Microcirculation in the macular area of eyes with an idiopathic epiretinal membrane

Colorimetric Analyses of the Optic Nerve Head and Retina Indicate Increased Blood Flow After Vitrectomy

Purpose

The purpose of this study was to evaluate the impact of vitrectomy and posterior hyaloid (PH) peeling on color alteration of optic nerve head (ONH) and retina as a surrogate biomarker of induced perfusion changes.

Methods

Masked morphometric and colorimetric analyses were conducted on preoperative (<1 month) and postoperative (<18 months) color fundus photographs of 54 patients undergoing vitrectomy, either with (44) or without (10) PH peeling and 31 years of age and gender-matched control eyes. Images were calibrated according to the hue and saturation values of the parapapillary venous blood column. Chromatic spectra of the retinal pigment epithelium and choroid were subtracted to avoid color aberrations. Red, green, and blue (RGB) bit values over the ONH and retina were plotted within the constructed RGB color space to analyze vitrectomy-induced color shift. Vitrectomy-induced parapapillary vein caliber changes were also computed morphometrically.

Results

A significant post-vitrectomy red hue shift was noted on the ONH (37.1 degrees ± 10.9 degrees vs. 4.1 degrees ± 17.7 degrees, P < 0.001), which indicates a 2.8-fold increase in blood perfusion compared to control (2.6 ± 1.9 vs. 0.9 ± 1.8, P < 0.001). A significant post-vitrectomy increase in the retinal vein diameter was also noticed (6.8 ± 6.4% vs. 0.1 ± 0.3%, P < 0.001), which was more pronounced with PH peeling (7.9 ± 6.6% vs. 3.1 ± 4.2%, P = 0.002).

Conclusions

Vitrectomy and PH peeling increase ONH and retinal blood flow. Colorimetric and morphometric analyses offer valuable insights for future artificial intelligence and deep learning applications in this field.

Translational Relevance

The methodology described herein can easily be applied in different clinical settings and may enlighten the beneficial effects of vitrectomy in several retinal vascular diseases.

[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.

Retinal vessel geometry in patients with idiopathic epiretinal membrane

We investigated the associations between retinal vascular geometric measurements and idiopathic epiretinal membrane (ERM). Whether changes in retinal vascular geometry are independent of systemic cardiovascular risk factors was also evaluated. This retrospective, cross sectional study included 98 patients with idiopathic ERM, and 99 healthy age-matched controls. Quantitative retinal vascular parameters were measured from digital retinal fundus photographs using a semi-automated computer-assisted program. Multivariate logistic regression analyses were performed to evaluate associations between retinal vascular geometric parameters and the presence of idiopathic ERM after adjusting for systemic cardiovascular risk factors. There was no significant difference in the baseline characteristics of the two groups, except that the ERM group had a higher proportion of females than the control group. In multivariate regression analyses, female sex (odds ratio [OR] 0.402; 95% CI 0.196-0.802; P = 0.011), wider retinal venular caliber (OR 16.852; 95% CI 5.384-58.997; P < 0.001) and decreased total fractal dimension (OR 0.156; 95% CI 0.052-0.440; P = 0.001) were associated with idiopathic ERM. Idiopathic ERM was associated with alterations in global retinal microvascular geometric parameters, wider retinal venules, and less complex vascular branching patterns, independent of cardiovascular risk factors.

Correlation between Visual Acuity and Optical Coherence Tomography Angiography Parameters in Unilateral Idiopathic Epiretinal Membrane

Background: The tangential traction by idiopathic epiretinal membrane (iERM) may alter the hemodynamics of the macula. We investigated the correlation between visual acuity and the optical coherence tomography angiography (OCTA) parameters in unilateral iERM. Methods: We included 61 eyes of 61 consecutive patients with unilateral iERM between January 2018 and December 2018. The flow area of the retinal superficial capillary plexus (SCP), deep capillary plexus (DCP), and choroidal capillary plexus (CCP) were measured using OCTA. The normal fellow eyes were used for comparison. The iERM patients were divided into those with a presence of foveal concavity and those with a loss of foveal concavity. Results: When compared with fellow eyes, the flow areas showed a statistically significant decrease in the SCP and CCP of those with iERM (p = 0.037 and p = 0.011, respectively). In the DCP, no significant reduction in flow area was found in iERM (p = 0.054). The flow area of the CCP was the only factor significantly associated with best vision (p = 0.012). No significant differences in the flow areas of the SCP, DCP, and CCP were found between the presence and loss of foveal concavity. Conclusions: The flow area of the CCP is an important determinant of vision, emphasizing the crucial role of choroidal circulation in iERM. Moreover, mechanical stretch by iERM is not the only mechanism affecting the flow area.

Intraretinal microvascular changes after ERM and ILM peeling using SSOCTA

BACKGROUND

To prospectively investigate retinal vascular changes in patients undergoing epiretinal membrane (ERM) and internal limiting membrane (ILM) peeling using swept source optical coherence tomography angiography (SSOCTA).

METHODS

Consecutive patients were grouped based on ERM severity and followed using SSOCTA up to month 3 after surgical intervention. Superficial and deep foveal avascular zone (s/dFAZ) as well as foveal and parafoveal vessel density (VD) were correlated with ERM severity and visual acuity. Differences between groups were evaluated.

RESULTS

Significant correlations were found between ERM severity and baseline sFAZ, dFAZ and best corrected visual acuity (BCVA), central retinal subfield thickness (CST) and ΔCST (r = -0.52, r = -0.43, r = -0.42, r = 0.58, r = 0.39; all p<0.05). Vascular flow parameters did not correlate with age, peeling size, pseudophakia or CST, but correlated with intraretinal cysts presence. No associations of BCVA with any of the OCTA parameters across time were found. Significant differences between ERM severity groups 1 and 2 were found for sFAZ at baseline (p = 0.005) and at the 3-month follow-up (p = 0.014), and for dFAZ at baseline (p = 0.017). Superficial foveal and parafoveal VD were not significantly different between groups (all p>0.05).

CONCLUSIONS

This study clearly shows that ERM severity based on ERM staging has to be taken into account when undertaking studies in patients with idiopathic ERM using SSOCTA. Further, specific changes in the superficial and deep retinal vasculature in eyes undergoing ERM and ILM peeling were found. However, the clinical usefulness and prognostic value for post-surgical treatment BCVA of the SSOCTA-derived variables (sFAZ and dFAZ area, as well as foveal and parafoveal VD) used remains questionable.

Macular capillary plexuses after epiretinal membrane surgery: an optical coherence tomography angiography study

AIMS

To investigate macular vascular integrity using optical coherence tomography angiography (OCTA) in patients undergoing vitrectomy for idiopathic epiretinal membrane (ERM) removal and to determine its association with structural and visual outcomes.

METHODS

Forty-three patients with unilateral ERM who were followed for ≥6 months after surgery were included. Ophthalmological evaluations included best-corrected visual acuity (BCVA) and spectral-domain OCT (SD-OCT) before surgery and 6 months after surgery. We obtained en face OCTA images of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) for both eyes 6 months after ERM removal. We compared eyes with ERM to unaffected fellow eyes as controls and used interocular differences in the analyses.

RESULTS

Compared with the fellow eyes, eyes with ERM after surgery had a lower parafoveal vascular density (VD) and a smaller foveal avascular zone (FAZ) area in both SCP and DCP (all p<0.001). Interocular differences in the FAZ area and parafoveal VD were correlated with preoperative and postoperative central foveal thicknesses (all p<0.05). In addition, interocular differences in macular vascular integrity had a tendency to be correlated with SD-OCT parameters of the inner retinal layers. Finally, greater interocular differences in the FAZ area and parafoveal VD of both plexuses were significantly associated with worse postoperative BCVAs (all p<0.05).

CONCLUSIONS

Assessing macular capillary plexuses via OCTA may be useful to quantify structural changes of the inner retinal layer and predict visual function in patients undergoing ERM removal surgery.

Focal Nonperfusion of Deep Retinal Capillary Plexus in Eyes With Epiretinal Membranes Revealed by Optical Coherence Tomography Angiography

BACKGROUND AND OBJECTIVE

To evaluate the leakage pattern in eyes with idiopathic epiretinal membranes (ERM) using fluorescein angiography (FA) and the structure of the retinal capillary plexus with optical coherence tomography angiography (OCTA).

PATIENTS AND METHODS

The authors enrolled patients with idiopathic macular ERM in the consecutive case series study. All patients were evaluated using FA at the central macula area and OCTA at the central 3 mm × 3 mm.

RESULTS

Six patients (seven eyes) with ERM completed this preliminary study. The authors examined five eyes that showed increased macular thickness without a lamellar hole and two eyes that showed combined ERM with a lamellar hole. In the five eyes with ERM alone, the irregular focal hypofluorescent areas in FA corresponded to the locations of absent or low flow signals within vasculatures in the deep retinal capillary plexus seen in OCTA, whereas most of the superficial retinal capillary plexus was not affected, except vascular tortuosity in OCTA. In the two eyes combined with lamellar hole, OCTA showed central cystic lesions without vasculatures, but no low flow signals within vasculatures in the deep retinal capillary plexus beyond the hole. These focal irregular, absent, or low flow signals within vasculatures in the deep retinal plexus improved 1 month after surgical removal of the ERM in one eye.

CONCLUSION

Mechanical stress exerted from the ERM might affect deep retinal capillary flow more profoundly than the superficial capillary flow, which would account for the fluorescence changes seen in FA. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:404-409.].

Scanning laser Doppler flowmeter study of retinal blood flow in macular area of healthy volunteers

AIM

To compare the interocular and intraocular differences of capillary perfusion, and the intraocular regional differences of retinal blood flow in the macular area of healthy volunteers.

METHODS

Tissue blood flow in the macula was examined in both eyes of 20 healthy volunteers with the Heidelberg retinal flowmeter. Blood flow measurements were made in a 10 degrees x 2.5 degrees area superior and inferior to the macula. The mean blood flow (MBF) was calculated by an automatic full field perfusion image analyser program. The MBF in the right and left eyes and in the superior and inferior macular areas of the same eye were compared.

RESULTS

The ratios of the MBF in the right eye to the left eye in the macular areas were 1.00, and 1.03, respectively. The ratio of the MBF in the superior macular area to the inferior area was 1.01 for the right eyes and 1.04 for the left eyes.

CONCLUSIONS

Because no significant differences were found in the MBF between the two eyes and between the superior and inferior macular areas in the same eye, interocular (for example, affected eye versus fellow eye) and intraocular (superior versus inferior macular areas) comparisons of MBF can be made to determine if changes in retinal perfusion have occurred.

In situ confirmation of retinal blood flow improvement after carotid endarterectomy in a patient with ocular ischemic syndrome

PURPOSE

To report a patient with ocular ischemic syndrome due to an internal carotid artery stenosis in whom we confirmed improved retinal blood flow noninvasively after carotid endarterectomy.

DESIGN

Observational case report.

METHODS

Retinal flowmetry.

RESULTS

In a 72-year-old hypertensive man with a transient ischemic attack including dysgraphia, carotid angiography revealed approximately 90% stenosis of the left internal carotid artery. Standard carotid endarterectomy was performed. Postoperatively, good patency of the left internal carotid artery was confirmed by magnetic resonance angiography. We measured tissue blood flow in the fundus of each eye using a Heidelberg retina flowmeter before and after endarterectomy. Preoperative measurements showed reduction of blood flow in the left fundus, while values 3 months after surgery indicated a significant improvement of blood flow (P <.05, one-factor analysis of variance [ANOVA]).

CONCLUSIONS

Retinal flowmetry can noninvasively detect differences in retinal blood flow between eyes in a patient with unilateral internal carotid artery stenosis and also assess the improvement of retinal blood flow after carotid endarterectomy.