Retromode Imaging Technology for Detecting Drusen-Like Deposits in Healthy Adults.

PURPOSE: To investigate the ability of retromode imaging technology to visualize drusen-like deposits (DLDs) in the macular region of healthy individuals without retinal diseases. Additionally, the correlation between subject age and the density of DLDs was assessed and their topographic distribution was evaluated. DESIGN: Prospective, observational, cross-sectional study SUBJECTS: Healthy volunteers (aged ≥ 35 years) without macular diseases. METHODS: This study evaluated macular images in healthy adults using color fundus photography (FP) and retromode imaging. Two masked graders counted the number of DLDs identifiable with each modality. The standardized ETDRS concentric rings were adopted to divide DLDs based on their topographic distribution. MAIN OUTCOME MEASURES: Comparison of the number of DLDs detected with each imaging modality. The association between DLDs and age. The topographic distribution of macular DLDs with retromode imaging. RESULTS: The study included 91 eyes of 52 healthy volunteers (mean ± standard deviation age, 57.9 ± 10.9 years; range, 36-82 years). Overall, at least 1 DLD was present in 63.74% of eyes on color FP and 96.71% on retromode. Retromode imaging allowed detection of significantly more DLDs compared with color FP within the ETDRS grid (median [interquartile range], 4 [1-14] vs. 0 [0-0] respectively; P < 0.001). The density of DLDs was higher in the outer and inner rings compared with the central subfield (relative risk [RR], 16.70; 95% confidence interval [CI], 10.3-27.3 vs. RR 17.1; 95% CI, 10.5-27.6, respectively). Age was significantly correlated with DLDs density in all 3 sectors (all P < 0.05). CONCLUSIONS: Retromode technology allowed the detection of a significantly higher number of DLDs compared with FP in the macula of healthy individuals. This noninvasive imaging modality could be used to investigate the effect of the aging process on the macula, fostering a better understanding of the pathophysiology of age-related macular diseases. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Functional and anatomic changes between early postoperative recovery and long-term follow-up after combined epiretinal and internal limiting membrane peeling.

OBJECTIVE: To evaluate short- and long-term changes in best-corrected visual acuity (BCVA) and retinal layer thicknesses after combined epiretinal membrane (ERM) and internal limiting membrane (ILM) peeling for macular holes and symptomatic ERMs. DESIGN: Retrospective observational case series. PARTICIPANTS: Patients with ERMs or with macular holes and ERMs treated with combined ERM and ILM peeling. METHODS: Study eyes (n = 36) and healthy fellow eyes (n = 17) were evaluated using the automated segmentation of retinal layers performed by SPECTRALIS software that automatically calculated the average central retinal thickness and the average thickness in each of the individual retinal layers. The analysis was performed at 6-18 months after surgery and after 60 months. MAIN OUTCOME MEASURES: Changes in BCVA and retinal layer thicknesses determined by automated segmentation at the first and last follow-up visits. RESULTS: BCVA improved from a baseline 0.48 ± 0.25 logMAR (20/60 Snellen) to 0.18 ± 0.18 logMAR (20/30 Snellen) at the short-term postoperative examination (p < 0.0001). Between first and last follow-up visit, 5 eyes (14%) were classified as better, 28 (78%) as stable, and 3 (8%) as worse. BCVA of the control fellow eyes remained stable during the follow-up. The thicknesses of retinal layers decreased significantly (p < 0.009). At the last follow-up, the ganglion cell layer was thinner and the inner nuclear layer was thicker in the operated eyes compared with the healthy fellow eyes. CONCLUSION: Combined ERM and ILM peeling may improve BCVA in some patients. However, over a long follow-up period, it can be associated with progressive ganglion cell layer thinning that could affect BCVA stability.

Full-Thickness Macular Hole: Are Supra-RPE Granular Deposits Remnants of Photoreceptors Outer Segments? Clinical Implications.

PURPOSE: To describe the presence of specific morphological characteristics of idiopathic, full-thickness macular hole (MH) potentially influencing postoperative best corrected visual acuity (BCVA) and surgical outcomes. DESIGN: Retrospective, multicenter and interventional case series. METHODS: Clinical charts and multimodal imaging pictures of 149 eyes of 143 consecutive patients diagnosed with MH, treated surgically and with a minimum follow-up of 12 months, were reviewed. RESULTS: Supra-retinal pigment epithelium (RPE) granular deposits were diagnosed in 121 of 149 eyes (81.2%). A smooth morphology was identified in 58 of 149 eyes (38.9%), whereas a bumpy border was present 91 of 149 eyes (61.1%). Photoreceptor disruption was mainly located close to the MH aperture. In 8% of the included cases, preoperative anatomical progression from smooth to bumpy morphology was noted. The presence of supra-RPE granular deposits was a significant predictor of lower postoperative BCVA only in univariate analysis (P < .001). The presence of a bumpy border was significantly correlated with lower postoperative BCVA in both univariate and multivariate analysis (P < .001). BCVA gain was significantly lower in MH with bumpy borders (P < .001). A bumpy border was also significantly associated with poor postoperative anatomical restoration (P < .001). CONCLUSIONS: Supra RPE-granular deposits and a bumpy morphology may be indicators of photoreceptor disruption in MH. A bumpy morphology may suggest deeper and potentially irreversible photoreceptor damage, and may negatively influence both functional and anatomical recovery.

Quantitative autofluorescence findings in patients undergoing hydroxychloroquine treatment.

BACKGROUND: To measure quantitative autofluorescence (qAF) in patients under treatment with hydroxychloroquine (HCQ) and at risk of retinal toxicity but with no apparent signs of retinal toxicity and to compare it with that of untreated subjects. METHODS: Consecutive patients at risk for the development of HCQ retinal toxicity (duration of treatment >5 years or daily HCQ dose >5 mg/kg of actual body weight [ABW]) but no alterations on spectral domain-optical coherence tomography, short-wavelength autofluorescence and 10-2 visual field examination were recruited. Healthy subjects matched by age and sex were also enrolled in the study. All subjects underwent qAF measurements in one eye. Images were analysed using the conventional qAF grid by Delori calculating the qAF of eight sectors of the intermediate ring and the mean of those values (qAF8 ). RESULTS: Thirty-nine patients treated with HCQ (38 females, mean age 52.1 ± 8.6 years) and 39 untreated subjects (38 females, mean age 51.2 ± 8.6 years) were included. In both HCQ patients and untreated subjects, qAF8 was positively correlated with age (p = 0.004). Although HCQ patients showed a higher mean qAF8 compared with untreated subjects (294.7 ± 65.3 vs. 268.9 ± 57.5), the difference was not significant (p = 0.068). HCQ patients showed significantly higher mean qAF values in the inferior-temporal, inferior and inferior-nasal sectors of the intermediate ring of qAF grid compared with untreated subjects (all p < 0.05). CONCLUSIONS: These results suggest a possible preclinical increase of qAF values in inferior parafoveal sectors probably induced by HCQ exposure.

LONGITUDINAL FOLLOW-UP OF CHOROIDAL GRANULOMAS WITH INDOCYANINE GREEN ANGIOGRAPHY AND OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY: A Lesion-Based Analysis.

PURPOSE: To investigate choroidal granulomas visualized by indocyanine green angiography (ICGA) and optical coherence tomography angiography (OCTA) in response to treatment. METHODS: Ten eyes of eight patients with tubercular, sarcoid, or Vogt-Koyanagi-Harada-associated choroidal granulomas were evaluated in this multicentric study. All patients underwent ICGA and OCTA at baseline, 1, and 3 months after treatment onset. Granulomas were identified as hypofluorescent lesions on intermediate ICGA phases. Late ICGA behavior and OCTA visualization were assessed. RESULTS: On baseline intermediate ICGA, 222 choroidal granulomas were detected. Overall, 174/222 granulomas were detected on baseline OCTA images. At 1 month, 28% of lesions were healed and 48 late ICGA hyperfluorescent lesions were identified. At 3 months, 63% of baseline lesions were healed, with 33 persistent late hyperfluorescent lesions. Optical coherence tomography angiography sensitivity was reduced at 1 and 3 months compared with baseline. Some flow-voids detected on OCTA at 1 and 3 months did not correspond to any visible lesion on ICGA. CONCLUSION: Different healing behaviors of choroidal granulomas were identified combining ICGA and OCTA analysis. Late ICGA hyper-fluorescent lesions may be the consequence of a possible fibrotic shift. Structural changes in the choroid may persist after active granulomas resolution resulting in persistent flow voids on OCTA.

Photodynamic Therapy for the Treatment of Vascularized Intraretinal Tuberculoma.

PURPOSE: To report a case of intraretinal tubercular granuloma successfully treated with photodynamic therapy (PDT). METHODS: Retrospective case report. Multimodal imaging was performed at each follow-up visit. RESULTS: The tuberculoma did not regress and did not significantly reduce its exudation after anti-tubercular therapy (ATT), systemic steroid therapy and intravitreal anti-VEGF. Second line treatment with PDT was attempted. The lesion showed a regression with reduced sub-retinal fluid and intra-retinal exudates. A second PDT was performed for reactivation of the lesion 5 months after the first treatment. Further regression of the lesion was observed. CONCLUSION: PDT may be a valuable second-line therapeutic approach for vascularized intraretinal granulomas.

Optical Coherence Tomography Angiography Findings of Iris Ischemia and Reperfusion in Cytomegalovirus Panuveitis.

PURPOSE: To report a case of iris ischemia in an eye affected by Cytomegalovirus (CMV)-related Chronic Retinal Necrosis (CRN) with partial reperfusion after antiviral therapy demonstrated by optical coherence tomography angiography (OCTA). METHODS: Retrospective case report. Multimodal imaging was performed at each follow-up visits. RESULTS: At baseline, the clinical findings and PCR on aqueous confirmed the diagnosis of CMV-induced CRN, while OCTA and Fluorescein Angiography showed multi-sectoral retinal and iris non-perfusion. After three weekly intravitreal injections of Foscarnet and retinal photocoagulation, the clinical and angiographic picture improved, with partial reperfusion of both retinal and iris vasculature. CONCLUSION: Retinal and iris non-perfusion in CRN can be partially reversible, if prompt treatment is administered. OCTA of the anterior segment allowed an accurate follow-up of the iris vasculature and its perfusion.

Acute Posterior Ocular Toxoplasmosis: An Optical Coherence Tomography Angiography and Dye Angiography Study.

PURPOSE: To compare Indocyanine Green (ICGA) and fundus fluorescein angiography (FFA) with Optical Coherence Tomography Angiography (OCTA) findings in toxoplasmic chorioretinitis (TCR). METHODS: Patients affected by active TCR were included. FFA, ICGA, and OCTA images were analyzed and lesions were compared between different modalities. Satellite dark dots (SDD) were compared between modalities. RESULTS: Fifteen patients were enrolled. The mean lesion area was similar between fundus photography (FP), FFA, and OCTA-Retina. The mean lesion area was similar between ICGA and OCTA-Choroid slab. ICGA and OCTA-Choroid showed a larger extension of the lesion compared to FP, FFA, and OCTA-Retina (p = .01, 0.0001, and 0.0002 for ICG angiography and p = .03, 0.008, and 0.0002 for OCTA-Choroid, respectively). On OCTA B-scans, the retinal flow defects were smaller than the underlying choroidal non-perfusion. The number of SDD was similar between ICGA and OCTA. CONCLUSIONS: OCTA is a reliable method to assess retinal and choroidal involvement in TCR. OCTA confirmed a wider involvement of the choroid than the retina.

Prechoroidal cleft thickness correlates with disease activity in neovascular age-related macular degeneration.

PURPOSE: The purpose of this study was to investigate the structural variations of the hyporeflective pocket of fluid (prechoroidal cleft) located between Bruch's membrane and the hyperreflective material within the pigment epithelial detachment (PED) in patients with neovascular age-related macular degeneration (nAMD). METHODS: In this retrospective, observational case series study, patients diagnosed with nAMD and prechoroidal cleft associated with other activity signs of the macular neovascularization (MNV) were included. Structural optical coherence tomography (OCT) scans were evaluated to obtain anatomical measurements of prechoroidal cleft and PED at three different visits (T0, inactive MNV; T1, active MNV; T2, treated inactive MNV). The variations in size of the cleft and the PED were correlated with nAMD activity. RESULTS: Twenty-nine eyes from 27 patients were included. The subfoveal measurements showed a significant increase of prechoroidal cleft height and width from T0 to T1 (P < 0.05) and a subsequent decrease of the cleft height after treatment with anti-VEGF agents (P = 0.004). A similar significant trend was observed for the greatest prechoroidal cleft height and width, obtained assessing the whole OCT raster. In the multivariate analysis, the cleft height was significantly affected by both time (P = 0.001) and PED height (P < 0.0001). By contrast, the effect of fibrovascular tissue size within the PED was not significant. Visual acuity did not correlate with prechoroidal cleft size. CONCLUSION: Prechoroidal cleft increased in association with MNV reactivation and decreased after treatment. Our results suggest that prechoroidal cleft could represent an accumulation of fluid actively exudating from the MNV and should be considered a sign of nAMD activity.

An en face swept source optical coherence tomography study of the vitreous in eyes with anterior uveitis.

PURPOSE: To analyse vitreous anatomy patients with anterior uveitis (AU) using swept source optical coherence tomography (SS-OCT). METHODS: Patients with newly diagnosed AU and healthy participants were scanned using 16-mm SS-OCT B-scans and 12 × 12 mm cube centred at the fovea. Linear SS-OCT scans were evaluated to identify the premacular bursa (PB) above the macula and the Cloquet's canal above the optic disc. A dynamic evaluation of the 12 × 12 mm cube enabled en face measurement of the vertical and horizontal diameters of the PB and the presence/absence of communication between the PB and Cloquet's canal. RESULTS: One hundred and thirty-five subjects were included in the study. Forty-five patients were healthy (mean age 33.47 years). En face measurements of the horizontal and vertical PB mean diameters were 5.2 mm and 4.7 mm. In 90 subjects with AU (mean age 30.10 years), the mean horizontal and vertical diameter of the PB were significantly larger (p < 0.01). Thirty-seven eyes with AU presented with cystoid macular oedema (CME). The mean diameters of the PB in this subgroup were significantly larger (p < 0.01). In 75% of the entire cohort (51% of eyes in the control group, 87% of eyes with AU and 100% of eyes with AU and CME), a channel connecting the PB and Cloquet's canal could be identified. CONCLUSIONS: SS-OCT identification of a connecting channel between the PB and the Cloquet's canal suggests that inflammatory cytokines may drain from the anterior chamber through this system of channels, thus increasing the risk of CME.

Retinal vessels modifications in acute and post-COVID-19.

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by SARS-CoV-2 primarily affecting the respiratory system which can damage vessels walls virtually in any body district. Changes affecting retinal vessels are a good marker for systemic vascular alterations. This study investigated retinal vessels during the acute phase of COVID-19 and after patients recovery. Fifty-nine eyes from 32 COVID-19 patients and 80 eyes from 53 unexposed subjects were included. Mean arteries diameter (MAD) and mean veins diameter (MVD) were assessed through semi-automatic analysis on fundus color photos at baseline and 6 months later in patients and subjects unexposed to the virus. At baseline MAD and MVD were significantly higher in COVID-19 patients compared to unexposed subjects (p < 0.0001). Both MAD and MVD significantly decreased in COVID-19 patients at follow-up (from 97.5 ± 10.9 to 92.2 ± 11.4 µm, p < 0.0001 and from 133.1 ± 19.3 to 124.6 ± 16.1 µm, p < 0.0001, respectively). Despite this reduction vessels diameter remained significantly higher in severe COVID-19 patients compared to unexposed subjects. Transient retinal vessels dilation could serve a biomarker for systemic inflammation while long-lasting alterations seen in severe COVID-19 likely reflect irreversible structural damage to the vessels walls and should be further investigated for their possible effects on tissues perfusion and function.

Outer Retinal Layer Thickening Predicts the Onset of Exudative Neovascular Age-Related Macular Degeneration.

PURPOSE: To assess changes in outer retinal layer (ORL) thickness before the development of exudative macular neovascularization (MNV) in eyes with age-related macular degeneration. DESIGN: Retrospective observational case series. METHODS: Eyes with age-related macular degeneration that eventually developed exudative MNV followed with sequential optical coherence tomography for ≥2 years before the exudation occurred were enrolled. The ORL thickness was automatically calculated by the optical coherence tomography software for each sector of the early treatment diabetic retinopathy study map at each follow-up visit. The ORL thickness change from baseline to the day when the exudative MNV developed was compared between sectors that eventually developed exudative MNV and those that did not. RESULTS: Forty-seven eyes (47 patients) were included. At baseline (24 ± 3 months before exudative MNV), mean (standard deviation) ORL thickness of sectors that eventually developed exudative MNV was similar to that of sectors that did not (85.2 [8.2] µm vs 86.8 [5.7] µm, P = .08). ORL thickness significantly increased in sectors that developed exudative MNV compared with those that did not (+5.8 [10.4] µm vs -2.8 [3.6] µm, P < .01). The regression model based on these data predicted an increase in ORL thickness from baseline of +4.2% 55 days and +11.1% 30 days before exudative MNV was detected. The ORL thickness of areas that did not develop exudative MNV did not change. CONCLUSION: Thickening of the ORL begins in the area where exudative MNV will develop long before the exudation, accelerating significantly in the last 2 months. The occurrence of exudative MNV could be predicted by 2 months using this simple analysis.

Comparison between Widefield Optical Coherence Tomography Devices in Eyes with High Myopia.

BACKGROUND: To compare four different optical coherence tomography (OCT) devices for visualization of retinal and subretinal layers in highly myopic eyes. METHODS: In this prospective, observational, cross-sectional study, consecutive patients with high myopia and control subjects were imaged by four OCT devices: Spectralis OCT2, PlexElite 2.0 100 kHz, PlexElite 2.0 200 kHz and the Canon Xephilio OCT-S1. The acquisition protocol for comparison consisted of single vertical and horizontal line scans centered on the fovea. Comparison between the devices in the extent of visible retina, presence of conjugate image or mirror artifacts, visibility of the sclerochoroidal interface and retrobulbar tissue. RESULTS: 30 eyes with high myopia and 30 control subjects were analyzed. The visualized RPE length was significantly different between the OCT devices with Xephilio OCT-S1 imaging the largest extent (p < 0.0001). The proportion of eyes with conjugate image artifact was significantly higher with the Spectralis OCT (p < 0.0001), and lower with the PlexElite 200 kHz (p < 0.0001). No difference in visibility of the sclerochoroidal interface was noted among instruments. The retrobulbar tissue was visible in a higher proportion of eyes using swept-source PlexElite 100 kHz and 200 kHz (p < 0.007) compared to the other devices. CONCLUSIONS: In highly myopic eyes, the four OCT devices demonstrated significant differences in the extent of the retina imaged, in the prevalence of conjugate image artifact, and in the visualization of the retrobulbar tissue.

Optical coherence tomography features of the repair tissue following RPE tear and their correlation with visual outcomes.

To assess the optical coherence tomography (OCT) features of the repair tissue after retinal pigment epithelial (RPE) tear in neovascular age-related macular degeneration. Retrospective, observational study. Medical and imaging records of patients that developed tears after starting anti-VEGF treatment and with at least 12 months of follow-up were reviewed. OCT reflectivity of the RPE-subretinal hyperreflective tissue (SHT) complex was measured at 6, 12 and 18 months (when available). Reflectivity of the adjacent unaffected RPE-Bruch's membrane was taken as internal reference. Other variables: grade and rip occurrence (early/late); number of intravitreal injections; type of macular neovascularization; sub-macular hemorrhage (SMH) at onset. Forty-nine eyes (age: 76.1 ± 7.0 years; VA: 0.54 ± 0.27 LogMAR) were included. Thirty-eight eyes had OCT signs of healing during the follow-up, with 21 showing SMH at baseline. Final VA positively correlated with the number of injections and negatively correlated with the RPE-SHT reflectivity and the presence of SMH (p < 0.001). Reflectivity of the RPE-SHT complex was positively associated with time and SMH at baseline (p < 0.05). In our study, most eyes showed signs of tissue repair after RPE tear. The reflectivity of repair tissue, the SMH presence and the number of anti-VEGF injections appeared to be major predictors of visual outcomes.

Microaneurysms visualisation using five different optical coherence tomography angiography devices compared to fluorescein angiography.

BACKGROUND: To compare fluorescein angiography (FA) and five different optical coherence tomography angiography (OCTA) devices and to test their reproducibility in the evaluation of retinal microaneurysms (MAs) secondary to diabetic retinopathy (DR). METHODS: On the same day, patients with DR were imaged with FA and five OCTA devices: prototype Spectralis OCTA, prototype PlexElite, RTVue XR Avanti, AngioPlex and DRI OCT Triton. For all OCTA devices, a 3×3 volume scan pattern was performed. MAs were evaluated for the superficial capillary plexus (SCP) and deep capillary plexus (DCP). RESULTS: Twenty eyes of 15 patients with DR were included. FA counted a significantly higher number of MAs compared to OCTA devices. Spectralis OCTA obtained a significantly higher number of MAs compared to PlexElite, RTVue XR Avanti, AngioPlex and DRI OCT Triton (p<0.0001). PlexElite and AngioPlex showed a greater number of MAs in the SCP, Spectralis OCTA, RTVue XR Avanti and DRI OCT Triton in the DCP. Higher sensitivity (43.3%) but lowest specificity (54.4%) was observed for Spectralis OCTA compared to other devices. The higher specificity (78.5%) and positive predictive value (83.3%) were observed for DRI OCT Triton. CONCLUSIONS: FA remains the best imaging modality to visualise retinal MAs. Spectralis OCTA was able to detect more MAs compared to other devices, likely due to the higher number of B-scans in the scanned area as well as due to the higher number of repeated B-scans. The high variability between OCTA devices should be taken into account for future clinical trials as in clinical practice.

CHOROIDAL GRANULOMAS VISUALIZED BY SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY.

PURPOSE: To assess the visualization of choroidal granulomas with swept-source optical coherence tomography angiography (OCTA). METHODS: Consecutive patients with granulomatous choroiditis due to tuberculosis, sarcoidosis, or Vogt-Koyanagi-Harada disease underwent baseline OCTA images using a 12 × 12-mm field of view, and the choroidal slabs were analyzed by two independent examiners who counted the oval areas of flow void. Simultaneously, indocyanine green angiography (ICGA) and enhanced-depth imaging OCT were performed to mark visible choroidal changes corresponding to granulomatous lesions. The lesion areas on OCTA and ICGA were assessed using the in-built caliper tool. RESULTS: Three hundred and one round-shaped areas of flow void on OCTA, 209 hypofluorescent round lesions on ICGA, and 42 hyporeflective choroidal lesions on enhanced-depth imaging OCT were identified in 23 eyes from 14 patients. Of the 209 ICGA granulomas, 197 (94.3%) had a corresponding round area of flow void on OCTA that was interpreted as a granuloma. One hundred and four additional round flow voids were identified on OCTA that did not correspond to any hypofluorescent lesion on ICGA. The mean area of the 197 granulomas detected with both imaging modalities was significantly larger on ICGA (mean 0.33 mm2) than that on OCTA (mean 0.28 mm2). CONCLUSION: Optical coherence tomography angiography seems to be an optimal imaging method for the visualization of choroidal granulomas.

Optical Coherence Tomography Findings of Underlying Choroidal Neovascularization in Punctate Inner Choroidopathy.

Purpose: To analyze findings on optical coherence tomography (OCT) suggestive of choroidal neovascularization (CNV) in lesions of punctate inner choroidopathy (PIC). Methods: In this multi-center retrospective study, clinical data of patients with PIC were retrospectively analyzed. Quantitative data (height, width, and volume of PIC lesions), and qualitative data (disruption of ellipsoid zone (EZ)/Bruch's membrane (BM), outer retinal fuzziness, and choroidal back-shadowing) were compared between CNV+ and CNV- groups using Mann-Whitney U-test and Fischer's exact test. Results: In total, 35 eyes (29 patients; 21 women; mean age: 33.3 ± 6.5 years) were selected for analysis. Of the 35 PIC lesions studied, 17 had underlying CNV. Lesions with CNV+ had larger height, width, and volume (p < 0.001) and several distinctive features, such as disruption of EZ and BM, outer retinal fuzziness, and hypo-reflective back-shadowing (p < 0.001) compared with CNV-lesions. Conclusions: Quantitative and qualitative OCT analysis can aid in the prediction of an underlying CNV in the eyes with PIC.

Clinical Evaluation of an Instrument-Integrated OCT-Based Distance Sensor for Robotic Vitreoretinal Surgery.

Purpose: To assess the efficacy of an instrument-integrated OCT (iiOCT)-based distance sensor during robotic vitreoretinal surgery using the Preceyes Surgical System (PSS; Preceyes B.V.). Design: Single-center interventional study. Participants: Patients requiring vitreoretinal surgery. Methods: Five patients were enrolled. Standard preoperative OCT images were obtained. After vitrectomy, a predefined set of actions was performed using the iiOCT-based sensor. Images then were processed to assess the signal-to-noise ratio (SNR) at various angles to the retina and at different distances between the instrument tip and the retinal surface. Preoperative and intraoperative OCT images were compared qualitatively and quantitatively. Main Outcomes Measures: The feasibility in performing surgical tasks using the iiOCT-based sensor during vitreoretinal surgery, the SNR when imaging the retina, differences among intraoperative and preoperative OCT images, and characteristics of intraoperative retinal movements detected with the iiOCT-based probe. Results: Surgeons were able to perform all the tasks but one. The PSS was able to maintain a fixed distance. The SNR of the iiOCT-based sensor signal was adequate to determine the distance to the retina and to control the PSS. Analysis of iiOCT-based sensor A-scans identified 3 clearly distinguishable retinal layers, including the inner retinal boundary and the interface at the retinal pigment epithelium-Bruch's membrane. Thickness values differed by less than 5% from that measured by preoperative OCT, indicating its accuracy. The Fourier analysis of iiOCT-based sensor recordings identified anteroposterior retinal movements attributed to heartbeat and respiration. Conclusions: This iiOCT-based sensor was tested successfully and promises reliable use during robot-assisted surgery. An iiOCT-based sensor is a promising step toward OCT-guided robotic retinal surgery.