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

BACKGROUND: This 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. METHODS: Ten 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. RESULTS: We 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. CONCLUSION: Nearly half of prescription spectacles delivered directly by online vendors did not meet either the optical requirements of the patient's visual needs or the physical requirements for the patient's safety.

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

BACKGROUND: Athletes 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. METHODS: One 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. RESULTS: Results 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. CONCLUSIONS: The 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.

Sleep deprivation does not mimic alcohol intoxication on field sobriety testing.

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 24 h. 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.

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

BACKGROUND: The 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. METHODS: A 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. RESULTS: Differences-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°. CONCLUSIONS: The 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.

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 wearer's 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.

Ultraviolet and short wavelength visible light exposure: why ultraviolet protection alone is not adequate.

The danger of exposure to ultraviolet (UV) radiation in both the natural environment and artificial occupational settings has long been recognized by national and international standards committees and worker safety agencies. There is an increasing body of literature that suggests that protection from UV exposure is not enough. Unprotected exposure to the short wavelengths of the visible spectrum, termed the "blue light hazard", is gaining acceptance as a true risk to long-term visual health. Global standards and experts in the field are now warning that those individuals who spend considerable time outdoors should seek sun filter eyewear with high impact resistant lenses that provide 100% UV filtration, high levels of blue light filtration, and full visual field lens/frame coverage as provided by high wrap eyewear. The Skin Cancer Foundation has endorsed certain sunglasses as "product[s]...effective [as] UV filter[s] for the eyes and surrounding skin". However, such endorsement does not necessarily mean that the eyewear meets all the protective needs for outdoor use. There are several brands that offer products with such protective characteristics. Performance sun eyewear by Nike Vision, available in both corrective and plano (nonprescription) forms, is one such brand incorporating these protective features.

Nystagmus testing in intoxicated individuals.

BACKGROUND: Law enforcement officers routinely conduct psychophysical tests to determine if an impaired driver may be intoxicated or in need of medical assistance. Testing includes assessment of eye movements, using the Horizontal Gaze Nystagmus (HGN) and Vertical Gaze Nystagmus (VGN) tests, which are conducted at roadside by patrol officers. These tests previously have been validated when the subject is placed in a standing posture with head upright. However, certain conditions require that the subject be tested while seated or supine. Under these conditions, Positional Alcohol Nystagmus (PAN) could be induced and mistaken for HGN or VGN. METHODS: The study was conducted at law enforcement training academy alcohol workshops in the Pacific Northwest. Ninety-six volunteer drinkers were tested when sober and three times after drinking alcohol by 40 volunteer officers experienced in administering the tests. Blood alcohol concentration (BAC) was measured objectively with a calibrated breath analysis instrument each time a subject was tested. RESULTS: The number of eye movement signs observed during the HGN test at any posture increases with increasing BAC. The presence of VGN at any test posture occurs only in the presence of signs of HGN and only at high levels of impairment. PAN was most often observed at BACs of 0.08% and higher, but was never confused with the observation of HGN or VGN, regardless of test posture. CONCLUSIONS: The HGN test administered in the standing, seated, and supine postures is able to discriminate impairment at criterion BACs of 0.08% and 0.10%. The VGN test can identify high levels of impairment at any test posture. Therefore, these tests can be used by an officer to determine if a driver is impaired, regardless of whether the driver is standing, seated, or supine.

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.