Effect of aftermarket automobile window tinting films on driver vision.

This study was conducted to determine the level of automobile window tint that causes a significant reduction of vision for automobile drivers. Contrast sensitivity was measured on 20 participants, of whom 10 were age 20 to 29 years and 10 were age 60 to 69 years, through a stock automobile window (control) and two windows darkened with plastic film. For the younger drivers, a car window with 37% transmittance did not significantly reduce contrast sensitivity, but a darker tint of 18% transmittance reduced contrast sensitivity at higher spatial frequencies. For the older drivers, a tint of 37% transmittance significantly reduced mid-to- high spatial frequency contrast sensitivity. The typical state standard (no tint with less than 35% transmittance) would thus seem to be appropriate for younger drivers; however, further examination of the standard may be necessary in regard to older drivers. Actual or potential applications of this research include guidelines and regulations regarding tinting of automobile windows.

Frequency of convergence insufficiency among fifth and sixth graders. The Convergence Insufficiency and Reading Study (CIRS) group.

PURPOSE: To estimate the frequency of convergence insufficiency (CI) and its related clinical characteristics among 9- to 13-year-old children. METHODS: Fifth and sixth graders were screened in school settings at three different study sites. Eligible children with 20/30 or better visual acuity, minimal refractive error, no strabismus, and exophoria at near were evaluated according to a standardized protocol to determine the presence and severity of CI. These children were classified according to the presence and number of the following clinical signs: (1) exophoria at near > or =4delta than far, (2) insufficient fusional convergence, and (3) receded nearpoint of convergence. Also, children were classified as accommodative insufficient (AI) if they failed Hofstetter's minimum amplitude formula or had greater than a + 1.00 D lag on Monocular Estimate Method retinoscopy. RESULTS: Of 684 children screened, 468 (68%) were eligible for further evaluation. Of these, 453 had complete data on CI measurements and were classified as: no CI (nonexophoric at near or exophoric at near and < 4delta difference between near and far) (78.6%); low suspect CI (exophoric at near and one clinical sign: exophoria at near > or =4delta than far) (8.4%); high suspect CI (exophoric at near and two clinical signs) (8.8%); and definite CI (exophoric at near and three clinical signs) (4.2%). CI status varied according to ethnicity and study site (p < 0.0005), but not gender. The frequency of AI increased with the number of CI-related signs. For CI children with three signs, 78.9% were classified as also having AI. CONCLUSIONS: These findings suggest that CI (defined as high suspect and definite) is frequent (13%) among fifth and sixth grade children. In addition, there is a high percentage of CI children with an associated AI.

Prospective comparison of convergence insufficiency and normal binocular children on CIRS symptom surveys. Convergence Insufficiency and Reading Study (CIRS) group.

PURPOSE: To test the validity-related evidence of a child and a parent symptom survey developed by the Convergence Insufficiency and Reading Study (CIRS) group. METHODS: A case comparison method was used to measure differences in symptoms between 14 school-aged children (ages 8 to 13 years) with Convergence Insufficiency (CI) and 14 children with normal binocular vision (NBV). RESULTS: A pooled t-test indicated that CI children and their parents scored higher than the NBV children and their parents on the child's survey (p<0.001) and parent's survey (p<0.001), respectively. CI children also scored significantly higher (p<0.03) on the Conners' Rating Scale for Parents. CONCLUSIONS: The results suggest that the CIRS symptom survey is a valid instrument for differentiating CI children from those with normal binocular vision. Additionally, children in this age group were able to respond to a broad range of symptom questions associated with CI.

The incidence of glassy corneal striae.

Glassy corneal striae (GCS) are fine colorless lines that run parallel to each other in a vertical or near-vertical orientation in the central cornea near the level of Descemet's membrane. It is postulated that GCS "brace" the stroma, thus adding stability to the cornea. The purpose of this study was to determine the incidence of GCS in patients with "normal" corneas and to determine whether a correlation exists between the presence of GCS and gender, age, iris color, or corneal astigmatism (toricity). Modified marginal retro-illumination biomicroscopy was used to evaluate the cornea for the presence of GCS. One hundred thirteen "normal" right corneas were evaluated for the presence of GCS. A total of 85.8% (97/113) of subjects in our study sample exhibited GCS. However, we were unable to establish a statistically significant correlation between the presence of GCS and gender, age, iris color, or corneal toricity.

Normative values for the nearpoint of convergence of elementary schoolchildren.

BACKGROUND: Nearpoint of convergence (NPC) values of 8 to 10 cm are widely used to diagnose binocular dysfunctions such as convergence insufficiency. However, there are no published age-related normative values in the literature to substantiate these values. METHODS: Subjects were 297 schoolchildren in kindergarten, third grade, and sixth grade who had passed a school-based Modified Clinical Technique vision screening. Each child had the NPC break and recovery taken three times using a standardized protocol developed by the Convergence Insufficiency and Reading Study group. The examiners used an Astron International (ACR/21) Accommodative Rule with a movable column of 20/30 letters as the target. RESULTS: For each grade, the distribution of NPC break was right skewed, with a concentration of values between 1 and 6 cm. At least 85% of the subjects in each grade had an NPC break < or = 6 cm. NPC break values (mean +/- SD) were 3.3 +/- 2.6 cm for kindergartners, 4.1 +/- 2.4 cm for third graders, and 4.3 +/- 3.4 cm for sixth graders, and the means were found to be statistically different (analysis of variance, p = 0.031). NPC recoveries (mean +/- SD) for the three groups were 7.3 +/- 4.8 cm, 8.7 +/- 4.2 cm, and 7.2 +/- 3.9 cm, respectively, which were also significantly different (analysis of variance, p = 0.027). The recovery distributions were more symmetric and less skewed than those for break. For each grade level, there was a strong positive relationship between NPC recovery and NPC break, but the difference between NPC recovery and break had a low correlation with the NPC break. SUMMARY: Kindergartners had somewhat better NPC breaks than third or sixth graders, whereas no clear age trend was present for NPC recovery. A supporting study using a random sample of clinic patients (aged 10-12 years) suggests that patients with NPC breaks > 6 cm are more than twice as likely to be symptomatic than patients with NPC breaks < or = 6 cm. Based on these results and the NPC break distributions in this study, a clinical cutoff value of 6 cm is suggested for patients of elementary school age. A cutoff value in the 6- to 10-cm range is recommended for children of elementary school age in a screening context. The exact value within this range depends on the level of concern with identifying patients who have visual signs and symptoms associated with a receded NPC.

Efficacy of hand washing procedures on bacterial contamination of hydrogel contact lenses.

The effect of various hand washing regimens on transfer of bacterial contaminants from the hands to a hydrogel contact lenses was evaluated. Each of 47 subjects performed 5 different hand washing procedures, and then handled a new, sterile hydrogel contact lens. The lenses were cultured to determine colony-forming units (CFUs) and microbial identity. Median CFUs on lenses handled after washing with water, soap and water, or soap and water followed by towel drying were higher than the median CFU for lenses handled after no hand washing. The median CFU for lenses handled after soap and water washing followed by an alcohol wipe was not different from the no washing group. The majority of the contaminants were identified as Staphylococcus epidermidis. These results show that ordinary hand washing alone does not decrease, and may even increase, the amount of contaminants transferred from the hands to a hydrogel lens. Use of an alcoholic wipe after hand washing reverses this effect. Hand washing is still recommended in contact lens hygiene for removal of more pathogenic contaminants.

Comparison of carboxymethylcellulose vs. hydroxypropyl methylcellulose as a gonioscopic fluid.

BACKGROUND: Hydroxypropyl methylcellulose (HPMC), a popular gonioscopic solution, can cause discomfort and blurred vision. These side effects have been attributed to the preservative benzalkonium chloride (BAK). Carboxymethylcellulose (CMC), an unpreserved, viscous solution, might well provide adequate patient comfort and cushioning during gonioscopy without producing blur or irritation. METHODS: The effects of CMC and HPMC during gonioscopy were evaluated in 55 human subjects. Corneal staining, comfort, subjective vision, and measured visual acuity (VA) were assessed. RESULTS: In comparison with HPMC, CMC effected less corneal staining, greater comfort, and better vision after the procedure, CONCLUSION: CMC proved to be a viable and superior alternative to HPMC as a gonioscopic solution.

A comparison of drop instillation and spray application of 1% cyclopentolate hydrochloride.

We compared the objective cycloplegic refractive error of 37 hyperopic children (ages 18 months to 6 years). Cycloplegia was by spray application to the closed eye, or by a one-drop instillation to the open eye. Patients were initially screened for hyperopia using a masked noncycloplegic retinoscopy with loose trial lenses. Spray and drop cycloplegias (1% cyclopentolate hydrochloride; 1% Spectro Pentolate) were administered to each patient in random order within a 2-week period. A masked cycloplegic retinoscopy was performed 20 min after drug administration for patients with "light" iris coloration and after 40 min for those with "dark" irides. One examiner conducted all cyclopentolate administrations; a separate examiner (masked to application method) conducted all refractive testing. For right eyes, the mean spherical equivalent refractive error after spray application was 1.76 D (SD = 1.63 D) and after drop instillation 1.78 D (SD = 1.85 D). Results were similar for the left eyes. These small differences were not statistically significant (ANOVA, F = 0.05, p = 0.82). The absolute difference in spherical equivalent was 0.50 D or less in 93% of all subject eyes. A scaling system was used to rate the ease of administration and the patient's response to each method. Using an exact test of marginal homogeneity, the response rating for the spray method was significantly better (p = 0.038). The spray application of cyclopentolate hydrochloride is easier to administer and is an effective alternative to traditional drop instillation.

Dyslexia and visual perception: is there a relation?

Opinions differ concerning the relation between dyslexia and visual perception. In this pilot study we addressed this question by analyzing the results of visual perceptual testing on 19 elementary grade subjects diagnosed as having dyseidesia, one type of dyslexia that manifests as problems with sight-word recognition. The subjects, who have different degrees of severity of dyseidesia, were compared with 11 subjects tested as nondyslexic, but with reading problems. The Dyslexia Determination Test (DDT) and the Test of Visual Perceptual Skills (TVPS) were given to all subjects. Both multivariate analysis of variance (MANOVA) and univariate one-way analysis of variance (ANOVA) to test for differences in performance among four test groups (ranging from nondyslexic to increasing levels of severity of dyseidesia) showed no trends of either statistical or clinical importance. An individual with reading problems may be nondyslexic but have poor visual perceptual skills, or may be dyslexic with good visual perceptual skills. These results are consistent with the contention that reading problems caused by dyseidesia (as defined by the DDT) and those caused by visual perceptual deficiencies (as defined by the TVPS) are different. Although dyseidetic dyslexia results in characteristic coding patterns producing specific reading problems, it is probable that visual perceptual deficiencies contribute to learning problems that include general reading problems. Each condition would, therefore, require different forms of therapy. Limitations of this study and recommendations for future research are discussed.

Validity of the dyslexia screener.

Optometrists see many patients who complain of reading difficulty. The Dyslexia Screener (TDS) is an instrument which has been developed to determine, within 5 min, whether or not a patient shows evidence of having one of the three basic types of dyslexia (a coding problem in reading and spelling). Results using TDS were compared with the Dyslexia Determination Test (DDT). TDS rating scores were shown to contain much of the same clinical information as the DDT rating scores.