Revisiting the Drasdo Model: Implications for Structure-Function Analysis of the Macular Region

Purpose: To provide a consistent implementation of a retinal ganglion cell (RGC) displacement model proposed by Drasdo et al. for macular structure-function analysis, customizable by axial length (AL). Methods: The effect of axial length on the shape of the inner retina was measured on 235 optical coherence tomography (OCT) scans from healthy eyes, to provide evidence for geometric scaling of structures with eye size. Following this assumption, we applied the Drasdo model to map perimetric stimuli on the radially displaced RGCs using two different methods: Method 1 only displaced the center of the stimuli; Method 2 applied the displacement to every point on the edge of the stimuli. We compared the accuracy of the two methods by calculating, for each stimulus, the number of expected RGC receptive fields and the number RGCs calculated from the histology map, expected to be equivalent. The same calculation was repeated on RGC density maps derived from 28 OCT scans from 28 young healthy subjects (age < 40 years) to confirm our results on clinically available measurements. Results: The size of the retinal structures significantly increased with AL (P < 0.001) and was well predicted by geometric scaling. Method 1 systematically underestimated the RGC counts by as much as 60%. No bias was observed with Method 2. Conclusions: The Drasdo model can effectively account for AL assuming geometric scaling. Method 2 should be used for structure-function analyses. Translational Relevance: We developed a free web App in Shiny R to make our results available for researchers

Visual Field Endpoints Based on Subgroups of Points May Be Useful in Glaucoma Clinical Trials: A Study With the Humphrey Field Analyzer and Compass Perimeter

PRECIS: Visual field endpoints based on average deviation of specific subsets of points rather than all points may offer a more homogenous dataset without necessarily worsening test-retest variability and so may be useful in clinical trials. PURPOSE: To characterize outcome measures encompassing particular subsets of visual field points and compare them as obtained with Humphrey (HVF) and Compass perimeters. METHODS: 30 patients with imaging-based glaucomatous neuropathy performed a pair of 24-2 tests with each of 2 perimeters. Non-weighted mean deviation (MD) was calculated for the whole field and separate vertical hemifields, and again after censoring of points with low sensitivity (MDc) and subsequently including only "abnormal" points with total deviation probability of <5% (MDc5%) or <2% (MDc2%). Test-retest variability was assessed using Bland-Altman 95% limits of agreement (95%LoA). RESULTS: For the whole field, using HVF, MD was -7.5±6.9▒dB, MDc -3.6±2.8▒dB, MDc5% -6.4±1.7▒dB and MDc2% -7.3±1.5▒dB. With Compass MD was -7.5±6.6, MDc -2.9±1.7▒dB, MDc5% -6.3±1.5, and MDC2% -7.9±1.6. The respective 95% LoA were 5.5, 5.3, 4.6 and 5.6 with HVF, and 4.8, 3.7, 7.1 and 7.1 with Compass. The respective number of eligible points were 52, 42±12, 20±11 and 15±9 with HVF, and 52, 41.2±12.6, 10±7 and 7±5 with Compass. With both machines, standard deviation (SD) and 95%LoA increased in hemifields compared to the total field, but this increase was mitigated after censoring. CONCLUSIONS: Restricting analysis to particular subsets of points of interest in the visual field after censoring points with low sensitivity, as compared with using the familiar total field mean deviation, can provide outcome measures with a broader range of mean deviation, a markedly reduced SD and therefore more homogenous dataset, without necessarily worsening test-retest variability

Evidence for alterations in fixational eye movements in glaucoma

BACKGROUND: Fixation changes in glaucoma are generally overlooked, as they are not strikingly evident as in macular diseases. Fundus perimetry might give additional insights into this aspect, along with traditional perimetric measures. In this work we propose a novel method to quantify glaucomatous changes in fixation features as detected by fundus perimetry and relate them to the extent of glaucomatous damage. METHODS: We retrospectively analysed fixation data from 320 people (200 normal subjects and 120 with glaucoma) from the Preferred Retinal Locus (PRL) detection of a Compass perimeter. Fixation stability was measured as Bivariate Contour Ellipse Area (BCEA), and using two novel metrics: (1) Mean Euclidean Distance (MED) from the Preferred Retinal Locus, and (2) Sequential Euclidean Distance (SED) of sequential fixation locations. These measures were designed to capture the spread of fixation points, and the frequency of position changes during fixation, respectively. RESULTS: In the age corrected analysis, SED was significantly greater in glaucomatous subjects than controls (P = 0.002), but there was no difference in BCEA (P = 0.15) or MED (P = 0.054). Similarly, SED showed a significant association with Mean Deviation (P  0.14 for both). CONCLUSION: Changes in the scanning pattern detected by SED are better than traditional measures of fixation spread (BCEA) for describing the changes in fixation stability observed in glaucoma

Urinary and sexual outcomes in long-term (5+ years) prostate cancer disease free survivors after radical prostatectomy

<p>Abstract</p> <p>Background</p> <p>After long term disease free follow up (FUp) patients reconsider quality of life (QOL) outcomes. Aim of this study is assess QoL in prostate cancer patients who are disease-free at least 5 years after radical prostatectomy (RP).</p> <p>Methods</p> <p>367 patients treated with RP for clinically localized pCa, without biochemical failure (PSA ≤ 0.2 ng/mL) at the follow up ≥ 5 years were recruited.</p> <p>Urinary (UF) and Sexual Function (SF), Urinary (UB) and Sexual Bother (SB) were assessed by using UCLA-PCI questionnaire. UF, UB, SF and SB were analyzed according to: treatment timing <it>(age at time of RP, FUp duration, age at time of FUp)</it>, tumor characteristics <it>(preoperative PSA, TNM stage, pathological Gleason score)</it>, nerve sparing (NS) procedure, and hormonal treatment (HT).</p> <p>We calculated the differences between 93 NS-RP without HT (group A) and 274 non-NS-RP or NS-RP with HT (group B). We evaluated the correlation between function and bother in group A according to follow-up duration.</p> <p>Results</p> <p>Time since prostatectomy had a negative effect on SF and a positive effect SB (both p < 0.001). Elderly men at follow up experienced worse UF and SF (p = 0.02 and p < 0.001) and better SB (p < 0.001).</p> <p>Higher stage PCa negatively affected UB, SF, and SB (all: p ≤ 0.05). NS was associated with better UB, SF and SB (all: p ≤ 0.05); conversely, HT was associated with worse UF, SF and SB (all: p ≤ 0.05).</p> <p>More than 8 years after prostatectomy SF of group A and B were similar. Group A subjects (NS-RP without HT) demonstrated worsening SF, but improved SB, suggesting dissociation of the correlation between SF and SB over time.</p> <p>Conclusion</p> <p>Older age at follow up and higher pathological stage were associated with worse QoL outcomes after RP. The direct correlation between UF and age at follow up, with no correlation between UF and age at time of RP suggests that other issues (i.e: vascular or neurogenic disorders), subsequent to RP, are determinant on urinary incontinence. After NS-RP without HT the correlation between SF and SB is maintained for 7 years, after which function and bother appear to have divergent trajectories.</p

Jet energy measurement with the ATLAS detector in proton-proton collisions at root s=7 TeV

The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of √s = 7TeV corresponding to an integrated luminosity of 38 pb-1. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0. 4 or R=0. 6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pT≥20 GeV and pseudorapidities {pipe}η{pipe}<4. 5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2. 5 % in the central calorimeter region ({pipe}η{pipe}<0. 8) for jets with 60≤pT<800 GeV, and is maximally 14 % for pT<30 GeV in the most forward region 3. 2≤{pipe}η{pipe}<4. 5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pT, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pT jets recoiling against a high-pT jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pT jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined. © 2013 CERN for the benefit of the ATLAS collaboration