Gregory W. Good

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.

The effect of experience on the detection of small eye movements.

Purpose The purpose of this study was to determine whether experience improves detection of small eye movements similar to those seen in the cover test during ideal conditions. Methods Three groups of examiners with varying amounts of experience in eye movement detection tasks were studied. Eight examiners were 1st-year optometry students, six were 4th-year optometry students, and six were practicing optometrists. To determine thresholds for eye movement detection, examiners indicated the horizontal direction in which the eyes of one of the experimenters moved. The direction and extent of each eye movement was randomly selected. The extent of the eye movement was one of eight logarithmic steps from a maximum that was determined through an initial session where the approximate sensitivity of the examiners was found (generally ± 1.75 prism diopters). Results Detection thresholds were determined by fitting the data with a cumulative Gaussian function. The mean horizontal eye movement eye movement necessary to obtain 99% correct judgments was 2.65 prism diopters for the 1st-year students, 2.47 prism diopters for the 4th-year students, and 2.40 prism diopters for the practicing optometrists. Conclusions The results indicate that during ideal conditions, little or no training is required for efficient detection of small eye movements.

Chronic solar radiation exposure and endothelial polymegethism

Acute exposure of ultraviolet radiation to the cornea has previously been shown to produce endothelial pleomorphism and polymegethism. The reciprocity of exposure intensity and duration typically seen with the photochemical effects of ultraviolet radiation on biological tissue predicts a similar effect with chronic exposure. This was tested by comparing the regularity of the hexagonal endothelial mosaic for a group of workers (n = 9) chronically exposed to solar radiation to that for an age-matched control group (n = 18). Although the mean cell area of the endothelium was similar between groups (p greater than 0.10), a significant difference (p less than 0.01) was demonstrated in the degree of polymegethism. This supports the contention that chronic ultraviolet radiation exposure may contribute to increased polymegethism seen with age.

Use of horizontal gaze nystagmus as a part of roadside sobriety testing

Alcohol is a central nervous system depressant that can affect eye movement control. Even at low blood alcohol concentrations (BACs) smooth pursuit eye tracking can be lost and horizontal nystagmoid movements become apparent at relatively small angles of lateral gaze. Law enforcement officers across the nation are being taught evaluation techniques to use these eye movement signs as an indicator of alcohol intoxication. Information obtained at the Ohio State Highway Patrol (OSHP) course on the Advanced Detection, Apprehension, and Prosecution of subjects suspected of driving a vehicle while intoxicated is presented here including the testing and scoring techniques of the horizontal gaze nystagmus sobriety test.

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.

Color Discrimination in Heterozygous Deutan Carriers

Purpose. The color discrimination abilities of heterozygous deutan female carriers were measured using color mixture thresholds and compared with those of suspected nonheterozygous normal subjects. Methods. Eight test subjects and 26 control subjects were run on a computer-controlled color test (color mixture thresholds) that presented 1° diameter spots on a color television monitor for 1/60 of a second. A QUEST procedure was used to determine visual thresholds for spots varying in brightness and/or color. Individual data points were graphed on an X/Y plot and fitted with an ellipse. The major and minor diameters of the ellipse represent the color and brightness thresholds, respectively. Results. The mean axis angle of the ellipse for the heterozygous carriers did not differ from that for the controls (15.75° vs. 14.93°, p = 0.428, Mann-Whitney test). The carriers did show, however, a larger mean major axis length (68.79 vs. 46.78, p = 0.0218, Mann-Whitney test). Additionally, the length-to-width ratios for the carriers were higher than the controls (9.34 vs. 6.80, p = 0.0403, Mann-Whitney test). Conclusions. Deutan-carriers do show reduced color purity discrimination as measured using color mixture thresholds compared with nonheterozygous, color vision normals.

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.

Ophthalmic lens retention in safety frames

Lens retention in metal and zyl safety frames was tested using both a high mass (500 g), low velocity impact (HM-LV), and a low mass (1.04 g), high velocity impact (LM-HV) for piano polycarbonate lenses of various thicknesses. The results showed that the metal safety frames retained lenses better than the zyl (p / 0.01) after a HM-LV impact. For the LM-HV impact, metal and zyl frames performed equally (p=1.00). Lens thickness was not a factor in lens in frame retention for the HM-LV impact (p=0.958). However, for the LM-HV impact, 1.6-mm thick lenses were more easily displaced than lenses with thicknesses of 2.0, 2.4, and 3.2 mm (p=0.003).

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.

Eikonic lens design for minus prescriptions.

Abstract Designing size lenses for aniseikonia correction usually involves considering only the shape factor of the total spectacle magnification. However, for minus prescriptions, an increase in the shape magnification of a lens does not always result in total lens magnification. As the front curve of a lens is steepened (which increases the shape magnification), the sagittal depth of the lens is increased, which effectively increases the vertex distance. For a minus lens, an increased vertex distance means decreased power magnification; depending upon the lens power, the decrease in power magnification can totally offset the increase in shape magnification. The shape factor‐power factor relationship of high minus size lenses is presented, along with general guidelines for proper design of size lenses.