Comparison of retinal nerve fiber layer and macular thickness for discriminating primary open-angle glaucoma and normal-tension glaucoma using optical coherence tomography

Purpose The aim of this study was to evaluate the discrimination capabilities of macular and peripapillary retinal nerve fiber layer (pRNFL) thickness parameters as measured using spectral domain optical coherence tomography (SD-OCT) between primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG). Methods A total of 90 subjects were enrolled: 30 healthy subjects, 30 subjects with POAG and 30 subjects with NTG, consecutively. Retinal nerve fiber layer thickness, macular thickness and volume measurements were obtained with circular and radial SD-OCT scans. All parameters were compared between groups using an analysis of variance test. Areas under receiver-operating characteristic (AROC) curves with sensitivities at specificities greater than or equal to 90 per cent were generated to compare discrimination capabilities of various parameters between POAG and NTG. Results Macular thickness and volume measurements were the highest in normal subjects, followed by NTG and POAG (p < 0.05). Average retinal nerve fiber layer thickness had perfect discrimination for normal-POAG (AROC: 1.000; sensitivity: 100 per cent) and near perfect discrimination for normal-NTG (AROC: 0.979; sensitivity: 93 per cent) as well as NTG-POAG pairs (AROC: 0.900; sensitivity: 60 per cent). Inferior outer macular thickness (IOMT) and total volume were the best macular thickness and volume parameters having similar AROCs and sensitivities between normal and POAG (IOMT, AROC: 0.987; sensitivity: 92 per cent and total volume, AROC: 0.997; sensitivity: 97 per cent), normal and NTG (IOMT, AROC: 0.862, sensitivity: 47 per cent and total volume, AROC: 0.898, sensitivity: 67 per cent) and also between NTG and POAG (IOMT, AROC: 0.910, sensitivity: 53 per cent and total volume, AROC: 0.922, sensitivity: 77 per cent). In each comparison group, there was no statistically significant difference in AROCs between average retinal nerve fiber layer and inferior outer macular thickness, as well as total volume. Conclusions The macular parameters offer comparable performance to pRNFL parameters for the discrimination of NTG and POAG. Average retinal nerve fiber layer thickness, total macular volume and inferior outer macular thickness were the best SD-OCT parameters with superior discriminating capabilities

Predicting individual contrast sensitivity functions from acuity and letter contrast sensitivity measurements.

Contrast sensitivity (CS) is widely used as a measure of visual function in both basic research and clinical evaluation. There is conflicting evidence on the extent to which measuring the full contrast sensitivity function (CSF) offers more functionally relevant information than a single measurement from an optotype CS test, such as the Pelli-Robson chart. Here we examine the relationship between functional CSF parameters and other measures of visual function, and establish a framework for predicting individual CSFs with effectively a zero-parameter model that shifts a standard-shaped template CSF horizontally and vertically according to independent measurements of high contrast acuity and letter CS, respectively. This method was evaluated for three different CSF tests: a chart test (CSV-1000), a computerized sine-wave test (M&amp;S Sine Test), and a recently developed adaptive test (quick CSF). Subjects were 43 individuals with healthy vision or impairment too mild to be considered low vision (acuity range of -0.3 to 0.34 logMAR). While each test demands a slightly different normative template, results show that individual subject CSFs can be predicted with roughly the same precision as test-retest repeatability, confirming that individuals predominantly differ in terms of peak CS and peak spatial frequency. In fact, these parameters were sufficiently related to empirical measurements of acuity and letter CS to permit accurate estimation of the entire CSF of any individual with a deterministic model (zero free parameters). These results demonstrate that in many cases, measuring the full CSF may provide little additional information beyond letter acuity and contrast sensitivity

Multi-line Adaptive Perimetry (MAP): A New Procedure for Quantifying Visual Field Integrity for Rapid Assessment of Macular Diseases.

PurposeIn order to monitor visual defects associated with macular degeneration (MD), we present a new psychophysical assessment called multiline adaptive perimetry (MAP) that measures visual field integrity by simultaneously estimating regions associated with perceptual distortions (metamorphopsia) and visual sensitivity loss (scotoma).MethodsWe first ran simulations of MAP with a computerized model of a human observer to determine optimal test design characteristics. In experiment 1, predictions of the model were assessed by simulating metamorphopsia with an eye-tracking device with 20 healthy vision participants. In experiment 2, eight patients (16 eyes) with macular disease completed two MAP assessments separated by about 12 weeks, while a subset (10 eyes) also completed repeated Macular Integrity Assessment (MAIA) microperimetry and Amsler grid exams.ResultsResults revealed strong repeatability of MAP and high accuracy, sensitivity, and specificity (0.89, 0.81, and 0.90, respectively) in classifying patient eyes with severe visual impairment. We also found a significant relationship in terms of the spatial patterns of performance across visual field loci derived from MAP and MAIA microperimetry. However, there was a lack of correspondence between MAP and subjective Amsler grid reports in isolating perceptually distorted regions.ConclusionsThese results highlight the validity and efficacy of MAP in producing quantitative maps of visual field disturbances, including simultaneous mapping of metamorphopsia and sensitivity impairment.Translational relevanceFuture work will be needed to assess applicability of this examination for potential early detection of MD symptoms and/or portable assessment on a home device or computer

A CHARACTERIZATION MODEL WITH SPATIAL AND TEMPORAL RESOLUTION FOR LIFE CYCLE IMPACT ASSESSMENT OF PHOTOCHEMICAL PRECURSORS IN THE UNITED STATES

Photochemical pollution is formed due to the chemical reactions of atmospheric NOx, volatile organic compounds, CO, and CH4 in the presence of sunlight. It is a complex, non-linear process influenced by several parameters which change spatially and temporally. Ozone, which is the most common photochemical, damages human health, ecosystems, and man-made materials. It also contributes to climate change. Traditional life cycle impact assessment methodologies have used aggregated impact factors for a country or even for a continent, neglecting these variations.This research assesses the geographical and temporal variability in the characterization factors for emissions of NOx and VOC over the continental US by developing monthly state-level factors. A photochemical air quality modeling system (CAMx-MM5-SMOKE) is used to simulate the process of formation, transformation, transport, and removal of photochemical pollutants. Characterization factors are calculated at three levels along the cause-effect chain, namely, fate level, human and ecosystem exposure level, and human effect level. The results indicate that a spatial variability of one order of magnitude and a temporal variability of two orders of magnitude exist in both the fate level and human exposure and effect level characterization factors for NOx. The highest temporal variation in the characterization factors for NOx is seen in the Northeastern US. The summer time characterization factors for NOx are higher than the winter time factors. However, for anthropogenic VOC, the summer time factors are lower than the winter time in almost half of the states. The ecosystem exposure factors for NOx and VOC do not follow a regular pattern and show a spatial variation of about three orders of magnitude. The fate, human exposure, and human effect level factors correlate well as all three are dependent on the atmospheric concentration of ozone. However, they are poorly correlated with the ecosystem exposure factors. Sensitivity analysis of the characterization factors for meteorology and emissions inputs shows variation between negative 90% and positive 180%. This is still lower than the spatial and temporal variations. A life cycle assessment case study is included to illustrate the use of the disaggregated characterization factors

Glare and Ocular Diseases

Glare is the result of veiling luminance from the different light sources we are exposed to in our everyday lives. The luminance from glare can cause problems ranging from the discomfort of our eyes to vision loss. All individuals are affected by glare issues but those problems are intensified in patients living with ocular diseases. Therefore, understanding the effects of glare is applicable to elucidating visual function and pathology. This makes glare testing highly necessary in both clinic and research. However, there are many components involved in glare testing that makes attaining valid results difficult. This is evident in the flaws of current glare devices and the lack of a standardization of measuring glare. Despite the insufficiency of most glare devices, evaluating those weaknesses can potentially lead to a better understanding of glare and glare testing

Predicting the necessity of LASIK enhancement after cataract surgery in patients with multifocal IOL implantation

Pinakin Gunvant1,2, Anna Ablamowicz2, Subba Gollamudi31Western University of Health Sciences, College of Optometry, Pomona, CA, 2Southern College of Optometry, Memphis, TN, 3Eye Specialty Group, Memphis, TN, USAPurpose: To investigate if the parameters measured routinely prior to cataract surgery with multifocal intraocular lens (IOL) implantation can predict the necessity of additional laser in situ keratomileusis (LASIK) to improve visual outcome.Methods: Records of patients undergoing cataract surgery between January 2008 and December 2009 were reviewed. Individuals satisfied with visual outcome of cataract surgery and not satisfied were grouped (group 1 and 2, respectively). Preoperative data of refractive error, axial length, corneal astigmatism, intraocular pressure, and postoperative uncorrected visual acuity were recorded. Data was available for 62 patients (104 eyes), of which LASIK enhancement was deemed necessary in 21 eyes (20%; group 2). The receiver operator characteristic curves were used to discriminate between the groups and linear regression analysis was performed to predict the postoperative visual outcome.Results: The astigmatism measured preoperatively using manifest refraction had an accuracy of 64% in discriminating between the groups. Age, spherical component of refraction, axial length, corneal astigmatism, and intraocular pressure were very close to chance prediction 59%, 57%, 56%, 51%, and 51%, respectively. The postoperative uncorrected visual acuity had an accuracy of 79% in discriminating the groups. Individuals with uncorrected visual acuity worse than 20/40 after cataract surgery were most likely to undergo LASIK enhancement; however, approximately 20% of group 2 underwent LASIK enhancement despite having visual acuity of 20/30 or better. When combined, preoperative visual acuity accounted for just 7% of variance in postoperative uncorrected visual acuity.Conclusion: Requirement of LASIK enhancement after cataract surgery with multifocal IOL implant is complex in nature, and parameters routinely measured before surgery cannot successfully identify the group requiring LASIK enhancement or predict postoperative uncorrected visual acuity.Keywords: refractive error, axial length, corneal astigmatism, intraocular pressure, uncorrected visual acuity, visual outcome, multivariate analysis, LASIK enhancemen

Hypernatremia in exclusively breastfed term neonates

Background: Hypernatremia is known to occur in exclusively breastfed neonates in the first few days of life, and its clinical presentation is usually nonspecific. Early identification and prompt treatment of this condition are necessary to prevent morbidity and mortality. Objective: The objective of the study was to evaluate the clinical features, causative factors, complications, and outcome of hypernatremia in exclusively breastfed term newborns. Materials and Methods: A prospective study of exclusively breastfed healthy term neonates with hypernatremia (serum sodium ≥150 mg/dl) was carried out from March 2016 to February 2017. The presenting symptoms, clinical signs, birth and feeding history, and laboratory investigations of the subjects were noted and analyzed. Results: Hypernatremia was noted in 35 (1.6%) of the total term neonates. The condition was more common in babies delivered by cesarean section (34.3%), firstborn neonates (74.3%), and during the summer months (74.3%). Mean age of presentation was 4.06±1.43 days. The most common findings were weight loss ˃7 % from the birth weight (74.3%), feeding problems (71.4%), and decreased frequency of urine (60%). Serum sodium levels ranged from 150.5 to 187 mEq/dl. Acute kidney injury was noted in 4 (11.4%) cases. All the patients were discharged, and there was no mortality. Conclusion: Hypernatremia is a common condition in exclusively breastfed neonates. It occurs due to inadequate intake of breast milk by the neonate and is exaggerated in hot environment. Daily weighing of the neonates and monitoring the frequency of urine are important for early detection. Addressing feeding problems early is a simple yet effective measure to prevent this condition