Retrospective, controlled observational case study of patients with central retinal vein occlusion and initially low visual acuity treated with an intravitreal dexamethasone implant

Background Patients with initially low visual acuity were excluded from the therapy approval studies for retinal vein occlusion. But up to 28 % of patients presenting with central retinal vein occlusion have a baseline BCVA of less than 34 ETDRS letters (0.1). The purpose of our study was to assess visual acuity and central retinal thickness in patients suffering from central retinal vein occlusion and low visual acuity (<0.1) in comparison to patients with visual acuity (≥0.1) treated with Dexamethasone implant 0.7 mg for macular edema. Methods Retrospective, controlled observational case study of 30 eyes with macular edema secondary to central retinal vein occlusion, which were treated with a dexamethasone implantation. Visual acuity, central retinal thickness and intraocular pressure were measured monthly. Analyses were performed separately for eyes with visual acuity <0.1 and ≥0.1. Results Two months post intervention, visual acuity improved only marginally from 0.05 to 0.07 (1 month; p = 0,065) and to 0.08 (2 months; p = 0,2) in patients with low visual acuity as compared to patients with visual acuity ≥0.1 with an improvement from 0.33 to 0.47 (1 month; p = 0,005) and to 0.49 (2 months; p = 0,003). The central retinal thickness, however, was reduced in both groups, falling from 694 to 344 μm (1 month; p = 0.003,) to 361 μm (2 months; p = 0,002) and to 415 μm (3 months; p = 0,004) in the low visual acuity group and from 634 to 315 μm (1 month; p < 0,001) and to 343 μm (2 months; p = 0,001) in the visual acuity group ≥0.1. Absence of visual acuity improvement was related to macular ischemia. Conclusions In patients with central retinal vein occlusion and initially low visual acuity, a dexamethasone implantation can lead to an important reduction of central retinal thickness but may be of limited use to increase visual acuity

Analysis of surgical intervention populations using generic surgical process models.

International audiencePURPOSE: According to differences in patient characteristics, surgical performance, or used surgical technological resources, surgical interventions have high variability. No methods for the generation and comparison of statistical 'mean' surgical procedures are available. The convenience of these models is to provide increased evidence for clinical, technical, and administrative decision-making. METHODS: Based on several measurements of patient individual surgical treatments, we present a method of how to calculate a statistical 'mean' intervention model, called generic Surgical Process Model (gSPM), from a number of interventions. In a proof-of-concept study, we show how statistical 'mean' procedure courses can be computed and how differences between several of these models can be quantified. Patient individual surgical treatments of 102 cataract interventions from eye surgery were allocated to an ambulatory or inpatient sample, and the gSPMs for each of the samples were computed. Both treatment strategies are exemplary compared for the interventional phase Capsulorhexis. RESULTS: Statistical differences between the gSPMs of ambulatory and inpatient procedures of performance times for surgical activities and activity sequences were identified. Furthermore, the work flow that corresponds to the general recommended clinical treatment was recovered out of the individual Surgical Process Models. CONCLUSION: The computation of gSPMs is a new approach in medical engineering and medical informatics. It supports increased evidence, e.g. for the application of alternative surgical strategies, investments for surgical technology, optimization protocols, or surgical education. Furthermore, this may be applicable in more technical research fields, as well, such as the development of surgical workflow management systems for the operating room of the future

Macular Pigment Optical Density Measured by Heterochromatic Modulation Photometry

Purpose: To psychophysically determine macular pigment optical density (MPOD) employing the heterochromatic modulation photometry (HMP) paradigm by estimating 460 nm absorption at central and peripheral retinal locations. Methods: For the HMP measurements, two lights (B: 460 nm and R: 660 nm) were presented in a test field and were modulated in counterphase at medium or high frequencies. The contrasts of the two lights were varied in tandem to determine flicker detection thresholds. Detection thresholds were measured for different R:B modulation ratios. The modulation ratio with minimal sensitivity (maximal threshold) is the point of equiluminance. Measurements were performed in 25 normal subjects (11 male, 14 female; age: 30±11 years, mean ± sd) using an eight channel LED stimulator with Maxwellian view optics. The results were compared with those from two published techniques – one based on heterochromatic flicker photometry (Macular Densitometer) and the other on fundus reflectometry (MPR). Results: We were able to estimate MPOD with HMP using a modified theoretical model that was fitted to the HMP data. The resultant MPODHMP values correlated significantly with the MPODMPR values and with the MPODHFP values obtained at 0.25° and 0.5° retinal eccentricity. Conclusions: HMP is a flicker-based method with measurements taken at a constant mean chromaticity and luminance. The data can be well fit by a model that allows all data points to contribute to the photometric equality estimate. Therefore, we think that HMP may be a useful method for MPOD measurements, in basic and clinical vision experiments.</sub

Agreement between MPOD measured with heterochromatic modulation photometry and with heterochromatic flicker photometry.

<p>a) The relationship between MPOD measured with HMP and with HFP (the latter measured with a 0.5° diameter ring). A significant correlation is found with HFP measurements at 0.25° and 0.5° retinal eccentricities, but not at 1.0° and 1.75°. b) The Bland-Altman plot shows that MPOD_HMP values were systematically smaller than MPOD_HFP at 0.5°: mean difference −0.22 with 95%-confidence interval of [−.28, −.15].</p

Measurement of macular pigment optical density using HMP.

<p>A) Determination of the macular pigment optical density (MPOD) from the photometric matches. The modulation sensitivity (1/threshold) curves for central and peripheral fixation are plotted against modulation ratio on a log-log-scale. The curve for central fixation is shifted upward for better visualization (black arrow). The minimum of the modulation sensitivity curves is determined by fitting a theoretical function to the data. Because the CIE luminances <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110521#pone.0110521-Stockman1" target="_blank">[38]</a> of both lights are identical, the position of the flicker minimum on the ordinate is zero for an observer with a luminous sensitivity identical to the CIE standard observer's. A shift of the minimum of the modulation sensitivity curve to the left indicates a higher sensitivity for the 460 nm light, a shift to the right indicates a lower sensitivity. The MPOD (expressed in optical density units at 460 nm) is calculated by subtracting the minimum flicker point for peripheral fixation from that obtained for central fixation. B) Modulation ratio-sensitivity curves together with the fitted models for all 24 observers. The curves measured under central (C) and peripheral (P) absorption were shifted vertically, so that the position on the Y-axis at x = −1.5 for both curves of each observer is equal. For facility of inspection, the curves for the individual observers were ordered in a way that MPOD increases from left to right and from bottom to top.</p

Modeling the modulation sensitivity functions.

<p>A) A revision of the Pokorny, Smith and Lutze model <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110521#pone.0110521-Pokorny1" target="_blank">[15]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110521#pone.0110521-Pokorny2" target="_blank">[17]</a> was fit to the modulation sensitivity threshold data (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110521#pone-0110521-g002" target="_blank">Figure 2b</a> for original data and model fits). The derivation of the model is described in detail in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110521#pone.0110521.s004" target="_blank">Appendix S1</a>. In contrast to the original HMP function, the shape of the new function varies with changes in the horizontal position of the equiluminant point. A prediction from the model is that the difference between the heights of the asymptotes of the modulation sensitivity function (ΔS) is equal to the horizontal shift of the minimum flicker point (h). B) The difference in the asymptotes for this theoretical relationship is evident in our data.</p

Correlation between macular pigment optical densities measured by different methods.

<p>Significant correlations are reported with the Pearson R correlation coefficient and the p-values (without Bonferroni correction) in brackets. The correlations between HMP and MPR as well as HMP and HFP are the primary outcome measures (<b>bold</b>). MPOD measured with HMP correlates significantly with MPOD-MPR, and also with MPOD-HFP at two locations; however, only the correlation with HFP at 0.25° remains significant after Bonferroni correction for testing at four locations.</p><p>*The significances of the correlations with HFP have to be corrected for testing at four locations. The positive correlations with HFP at 0.25° and at 0.5° remain significant even after Bonferroni correction.</p><p>Correlation between macular pigment optical densities measured by different methods.</p

Photometric matches for central (bottom) and peripheral fixation (top) and the resultant MPOD values.

<p>Under the assumption that only macular pigment is responsible for differences in luminous sensitivity, the MPOD is calculated as the difference between the HMP minimum points.</p