Intercollegiate usage schedule and the impact resistance of used football helmet faceshields.

PURPOSE: Although new polycarbonate helmet faceshields can withstand impacts exceeding forces of 2,400 N, repeated impacts and ultraviolet radiation degrade the structural integrity. In this study, the impact resistances of unused, solar-radiated, and of game-used faceshields were analyzed. Also, Division 1 National Collegiate Athletic Association football programs were surveyed concerning their faceshield practices. METHODS: Impact resistance was tested by impacting faceshields with baseballs at velocities exceeding 67.1 m/s. Twenty-four new faceshields were exposed to southern daylight, 3 hours per day for 3 months before testing. Subsequent testing was performed on 60 game-used faceshields. Additionally, a faceshield utilization survey was distributed to 117 college programs. RESULTS: Solar-irradiated shields did not fail at maximum test velocity. The survivability of nonimpacted shields was greater than game-worn shields (P = 0.0003). Fifty-nine surveys were returned with 58 programs reporting faceshield use. Approximately 21 players per program use a faceshield. The main reason reported for use was aesthetic. Only 21% of reporting programs require a faceshield for players with reduced visual acuity in 1 eye. CONCLUSION: Faceshields lose impact resistance with typical use. Programs should incorporate a policy for replacement and require that players with reduced vision in at least 1 eye wear a faceshield.

Optical quality and impact resistance comparisons of 2 football helmet faceshields.

BACKGROUND: Currently there is no standard that specifically addresses the optical and impact performance of football protective faceshields. This study compared the impact resistance and optical quality between 2 popular football faceshields. Testing was performed only on new faceshields. METHODS: To test impact resistance, baseballs were propelled at the faceshields with velocities up to 66.4 m/sec. Structural integrity was evaluated after each impact. Ten visors from each of 2 companies underwent a single impact at various velocities. Two visors from each company were impacted 3 times to evaluate the effects of repeated blows. Additional visors were conditioned to -10 degrees C and impacted once. Additionally, prismatic power, refractive power, haze, visible light, and ultraviolet (UV) transmittance, and optical distortion were measured to evaluate optical quality. All testing was done with faceshields mounted to facemask and, when appropriate, to a helmet. RESULTS: None of these new faceshields fractured even with impact velocities up to 66.4 m/sec. With regard to optical quality, both protectors met the optical requirements for the standards of faceshields for selected sports (ASTM F803-2003). CONCLUSIONS: Both faceshields tested should protect football players from anticipated impacts while providing adequate optical quality for satisfactory visual performance.

The reliability of the Lanthony Desaturated D-15 test.

PURPOSE: The Lanthony Desaturated Panel D-15 has been used to measure fine color discrimination for congenital and acquired color vision defects. This study investigated the test-retest reliability of the test using an intertest interval of approximately 1 month. METHODS: One hundred twenty-six color vision normals (mean age = 34.5 years) were administered several color vision tests, including the Lanthony Desaturated D-15. Normal color vision status was confirmed using the anomaloscope and HRR color plates. The color vision tests were readministered 3 to 6 weeks after initial testing. The results of the Lanthony test were expressed using the color confusion index of Bowman. The difference in Color Confusion Index (CCI) between the two administrations was calculated and used to determine the intraclass correlation coefficient. RESULTS: The overall mean CCI for the two administrations for these subjects was 1.11 +/- 0.136. The mean difference in CCI score between test administrations was -0.02 +/- 0.128. There was a strong correlation between the absolute value of the difference in CCI and the mean CCI for each subject (r = 0.51, p < 0.0001). The intraclass correlation coefficient was 0.56 (95% confidence interval, 0.43-0.67). CONCLUSIONS: Although the Lanthony Desaturated D-15 test can be used to assess fine color discrimination, there is considerable within-subject variability in test results. The intraclass correlation coefficient is less than that recommended for use in clinical testing or research. Clinicians should consider at least three administrations of the test at each sitting to ensure precision and we recommend taking the mean of those three tests.

Dynamic visual fields of one-eyed observers.

BACKGROUND: The horizontal binocular visual field can extend to more than 200 degrees, while a monocular field is limited to 160 degrees. Additionally, the nose and other facial structures may block the monocular field further during certain eye movements. The purpose of this study was to compare the monocular against the binocular visual field and determine if head and eye movements can functionally overcome any measured deficit. METHODS: In Experiment 1, visual fields were measured monocularly with a bowl perimeter using 5 fixation positions. Binocular visual fields were calculated by combining the monocular visual field with its mirror image. In Experiment 2, subjects were allowed to make head, eye, and body movements to search for flashing lights 360 degrees around them, spaced every 45 degrees. The numbers of lights identified were compared for the subjects performing monocularly versus binocularly. RESULTS: The size of the overall monocular visual field was found to vary between 48% and 76% of the binocular visual field, depending on eye position. For the flashing light experiment, head and eye movements could not overcome the entire visual-field deficit with monocular viewing. Monocular performance remained 11.4% less than binocular performance. CONCLUSIONS: The visual-field deficit seen with monocular viewing is greatest with nasal fixation, and head and eye movements cannot totally compensate for this deficit when viewing time is limited. Vision standards that require full visual fields in each eye are more appropriate for occupations in which peripheral visual targets must be identified and visual search time is limited.

The reliability and validity of hand-held refractometry water content measures of hydrogel lenses.

PURPOSE: To investigate within- and between-examiner reliability and validity of hand-held refractometry water content measures of hydrogel lenses. METHODS: Nineteen lenses of various nominal water contents were examined by two examiners on two occasions separated by 1 hour. An Atago N2 hand-held refractometer was used for all water content measures. Lenses were presented in a random order to each examiner by a third party, and examiners were masked to any potential lens identifiers. Intraclass correlation coefficients (ICC), 95% limits of agreement, and Wilcoxon signed rank test were used to characterize the within- and between-examiner reliability and validity of lens water content measures. RESULTS: Within-examiner reliability was excellent (ICC, 0.97; 95% limits of agreement, -3.6% to +5.7%), and the inter-visit mean difference of 1.1 +/- 2.4% was not biased (p = 0.08). Between-examiner reliability was also excellent (ICC, 0.98; 95% limits of agreement, -4.1% to +3.9%). The mean difference between examiners was -0.1 +/- 2.1% (p = 0.83). The mean difference between the nominally reported water content and our water content measures was -2.1 +/- 1.7% (p < 0.001); the 95% limits of agreement for this difference were -5.4% to +1.1%. CONCLUSION: There is good reliability within and between examiners in measuring water content of hydrogel lenses. However, with our sample of lenses, examiners tended to overestimate the nominal water content of hydrogel lenses. As discussed, this bias may be associated with the Brix scale used in refractometry and is material dependent. Therefore, investigators may need to account for bias when measuring hydrogel lens water content via hand-held refractometry.

A non-policing honey bee colony (Apis mellifera capensis).

In the Cape honey bee Apis mellifera capensis, workers lay female eggs without mating by thelytokous parthenogenesis. As a result, workers are as related to worker-laid eggs as they are to queen-laid eggs and therefore worker policing is expected to be lower, or even absent. This was tested by transferring worker- and queen-laid eggs into three queenright A. m. capensis discriminator colonies and monitoring their removal. Our results show that worker policing is variable in A. m. capensis and that in one colony worker-laid eggs were not removed. This is the first report of a non-policing queenright honey bee colony. DNA microsatellite and morphometric analysis suggests that the racial composition of the three discriminator colonies was different. The variation in policing rates could be explained by differences in degrees of hybridisation between A. m. capensis and A. m. scutellata, although a larger survey is needed to confirm this.