Association between displacement and thickness of macula after vitrectomy in eyes with epiretinal membrane

A novel vector field analysis for quantitative structure changes after macular epiretinal membrane surgery

The aim of this study was to introduce novel vector field analysis for the quantitative measurement of retinal displacement after epiretinal membrane (ERM) removal. We developed a novel framework to measure retinal displacement from retinal fundus images as follows: (1) rigid registration of preoperative retinal fundus images in reference to postoperative retinal fundus images, (2) extraction of retinal vessel segmentation masks from these retinal fundus images, (3) non-rigid registration of preoperative vessel masks in reference to postoperative vessel masks, and (4) calculation of the transformation matrix required for non-rigid registration for each pixel. These pixel-wise vector field results were summarized according to predefined 24 sectors after standardization. We applied this framework to 20 patients who underwent ERM removal to obtain their retinal displacement vector fields between retinal fundus images taken preoperatively and at postoperative 1, 4, 10, and 22 months. The mean direction of displacement vectors was in the nasal direction. The mean standardized magnitudes of retinal displacement between preoperative and postoperative 1 month, postoperative 1 and 4, 4 and 10, and 10 and 22 months were 38.6, 14.9, 7.6, and 5.4, respectively. In conclusion, the proposed method provides a computerized, reproducible, and scalable way to analyze structural changes in the retina with a powerful visualization tool. Retinal structural changes were mostly concentrated in the early postoperative period and tended to move nasally.

RHOMBUS DEFORMATION OF RETINAL LATERAL DISPLACEMENT AFTER EPIRETINAL MEMBRANE REMOVAL REVEALED BY DIFFEOMORPHIC IMAGE REGISTRATION

PURPOSE

To establish an analysis method using diffeomorphic image registration and evaluate microvascular displacement through epiretinal membrane (ERM) removal.

METHODS

Medical records of eyes that underwent vitreous surgery for ERM were reviewed. Postoperative optical coherence tomography angiography (OCTA) images were converted to the corresponding preoperative images according to a configured algorithm using diffeomorphism.

RESULTS

Thirty-seven eyes with ERM were examined. Measured changes in the foveal avascular zone (FAZ) area showed a significant negative correlation with central foveal thickness (CFT). The average amplitude of microvascular displacement calculated for each pixel was 69 ± 27 µ m in the nasal area, which was relatively smaller than that in other areas. The vector map, which included both the amplitude and the vector of microvasculature displacement, showed a unique vector flow pattern called the rhombus deformation sign in 17 eyes. Eyes with this deformation sign showed less surgery-induced changes in the FAZ area and CFT and a milder ERM stage than those without this sign.

CONCLUSION

The authors calculated and visualized microvascular displacement using diffeomorphism. The authors found a unique pattern (rhombus deformation) of retinal lateral displacement through ERM removal, which was significantly associated with the severity of ERM.

Microperimetric evaluation for different methods of epiretinal membrane surgery

PURPOSE

To investigate the anatomic and functional outcomes using microperimetry for the surgical methods for idiopathic epiretinal membranes (ERM).

METHODS

This retrospective study included 41 eyes from 41 patients. All patients underwent combined epiretinal membrane and cataract surgery. Best-corrected visual acuity (BCVA), optical coherence tomography, and microperimetry were performed before and 6 months and 1 year after surgery. The patients were divided into 3 groups; "ERM removal only without indocyanine green (ICG) staining", "ERM and internal limiting membrane (ILM) removal without ICG staining", and "ERM and ILM removal with ICG staining".

RESULTS

Preoperatively, the ages, BCVAs, central macular thickness (CMT), and mean retinal sensitivities of central 6° (MRSs) of the groups were not significantly different (p > 0.05). Postoperatively, the MRSs of the "ERM removal only without ICG staining" and "ERM and ILM removal without ICG staining" groups were not significantly different (p > 0.05). The MRSs of the "ERM and ILM removal without ICG staining" and "ERM and ILM removal with ICG staining" groups were not significantly different (p > 0.05). However, the MRSs of the "ERM and ILM removal with ICG staining" group significantly reduced than "ERM removal only without ICG staining" group (p < 0.05).

CONCLUSION

This retrospective study found reduced retinal sensitivity in ERM and ILM removal with ICG staining group compared to ERM removal only without ICG staining. Further studies with larger sample sizes are required.

Displacement of the retina and changes in the foveal avascular zone area after internal limiting membrane peeling for epiretinal membrane

PURPOSE

We investigated the differences in displacement of the outer and inner macular retina toward the optic disc after vitrectomy with internal limiting membrane (ILM) peeling for epiretinal membrane (ERM). Foveal avascular zone (FAZ) area changes were also investigated.

STUDY DESIGN

Retrospective observational study METHODS: This retrospective observational case series included 45 eyes of 43 patients that underwent vitrectomy with ERM and ILM peeling for ERM and 38 normal eyes. The locations of the centroid of the FAZ (C-FAZ, center of the foveal inner retina) and foveal bulge (center of the foveal outer retina) were determined using 3×3mm superficial optical coherence tomography angiography. C-FAZ and foveal bulge displacements, and the pre- and postoperative FAZ areas and their associated factors, were investigated.

RESULTS

Postoperative C-FAZ dislocated significantly more toward the optic disc than in pre-operative or normal eyes (P<0.001). C-FAZ and foveal bulge displaced toward the optic disc after surgery; C-FAZ showed significantly greater displacement than foveal bulge (P<0.001). The pre- and postoperative FAZ areas were correlated (P=0.01). Preoperative FAZ areas ≧0.10mm² were reduced after surgery, and FAZ areas < 0.10mm² were increased, independent of foveal displacement.

CONCLUSION

ILM peeling during vitrectomy for ERM caused larger displacement of the inner and smaller displacement of the outer retinas, towards the optic disc. Postoperative changes in the FAZ area were dependent on the baseline FAZ area, but not on the foveal displacement. ILM may physiologically exert centrifugal tractional forces on the fovea.

Vascular tortuosity analysis in eyes with epiretinal membrane imaged by optical coherence tomography angiography

Background

This study aimed to evaluate macular vessel tortuosity using optical coherence tomography angiography (OCTA) and its association with visual outcomes in eyes undergoing surgery for epiretinal membrane (ERM).

Methods

The study included 22 consecutive patients who underwent vitrectomy for ERM between May 2019 and July 2020 and OCTA at Osaka University Hospital. All patients underwent ophthalmologic examinations, including swept-source OCTA. Standard vitrectomy was performed, and the patients were followed up for 6 months postoperatively. Distortion of retinal vessels was calculated using two parameters: the actual vessel length in the vessel section (VL) and the direct vessel branching point distance (BD) in the three quadrants (nasal, temporal, and superior-inferior) of the macula. We analyzed the correlation between these parameters and visual outcomes.

Results

Significantly longer VL was found at 1, 3, and 6 months postoperatively (p = 0.006, 0.008, and 0.022, respectively) in the temporal quadrant compared to baseline temporal VL. Significantly shorter VL was found in nasal quadrants at 1 and 3 months (p = 0.046 and p = 0.018) in the comparison of nasal baseline VL. VL/BDs were correlated with the same postoperative best-corrected visual acuity (BCVA) at 1, 3, and 6 months (p = 0.035, 0.035, and 0.042, respectively) in the superior-inferior quadrant. A significant association of changes in VL and BCVA was found at 3 and 6 months postoperatively in the nasal quadrant (p = 0.018 and 0.0455, respectively).

Conclusions

Changes in vascular distortion after ERM surgery can be measured using OCTA. The change in vessels around the macula became more linear; this was associated with visual outcomes after surgery.

Unsuspected Central Vision Decrease from Macular Ganglion Cell Loss after Posterior Segment Surgery

PURPOSE

To describe a novel post-surgical complication of circumscribed macula ganglion cell loss as an apparent cause of unsuspected vision loss following posterior segment surgery.

METHODS

Patients were seen in referral and were evaluated with comprehensive examination to include optical coherence tomography (OCT) and microperimetry.

RESULTS

All 8 patients had a sudden central vision loss following vitrectomy and many patients suspected the central loss was present even before the eye patch was removed on the first postoperative day. Of the 8, 1 had a vitrectomy with no membrane peeling while the remaining 7 had membrane peeling. The mean post-operative visual acuity was 20/200. The mean ganglion cell layer (GCL) volume was 0.69 µm3 in the involved eye and 1.035 µm3 in the fellow eye (P<.001). The global retinal nerve fiber layer (RNFL) thicknesses in the involved and fellow eyes were 81.3 and 90 µm respectively (P = .08). The outer retinal architecture was unremarkable in the involved eyes and did not appear to explain the poor acuity. The GCL volume loss was not necessarily associated with RNFL thicknesses that were in the abnormal range or in optic nerve pallor. Microperimetry showed severe depression of the threshold sensitivities.

CONCLUSION

Severe loss of the macular ganglion cells may occur after vitrectomy and is associated with central vision loss. The diagnosis is made by having a high index of suspicion when examining OCT B-scan images and by evaluating GCL volumes. The frequency of this occurrence is currently unknown.