RECOVERY OF RETINAL FUNCTION AFTER RECENT-ONSET RHEGMATOGENOUS RETINAL DETACHMENT IN RELATION TO TYPE OF SURGERY

Silicone oil insulation effects on flash electroretinogram and visual evoked potential in patients with retinal detachment

BACKGROUND

Silicone oil is used as endotamponade following vitreoretinal surgery to maintain the retina reattached when indicated. This study investigates the hypothesis that silicone oil causes insulation effects on the retina by affecting its response to light.

METHODS

Electrophysiological responses to a flash stimulus were recorded using full-field electroretinography (ERG) and visual evoked potentials (VEP). Recordings were performed in 9 patients who underwent surgery for retinal detachment, before (1-2 days) and after (2-3 weeks) silicone oil removal (SOR) in both the study and the control eye. Flash ERG and VEP recordings were performed according to the ISCEV standard protocol.

RESULTS

Statistically significant differences were found in the study eye in the amplitudes of the ERG responses and their corresponding ratios, i.e. the amplitude after SOR over the amplitude before SOR, in all conditions tested. No differences were observed in the control eye. The mean ratio of photopic ERG response was 3.4 ± 2.4 for the study and 1.0 ± 0.3 for the control eye (p<0.001). The mean ratio of ERG flicker response was 3.1 ± 2.4 and 1.0 ± 0.3, respectively (p = 0.003). Scotopic flash ERG ratio was 5.0 ± 4.4 for the study and 1.3 ± 0.6 for the control eye (p = 0.012). No differences were observed for the amplitude and latency of flash VEP response after SOR.

CONCLUSIONS

Silicone oil causes a reduction in flash ERG responses; no effect was found on flash VEP responses. ERGs in eyes filled with silicone oil should not be considered representative of retinal functionality, in contrast to VEPs, which are not affected by silicone oil presence.

Coming of Age for the Photoreceptor Synapse

Purpose

To discuss the potential contribution of rod and cone synapses to the loss of visual function in retinal injury and disease.

Methods

The published literature and the authors' own work were reviewed.

Results

Retinal detachment is used as a case study of rod spherule and cone pedicle plasticity after injury. Both rod and cone photoreceptors terminals are damaged after detachment although the structural changes observed are only partially overlapping. For second-order neurons, only those associated with rod spherules respond consistently to injury by remodeling. Examination of signaling pathways involved in plasticity of conventional synapses and in neural development has been and may continue to be productive in discovering novel therapeutic targets. Rho kinase (ROCK) inhibition is an example of therapy that may reduce synaptic damage by preserving normal synaptic structure of rod and cone cells.

Conclusions

We hypothesize that synaptic damage contributes to poor visual restoration after otherwise successful anatomical repair of retinal detachment. A similar situation may exist for patients with degenerative retinal disease. Thus, synaptic structure and function should be routinely studied, as this information may disclose therapeutic strategies to mitigate visual loss.

MULTIFOCAL ELECTRORETINOGRAPHY AND SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY IN MACULA-OFF RHEGMATOGENOUS RETINAL DETACHMENT: A Prospective Cohort Study

PURPOSE

To analyze the temporal trends in structural changes using spectral-domain optical coherence tomography and functional changes using multifocal electroretinogram after rhegmatogenous retinal detachment surgery.

METHODS

This prospective cohort study enrolled 69 patients with macula-off rhegmatogenous retinal detachment who underwent successful surgery. Early Treatment Diabetic Retinopathy Study visual acuity, multifocal electroretinogram evaluation of the central 5°, and spectral-domain optical coherence tomography were recorded at 1, 3, 6, and 12 months (M) after surgery. The fellow eye served as the control group for multifocal electroretinogram parameters.

RESULTS

Between M1 and M12, visual acuity improved from 64 to 75 letters (P = 0.001) and implicit time of N1 decreased from 27.8 to 25.2 milliseconds (P = 0.001), whereas the other parameters did not vary significantly. Amplitude and implicit time values did not reach normal values at M12. Alterations of the ellipsoid zone and the external limiting membrane decreased over time (P = 0.001). P1 implicit time correlated independently with the alteration of the external limiting membrane (P = 0.007).

CONCLUSION

Foveal wave amplitudes remain lower than normal values after successful surgery of rhegmatogenous retinal detachment, whereas anatomical improvement was found for outer retinal abnormalities and subretinal edema fluid. Retinal recovery improves N1 implicit time over time. Disruption of external limiting membrane seems to be predictive of increased P1 implicit time.

Electroretinographic recordings with skin electrodes to assess effects of vitrectomy with gas tamponade on eyes with rhegmatogenous retinal detachment

The purpose of this study was to evaluate the retinal function by electroretinograms (ERGs) recorded with the RETeval system using skin electrodes after pars plana vitrectomy (PPV) with gas tamponade in eyes with a rhegmatogeneous retinal detachment (RRD). Flicker ERGs were recorded from 17 eyes with an RRD before (baseline), within 2 weeks after the PPV when the size of the tamponade gas was approximately one-half of the vitreous cavity (P1), and when the gas had been completely absorbed (P2). The amplitudes of the flicker ERGs at each phase were compared to that at the baseline. The median (25th, 75th percentile) of the amplitude was 10.0 µV (5.5, 13.0 µV) at the baseline, 11.7 µV at P1 (7.8, 14.8 µV; P = 0.003), and 17.1 µV at P2 (11.7 23.3 μV; P < 0.001). The ratio of the amplitudes in the affected eye to that in the fellow eye at the baseline and at each phase was calculated, and the ratio of the amplitudes at P1 and P2 were significantly and positively correlated (P = 0.723, P = 0.001; Spearman's rank correlation coefficient). We conclude that recordings the flicker ERGs with skin electrodes can be used to assess the physiology of eyes even with the vitreous cavity half-filled with the gas used to tamponade the retina.

Disturbed interhemispheric functional connectivity in visual pathway in individuals with unilateral retinal detachment: A resting state fMRI study

Previous neuroimaging studies demonstrated that retinal detachment (RD) subjects were associated with abnormal spontaneous brain activities; however, whether the altered interhemispheric functional connectivity (FC) occurred in RD patients remains unknown. The current study tried to explore the alternations of interhemispheric FC of the whole brain in unilateral RD patients using the voxel-mirrored homotopic connectivity (VMHC) method and their connections to clinical features. Methods: We recruited 30 patients with RD (16 males and 14 females) and 30 healthy controls (HCs) (16 males and 14 females) whose age and sex were closely matched. All subjects underwent the rs-fMRI scans. The VMHC method was applied to directly assess the hemispheres’ functional interaction. The VMHC in these brain areas, which could be used as biomarkers to differentiate RD from HC, was identified by the receiver operating characteristic (ROC) curve analyses. The relations between these patients’ clinical features and their mean VMHC signal values in multiple brain regions were calculated by Pearson correlation analysis. Results: RD patients had significantly lower VMHC values than HCs in the bilateral occipital lobe (Brodmann areas, BA 18), bilateral superior temporal gyrus (BA 39), and bilateral cuneus (BA 19). Moreover, the mean VMHC signal values of the bilateral cuneus were in positive correlation with the duration of the RD (r = 0.446, P = 0.013). Conclusion: Our results provided an evidence of disturbed interhemispheric FC in the visual area occurred in RD patients, which might provide some useful information to understand the neural mechanism of RD patients with acute vision loss. Furthermore, the VMHC values might indicate the progress of the RD.

Preoperative Electrophysiological Characterization of Patients with Primary Macula-involving Rhegmatogenous Retinal Detachment

Purpose:

To determine 1) which components of retinal function are impaired after rhegmatogenous retinal detachment, 2) which outer retinal pathways (rod- or cone-driven) are more severely affected, and 3) whether there is concomitant inner retinal dysfunction.

Methods:

We conducted a prospective observational study in a large academic institution. We performed preoperative electroretinography on eight patients to assess outer and inner retinal function. In all cases, a comparison between the eye with the detached retina and the control fellow eye was made.

Results:

Eyes with a detached retina had significantly lower a-wave and b-wave amplitudes with respect to both rod- and cone-dominated testing parameters (P < 0.05) and reduced 30 Hz flicker responses compared to fellow eyes (P < 0.05); the effect size was similar for all significantly reduced parameters (r~0.6). There were no significant differences between eyes with detached retinas and control fellow eyes with respect to b/a-wave ratios, a-wave latencies, or b-wave latencies.

Conclusion:

Patients with rhegmatogenous retinal detachment have preoperative outer retinal dysfunction equally affecting both rod- and cone-driven pathways, and they have minimal inner retinal dysfunction.

Macular dysfunction in patients with macula-on rhegmatogenous retinal detachments

AIMS

To assess macular function in patients with macula-on rhegmatogenous retinal detachments (RRDs) using focal macular electroretinography (FMERG).

METHODS

This is a prospective, observational case series of 27 patients diagnosed with a macula-on RRD. Foveal attachment was confirmed on spectral-domain optical coherence tomography. Eyes with any macular disorder, cataract, vitreous opacity or vitreous haemorrhage were excluded. FMERG was recorded in the affected and fellow eyes using a round stimulus 15° in diameter. The status of four retinal factors in the affected eyes was examined, that is, the number of involved quadrants, number of quadrants with retinal breaks, presence of an RRD invading the vascular arcade, and presence of a giant retinal tear. The implicit time and amplitude of the a-wave, b-wave and oscillatory potentials (OPs) were compared between the affected and fellow eyes using Wilcoxon signed-rank test. The influence of the four retinal factors on each FMERG component of the affected eyes was also evaluated using Mann-Whitney U test and Kruskal-Wallis test.

RESULTS

Significant reductions in the amplitudes of the a-waves (p=0.001), b-waves (p<0.001) and OPs (p=0.001) were observed in the affected eyes compared with the fellow eyes. There was no significant difference between the affected and fellow eyes in the implicit times of any components. None of the four retinal factors affected the parameters in the affected eyes.

CONCLUSION

Altered FMERG responses suggested the presence of macular dysfunction in eyes with macula-on RRDs.

Postoperative Recovery of Light Sensitivity in Eyes with Rhegmatogenous Retinal Detachment

PURPOSE

To investigate whether postoperative light sensitivity recovers completely to the level prior to the development of rhegmatogenous retinal detachment (RRD) after successful surgery.

METHODS

We retrospectively studied 44 eyes of 44 patients with RRD who were successfully operated and who underwent Humphrey central 30-2 perimetry postoperatively. The averaged total deviation in Humphrey perimetry in the reattached retina was compared with that of the horizontal or vertical counterpart in the preoperatively non-detached retina.

RESULTS

The averaged total deviation in the reattached retina was significantly lower than in its counterpart (p < 0.0001). The averaged residual loss of light sensitivity did not correlate with postoperative visual acuity (p = 0.8047) or with its change (p = 0.1242).

CONCLUSIONS

Light sensitivity in the detached retina in eyes with RRD does not completely recover after successful surgery.

Inner and outer central retinal findings after surgery for rhegmatogenous retinal detachment using different spectral-domain optical coherence tomography devices

PURPOSE

The aim of the study was to analyse macular changes after rhegmatogenous retinal detachment (RRD) repair using spectral-domain optical coherence tomography (SD-OCT).

METHODS

Forty eyes with macula-on and 27 eyes with macula-off RRD underwent scleral buckling or vitrectomy and were postoperatively imaged using 2 SD-OCT devices (Cirrus® HD-OCT, RTVue-100®). Measurement of total and inner macular thickness consisting of ganglion cell layer + inner plexiform layer (GCL-IPL) using Cirrus or retinal nerve fibre layer + ganglion cell layer + inner plexiform layer (RNFL-GCL-IPL) using RTVue was performed. Results of inner macular thickness were compared with image results of 40 healthy controls. Qualitative analysis of inner and outer retinal layers was additionally assessed.

RESULTS

Measurement of overall retinal thickness within the 9 ETDRS sectors was highly correlated between both OCTs (Pearson's r, range 0.88-0.99; p < 0.001). Correlation of RNFL-GCL-IPL complex between OCTs was excellent in both surgery groups (Pearson's r, range 0.73-0.88; p < 0.001) and normal controls (Pearson's r, range 0.79-0.90; p < 0.001). The RNFL-GCL-IPL complex was thicker in both surgery groups compared to normal controls using Cirrus. Outer retinal findings of macula-off patients were seen in four eyes (14.8 %). Visual acuity (VA) significantly improved in both groups independent of preoperative VA or duration of symptoms.

CONCLUSION

Agreement between both OCTs was excellent for overall and inner retinal thickness, although RTVue measured a thicker RNFL-GCL-IPL complex. Thinning of inner retinal layers as a potential cause of poor VA was rarely detected, possibly due to tractional changes at the vitreomacular interface. VA improved even in patients with macula-involving RRD.

Cone implicit time as a predictor of visual outcome in macular hole surgery

PURPOSE

To investigate whether preoperative retinal function measured by full-field ERG and multifocal ERG is correlated to postoperative visual acuity after macular hole surgery.

METHODS

Standard pars plana vitrectomy with removal of the internal limiting membrane (ILM) was performed on 19 consecutive patients undergoing macular hole surgery. Intraocular gas tamponade with a C2F6 gas-air mixture was employed, followed by a face-down position for at least 5 days. The patients were examined with the ETDRS chart, full-field ERG (Espion), multifocal ERG (Veris 6), and optical coherence tomography (OCT) preoperatively, and 6 weeks, 6 months, and 18 months after surgery.

RESULTS

The cone 30-Hz flicker implicit time in the full-field ERG reflecting retinal function was prolonged (p = 0.016) before surgery compared to aged-matched controls. After macula hole surgery, longstanding alteration of cone function reflected by mfERG and full-field ERG was verified 18 months after surgery. The prolonged cone 30-Hz flicker implicit time in the full-field ERG before surgery was significantly correlated to the ETDRS visual acuity 6 months postoperatively (p = 0.03).

CONCLUSIONS

Preoperative evaluation of retinal function with multifocal ERG and full-field ERG improves the understanding of the retinal recovery process after macular hole surgery. The cone implicit time in full-field 30-Hz flicker ERG could be a valid predictor of long-term visual outcome, which may be useful for selecting patients suitable for surgery.

The effect of subretinal viscoelastics on the porcine retinal function

The functional consequence of long-term retinal detachment in the porcine model is examined by multifocal electroretinography (mfERG). Retinal detachment (RD) in humans leaves permanent visual impairment, despite anatomical successful reattachment surgery. To improve treatment, adjuvant pharmaceutical therapy is needed, and can only be tested in a suitable animal model. The porcine model is promising and the mfERG is well validated in this model. RD was induced in 18 pigs by vitrectomy and healon injection of various concentrations. Preoperatively and 6 weeks postoperatively eight animals were examined by mfERG. The major component P1 was analyzed statistically. Indirect ophthalmoscopy and bilateral color fundus photography (FP) were performed. Selected animals underwent high-resolution optical coherence tomography (OCT). Examination by ophthalmoscopy and FP showed that the RDs remained detached for the 6 weeks of follow-up. The P1 amplitude of the mfERG did not differ significantly between the detached areas, the surrounding attached areas, and the healthy eye (p = 0.25). Similarly, P1 implicit time did not differ between the areas (p = 0.85). The lack of functional consequences of long-term RD makes the porcine model unsuitable for examining adjuvant pharmaceutical RD treatment. Future studies should focus on foveated primates.