer nuclear layer thickness, and symptom duration correlated closely but may behave asynchronously. These objective parameters, besides symptom duration, could be helpful when considering the timing of CSC treatment.

Purpose:

To clarify the correlations between changes in the photoreceptor layer (PRL) and other clinical characteristics during central serous chorioretinopathy.

Methods:

Patients with central serous chorioretinopathy with one eye affected were enrolled. Photoreceptor layer appearance within the detached area was evaluated, and its correlations with symptom duration, best-corrected visual acuity, and the difference in the foveal outer nuclear layer thickness between the affected and contralateral eyes were analyzed.

Results:

A total of 222 patients were included. The PRL outer border appeared either smooth, granulated, or as scattered dots attached to external limiting membrane. These different appearances were associated with elongation in symptom duration (18, 180, and 1,855 days), decreases in best-corrected visual acuity (6/10, 6/15, and 6/120), and increases in the difference of foveal outer nuclear layer thickness (−16, −32, and −60 μm). Among eyes with smooth PRL outer border, which had similar symptom duration, eyes with foveal PRL defect had poorer best-corrected visual acuity and greater reduction in outer nuclear layer thickness than the other eyes (all P = 0.00).

Conclusion:

Morphologic changes in PRL, best-corrected visual acuity, the reduction in foveal outer nuclear layer thickness, and symptom duration correlate closely but may behave asynchronously. These objective parameters, besides symptom duration, could be helpful when considering the timing of central serous chorioretinopathy treatment.

Reflectance and Thickness Analysis of Retinal Layers in Patients with Epiretinal Membranes Using Spectral-Domain OCT before and after Vitrectomy with Membrane Peeling

PURPOSE

To compare thickness and reflectance of retinal layer findings in patients with idiopathic epiretinal membranes (ERMs) before and after surgery with those of normal controls.

DESIGN

Retrospective study.

PARTICIPANTS

Patients with ERMs before and after surgery and healthy controls.

METHODS

Spectral-domain (SD) OCT imaging of eyes with ERMs before and after surgery and of healthy eyes were analyzed for morphologic appearance and using a customized algorithm to measure retinal layer reflectance and thickness. Findings were correlated with visual acuity outcomes.

MAIN OUTCOME MEASURES

Retinal layer thickness and reflectance.

RESULTS

Thirty-four ERM and 12 healthy eyes were identified. Mean preoperative best-corrected visual acuity (BCVA) improved from 0.53±0.31 logarithm of the minimum angle of resolution (logMAR; Snellen equivalent, 20/68) to 0.41±0.25 logMAR (Snellen equivalent, 20/51) after surgery (P = 0.030). Differences in reflectance and thickness of retinal layers were identified among the preoperative ERM, postoperative ERM, and healthy eyes. High preoperative reflectance of the internal limiting membrane (ILM) to outer plexiform layer (OPL) was correlated with better postoperative BCVA (r = -0.451; P = 0.007). A larger improvement in BCVA was correlated with preoperative thick measurements of the outer nuclear layer (r = 0.514; P = 0.002), high reflectance of the group of layers from the ILM to the OPL (r = 0.426; P = 0.012), and low reflectance of the photoreceptor layer (r = -0.453; P = 0.007). Using linear regression analysis, better postoperative BCVA was associated with better preoperative vision (standardized regression coefficient, 0.553; P = 0.001) and high reflectance of the group of layers from the ILM to OPL (standardized regression coefficient, -0.526; P = 0.001). A larger improvement in BCVA was associated with worse preoperative BCVA (standardized regression coefficient, -0.539; P < 0.001) and high reflectance of the group of layers from the ILM to OPL (standardized regression coefficient, -0.428; P = 0.001).

CONCLUSIONS

Quantitative differences in reflectance and thickness among preoperative, postoperative, and normal SD OCT imaging allow assessment of retina layer changes secondary to ERMs. High reflectance of the ILM to OPL correlated with and was associated with better postoperative BCVA and improvement in BCVA.

The relationship between foveal outer nuclear layer thickness in the active and resolved phases of central serous chorioretinopathy treated with half-dose photodynamic therapy

Background

To investigate the relationship between the foveal outer nuclear layer (ONL) thickness in the active and resolved phases of central serous chorioretinopathy (CSC), and its possible association with optical coherence tomography (OCT) parameters.

Methods

The medical records of CSC patients treated with half-dose photodynamic therapy (PDT) between August 2011 and October 2017 were reviewed. The difference between the foveal ONL thickness at 12 m after half-dose PDT and that before half-dose PDT was analyzed, and its association with OCT parameters was assessed using generalized linear models.

Results

Sixty-two patients were included. The mean difference in foveal ONL thickness was 9.15 ± 8.16 μm. The average ratios of the retinal detachment height to the subretinal space width on horizontal and vertical scans were 0.10 ± 0.04 and 0.12 ± 0.04, respectively. The ratio was independently associated with the degree of increase in the foveal ONL thickness difference on both the horizontal scans (β = 103.684, P = .000) and vertical scans (β = 67.569, P = .000), even after adjusting for potential confounders.

Conclusions

The majority of resolved CSC eyes showed some increase in foveal ONL thickness, and the degree of increase was related to the ratio of the retinal detachment height to the subretinal space width in their active phase. It suggested that the retina is stretched when it becomes detached, and recovers with resolution of the subretinal fluid. Therefore, besides photoreceptor cell death, retinal stretch may contribute to the reduction in foveal ONL thickness in eyes with active CSC.

Clinical significance of ectopic inner foveal layers in patients with idiopathic epiretinal membranes

BACKGROUND/OBJECTIVES

To evaluate the relationship between the presence of ectopic inner foveal layers (EIFL), choroidal thickness, and visual acuity (VA) in patients with epiretinal membranes (ERM) staged by spectral-domain optical coherence tomography (SD-OCT).

SUBJECTS/METHODS

A total of 242 eyes of 121 patients with unilateral idiopathic ERM were prospectively evaluated. ERM stages were defined based on the SD-OCT staging system as stage 1: negligible morphological or anatomical disruption, retinal layers, and foveal pit are identified; stage 2: characteristic stretching of the outer nuclear layer, absence of foveal depression, retinal layers are identified; stage 3: continuous EIFL crossing the central foveal area, absence of foveal depression, retinal layers are identified; and stage 4: anatomical disruption of the fovea, continuous EIFL crossing the entire foveal area, retinal layers are distorted.

RESULTS

Of 121 eyes with ERM, 23.1% had stage 1, 26.5% had stage 2, 39.7% had stage 3, and 10.7% had stage 4 disease. VA was better in eyes with stage 1 or 2 ERM than stage 3 or 4 ERM (p < 0.001). VA in logMAR was positively correlated with central foveal thickness (r = 0.557, p < 0.001) and EIFL thickness (r = 0.526, p < 0.001), but not with an outer nuclear layer thickness (r = 0.233, p = 0.123). In multivariate analysis, the presence of EIFL was an independent predictor of VA in eyes with ERM (p < 0.001). The presence and stage of ERM did not have a significant effect on choroidal thickness (p > 0.05).

CONCLUSIONS

The SD-OCT staging system according to the presence of EIFL is effective for grading retinal damage and visual loss in eyes with ERM.

INFLUENCE OF VITRECTOMY SURGERY ON THE INTEGRITY OF OUTER RETINAL LAYERS IN DIABETIC MACULAR EDEMA

PURPOSE

To investigate the influence of pars plana vitrectomy (PPV) on the integrity of photoreceptor layers in eyes with diabetic macular edema (DME) by using parallelism (a parameter that comprehensively reflects photoreceptor-retinal pigment epithelium [RPE] complex alterations) in spectral-domain optical coherence tomography (SD-OCT) imaging.

METHODS

A consecutive series of 64 eyes in 55 patients with diabetic macular edema who underwent pars plana vitrectomy were recruited into the study. Spectral-domain optical coherence tomography images were obtained preoperatively and 6 months after surgery. The morphologic features of the outer retinal layers were assessed quantitatively using parallelism and qualitatively by graders, including continuity of the external limiting membrane (ELM) line, continuity of the photoreceptor inner and outer segment (IS/OS) junction line, and the presence of hyperreflective foci in the outer retinal layers. The relationships between parallelism, visual acuity (VA), and photoreceptor layer status were evaluated.

RESULTS

After surgery, foveal thickness significantly decreased (P < 0.0001) and visual acuity improved (P < 0.0001) from baseline level. Postoperative parallelism (0.632 ± 0.137) was significantly higher than preoperative parallelism (0.531 ± 0.172) (P < 0.0001). A number of eyes with hyperreflective foci reduced after surgery, while separate evaluation of the inner and outer segment junction and external limiting membrane lines did not show significant changes. Moreover, preoperative and postoperative parallelism values showed significant correlations with postoperative visual acuity and serum lipid levels. Foveal thickness and logMAR visual acuity did not show significant correlations with any blood test data.

CONCLUSION

Pars plana vitrectomy might be effective for resolution of hyperreflective foci in outer retinal layers. Parallelism is a potential marker for localization of hyperreflective foci and useful as a predictive factor for postoperative visual acuity.

Variability of Retinal Thickness Measurements in Tilted or Stretched Optical Coherence Tomography Images

Purpose

To investigate the level of inaccuracy of retinal thickness measurements in tilted and axially stretched optical coherence tomography (OCT) images.

Methods

A consecutive series of 50 eyes of 50 patients with age-related macular degeneration were included in this study, and Cirrus HD-OCT images through the foveal center were used for the analysis. The foveal thickness was measured in three ways: (1) parallel to the orientation of the A-scan (Tx), (2) perpendicular to the retinal pigment epithelium (RPE) surface in the instrument-displayed aspect ratio image (Ty), and (3) thickness measured perpendicular to the RPE surface in a native aspect ratio image (Tz). Mathematical modeling was performed to estimate the measurement error.

Results

The measurement error was larger in tilted images with a greater angle of tilt. In the simulation, with axial stretching by a factor of 2, Ty/Tz ratio was > 1.05 at a tilt angle between 13° to 18° and 72° to 77°, > 1.10 at a tilt angle between 19° to 31° and 59° to 71°, and > 1.20 at an angle ranging from 32° to 58°. Of note with even more axial stretching, the Ty/Tz ratio is even larger. Tx/Tz ratio was smaller than the Ty/Tz ratio at angles ranging from 0° to 54°. The actual patient data showed good agreement with the simulation.

The Ty/Tz ratio was greater than 1.05 (5% error) at angles ranging from 13° to 18° and 72° to 77°, greater than 1.10 (10% error) angles ranging from 19° to 31° and 59° to 71°, and greater than 1.20 (20% error) angles ranging from 32° to 58° in the images axially stretched by a factor of 2 (b/a = 2), which is typical of most OCT instrument displays.

Conclusions

Retinal thickness measurements obtained perpendicular to the RPE surface were overestimated when using tilted and axially stretched OCT images.

Translational Relevance

If accurate measurements are to be obtained, images with a native aspect ratio similar to microscopy must be used.

The potential of spectral domain optical coherence tomography imaging based retinal biomarkers

Background

Biomarker”, a merged word of “biological marker”, refers to a broad subcategory of medical signs that objectively indicate the state of health, and well-being of an individual. Biomarkers hold great promise for personalized medicine as information gained from diagnostic or progression markers can be used to tailor treatment to the individual for highly effective intervention in the disease process. Optical coherence tomography (OCT) has proved useful in identifying various biomarkers in ocular and systemic diseases.

Main body

Spectral domain optical coherence tomography imaging-based biomarkers provide a valuable tool for detecting the earlier stages of the disease, tracking progression, and monitoring treatment response. The aim of this review article is to analyze various OCT based imaging biomarkers and their potential to be considered as surrogate endpoints for diabetic retinopathy, age related macular degeneration, retinitis pigmentosa and vitreomacular interface disorder. These OCT based surrogate markers have been classified as retinal structural alterations (macular central subfield thickness and cube average thickness); retinal ultrastructural alterations (disruption of external limiting membrane and ellipsoid zone, thinning of retinal nerve fiber layer and ganglion cell layer); intraretinal microangiopathic changes; choroidal surrogate endpoints; and vitreoretinal interface endpoints.

Conclusion

OCT technology is changing very quickly and throughout this review there are some of the multiple possibilities that OCT based imaging biomarkers will be more useful in the near future for diagnosis, prognosticating disease progression and as endpoint in clinical trials.

Inner-Retinal Irregularity Index Predicts Postoperative Visual Prognosis in Idiopathic Epiretinal Membrane

PURPOSE

To investigate the correlation between the inner-retinal irregularity index and visual outcomes before and after idiopathic epiretinal membrane (ERM) surgery.

DESIGN

Retrospective cohort study.

METHODS

We analyzed 66 eyes of 66 patients with idiopathic ERM. Ophthalmic examinations included best-corrected visual acuity (BCVA) measurements, metamorphopsia assessment, and spectral-domain optical coherence tomography before surgery and 1, 3, and 6 months post-surgery. Correlations between the inner-retinal irregularity index, defined as the length ratio between the inner plexiform layer and retinal pigment epithelium, and visual outcomes before and after ERM surgery were evaluated and compared with the correlation between the central foveal thickness, ganglion cell-inner plexiform layer (GC-IPL) thickness, interdigitation zone defect, and visual outcomes.

RESULTS

Inner-retinal irregularity index and central foveal thickness were significantly correlated with BCVA and metamorphopsia at each follow-up examination (all P < .05). The interdigitation zone defect correlated with BCVA at 3 and 6 months post-surgery (P < .001 and P < .015, respectively). However, GC-IPL thickness was not correlated with visual outcomes at any follow-up examination. The preoperative interdigitation zone defect was correlated with 6-month BCVA (P = .035) and the preoperative inner-retinal irregularity index was significantly correlated with the 6-month BCVA and marginally correlated with the 6-month metamorphopsia (P = .018 and P = .097, respectively).

CONCLUSION

The inner-retinal irregularity index was significantly correlated with visual outcomes before and after ERM surgery. This index can be used as a new surrogate marker for inner-retinal damage and a predictive prognostic marker in ERM.

Association between retinal hemorrhagic pattern and macular perfusion status in eyes with acute branch retinal vein occlusion

This prospective study included 63 eyes with acute branch retinal vein occlusion (BRVO) to evaluate the retinal hemorrhagic patterns at the posterior poles and explore their clinical relevance in macular perfusion differentiation. Retinal hemorrhagic patterns and macular perfusion status were evaluated via fundus photography and fluorescein angiography, respectively. Macular perfusion was judged as nonischemic in 30, ischemic in 28, and undeterminable in 5 among the 63 eyes. Predominant hemorrhagic patterns were flame-shaped in 39 (67.2%) and non-flame-shaped in 19 (32.8%) eyes. All 39 eyes with a flame-shaped hemorrhage showed a nonischemic macula. Of the 19 eyes classified as having a non-flame-shaped hemorrhage, 13 (68.4%) had an ischemic macula and 6 (31.6%) had a nonischemic macula (P < 0.001). Parallelism in eyes with a flame-shaped hemorrhage was higher than in those with a non-flame-shaped hemorrhage (P < 0.001), and in those with a nonischemic macula versus those with an ischemic macula (P < 0.001). The area under the curve for parallelism was 0.975 (P < 0.001), suggesting an accurate diagnostic parameter for macular perfusion differentiation. In conclusion, we objectively evaluated retinal hemorrhagic patterns at the posterior pole in BRVO using the parallelism method, which was useful in differentiating macular perfusion status.

Swept-Source Optical Coherence Tomography Correlations Between Retina and Choroid Before and After Vitrectomy for Epiretinal Membranes

PURPOSE

To describe retinal and choroidal morphology before and after surgery for epiretinal membranes (ERM) in swept-source OCT (SS-OCT). Additionally, to evaluate factors responsible for visibility of the suprachoroidal layer (SCL) and suprachoroidal space (SCS).

DESIGN

Prospective consecutive case series.

METHODS

Twenty-nine eyes of 29 patients with symptomatic, idiopathic ERM were included. Pars plana vitrectomy with ERM removal and ILM peeling was performed. We examined patients with SS-OCT twice preoperatively (9-12 months and 1 week before surgery), then postoperatively at 1 week and 6 and 12 months.

RESULTS

Twelve months after surgery visual acuity improved to 20/50 (0.48 logMAR), statistically significantly higher as compared to 1 week preoperatively (P < .001). Preoperative loss of visual acuity was commonly associated with progression of deformation of the plexiform layers, as central retinal thickness (CRT) did not decrease in this period, nor did photoreceptor defects increase. Choroidal thickness decreased 6 months after surgery (P = .02) and remained stable until 12 months postoperatively (P = .2). The outer choroidoscleral boundary was irregular in 16 eyes preoperatively but only in 4 eyes 12 months post surgery. SCS and SCL were visible in 15 eyes.

CONCLUSION

During the natural course of idiopathic ERM, deformation of the outer plexiform layer progresses and is associated with decreased visual acuity. Eyes with an initially irregular outer choroidoscleral boundary (CSB) recover visual acuity faster after vitrectomy with ILM peeling for ERM. Three factors are independently associated with the visibility of the SCS: disarrangement of plexiform layers, CRT, and multiple adhesion points between retina and ERM.

Metamorphopsia Associated with Branch Retinal Vein Occlusion

PURPOSE

To apply M-CHARTS for quantitative measurements of metamorphopsia in eyes with acute branch retinal vein occlusion (BRVO) and to elucidate the pathomorphology that causes metamorphopsia.

METHODS

This prospective study consisted of 42 consecutive patients (42 eyes) with acute BRVO. Both at baseline and one month after treatment with ranibizumab, metamorphopsia was measured with M-CHARTS, and the retinal morphological changes were examined with optical coherence tomography.

RESULTS

At baseline, metamorphopsia was detected in the vertical and/or horizontal directions in 29 (69.0%) eyes; the mean vertical and horizontal scores were 0.59 ± 0.57 and 0.52 ± 0.67, respectively. The maximum inner retinal thickness showed no association with the M-CHARTS score, but the M-CHARTS score was correlated with the total foveal thickness (r = 0.43, p = 0.004), the height of serous retinal detachment (r = 0.31, p = 0.047), and the maximum outer retinal thickness (r = 0.36, p = 0.020). One month after treatment, both the inner and outer retinal thickness substantially decreased. However, metamorphopsia persisted in 26 (89.7%) of 29 eyes. The posttreatment M-CHARTS score was not correlated with any posttreatment morphological parameters. However, the posttreatment M-CHARTS score was weakly correlated with the baseline total foveal thickness (r = 0.35. p = 0.024) and closely correlated with the baseline M-CHARTS score (r = 0.78, p < 0.001).

CONCLUSIONS

Metamorphopsia associated with acute BRVO was quantified using M-CHARTS. Initial microstructural changes in the outer retina from acute BRVO may primarily account for the metamorphopsia.

Potential measurement errors due to image enlargement in optical coherence tomography imaging

The effect of interpolation and super-resolution (SR) algorithms on quantitative and qualitative assessments of enlarged optical coherence tomography (OCT) images was investigated in this report. Spectral-domain OCT images from 30 eyes in 30 consecutive patients with diabetic macular edema (DME) and 20 healthy eyes in 20 consecutive volunteers were analyzed. Original image (OR) resolution was reduced by a factor of four. Images were then magnified by a factor of four with and without application of one of the following algorithms: bilinear (BL), bicubic (BC), Lanczos3 (LA), and SR. Differences in peak signal-to-noise ratio (PSNR), retinal nerve fiber layer (RNFL) thickness, photoreceptor layer status, and parallelism (reflects the complexity of photoreceptor layer alterations) were analyzed in each image type. The order of PSNRs from highest to lowest was SR > LA > BC > BL > non-processed enlarged images (NONE). The PSNR was statistically different in all groups. The NONE, BC, and LA images resulted in significantly thicker RNFL measurements than the OR image. In eyes with DME, the photoreceptor layer, which was hardly identifiable in NONE images, became detectable with algorithm application. However, OCT photoreceptor parameters were still assessed as more undetectable than in OR images. Parallelism was not statistically different in OR and NONE images, but other image groups had significantly higher parallelism than OR images. Our results indicated that interpolation and SR algorithms increased OCT image resolution. However, qualitative and quantitative assessments were influenced by algorithm use. Additionally, each algorithm affected the assessments differently.

Photoreceptors in diabetic retinopathy

Although photoreceptors account for most of the mass and metabolic activity of the retina, their role in the pathogenesis of diabetic retinopathy has been largely overlooked. Recent studies suggest that photoreceptors might play a critical role in the diabetes-induced degeneration of retinal capillaries, and thus can no longer be ignored. The present review summarizes diabetes-induced alterations in photoreceptor structure and function, and provides a rationale for further study of a role of photoreceptors in the pathogenesis of the retinopathy.