Association of retinal vessel density with retinal sensitivity in surgery for idiopathic epiretinal membrane

Microstructural and hemodynamic changes in the fundus after pars plana vitrectomy for different vitreoretinal diseases

BACKGROUND

Pars plana vitrectomy is the standard treatment for several vitreoretinal diseases. Continuous improvements in ophthalmic surgical techniques have led to excellent postoperative recovery of the anatomic structure of the fundus. However, postoperative visual outcomes are not always satisfactory.

METHODS

A literature search of articles published before 31 December 2022 was conducted on PubMed using the following keywords: "diabetic retinopathy," "rhegmatogenous retinal detachment," "idiopathic epiretinal membrane," "idiopathic macular hole," "vitrectomy," "optical coherence tomography," "optical coherence tomography angiography," "microstructure," "microstructural," "hemodynamic," "hemodynamics," and "microcirculation." Additional studies were identified by hand-searching references for relevant studies. Articles were screened for language, repetition, and relevance to the direction of study. Studies with a sample size ≥ 7 and the final follow-up time ≥ 4 weeks after vitrectomy were included in this review. Only articles published in English were included. Articles not related to our topic were excluded. Reviews and single case reports were excluded. We structured this review by disease category. The thickness of the retina and choroid, the area of the foveal avascular zone, the vessel density of the retinal and choroidal capillary plexus, and the potential association of related parameters with postoperative visual outcomes are the main outcome measures of studies included in this review.

RESULTS

A total of 48 studies were included in this review. There were contradictory results regarding the association between postoperative microcirculatory parameters and visual acuity in patients with diabetic macular edema, with some studies concluding that improvement in perimacular microcirculation may be an important factor that affects visual acuity, and others concluded that postoperative improvement in visual acuity was not related to changes in macular blood flow. The results of studies on the relationship between postoperative microstructural and microcirculatory parameters and visual acuity in rhegmatogenous retinal detachment, idiopathic epiretinal membrane, and idiopathic macular hole eyes have been inconsistent. In gas tamponade macula-off rhegmatogenous retinal detachment eyes, postoperative best-corrected visual acuity has been reported to correlate positively with vessel density of deep capillary plexus and negatively with foveal avascular zone area of superficial capillary plexus and deep capillary plexus. In silicone oil tamponade macula-off rhegmatogenous retinal detachment eyes, best-corrected visual acuity has been reported to be positively correlated with the retinal thickness of the parafoveal 3 mm temporal quadrant and positively correlated with the vessel density of the superficial capillary plexus in the foveal, parafoveal, and perifoveal area. In addition, best-corrected visual acuity was worse and associated with reduced thickness of the inner retina, ganglion cell layer, outer plexiform layer, and outer nuclear layer in silicone oil tamponade rhegmatogenous retinal detachment eyes compared to gas tamponade. Postoperative best-corrected visual acuity in idiopathic epiretinal membrane eyes was positively correlated with the foveal avascular zone area but negatively correlated with full retinal thickness and inner retinal thickness in the foveal and parafoveal areas. Improvement in postoperative best-corrected visual acuity in idiopathic macular hole eyes was associated with reduced inner retinal thickness and reduced foveal avascular zone area.

CONCLUSIONS

Microstructural and hemodynamic changes are involved in the recovery process after PPV for different vitreoretinal diseases. The thickness of each retinal layer in different regions of the macula, foveal avascular zone area, and vessel density of different retinal capillary plexuses in different macular regions may be potential prognostic factors for postoperative visual recovery. However, the results of the existing literature are inconsistent and require further study.

Correlation between retinal sensitivity and retinal vascular perfusion after idiopathic epiretinal membrane peeling

BACKGROUND

To evaluate the correlations between anatomical and functional changes after idiopathic epiretinal membrane (iERM) surgery.

METHODS

In this prospective, observational, single-center study, consecutive patients who underwent iERM peeling were enrolled. Reported data were pre- and postoperative best-corrected visual acuity (BCVA), retinal sensitivity (RS) and fixation stability values on microperimetry, structural macular features on SD-OCT and OCTA. RS of foveal and parafoveal area was analysed and two sub-groups were identified whether RS improved or remained unchanged/worsened after surgery; consequently, vascular perfusion density (VPD) of the same area was studied.

RESULTS

Twenty-nine eyes of 29 patients were examined. The post-operative improvement in terms of BCVA, RS and fixation within the central 4 degrees was significant (p < 0.001, p < 0.001, p = 0.001), as well as the foveal thickness and macular volume change/reduction (p < 0.001). The pre-operative superficial VPD, choriocapillaris VPD and capillary free zone (CFZ) area were significantly reduced compared to the fellow healthy eye (p = 0.001, p = 0.02, p < 0.001). Choriocapillaris VPD showed a statistically significant increase after surgery (p < 0.02). Superficial, deep and choriocapillaris VPD of the improved RS group showed a significant increase both in foveal (p = 0.03, p = 0.03, p = 0.01) and parafoveal areas (p = 0.01, p = 0.03, p = 0.001).

CONCLUSIONS

We reported a higher VPD in the retinal area that experienced a retinal sensitivity improvement 6 months after ERM surgery. This result objectifies the tight bond between visual function and retinal perfusion in ERM patients.

[Effects of internal limiting membrane peeling in epiretinal membrane surgery on OCT-angiography]

PURPOSE

To assess macular microvascular parameters using OCT-angiography (OCT-A) in idiopathic epiretinal membrane surgery with or without internal limiting membrane peeling.

MATERIALS AND METHODS

We retrospectively studied 17 eyes of 17 patients who underwent vitrectomy surgery for idiopathic epiretinal membrane with (n=10) or without (n=7) internal limiting membrane peeling. Patients operated on between July 2020 and June 2022 at the Colmar Hospital (France) by a single surgeon were evaluated before and 1 month after surgery, using OCT-A (Spectralis OCT-A module, Heidelberg Engineering®, Germany). The parameters studied were the area, perimeter and acircularity index of the foveal avascular zone (FAZ), the foveolar (FVD) and parafoveolar (PRVD) perfusion density and the macular vessel density ratio (MVR) in the superficial vascular complex (SVC) and the deep vascular complex (DVC). These parameters were measured using ImageJ software (National Institutes of Health, Bethesda, Maryland, USA).

RESULTS

We found no statistically significant difference between the two groups postoperatively in either area, perimeter, or acircularity index of the FAZ, FVD, PRVD, or MVR in either the SVC or DVC.

CONCLUSION

Our results with regard to macular microvasculature demonstrate no difference related to peeling of the internal limiting membrane and thus do not argue against this practice during epiretinal membrane surgery.

[Clinical and pathophysiological contribution of OCT-angiography to epiretinal membranes]

Epiretinal membranes may lead to centripetal contraction forces on the retina and its vessels. OCT-Angiography (OCT-A) is a recent tool which permits a non-invasive understanding of these vascular changes. This review focuses on the OCT-A findings in idiopathic epiretinal membranes, before and after surgery, and the role of internal limiting membrane peeling. It appears that contraction of the epiretinal membrane is associated with both a reduction in the area and perimeter of the foveal avascular zone and alterations in the superficial and deep capillary plexuses. These changes mainly reflect a vascular shift from the perifoveal to the foveal region, increasing with retinal deformation, but also probable dynamic changes in vascular flow. Membrane peeling allows at least partial improvement of these microvascular parameters. Nevertheless, some limitations of OCT-A, such as segmentation errors on a retina with highly modified architecture, can lead to a selection bias in the studies and should call for caution in the interpretation of the results. Finally, internal limiting membrane peeling contributes to changes in the retinal architecture after surgery, in particular by causing a centripetal movement of the macular capillaries and a displacement of the fovea toward the optic nerve head. This role should be clarified in future studies.

Quantitative assessment of retinal microvascular remodeling in eyes that underwent idiopathic epiretinal membrane surgery

Purpose: To explore the surgical outcomes of the macular microvasculature and visual function in eyes with idiopathic epiretinal membrane (iERM) using spectral-domain optical coherence tomography angiography (SD-OCTA). Methods: This observational, cross-sectional study included 41 participants who underwent iERM surgery with a 3-month (3M) follow-up. Forty-one healthy eyes formed the control group. The assessments included best-corrected visual acuity (BCVA) and mean sensitivity (MS) by microperimetry and SD-OCTA assessment of vessel tortuosity (VT), vessel density (VD), foveal avascular zone, and retinal thickness (RT). Results: The findings showed statistically significant differences in VT, foveal avascular zone parameters, RT, BCVA, and MS between the iERM and control groups (p < 0.05). After iERM surgery, the macular VT, SCP VD, and RT decreased significantly (p < 0.01) while the DCP VD increased (p = 0.029). The BCVA improved significantly (p < 0.001) and was associated with the MS (rs = -0.377, p = 0.015). MS was associated with the SCP VD and RT at 3M (SCP VD rs = 0.511, p = 0.001; RT rs = 0.456, p = 0.003). In the superior quadrant, the MS improved significantly (p < 0.001) and the improvement of MS was associated with the reduction of VT (β = -0.330, p = 0.034). Conclusion: Microcirculatory remodeling and perfusion recovery were observed within 3 months after iERM surgery. VT was a novel index for evaluating the morphology of the retinal microvasculature in eyes with iERM and was associated with MS in the superior quadrant.

Development of an anti-oxidative intraocular irrigating solution based on reactive persulfides

Anti-oxidative intraocular irrigating solutions (IISs) based on reactive persulfides, such as oxidized glutathione disulfide (GSSG), are commonly used worldwide. However, even with GSSG-based IISs, it has been shown that oxidative stress can occur during surgery, posing a risk to intraocular tissues. This study compared two IISs: one containing GSSG and one containing an oxidized glutathione trisulfide (GSSSG). Experimental in vivo irrigation with the IISs in rabbits showed that there was less leakage into the anterior chamber of rabbit serum albumin during perfusion with a 300-μM GSSSG IIS than with a 300-μM GSSG IIS. Experimental in vivo cataract surgery in rabbits showed that aqueous flare was suppressed 3 days after surgery with a 600-μM GSSSG IIS, but not with a 300-μM GSSSG or 300-μM GSSG IIS. Furthermore, an in vitro experiment, without any live tissue, showed that reactive oxygen species were suppressed more strongly with a 600-μM GSSSG IIS than with a 300-μM GSSG IIS. Thus, this study found that novel IISs based on GSSSG had anti-inflammatory and anti-oxidative effects during and after intraocular surgery and may decrease the rate of complications after surgery.

Screening of idiopathic epiretinal membrane using fundus images combined with blood oxygen saturation and vascular morphological features

PURPOSE

To achieve an accurate diagnosis of idiopathic epiretinal membrane (iERM) through analyzing retinal blood vessel oxygen saturation (SO2) and vascular morphological features in fundus images.

METHODS

Dual-modal fundus camera was used to obtain color fundus image, 570-nm, and 610-nm images. As iERM affects the macular area, a macular-centered semicircle area as region of interest (MROI) was selected and analyzed SO2 and vascular morphologies in it. Eventually, random forest (RF) and support vector machine (SVM) were as classifiers to diagnose iERM patients.

RESULTS

The arterial and venous SO2 levels of the iERM group were significantly higher than that of the control group. There were significant differences in the vessel density and fractal dimension on the artery for vascular morphology, while the tortuosity had a significant difference in the vein. By feeding the SO2 and the vascular morphological features into classifiers, an accuracy of over 82% was obtained, which is significantly better than the two separate inputs for classification.

CONCLUSION

Significant differences in SO2 and vascular morphologies between control and iERM groups confirmed that the occurrence of iERM may affect blood supply and vascular structures. Benefiting from the dual-modal fundus camera and machine learning models, accurate judgments can be made on fundus images. Extensive experiments proved the importance of blood vessel SO2 and vascular morphologies for diagnosis, which is of great significance for clinical screening.

Association of Microvasculature and Macular Sensitivity in Idiopathic Macular Epiretinal Membrane: Using OCT Angiography and Microperimetry

Purpose: To investigate the correlation between retinal capillary structure and macular function in patients with idiopathic epiretinal membrane (iERM) by using optical coherence tomography angiography (OCTA) and microperimetry.

Methods: This retrospective and observational study included 30 idiopathic ERM eyes of 30 consecutive patients. OCTA was performed to evaluate macular microvasculature including the superficial capillary plexus, deep capillary plexus, and foveal avascular zone. Best corrected visual acuity (BCVA) and microperimetry were measured at baseline and 3 months after surgery. Associations between macular microvasculature and visual function were assessed.

Results: Visual function including BCVA and macular sensitivity improved significantly at 3 months post-operatively (p < 0.001). At baseline, BCVA was positively correlated with foveal or parafoveal sensitivities and negatively correlated with central foveal thickness (p < 0.05). Pre-operative foveal sensitivity was significantly correlated with the vessel density of foveal or parafoveal superficial capillary plexus (p < 0.05). A multiple regression model revealed that pre-operative vessel density of foveal deep capillary plexus was an independent positive prognostic factor for post-operative BCVA (B = −0.020 ± 0.006, p = 0.006) and macular sensitivity (B = 0.200 ± 0.081, p = 0.027).

Conclusion: Integrated evaluation of iERM by using OCTA and microperimetry shows an association between microvasculature and macular sensitivity. Pre-operative vessel density of foveal deep capillary plexus assessed by OCTA may be a potentially valuable prognostic factor for iERM surgery.

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.