Label-Free Density Measurements of Radial Peripapillary Capillaries in the Human Retina

Radial peripapillary capillaries (RPCs) comprise a unique network of capillary beds within the retinal nerve fibre layer (RNFL) and play a critical role in satisfying the nutritional requirements of retinal ganglion cell (RGC) axons. Understanding the topographical and morphological characteristics of these networks through in vivo techniques may improve our understanding about the role of RPCs in RGC axonal health and disease. This study utilizes a novel, non-invasive and label-free optical imaging technique, speckle variance optical coherence tomography (svOCT), for quantitatively studying RPC networks in the human retina. Six different retinal eccentricities from 16 healthy eyes were imaged using svOCT. The same eccentricities were histologically imaged in 9 healthy donor eyes with a confocal scanning laser microscope. Donor eyes were subject to perfusion-based labeling techniques prior to retinal dissection, flat mounting and visualization with the microscope. Capillary density and diameter measurements from each eccentricity in svOCT and histological images were compared. Data from svOCT images were also analysed to determine if there was a correlation between RNFL thickness and RPC density. The results are as follows: (1) The morphological characteristics of RPC networks on svOCT images are comparable to histological images; (2) With the exception of the nasal peripapillary region, there were no significant differences in RPC density measurements between svOCT and histological images; (3) Capillary diameter measurements were significantly greater in svOCT images compared to histology; (4) There is a positive correlation between RPC density and RNFL thickness. The findings in this study suggest that svOCT is a reliable modality for analyzing RPC networks in the human retina. It may therefore be a valuable tool for aiding our understanding about vasculogenic mechanisms that are involved in RGC axonopathies. Further work is required to explore the reason for some of the quantitative differences between svOCT and histology

Real-world assessment of intravitreal dexamethasone implant (0.7 mg) in patients with macular edema: The CHROME study

© 2015 Lam et al.Background: The purpose of this study was to evaluate the real-world use, efficacy, and safety of one or more dexamethasone intravitreal implant(s) 0.7 mg (DEX implant) in patients with macular edema (ME). Methods: This was a retrospective cohort study of patients with ME secondary to retinal disease treated at ten Canadian retina practices, including one uveitis center. Best-corrected visual acuity (BCVA), central retinal thickness (CRT), intraocular pressure (IOP), glaucoma and cataract surgery, and safety data were collected from the medical charts of patients with ≥3 months of follow-up after the initial DEX implant.Results: One hundred and one patient charts yielded data on 120 study eyes, including diagnoses of diabetic ME (DME) (n=34), retinal vein occlusion (RVO, n=30; branch in 19 and central in 11), and uveitis (n=23). Patients had a mean age of 60.9 years, and 73.3% of the study eyes had ME for a duration of ≥12 months prior to DEX implant injection(s). Baseline mean (± standard error) BCVA was 0.63±0.03 logMAR (20/86 Snellen equivalents) and mean CRT was 474.4±18.2 μm. The mean number of DEX implant injections was 1.7±0.1 in all study eyes; 44.2% of eyes had repeat DEX implant injections (reinjection interval 2.3–4.9 months). The greatest mean peak changes in BCVA lines of vision occurred in study eyes with uveitis (3.3±0.6, P0.05). Significant decreases in CRT were observed: -255.6±43.6 µm for uveitis, -190.9±23.5 µm for DME, and -160.7±39.6 µm for RVO (P<0.0001 for all cohorts). IOP increases of ≥10 mmHg occurred in 20.6%, 24.1%, and 22.7% of DME, RVO, and uveitis study eyes, respectively. IOP-lowering medication was initiated in 29.4%, 16.7%, and 8.7% of DME, RVO, and uveitis study eyes, respectively. Glaucoma surgery was performed in 1.7% of all study eyes and cataract surgery in 29.8% of all phakic study eyes receiving DEX implant(s). onclusion: DEX implant(s) alone or combined with other treatments and/or procedures resulted in functional and anatomic improvements in long-standing ME associated with retinal disease.Link_to_subscribed_fulltex

The consequences of waiting for cataract surgery: a systematic review

BACKGROUND: Cataract surgery is the most common operative procedure performed in Canada, and how patients are affected by wait times for this surgery has important clinical, public health and health policy considerations. We conducted a systematic review to understand the relation between wait time for cataract surgery and patient outcomes and the variables that modify this relation. METHODS: We performed an electronic search of 11 databases and the proceedings of 4 conferences. The search was restricted to studies published after the transition to phacoemulsification (1990). We assessed the quality of the included studies using the Jadad Scale for randomized controlled trials and the Newcastle–Ottawa Scale for cohort and case–control studies. The data were found to be inappropriate for meta-analysis, thus we performed a qualitative synthesis. RESULTS: We found a total of 27 studies that met our inclusion criteria. When these studies were reviewed, a dichotomy was observed for the wait time–outcome relation: outcomes associated with wait times of ≤ 6 weeks were better than outcomes associated with wait times of ≥ 6 months. Patients who waited more than 6 months to receive cataract surgery experienced more vision loss, a reduced quality of life and had an increased rate of falls compared with patients who had wait times of less than 6 weeks. The outcomes associated with wait times between 6 weeks and 6 months remain unclear. INTERPRETATION: Patients who wait more than 6 months for cataract surgery may experience negative outcomes during the wait period, including vision loss, a reduced quality of life and an increased rate of falls

Methodology for quantitative measurements.

<p>Representative speckle variance optical coherence tomography (svOCT) image (A) and histology image (B) from the nasal peripapillary region illustrates the technique used to acquire quantitative measurements. Capillary density was determined by calculating the number of intersections between capillaries (circles) and a perpendicular, straight line (red line) drawn through the capillary network. Results were expressed as intersections per 100 μm. Capillary diameter was determined by calculating the perpendicular distance across the maximum chord axis of each vessel. This is as illustrated in the corresponding magnified regions (outlined in yellow dashed lines) of svOCT (C) and histology (D) images. Scale bar = 120μm (A & B) and 60μm (C and D)</p

A paired graphical representation of quantitative comparisons between speckle variance optical coherence tomography (svOCT) and histology data for the six eccentricities.

<p>The averaged value is presented as solid bars with standard deviations presented by error bars. Black solid bars represent data from svOCT images whilst grey solid bars represented data from confocal images. Data presented include (A) number of RPCs per 100 μm, (B) Inter-capillary distance or ICD in microns, and (C) RPCs diameter in microns. The data are presented as per study region and include the supero-temporal (ST), infero-temporal (IT), superior (Sup), temporal (Temp), inferior (Inf) and nasal (Nasal). Statistically significant difference (p<0.05) between the two techniques are marked with an asterisk.</p

Regions where radial peripapillary capillary network morphology and topography were studied quantitatively.

<p>Insets placed on a fluorescein angiogram illustrate the six different eccentricities that were studied with speckle variance optical coherence tomography and histology. Sup = Superior; ST = Supero-temporal; Temp = Temporal; IT = Infero-temporal; Inf = Inferior and N = Nasal regions.</p

Scatter plot of intercapillary distance (ICD) and retinal nerve fibre layer thickness (RNFL) with the speckle variance optical coherence tomography.

<p>Each region is colour coded. Sup = Superior; ST = Supero-temporal; Temp = Temporal; IT = Infero-temporal; Inf = Inferior and N = Nasal. Unit of measurement in both axes is in microns.</p