Retinal layers thickness changes following epiretinal membrane surgery

Anatomical changes in idiopathic epiretinal membrane at 2-year follow-up assessed using spectral domain optical coherence tomography and optical coherence tomographic angiography

PURPOSE

To evaluate anatomical changes in the low-stage partial attachment-type idiopathic epiretinal membrane (iERM) over 2 years.

METHODS

Data from patients with low-stage partial attachment-type iERM (stage 2) were analyzed. The main outcome measures were anatomical changes, including changes in the foveal avascular zone (FAZ) area, vessel density (VD) in the vascular plexus, and thickness of retinal sublayers during the follow-up period.

RESULTS

Thirty patients (mean age: 68±12 years) were included in the study. The FAZ area on the superficial vascular plexus (SVP) significantly decreased from baseline (0.12±0.08 mm2) to month 24 (0.10±0.08 mm2, p=0.024). However, the FAZ area on the deep vascular plexus (DVP) did not significantly decrease from baseline (0.15±0.13 mm2) to month 24 (0.14±0.14 mm2, p=0.099). VDs on both the SVP and DVP did not show significant change from baseline (29.51±8.14% vs. 28.35±5.63%) to month 24 (29.79±9.77%, p=0.564 vs. 28.17±5.75%, p=0.417). Parafoveal ganglion cell and inner plexiform layer (GCIPL) thickness decreased from baseline (108.77±13.61 μm) to month 24 (103.03±15.54 μm, p=0.004). The central total retinal layer thickness did not significantly change from baseline (396.07±64.86 μm) to month 24 (392.04±72.72 μm, p=0.570).

CONCLUSION

Even in low-stage ERM, inner retinal changes, including GCIPL thickness, occurred during follow-up periods, which might be owing to degenerative changes or centrifugal movement.

THE EFFECT OF INTERNAL LIMITING MEMBRANE PEELING ON THE INNER RETINAL LAYERS IN PATIENTS WITHOUT MACULAR PATHOLOGIC CONDITION

BACKGROUND

To examine the effect of internal limiting membrane peeling on the inner retinal layers in patients without macular pathological condition.

METHODS

A prospective nonrandomized trial of patients undergoing pars plana vitrectomy with internal limiting membrane peeling for pathologic condition outside the macula was performed. Optical coherence tomography including macular ganglion cell layer, inner plexiform layer, and peripapillary retinal nerve fiber layer imaging was performed before surgery, 1, 3, and 6 months postoperatively, and at the end of follow-up (ranges between 4 and 17 months). Patients with any macular pathological condition on optical coherence tomography before surgery were excluded. The main outcome measure was change in thickness of the ganglion cell layer and inner plexiform layer.

RESULTS

Ten patients who underwent pars plana vitrectomy with internal limiting membrane peeling for macula-on retinal detachment were included in the analysis. The mean age was 55 years, and the mean follow up was 10.8 months. All patients completed at least two postoperative follow-up visits that included an optical coherence tomography as per the protocol (range 2-6 months). There was an immediate reduction in the global (G), inferotemporal, superotemporal, and superior (S) ganglion cell layer thickness at the first follow up as compared with the preoperative state ( P = 0.028, P = 0.027, P = 0.026, and P = 0.027 respectively). From the first follow-up visit onward until the final follow-up, the thinning persisted, although there was no further statistically significant thinning.

CONCLUSION

Peeling of the internal limiting membrane causes significant ganglion cell layer thinning in maculae without pathologic condition before surgery. At up to 17 months of follow-up, this effect seems to be immediate and nonprogressive.

Mechanical impact of epiretinal membranes on the retina utilizing finite element analysis

BACKGROUND AND OBJECTIVE

Epiretinal membrane (ERM) is a transparent membrane that forms on the surface of the neurosensory retina, causing tangential traction on the retinal surface, which may contribute to cell proliferation and contraction. Epiretinal membranes (ERMs) may be asymptomatic in some patients, while in others the membranes can progress, resulting in macular thickening and macular traction, thus distorting and inducing loss of central visual function and metamorphopsia. Currently, treatment options include follow-up or pars plana vitrectomy with an ERM peel, aiming to relieve the macular traction and improve vision and metamorphopsia. No specific criteria exist for predicting which patients might progress and need early surgery to improve and maintain good vision. The decision for surgery is based on the individual's symptoms and the physician's judgment. This study aimed to evaluate the mechanical impact in terms of stress and deformations of the ERM and to qualitatively compare them with the clinical progression of fovea thickening observed through optical coherence tomography (OCT) images.

METHODS

Numerical simulation on a three-dimensional geometrical retina and ERM model was applied to isolate factors that can be used to predict its progression and prognosis. OCT images of 14 patients with ERM were used to derive the fovea thickness progression before and after vitrectomy surgery with ERM peeling.

RESULTS

The results clearly show that the increase in ERM contractility level increases the developed stress at the fovea, which spreads and advances toward its base. The highest stress level (2.1 kPa) was developed at the highest and asymmetric contractility, producing non-uniform distributed deformations that distort the fovea structure.

CONCLUSIONS

These findings imply that high and asymmetric ERM contractility should be evaluated clinically as a factor that might signal the need for early vitrectomy surgery to avoid irreversible visual loss. Moreover, the OCT images revealed that in some cases, the thickness of the fovea indeed remains high, even after ∼12 months postoperatively, which also indicates that the deformation of the fovea in these cases is irreversible.

Numerical simulation of mechanical properties of epiretinal membrane peeling

An epiretinal membrane (ERM) is a fibrocellular proliferation on the inner surface of the retina causing blurred and distorted central vision. Surgery is the only effective method for ERM removal. This paper investigated the mechanical properties of ERM peeling using the finite element (FE) method. A FE model of ERM formation on the retina surface was constructed. The failure criterion was applied to the attachment pegs to represent the adhesive force between the ERM and retina. The simulation results were consistent with the experimental data in published research. The maximum peeling force was 4.1 mN at a peeling velocity of 2 mm/s and an angle of 30°. The peeling force was minimum at the peeling angle of 45° and increased with the increase in peeling velocity and Young's modulus of the membrane. The outcome of this paper can improve the safety and efficiency of ERM removal.

DEEP LEARNING-BASED PREDICTION OF OUTCOMES FOLLOWING NONCOMPLICATED EPIRETINAL MEMBRANE SURGERY

PURPOSE

We used deep learning to predict the final central foveal thickness (CFT), changes in CFT, final best corrected visual acuity, and best corrected visual acuity changes following noncomplicated idiopathic epiretinal membrane surgery.

METHODS

Data of patients who underwent noncomplicated epiretinal membrane surgery at Severance Hospital from January 1, 2010, to December 31, 2018, were reviewed. Patient age, sex, hypertension and diabetes statuses, and preoperative optical coherence tomography scans were noted. For image analysis and model development, a pre-trained VGG16 was adopted. The mean absolute error and coefficient of determination (R 2 ) were used to evaluate the model performances. The study involved 688 eyes of 657 patients.

RESULTS

For final CFT, the mean absolute error was the lowest in the model that considered only clinical and demographic characteristics; the highest accuracy was achieved by the model that considered all clinical and surgical information. For CFT changes, models utilizing clinical and surgical information showed the best performance. However, our best model failed to predict the final best corrected visual acuity and best corrected visual acuity changes.

CONCLUSION

A deep learning model predicted the final CFT and CFT changes in patients 1 year after epiretinal membrane surgery. Central foveal thickness prediction showed the best results when demographic factors, comorbid diseases, and surgical techniques were considered.

Tomographic Structural Changes of the Inner Retina after Internal Limiting Membrane Peeling for Idiopathic Epiretinal Membrane

Purpose

To investigate the tomographic structural changes in the retinal layers after internal limiting membrane (ILM) peeling for idiopathic epiretinal membrane (ERM).

Methods

Sixty-nine eyes treated with vitrectomy and ILM peeling for idiopathic ERM were analyzed. Parafoveal retinal thickness was measured at baseline and 6 months after surgery.

Results

Total retinal thickness decreased significantly in the nasal and temporal subfields after surgery (p < 0.001), whereas the inner nuclear layer and outer nuclear layer showed nasal thickening (all, p < 0.001). The postoperative temporal/nasal subfield thickness ratio of each layer was significantly lower than that of fellow eyes. Eyes with larger ILM peeling showed a significantly lower temporal/nasal subfield thickness ratio (p = 0.033) than those with smaller sizes.

Conclusions

The retinal thickness of each layer showed anatomical changes from ILM peeling and ERM removal. Nasal parafoveal thickening and temporal thinning occurred in the inner retinal architecture, which might be affected by ILM peeling size.

Functional and Morphological Results of Epiretinal Membrane Surgery in Idiopathic versus Diabetic Epiretinal Membranes

PURPOSE

Idiopathic and diabetic epiretinal membranes (ERM) are different in terms of pathophysiology, etiology, and macular morphology, and thus might respond to surgical treatment differently. We aimed to compare the surgical results of two groups.

METHODS

Retrospective case series study of 71 eyes of 66 patients who underwent pars plana vitrectomy (PPV) due to idiopathic or diabetic ERM with at least 1-year follow-up. Examinations were performed before, and 1, 3, 6, and 12 months after surgery. The average macular thicknesses in nine sectors described by the Early Treatment Diabetic Retinopathy Study (ETDRS) were measured with spectral-domain optical coherence tomography (OCT), and BCVA was evaluated. ERM recurrence rates were investigated.

RESULTS

In both idiopathic and diabetic groups, retinal thickness (RT) changes occurred as long as 12 months after vitrectomy surgery for ERM. However, in the idiopathic group, significant changes were mainly seen in the first 6 months, while in the diabetic group changes slowed considerably between the third and sixth months, but again accelerated (becoming significant) during the last 6 months.

CONCLUSIONS

According to the findings of this study, as compared to those with idiopathic ERM, diabetic patients would likely see continuing benefits from ERM surgery 6 to 12 months post surgery. The BCVA changes of the two groups were similar. ILM peeling decreased ERM recurrence in the idiopathic group but not in the diabetic group.

The effect of hemodialysis on individual retinal layer thickness

PURPOSE

The aim of this study was to employ newly developed advanced image analysis software to evaluate changes in retinal layer thickness following hemodialysis.

METHODS

A non-randomized prospective study of patients with end-stage renal disease assessed on the same day before and after hemodialysis. Intraocular pressure and central corneal thickness were analyzed, and spectral domain optical coherence tomography results were automatically segmented using the Orion software and then compared. All patients had normal retinal optical coherence tomography findings before hemodialysis.

RESULTS

Of the 31 suitable end-stage renal disease patients treated with hemodialysis who provided consent to participate, seven were unable to complete all evaluations, leaving 24 patients for analysis in the final study group. Their mean age was 66.67±14.3 years (range: 35-88), and 62.5% were males. Mean central corneal thickness did not change following hemodialysis (563.4±30.2 µm to 553.1±47.2 µm, p=.247), while mean intraocular pressure decreased (14.48±2.5 mmHg to 13.16±2.28 mmHg, p=.028). Individual mean retinal layer thickness showed no significant change, including the retinal nerve fiber layer (40.9±6.8 µm to 40.1±5.2 µm, p=.412), the ganglion cell and the inner plexiform layer (68.66±8 µm to 69.03±7.6 µm, p=.639), and the photoreceptor layer (50.26±2.8 µm to 50.32±3.1 µm, p=.869). Total retinal thickness similarly remained constant, with a mean of 303.7±17.3 µm before and 304.33±18.4 µm after hemodialysis (p=.571).

CONCLUSIONS

Thickness of retinal layers, as assessed by individual segmentation, and central corneal thickness were not affected by hemodialysis treatment, while intraocular pressure was significantly reduced among patients with end-stage renal disease without pre-existing ocular pathology who were undergoing hemodialysis. These results support the view that hemodialysis does not have a negative impact on the retinal morphology of end-stage renal disease patients, who comprise a population with high rates of diabetic and/or hypertensive retinopathy as well as vision-threatening complications.

Epiretinal Membrane Surgery: Structural Retinal Changes Correlate with the Improvement of Visual Function

Several parameters have been studied for identifying the visual outcomes after pars plana vitrectomy (PPV) for epiretinal membrane (ERM) peeling. This retrospective study aimed to analyze structural retinal changes with spectral domain-optical coherence tomography (SD-OCT) and their correlations with visual acuity improvement in patients with ERM undergoing PPV. Twenty-one pseudophakic eyes were enrolled in the study. Ophthalmic evaluations included best corrected visual acuity (BCVA) and retinal layer thickness measurements with SD-OCT. The segmentation of the retina was divided into four parts: the inner retinal layer (IRL), composed of an internal limiting membrane, retinal nerve fiber layer, ganglion cell layer, and inner plexiform layer; inner nuclear layer (INL); outer plexiform layer (OPL); and outer nuclear layer (ONL). Correlations between changes in retinal layer thicknesses and BCVA were explored over a 6 month follow-up period. The postoperative thickness decrease of the INL was significantly correlated with thickness changes in all other measured retinal layers (p < 0.001). Non-parametric linear regression showed that postoperative improvement in BCVA was associated with a postoperatively decreased thickness in the IRL (p = 0.021), INL (p = 0.039), and OPL (p = 0.021). In eyes undergoing PPV, postoperative thickness decreases of the IRL, INL, and OPL were correlated with visual acuity improvements. Re-compaction of these retinal layers after relieving ERM-induced traction may be an important factor in postoperative visual function improvement.

Evaluation of retinal vascular structure after epiretinal membrane surgery by optical coherence tomography angiography

PURPOSE

To evaluate the retinal vascular structure before and after the epiretinal membrane (ERM) surgery by optical coherence tomography angiography (OCTA).

METHODS

Twenty-two eyes with ERM (study eyes) had been evaluated by OCTA for superficial capillary plexus (SCP) and deep capillary plexus (DCP) vessel density (VD) at foveal and parafoveal regions and foveal avascular zone (FAZ) before and after ERM removal surgery. Twenty-two fellow eyes were selected as control group.

RESULTS

Preoperative VD of SCP and DCP were significantly lower in ERM eyes than in controls in both foveal and parafoveal areas (p < 0.05, for all). The difference regressed in SCP (fovea: 18.04 ± 3.1 vs 19.98 ± 18 p = 0.002 and parafovea: 47.33 ± 3.54 vs 49.71 ± 28 p = 0.001), but persisted in DCP (fovea: 17.25 ± 3.52 vs 17.57 ± 4.01 p = 0.856 and parafovea: 50.12 ± 4.35 vs 50.93 ± 3.24 p = 0.791) in study eyes, postoperatively. Superficial and deep FAZ areas were significantly smaller in study eyes than controls. Postoperatively, superficial FAZ area enlarged (0.288 ± 0.10 vs 0.307 ± 0.08 p = 0.012), whereas deep FAZ area did not (0.324 ± 0.09 vs 0.338 ± 0.07 p = 0.435). FAZ area was correlated with the best-corrected visual acuity in ERM eyes.

CONCLUSION

Vascular damage in SCP and DCP was demonstrated by OCTA in eyes with ERM. ERM removal surgery mainly improves superficial changes caused by ERM. Changes in deep retinal flow may be associated with visual outcomes after ERM removal surgery.

Focal alteration of the intraretinal layers in neurodegenerative disorders

Focal intraretinal alterations have been studied to advance our understanding of the pathology of neurodegenerative diseases. The current literature involving focal alterations in the intraretinal layers was reviewed through PubMed using the search terms "focal alteration", "region of interest", "optical coherence tomography", "glaucoma", "multiple sclerosis", "Alzheimer's disease", "Parkinson disease", "neurodegenerative diseases" and other related items. It was found that focal alterations of intraretinal layers were different in various neurodegenerative diseases. The typical focal thinning might help differentiate various ocular and cerebral diseases, track disease progression, and evaluate the outcome of clinical trials. Advanced exploration of focal intraretinal alterations will help to further validate their clinical and research utility.

Focal Thickness Reduction of the Ganglion Cell-Inner Plexiform Layer Best Discriminates Prior Optic Neuritis in Patients With Multiple Sclerosis

Purpose

The goal was to visualize topographic thickness maps of the intraretinal layers and evaluate their discrimination abilities and relationships with clinical manifestations in patients with multiple sclerosis (MS) and a history of optic neuritis (ON).

Methods

Thirty patients with relapsing-remitting MS (34 eyes with a history of ON [MSON] and 26 non-ON fellow eyes [MSFE]) were recruited together with 63 age- and sex-matched controls (HC). Ultrahigh resolution optical coherence tomography was used to image the macula and the volumetric data set was segmented to yield six intraretinal layers. Topographic thickness maps were aligned and averaged for the visualization. The thickness maps were partitioned using the Early Treatment Diabetic Retinopathy Study (ETDRS) and related to Sloan low-contrast letter acuity (LCLA), Expanded Disability Status Scale (EDSS), and disease duration.

Results

Focal thickness reduction occurred in the macular retinal nerve fiber layer (mRNFL) and ganglion cell-inner plexiform layer (GCIPL), with the most profound reduction occurring in MSON eyes (P < 0.05). A horseshoe-like thickness reduction pattern (U Zone) in the GCIPL appeared in MSON. The thickness of the U Zone had better discrimination power than the ETDRS partitions (area under the curve = 0.97) and differentiated 96% of MSON from HC. The thickness of the U Zone was positively correlated to 2.5% LCLA (r = 0.38, P < 0.05) and 1.25% LCLA (r = 0.57, P < 0.05).

Conclusions

The horseshoe-like thickness reduction of the GCIPL appeared to be an ON-specific focal thickness alteration with the highest discrimination power of prior ON.

Visual Function and Disability Are Associated With Focal Thickness Reduction of the Ganglion Cell-Inner Plexiform Layer in Patients With Multiple Sclerosis

Purpose

The purpose of this study was to visualize the topographic thickness patterns of the intraretinal layers and their associations with clinical manifestations in patients with multiple sclerosis (MS).

Methods

Ninety-four eyes of 47 relapsing-remitting MS patients without history of optic neuritis were imaged using optical coherence tomography and compared with 134 eyes of 67 healthy subjects. Volumetric data centered on the fovea were segmented to obtain the thickness maps of six intraretinal layers. The thickness measurements partitioned using the Early Treatment Diabetic Retinopathy Study (ETDRS) partition were correlated to the Expanded Disability State Scale (EDSS) and Sloan low contrast visual acuity (LCVA). The receiver-operating characteristics (ROC) curves were calculated to obtain the area under the ROC curves (AUCs).

Results

The ganglion cell-inner plexiform layer (GCIPL) showed horseshoe-like thickness reduction profoundly at the nasal sector. The most profound thickness reduction zone (circular area, diameter = 1 mm) was located at 2 mm in the nasal sector and 0.4 mm inferior from the fovea, named the “M zone.” The thickness reduction of the M zone was −7.3 μm in MS eyes, which was the most profound alteration, compared to any ETDRS sectors. The AUC of the M zone was 0.75. The relationship between the thickness of the M zone and EDSS (r = −0.59, P < 0.001) or 2.5% LCVA (r = 0.51, P < 0.001) were ranked as the strongest relation compared to any ETDRS sectors.

Conclusions

This is the first study, to our knowledge, to visualize focal thickness alteration of GCIPL and reveal its relationship to visual function and disability in patients with MS without history of optic neuritis.