Karl Citek

Reliability of a computer-based system for measuring visual performance skills

BACKGROUNDnAthletes have demonstrated better visual abilities than nonathletes. A vision assessment for an athlete should include methods to evaluate the quality of visual performance skills in the most appropriate, accurate, and repeatable manner. This study determines the reliability of the visual performance measures assessed with a computer-based system, known as the Nike Sensory Station.nnnMETHODSnOne hundred twenty-five subjects (56 men, 69 women), age 18 to 30, completed Phase I of the study. Subjects attended 2 sessions, separated by at least 1 week, in which identical protocols were followed. Subjects completed the following assessments: Visual Clarity, Contrast Sensitivity, Depth Perception, Near-Far Quickness, Target Capture, Perception Span, Eye-Hand Coordination, Go/No Go, and Reaction Time. An additional 36 subjects (20 men, 16 women), age 22 to 35, completed Phase II of the study involving modifications to the equipment, instructions, and protocols from Phase I.nnnRESULTSnResults show no significant change in performance over time on assessments of Visual Clarity, Contrast Sensitivity, Depth Perception, Target Capture, Perception Span, and Reaction Time. Performance did improve over time for Near-Far Quickness, Eye-Hand Coordination, and Go/No Go.nnnCONCLUSIONSnThe results of this study show that many of the Nike Sensory Station assessments show repeatability and no learning effect over time. The measures that did improve across sessions show an expected learning effect caused by the motor response characteristics being measured.

Drug recognition expert evaluations made using limited data

The Drug Evaluation Classification (DEC) Program is used by Drug Recognition Expert (DRE) officers to determine whether a suspect is under the influence of a drug or drugs at the time of arrest, and, if so, what category of drug(s). The goal of this project was to investigate the relative importance of face-to-face interactions with the suspect, physical evidence (drugs or paraphernalia found), and confessions/statements made by the suspect (or others) in making these determinations. Seventy records of DRE evaluations were selected from a database containing information from all evaluations conducted in Oregon between 1996 and 1998. Each of the 70 records represented a suspect who had either taken a drug from one of four categories (CNS depressant, CNS stimulant, narcotic analgesic, or cannabis) or who had not taken a drug. To be included, the original DRE evaluation and the subsequent toxicology analysis had to agree that the suspect was under the influence of a drug from one of the four categories or not under the influence of a drug. Records from the 70 cases were submitted in written form to 18 Oregon DREs with statements made by suspects or arresting officers, confessions, toxicology results, and descriptions of drugs or paraphernalia found on the suspect omitted. Based only on the written reports of direct observations, and with physiological and psychophysical test results, the DREs attempted to determine whether each of the 70 suspects was under the influence of a drug or drugs, and, if so, what category of drug(s). If the officers determined that a suspect was under the influence of a drug, their accuracy in specifying the drug category was 81% for cannabis, 94% for narcotic analgesics, 78% for CNS stimulants, and 69% for CNS depressants. Overall accuracy in recognizing drug intoxication was 95%. These percentages indicate that although face-to-face interactions, physical evidence, and confessions/statements can be useful adjuncts to DRE decision-making, the majority of drug category decisions can be made solely on the basis of recorded suspect observations and DRE evaluation results.

Anti-reflective coatings reflect ultraviolet radiation.

Anti-reflective (AR) coatings provide numerous visual benefits to spectacle wearers. However, coating designers and manufacturers seem to have placed little or no emphasis on reflectance of wavelengths outside the visible spectrum. Ultraviolet (UV) radiation from sources behind the wearer can reflect from the back lens surface toward the wearers eye. Various clear lens materials, with and without AR coatings, were tested for their transmittance and reflectance properties. Although the transmittance benefits of AR coatings were confirmed, most coatings were found to reflect UV radiation at unacceptably high levels. Tinted sun lenses also were tested with similar results. Frame and lens parameters were evaluated, confirming that eyewear that incorporates a high wrap frame and high base curve lenses can prevent UV radiation from reaching the eye. The findings strongly suggest that clear, flat lenses should not be dispensed for long-term use in sunny environments, even if clip-on tints are provided.

Comparison of refractive error measurements in adults with Z-View aberrometer, Humphrey autorefractor, and subjective refraction.

BACKGROUNDnThe aim of this study was to evaluate whether measurements obtained with the Ophthonix Z-View aberrometer (Vista, California) and a Humphrey autorefractor (Zeiss Humphrey, Dublin, California) correlate with standard subjective refraction measurements, based on visual acuity results.nnnMETHODSnA retrospective data analysis was completed for 97 patients, age range 18 to 66 years, without evidence of systemic or ocular disease. All data were collected without dilation or cycloplegia. Refractive correction measurements (sphere, cylinder, axis) were converted to power vectors for analysis.nnnRESULTSnDifferences-versus-means plots show generally excellent agreement between the results of each instrument and subjective refraction, all r(2) > 0.77, with the Z-View consistently exhibiting less variability than the autorefractor (AR). Nonetheless, the Z-View tends to undercorrect myopia, whereas the AR tends to overcorrect myopia, with statistically significant mean differences (±SD) in spherical equivalents with respect to subjective refraction of 0.118 (±0.311) and -0.193 (±0.474) diopters (D), respectively. Both instruments tend to overcorrect astigmatism of less than -1.25 and -0.75 D, respectively, in some cases by as much as -0.87 D. Both instruments also tend to err in cylinder axis measurement for low astigmatism, often by more than 10°.nnnCONCLUSIONSnThe Ophthonix Z-View aberrometer is a useful objective clinical instrument that provides better accuracy than an AR, and its results can be used as a good starting point for a subjective refraction for most patients. It also measures higher-order aberrations not identified by other techniques. However, as with AR results, a spectacle prescription based solely on its measurements may not be appropriate for all patients.

Safety and compliance of prescription spectacles ordered by the public via the Internet

BACKGROUNDnThis study investigated prescription spectacles ordered from online vendors and delivered directly to the public for compliance with the optical tolerance and impact resistance requirements for eyewear dispensed in the United States.nnnMETHODSnTen individuals ordered 2 pairs of spectacles from each of 10 of the most visited Internet vendors, totaling 200 eyewear orders. Spectacles ordered consisted of ranges of lens and frame materials, lens styles, and refractive corrections reflecting current distributions in the United States. Evaluations included measurement of sphere power, cylinder power and axis, add power (if indicated), horizontal prism imbalance, and impact testing.nnnRESULTSnWe received and evaluated 154 pairs of spectacles, comprising 308 lenses. Several spectacles were provided incorrectly, such as single vision instead of multifocal and lens treatments added or omitted. In 28.6% of spectacles, at least 1 lens failed tolerance standards for at least 1 optical parameter, and in 22.7% of spectacles, at least 1 lens failed impact testing. Overall, 44.8% of spectacles failed at least 1 parameter of optical or impact testing.nnnCONCLUSIONnNearly half of prescription spectacles delivered directly by online vendors did not meet either the optical requirements of the patients visual needs or the physical requirements for the patients safety.

Sleep Deprivation Does Not Mimic Alcohol Intoxication on Field Sobriety Testing

Abstract:u2002 Previous research shows that sleep deprivation (SD) produces cognitive impairment similar to that caused by alcohol intoxication. Individual studies suggest that SD also causes deficits in motor skills that could be mistaken for intoxication. Consequently, SD often is used as a defense when an impaired driver is charged with driving while intoxicated. Twenty‐nine adult subjects participated in two test sessions each, one after a full night’s rest and the other after wakefulness of at least 24u2003h. Subjects consumed prescribed amounts of alcohol during each session. Law enforcement officers conducted field sobriety tests identical to those with which a driver would be assessed at roadside. Researchers also measured clinical responses of visual function and vital signs. The presence and number of validated impairment clues increase with increasing blood alcohol concentration but not with SD. Thus, SD does not affect motor skills in a manner that would lead an officer to conclude that the suspect is intoxicated, unless intoxication also is present.

Absence of Adaptive Plasticity after Voluntary Vergence and Accommodation

Subjects maintained their eyes crossed (verged) for a period of 8 min in darkness with monitoring provided by an infrared video system. Changes in resting vergence (RV) and resting focus (RF) were examined. Results showed: (i) visual stimulation was not necessary for adaptation of either RV or RF, but (ii) these purely motor effects were significantly smaller and more dissipative than those attributable to visually driven adaptation, and (iii) voluntary vergence amplitude was negatively correlated with pupil size. Assuming that voluntary vergence is driven by accommodation, then the voluntary signal must enter the oculomotor control system prior to the cross links between channels, but beyond the site of the visually driven adaptive elements.

GEN Is Not HGN

ceiling effect would not be present. Indeed, the ceiling effect strongly suggests that the A&SQ may perform better in samples of amblyopes with acuity much poorer than that of the sample we tested. We agree with Drs. Kelderman, Felius, and Passchier that our modest sample size of 102 amblyopes limits the extent of any interpretation of the Rasch analysis that can be made from our results, and we highlighted that point in our paper. We also agree that the Rasch model is not a panacea, as no model is. It does, however, provide scientific measurement properties of data that are otherwise ordinal. The main problem with the A&SQ does not appear to be whether it is unidimensional, but whether it provides a valid measurement of the quality of life of patients with strabismus and/or amblyopia. In the original Likert-scaled A&SQ, responses to all items (questions) were weighted equally. Unless all items are equally difficult or important, then simply adding them all up to get a final score does not provide a valid measurement. This observation is particularly true of the A&SQ when subjects are arbitrarily given a score of 4 if they are unable to answer a particular question. Our Rasch analysis of the A&SQ highlighted how different some items were from others (see Fig. 2 in our paper), so that responses to item 7, “miss the other person’s hand when shaking hands,” are weighted very differently from those to item 21, “squint or shut one eye in bright sunlight,” for example, and the difference seems logical. We also believe that the results from the A&SQ are probably not unidimensional. In their letter, Kelderman et al. criticize the validity of the Rasch analysis for assessing the dimensionality of the A&SQ and favor the use of traditional psychometric analysis (i.e., factor analysis). Comparisons between factor analysis results and Rasch analysis should be performed with caution, as the fundamental intent of each method differs. The principal component analysis identifies factors within a correlation matrix (i.e., factor structure underlying the items of the A&SQ), whereas the Rasch analysis determines whether there are other dimensions left once the initial latent trait (i.e., vision-related quality of life) has been extracted. Once subscales have been demonstrated to exist by factor analysis, they should be assessed for unidimensionality. For example, a questionnaire with several subscales (demonstrated using factor analysis) may be considered unidimensional (according to the Rasch analysis), since all the items in the questionnaire measure a single underlying trait. If both are not used, which one should be chosen? Factor analysis assumes that the data being analyzed are linear measures and not the ordinally labeled stochastic observations that are provided by the A&SQ. Studies that have compared factor analysis and the Rasch analysis have concluded that the Rasch analysis is much better at determining the identification of the core construct, particularly when the data are ordinal and factors correlate highly. In our report, not only do the results of the Rasch analysis strongly suggest that there is an important second dimension, but this dimension also includes a relatively large number of items (5 of a total of 23 items) and the inherent qualities of those items (mainly psychosocial) are all similar and seem logically different from most of the remainder, which assess difficulties with functional activities. Thus, we suggest that it may be more appropriate to provide two scores, since the breach of unidimensionality does not allow for appropriate summation of the items within the A&SQE. In turn, our proposed strategy may help to draw meaningful clinical conclusions about the consequences of living with strabismus or amblyopia or both. Marta Vianya-Estopa David B. Elliott Brendan T. Barrett