19,936 research outputs found
Long-term visual and microperimetry outcomes following autologous retinal pigment epithelium choroid graft for neovascular age-related macular degeneration
To describe the 2- to 4-year visual and microperimetry outcomes of autologous retinal pigment epithelium (RPE)-choroid graft in patients with neovascular age-related macular degeneration (AMD).In this retrospective cohort study, 12 patients with subfoveal neovascular AMD who had undergone autologous RPE-choroid graft between August 2004 and June 2005 were reviewed. Change in visual acuity (VA), contrast sensitivity (CS), fixation stability and retinal sensitivity on microperimetry after 2-3 years and the rates of late postoperative complications were examined.Patients were followed for 26-48 months (mean, 39). Median preoperative VA (logMAR) was 0.87 but declined to 1.43 (1 year), 1.46 (2 years) and 1.38 (3 years), P = 0.001. Median CS (logCS) was 0.75 preoperatively but declined to 0.45 at 2 years. Six patients had serial microperimetry. Fixation stability declined in 1 but improved in 2 patients. All 6 had decline in retinal sensitivity over the graft during follow up. Retinal detachment did not occur after 12 months but 8 developed epiretinal membrane, 12 had cystic retinal change over the graft and 4 developed recurrent choroidal neovascularization. However, 10 grafts retained autofluorescence signal at 18-48 months of follow up.Autologous RPE-choroid graft can maintain VA, stable fixation and retinal sensitivity in some patients for over 3 years. The spatial correlation between graft autofluorescence, outer retinal structures on optical coherence tomography and retinal sensitivity are consistent with photoreceptor cell rescue. However, we caution the use of this technique as there is high complication rate and delayed loss of retinal function
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Improving Visual Field Examination of the Macula Using Structural Information
Purpose: To investigate a novel approach for structure-function modeling in glaucoma to improve visual field testing in the macula.
Methods: We acquired data from the macular region in 20 healthy eyes and 31 with central glaucomatous damage. Optical coherence tomography (OCT) scans were used to estimate the local macular ganglion cell density. Perimetry was performed with a fundus-tracking device using a 10-2 grid. OCT scans were matched to the retinal image from the fundus perimeter to accurately map the tested locations onto the structural damage. Binary responses from the subjects to all presented stimuli were used to calculate the structure-function model used to generate prior distributions for a ZEST (Zippy Estimation by Sequential Testing) Bayesian strategy. We used simulations based on structural and functional data acquired from an independent dataset of 20 glaucoma patients to compare the performance of this new strategy, structural macular ZEST (MacS-ZEST), with a standard ZEST.
Results: Compared to the standard ZEST, MacS-ZEST reduced the number of presentations by 13% in reliable simulated subjects and 14% with higher rates (≥20%) of false positive or false negative errors. Reduction in mean absolute error was not present for reliable subjects but was gradually more important with unreliable responses (≥10% at 30% error rate).
Conclusions: Binary responses can be modeled to incorporate detailed structural information from macular OCT into visual field testing, improving overall speed and accuracy in poor responders.
Translational Relevance: Structural information can improve speed and reliability for macular testing in glaucoma practice
Quantifying the vertical fusion range at four distances of fixation in a normal population.
Aim: To compare the vertical fusional amplitudes in
isometropic participants with normal binocular
single vision at four distances of fixation: 33 cm,
1 m, 4 m, 6 m.
Methods: Vertical fusion ranges (break point and
recovery point) were measured with a Gulden
vertical prism bar with the participant fixing a 6/12
Snellen equivalent letter, twice at each distance.
Order effects were controlled with randomisation of
both fixation distance and prism direction.
Results: Twenty-seven participants were examined
(aged 20.4 ± 1.05 years). Base up and base down
measurements were similar, therefore measurements
were combined to give a total vertical range. Median
values for the break points were: 33 cm, 6(Δ) ; 1 m, 6(Δ);
4 m, 5.5(Δ); 6 m, 5.5(Δ); and for the recovery points were:
33 cm, 4(Δ); 1 m, 4(Δ); 4 m, 3.5(Δ); 6 m, 3.5(Δ). The
difference was significant between either of the near
measures (i.e. 33 cm and 1 m) and either of the far
measures (i.e. 4 m and 6 m).
Conclusions: The vertical fusion range appears to be
slightly greater at near than distance. However, the
difference is not clinically significant. Measurements
for distance, in a normal population, appear to be the
same whether a fixation distance of 4 m or 6 m is
used
Copyright as a Rule of Evidence
Many copyright doctrines serve to exclude from the copyright regime cases particularly prone to evidentiary complexity. The implicit logic is that, for these cases, the social costs of litigation would likely outweigh the social benefits derived from offering copyright protection in the first place. Doctrines that serve this evidentiary function include some doctrines for which an evidentiary purpose is readily apparent (for example, the requirement that eligible works be fixed in tangible form), and some for which the link is quite subtle (for example, the rule against protecting work that lacks creativity). Understanding these doctrines in this light helps to refine their proper scope and application. It also makes clear a problem facing copyright law more generally: the increasing divergence between the logical justifications for various copyright doctrines and their actual use by courts and commentators
Computational role of eccentricity dependent cortical magnification
We develop a sampling extension of M-theory focused on invariance to scale
and translation. Quite surprisingly, the theory predicts an architecture of
early vision with increasing receptive field sizes and a high resolution fovea
-- in agreement with data about the cortical magnification factor, V1 and the
retina. From the slope of the inverse of the magnification factor, M-theory
predicts a cortical "fovea" in V1 in the order of by basic units at
each receptive field size -- corresponding to a foveola of size around
minutes of arc at the highest resolution, degrees at the lowest
resolution. It also predicts uniform scale invariance over a fixed range of
scales independently of eccentricity, while translation invariance should
depend linearly on spatial frequency. Bouma's law of crowding follows in the
theory as an effect of cortical area-by-cortical area pooling; the Bouma
constant is the value expected if the signature responsible for recognition in
the crowding experiments originates in V2. From a broader perspective, the
emerging picture suggests that visual recognition under natural conditions
takes place by composing information from a set of fixations, with each
fixation providing recognition from a space-scale image fragment -- that is an
image patch represented at a set of increasing sizes and decreasing
resolutions
Expected-value bias in routine third-trimester growth scans.
OBJECTIVES: Operators performing fetal growth scans are usually aware of the gestational age of the pregnancy, which may lead to expected-value bias when performing biometric measurements. We aimed to evaluate the incidence of expected-value bias in routine fetal growth scans and assess its impact on standard biometric measurements. METHODS: We collected prospectively full-length video recordings of routine ultrasound growth scans coupled with operator eye tracking. Expected value was defined as the gestational age at the time of the scan, based on the estimated due date that was established at the dating scan. Expected-value bias was defined as occurring when the operator looked at the measurement box on the screen during the process of caliper adjustment before saving a measurement. We studied the three standard biometric planes on which measurements of head circumference (HC), abdominal circumference (AC) and femur length (FL) are obtained. We evaluated the incidence of expected-value bias and quantified the impact of biased measurements. RESULTS: We analyzed 272 third-trimester growth scans, performed by 16 operators, during which a total of 1409 measurements (354 HC, 703 AC and 352 FL; including repeat measurements) were obtained. Expected-value bias occurred in 91.4% of the saved standard biometric plane measurements (85.0% for HC, 92.9% for AC and 94.9% for FL). The operators were more likely to adjust the measurements towards the expected value than away from it (47.7% vs 19.7% of measurements; P < 0.001). On average, measurements were corrected by 2.3 ± 5.6, 2.4 ± 10.4 and 3.2 ± 10.4 days of gestation towards the expected gestational age for the HC, AC, and FL measurements, respectively. Additionally, we noted a statistically significant reduction in measurement variance once the operator was biased (P = 0.026). Comparing the lowest and highest possible estimated fetal weight (using the smallest and largest biased HC, AC and FL measurements), we noted that the discordance, in percentage terms, was 10.1% ± 6.5%, and that in 17% (95% CI, 12-21%) of the scans, the fetus could be considered as small-for-gestational age or appropriate-for-gestational age if using the smallest or largest possible measurements, respectively. Similarly, in 13% (95% CI, 9-16%) of scans, the fetus could be considered as large-for-gestational age or appropriate-for-gestational age if using the largest or smallest possible measurements, respectively. CONCLUSIONS: During routine third-trimester growth scans, expected-value bias frequently occurs and significantly changes standard biometric measurements obtained. © 2019 the Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology
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