David Xu

Evaluation of choroidal thickness in retinitis pigmentosa using enhanced depth imaging optical coherence tomography

Objective To describe the choroidal characteristics of patients with retinitis pigmentosa (RP) using enhanced depth imaging (EDI) and spectral domain (SD) optical coherence tomography (OCT). Purpose To investigate the spectral-domain ocular coherence tomography features of the choroid in patients with RP using EDI. Methods A prospective, case–control study of 21 patients from the Cole Eye Institute with RP imaged using the Spectralis OCT and an EDI protocol. Submacular choroidal thickness measurements were obtained beneath the fovea and at 500 µm intervals for 2.5 mm nasal and temporal to the centre of the fovea. These measurements were compared to choroidal thickness measurements from 25 healthy age-matched controls with similar refractive error range and no clinical evidence of retinal or glaucomatous disease. Statistical analysis was performed to compare choroidal thickness at each location between the two groups and to correlate choroidal thickness with best-corrected visual acuity and central retinal thickness. Results Mean ages were 40.6 years for control patients and 45.1 years for RP patients (p>0.05). Mean choroidal thickness measurements were 245.6±103 µm in RP patients and 337.8.2±109 µm in controls (p<0.0001). There was no correlation between subfoveal choroidal thickness and visual acuity or retinal thickness in the RP patients when compared to the control group. Conclusions Submacular choroidal thickness, as measured by SD–OCT EDI, is significantly reduced in patients with RP, but did not correlate with visual acuity or retinal thickness in RP patients. Further research is needed to understand better the pathophysiological significance of the choroidal alterations present in RP.

Intrasurgical Dynamics Of Macular Hole Surgery: An Assessment of Surgery-induced Ultrastructural Alterations with Intraoperative Optical Coherence Tomography

Purpose: To evaluate the intrasurgical retinal architectural and macular hole (MH) geometric alterations that occur during surgical MH repair using intraoperative optical coherence tomography. Methods: A retrospective, multisurgeon, single-center, consecutive case series of 21 eyes undergoing surgical repair for MH with concurrent intraoperative optical coherence tomography using a custom microscope–mounted optical coherence tomography system was performed. All patients underwent surgical repair with pars plana vitrectomy, membrane peel, and gas tamponade. A novel three-dimensional segmentation algorithm was used for volumetric analysis of intrasurgical changes of MH geometry after surgical repair. Intraoperative optical coherence tomographic characteristics analyzed included MH volume, minimum diameter, base area, and hole height. Outer retinal architecture changes were analyzed both quantitatively and qualitatively. Results: All 21 eyes were successfully imaged with intraoperative optical coherence tomography. Nineteen of 21 eyes had images of sufficient signal strength to allow for quantitative analysis. Significant changes were noted in MH geometry after internal limiting membrane peeling including increased MH volume, increased base area, and decreased top area (all P < 0.03). Additionally, increased subretinal hyporeflectance was noted by expansion of the height between the inner segment/outer segment and retinal pigment epithelium bands (P = 0.008). Peeling methods and surgeon experience did not correlate with the magnitude of architectural alterations. Macular hole algorithm measurements and alterations were associated with visual outcome and MH closure. Conclusion: Significant alterations occur in MH geometry and outer retinal structure after internal limiting membrane peeling. These changes are subclinical and unable to be appreciated with en face surgical microscope viewing and require intraoperative optical coherence tomography for visualization. Preliminary analysis of these measurements identified an association with visual outcome and successful MH closure. The functional significance of these changes deserves further study.

A Novel Segmentation Algorithm for Volumetric Analysis of Macular Hole Boundaries Identified with Optical Coherence Tomography

PURPOSE To demonstrate a novel algorithm for macular hole (MH) segmentation and volumetric analysis. METHODS A computer algorithm was developed for automated MH segmentation in spectral-domain optical coherence tomography (SD-OCT). Algorithm validation was performed by trained graders with performance characterized by absolute accuracy and intraclass correlation coefficient. A retrospective case series of 56 eyes of 55 patients with idiopathic MHs analyzed using the custom algorithm to measure MH volume, base area/diameter, top area/diameter, minimum diameter, and height-to-base diameter ratio. Five eyes were excluded due to poor signal quality (1), motion artifact (1), and failure of surgical closure (3) for a final cohort of 51 eyes. Preoperative MH measurements were correlated with clinical MH stage, baseline, and 6-month postoperative best-corrected Snellen visual acuity (BCVA). RESULTS The algorithm achieved 96% absolute accuracy and an intraclass correlation of 0.994 compared to trained graders. In univariate analysis, MH volume, base area, base diameter, top area, top diameter, minimum diameter, and MH height were significantly correlated to baseline BCVA (P value from 0.0003-0.011). Volume, base area, base diameter, and height-to-base diameter ratio were significantly correlated to 6-month postoperative BCVA (P value from <0.0001-0.029). In multivariate analysis, only base area (P < 0.0001) and volume (P = 0.0028) were significant predictors of 6-month postoperative BCVA. CONCLUSIONS The computerized segmentation algorithm enables rapid volumetric analysis of MH geometry and correlates with baseline and postoperative visual function. Further research is needed to better understand the algorithms role in prognostication and clinical management.

Automated volumetric analysis of interface fluid in descemet stripping automated endothelial keratoplasty using intraoperative optical coherence tomography.

PURPOSE We demonstrated a novel automated algorithm for segmentation of intraoperative optical coherence tomography (iOCT) imaging of fluid interface gap in Descemet stripping automated endothelial keratoplasty (DSAEK) and evaluated the effect of intraoperative maneuvers to promote graft apposition on interface dimensions. METHODS A total of 30 eyes of 29 patients from the anterior segment arm of the PIONEER study was included in this analysis. The iOCT scans were entered into an automated algorithm that delineated the spatial extent of the fluid interface gap in three dimensions between donor and host cornea during surgery. The algorithm was validated against manual segmentation, and performance was evaluated by absolute accuracy and intraclass correlation coefficient. Patients underwent DSAEK using a standard sequence of maneuvers, including controlled elevation of IOP and compressive corneal sweep to promote graft adhesion. Measurement of interface fluid volume, en face area, and maximal interface height were compared between scans before anterior chamber infusion, after pressure elevation alone, and after corneal sweep with pressure elevation using dependent-samples t-test. RESULTS The algorithm achieved 87% absolute accuracy and an intraclass correlation of 0.96. Nine datasets of a total of 84 (11%) required human correction of segmentation errors. Mean interface fluid volume was significantly decreased by corneal sweep (P = 0.021) and by both maneuvers combined (P = 0.046). Mean en face area was significantly decreased by corneal sweep (P = 0.010) and the maneuvers combined (P < 0.001). Maximal interface height was significantly decreased by pressure elevation (P = 0.010), corneal sweep (P = 0.009), and the maneuvers combined (P = 0.010). CONCLUSIONS Quantitative analysis of iOCT volumetric scans shows the significant effect of controlled pressure elevation and corneal sweep on graft apposition in DSAEK. Computerized iOCT analysis yields objective measurements of interface fluid intraoperatively, which provides information on anatomic outcomes and could be used in future trials.

Comparison of intravitreal ranibizumab and bevacizumab for the treatment of macular edema secondary to retinal vein occlusion

AIM To compare the efficacy of ranibizumab and bevacizumab for macular edema due to retinal vein occlusion (RVO). METHODS A retrospective study was conducted at a single academic institution. Eighty-one patients naïve to anti-VEGF therapy with RVO and macular edema were identified. Twenty-six eyes were treated with ranibizumab, 33 eyes with bevacizumab, and 22 eyes with bevacizumab then switched to ranibizumab (crossover). The main outcome was change in visual acuity at 3 months, 6 months, and final visit. RESULTS The mean visual acuity improved from 20/80 to 20/40 in the ranibizumab (R) group and from 20/125 to 20/60 in the bevacizumab (B) group (P=0.66). The mean change in central subfield thickness (CST) was -186 and -212µm, respectively (P=0.69). Mean time between injections was 94±21.1d in the R group and 103.8±10.5d in the B group (P=0.78). In the crossover group, mean initial visual acuity was 20/125, reached 20/60 at crossover, and remained 20/60 at conclusion (P=0.91). CONCLUSION Both ranibizumab and bevacizumab are effective for the treatment of RVO and appear to have similar visual and anatomic outcomes. Changing treatments from bevacizumab to ranibizumab did not result in further gains in visual acuity.

QUININE TOXICITY: MULTIMODAL RETINAL IMAGING AND ELECTRORETINOGRAPHY FINDINGS.

Purpose: To report the multimodal retinal imaging and electroretinography (ERG) findings of two cases with quinine toxicity. Methods: Retrospective case series describing the retinal imaging and ERG findings in two patients with retinal toxicity due to remote quinine exposure. Color fundus photography, fundus autofluorescence, spectral domain optical coherence tomography, and full-field ERG findings are described. Results: Two patients with longstanding decreased vision were found to have bilateral optic disk pallor and retinal vascular attenuation indicative of chronic sequela after acute quinine toxicity. Inner retinal atrophy was identified on spectral domain optical coherence tomography, and full-field ERG was consistent with generalized inner retinal dysfunction in both patients. Fundus autofluorescence failed to demonstrate any evidence of outer retinal or retinal pigment epithelial abnormalities. Conclusion: Quinine toxicity may be associated with vision loss secondary to inner retinal atrophy. We report two cases with a clear history of acute quinine exposure leading to similar retinal imaging findings and distinctive ERG abnormalities. Clinicians should be aware of this uncommon condition as ingestion history may be remote.

EN FACE OPTICAL COHERENCE TOMOGRAPHY OF MULTIPLE EVANESCENT WHITE DOT SYNDROME.

Purpose: To report novel en face imaging findings of multiple evanescent white dot syndrome. Methods: A 25-year-old woman presented with photopsia and vision loss affecting the left eye. Ophthalmic examination, color fundus photography, fluorescein angiography, spectral domain optical coherence tomography (SD-OCT), fundus autofluorescence, en face OCT, and OCT angiography were performed. Results: The diagnosis of multiple evanescent white dot syndrome was made based on clinical examination and multimodal imaging findings. Fundus autofluorescence demonstrated numerous hyperautofluorescent spots that corresponded to multifocal areas of ellipsoid loss with SD-OCT. En face OCT illustrated multiple small round hyperreflective “dots” at the level of the outer nuclear layer that precisely colocalized over numerous hyporeflective “spots” at the level of the ellipsoid zone. Optical coherence tomography angiography demonstrated normal flow within the superficial and deep retinal capillary plexus and the choroid in the left eye. Conclusion: We report the unique en face OCT pattern of hyperreflective dots (at the level of the outer nuclear layer) that precisely colocalized over larger hyporeflective spots (at the level of the ellipsoid zone) in multiple evanescent white dot syndrome. This finding may provide a signature pattern of recognition for this elusive disorder.