Relationship between visual field loss and contrast threshold elevation in glaucoma

BACKGROUND: There is a considerable body of literature which indicates that contrast thresholds for the detection of sinusoidal grating patterns are abnormally high in glaucoma, though just how these elevations are related to the location of visual field loss remains unknown. Our aim, therefore, has been to determine the relationship between contrast threshold elevation and visual field loss in corresponding regions of the peripheral visual field in glaucoma patients. METHODS: Contrast thresholds were measured in arcuate regions of the superior, inferior, nasal and temporal visual field in response to laser interference fringes presented in the Maxwellian view. The display consisted of vertical green stationary laser interference fringes of spatial frequency 1.0 c deg(-1 )which appeared in a rotatable viewing area in the form of a truncated quadrant extending from 10 to 20° from fixation which was marked with a central fixation light. Results were obtained from 36 normal control subjects in order to provide a normal reference for 21 glaucoma patients and 5 OHT (ocular hypertensive) patients for whom full clinical data, including Friedmann visual fields, had been obtained. RESULTS: Abnormally high contrast thresholds were identified in 20 out of 21 glaucoma patients and in 2 out of 5 OHT patients when compared with the 95% upper prediction limit for normal values from one eye of the 36 normal age-matched control subjects. Additionally, inter-ocular differences in contrast threshold were also abnormally high in 18 out of 20 glaucoma patients who had vision in both eyes compared with the 95% upper prediction limit. Correspondence between abnormally high contrast thresholds and visual field loss in the truncated quadrants was significant in 5 patients, borderline in 4 patients and absent in 9 patients. CONCLUSION: While the glaucoma patients tested in our study invariably had abnormally high contrast thresholds in one or more of the truncated quadrants in at least one eye, reasonable correspondence with the location of the visual field loss only occurred in half the patients studied. Hence, while contrast threshold elevations are indicative of glaucomatous damage to vision, they are providing a different assessment of visual function from conventional visual field tests

Dialysis and pediatric acute kidney injury: choice of renal support modality

Dialytic intervention for infants and children with acute kidney injury (AKI) can take many forms. Whether patients are treated by intermittent hemodialysis, peritoneal dialysis or continuous renal replacement therapy depends on specific patient characteristics. Modality choice is also determined by a variety of factors, including provider preference, available institutional resources, dialytic goals and the specific advantages or disadvantages of each modality. Our approach to AKI has benefited from the derivation and generally accepted defining criteria put forth by the Acute Dialysis Quality Initiative (ADQI) group. These are known as the risk, injury, failure, loss, and end-stage renal disease (RIFLE) criteria. A modified pediatrics RIFLE (pRIFLE) criteria has recently been validated. Common defining criteria will allow comparative investigation into therapeutic benefits of different dialytic interventions. While this is an extremely important development in our approach to AKI, several fundamental questions remain. Of these, arguably, the most important are “When and what type of dialytic modality should be used in the treatment of pediatric AKI?” This review will provide an overview of the limited data with the aim of providing objective guidelines regarding modality choice for pediatric AKI. Comparisons in terms of cost, availability, safety and target group will be reviewed

Visual evoked potential repeatability using the Diopsys NOVA LX fixed protocol in normal older adults

Richard C Trevino,1 Carolyn E Majcher,1 Adreain M Henry,1 Melinda Rodriguez,1 William E Sponsel1–3 1Rosenberg School of Optometry, University of the Incarnate Word, San Antonio, TX, USA; 2WESMDPA Baptist Medical Center Glaucoma Service, San Antonio, TX, USA; 3Department of Biomedical Engineering, University of Texas San Antonio, San Antonio, TX, USA Purpose: The purpose of this study was to evaluate the intrasession and intersession repeatability of visual evoked potentials in normal adults over 40 years of age as recorded using the Diopsys NOVA LX fixed protocol.Methods: Inclusion criteria were adults aged over 40 years with best corrected distance acuity of 20/40 or better in each eye. Subjects underwent three consecutive visual evoked potential examinations using the Diopsys NOVA LX fixed protocol. All examination procedures were carried out in accordance with the manufacturer recommendations. To assess intersession repeatability, nine subjects returned in 2–6 weeks for repeat examination.Results: A total of 46 subjects were recruited. Mean ± SD age: 53±9 years (range: 40–84 years); 69% of subjects were female and 80% were non-white. Coefficients of variation (CVs) and intraclass correlation coefficients (ICCs) revealed greater repeatability for P100 latency (CV: 3%–7%; ICC: 0.39–0.76) than for P100 amplitude (CV: 21%–33%; ICC: 0.34–0.69) and greater repeatability for recordings made with high contrast stimuli (amplitude CV: 21%–23%; latency CV: 3%–7%) than low contrast stimuli (amplitude CV: 24%–33%; latency CV: 6%–7%). Minimum detectable change values ranged between 4.50 and 9.95 µv for amplitude and 8.16–15.26 ms for latency. Repeatability was not influenced by age, sex, or race.Conclusion: The Diopsys NOVA LX fixed protocol demonstrated clinically acceptable intrasession and intersession repeatability in these healthy older adults, with latency being more repeatable than amplitude and examinations employing high contrast stimuli being more repeatable than those using low contrast stimuli. Keywords: electrophysiology, visual evoked potential, glaucoma, repeatabilit