Kathleen M. Mohan

Amblyopia in astigmatic preschool children

Best-corrected acuity was measured for vertical and horizontal gratings and for recognition acuity optotypes (Lea Symbols) in a group of three- to five-year-old children with a high prevalence of astigmatism. Results showed meridional amblyopia (MA) among children with simple/compound myopic or mixed astigmatism, due to reduced acuity for horizontal gratings. Children with simple/compound hyperopic astigmatism showed no MA, but did show reduced acuity for both grating orientations. Reduced best-corrected recognition acuity was shown by both myopic/mixed and hyperopic astigmats. These results suggest that optical correction of astigmatism should be provided prior to age three to five years, to prevent development of amblyopia.

Stimulus motion increases measured visual field extent in children 3.5 to 30 Months of age

Purpose To examine the influence of stimulus motion on measured visual field extent of 3.5- to 30-month-old children and adults. Methods Each subject was tested with LED-hybrid and LED-kinetic perimetry procedures, using a black double-arc perimeter. Targets in both procedures were identical in size, color, luminance, contrast, and flicker rate. However, in the LED-hybrid procedure, peripheral targets were sequentially illuminated from more peripheral to more central locations, whereas in the LED-kinetic procedure, a peripheral target on a black wand was manually moved centrally along the perimeter arm. A subset of subjects was also tested with white sphere kinetic perimetry (WSKP). Results The LED-kinetic procedure produced larger measured visual field extent than the LED-hybrid procedure in 3.5-, 11-, 17-, and 30-month-olds, but not in 7-month-olds or adults. Data from subjects tested with WSKP indicated that both stimulus motion and discrepancies in scoring methods contributed to the difference reported previously between visual field measurements obtained with WSKP vs. LED-hybrid perimetry. Conclusion In infants and toddlers, measured visual field extent is larger for moving than for nonmoving targets. Further research is needed to determine whether the effect of motion is related to the visual system or to attentional factors.

Inter-rater and intra-rater reliability in the interpretation of MTI Photoscreener photographs of Native American preschool children.

Purpose To evaluate inter- and intra-rater reliability for the interpretation of MTI Photoscreener photographs taken in a population of Native American preschool children with a high prevalence of astigmatism. Methods Photographs of 369 children were rated by 11 nonexpert and 3 expert raters. Photographs for each child were scored as pass, refer, or retake. Nonexpert raters scored photos on two separate occasions, permitting analysis of intra-rater reliability. Results Analyses of pass/refer responses only: inter-rater reliability was moderate to substantial among nonexpert raters and substantial among expert raters. Intra-rater reliability among nonexperts was substantial. Analyses of all responses (pass, refer, and retake): inter-rater reliability for pass and refer scores was moderate among nonexperts and substantial among experts; for retake scores inter-rater reliability was slight for nonexperts and moderate for experts. Intra-rater reliability among nonexperts was substantial for pass and refer scores and moderate for retake scores. Conclusions In this population with a high prevalence of astigmatism, whether MTI photoscreening results are interpretable is much more variable among and within raters than whether an interpretable photograph should be scored as pass or refer. The level of agreement among raters in the current study was influenced by the experience of the raters. In addition, nonexpert raters were more likely to deem a photograph uninterpretable than expert raters.

The Influence of Stimulus Size on Measured Visual Field Extent in Infants

Purpose. To compare measured visual field extent for a 6° stimulus (typical size used in studies of infants) with a 1.5° stimulus (similar to the largest size used in Goldmann perimetry) in young infants. Methods. A total of 120 infants (60 each at 3.5 months and 7 months of age) and 24 adults were tested monocularly with a kinetic perimetry procedure using a black double-arc perimeter. Each subject was tested with either a 6° or 1.5° white sphere, which was mounted on a black wand and moved smoothly toward the intersection of the perimeter arms at 3.4°/s. Visual field extent along each perimeter arm was defined as the median of 2 to 3 measurements of the position of the leading edge of the stimulus when the subject made an eye movement toward the stimulus. Results. The 6° stimulus produced larger measured visual field extent than the 1.5° stimulus in 3.5-month olds (temporal field only) and in 7-month olds (nasal and temporal field), but not in adults. Conclusions. Using the testing conditions of the present study, increasing stimulus size beyond the largest used in a Goldmann perimeter (∼2°) increases measured visual field extent in young infants, but not in adults. This may relate to differences in peripheral summation areas or to differences in attentional factors between infants and adults.

Measured visual field extent varies with peripheral stimulus flicker rate in very young children.

Purpose. The purpose of this article is to describe measured visual field extent in very young children in response to variation in peripheral stimulus flicker rate. Methods. Binocular visual field extent was measured using a black, double-arc perimeter and an LED static perimetry procedure in 120 11-month-old, 120 17-month-old, and 120 30-month-old children and 40 adults. Each subject was tested with one of four flicker rates: 1 Hz, 10 Hz, 20 Hz, or 40 Hz. An interpolated estimate of the eccentricity at which 50% of subjects detected the peripheral stimulus and the mean of the farthest eccentricity at which subjects detected the peripheral stimulus were calculated for each flicker rate for each age group. Results. In 11-, 17-, and 30-month-old children, but not in adults, measured visual field extent (eccentricity at which the stimulus was detected) varied significantly with rate of stimulus flicker. The largest measured visual field extent was produced by a 10-Hz stimulus and the smallest was produced by 1-Hz and 40-Hz stimuli. Measured visual field extent in children was similar to that of adults for 10-Hz flicker, but smaller than that of adults for 1-Hz, 20-Hz, and 40-Hz flicker. Conclusions. These results underscore the importance of standardizing stimulus parameters when developing tests for clinical assessment of visual fields in children. Furthermore, for longitudinal assessment of young patients, use of a 10-Hz flicker rate, in combination with the other parameters used in the present study, would help to avoid difficulties in interpretation that could arise from an interaction between age-related and disease-related changes that might occur if other stimulus flicker rates were used.

Does rate of stimulus presentation affect measured visual field extent in infants and toddlers

PURPOSE To evaluate the effect of stimulus presentation rate on the measurement of visual field extent in infants and toddlers. METHODS Visual field extent was measured for 300 children (N = 60 at 3.5, 7, 11, 17, and 30 months) and 24 adults using hybrid static-kinetic perimetry. Flickering light-emitting diode (LED) stimuli were illuminated sequentially, peripherally to centrally at 10.2 degrees intervals, along 4 diagonal meridia at 2 stimulus presentation rates: 2 s/stimulus (equivalent to 5 degrees/s) and 3 s/stimulus (equivalent to 3 degrees/s). Rate of presentation was a between-subjects variable. RESULTS No effect of stimulus presentation rate was found for adults. The faster rate of stimulus presentation yielded smaller measured visual field extent for children between the ages of 7 and 30 months. The apparent difference seen with 3.5-month-olds did not reach significance. CONCLUSIONS Faster rates of stimulus presentation may result in underestimation of visual field extent in children between the ages of 7 and 30 months.

The effect of flicker rate on measured visual field extent in very young children.

Purpose. To investigate the effect of flicker rate on measured visual field extent in toddlers. Methods. A total of 270 full-term children (90 each at 11-, 17-, and 30-months of age) and 36 adults were tested binocularly with an LED static perimetry procedure using a black double-arc perimeter. Each subject was tested with one of three flicker rates: 0, 3, or 10 Hz. The median farthest location seen and an interpolated estimate of the location at which 50% of the subjects detected the peripheral stimulus were calculated for each age group for each flicker rate. Results. For 11-, 17-, and 30-month-old subjects, but not adults, flickering stimuli produced a larger measured visual field extent than nonflickering stimuli. For the 10-Hz stimuli, measured visual field extent in children did not differ from that of adults. Conclusions. In infants and young children, binocular measured visual field extent is enhanced by peripheral stimulus flicker. Maturity of the measured visual field depends on the stimulus parameters used during testing.

Visual Motor and Perceptual Task Performance in Astigmatic Students

Purpose. To determine if spectacle corrected and uncorrected astigmats show reduced performance on visual motor and perceptual tasks. Methods. Third through 8th grade students were assigned to the low refractive error control group (astigmatism < 1.00 D, myopia < 0.75 D, hyperopia < 2.50 D, and anisometropia < 1.50 D) or bilateral astigmatism group (right and left eye ≥ 1.00 D) based on cycloplegic refraction. Students completed the Beery-Buktenica Developmental Test of Visual Motor Integration (VMI) and Visual Perception (VMIp). Astigmats were randomly assigned to testing with/without correction and control group was tested uncorrected. Analyses compared VMI and VMIp scores for corrected and uncorrected astigmats to the control group. Results. The sample included 333 students (control group 170, astigmats tested with correction 75, and astigmats tested uncorrected 88). Mean VMI score in corrected astigmats did not differ from the control group (p = 0.829). Uncorrected astigmats had lower VMI scores than the control group (p = 0.038) and corrected astigmats (p = 0.007). Mean VMIp scores for uncorrected (p = 0.209) and corrected astigmats (p = 0.124) did not differ from the control group. Uncorrected astigmats had lower mean scores than the corrected astigmats (p = 0.003). Conclusions. Uncorrected astigmatism influences visual motor and perceptual task performance. Previously spectacle treated astigmats do not show developmental deficits on visual motor or perceptual tasks when tested with correction.

Interrater and test-retest reliability of the beery visual-motor integration in schoolchildren

PURPOSE To assess interrater and test-retest reliability of the 6th Edition Beery-Buktenica Developmental Test of Visual-Motor Integration (VMI) and test-retest reliability of the VMI Visual Perception Supplemental Test (VMIp) in school-age children. METHODS Subjects were 163 Native American third- to eighth-grade students with no significant refractive error (astigmatism <1.00 D, myopia <0.75 D, hyperopia <2.50 D, anisometropia <1.50 D) or ocular abnormalities. The VMI and VMIp were administered twice, on separate days. All VMI tests were scored by two trained scorers, and a subset of 50 tests was also scored by an experienced scorer. Scorers strictly applied objective scoring criteria. Analyses included interrater and test-retest assessments of bias, 95% limits of agreement, and intraclass correlation analysis. RESULTS Trained scorers had no significant scoring bias compared with the experienced scorer. One of the two trained scorers tended to provide higher scores than the other (mean difference in standardized scores = 1.54). Interrater correlations were strong (0.75 to 0.88). VMI and VMIp test-retest comparisons indicated no significant bias (subjects did not tend to score better on retest). Test-retest correlations were moderate (0.54 to 0.58). The 95% limits of agreement for the VMI were -24.14 to 24.67 (scorer 1) and -26.06 to 26.58 (scorer 2), and the 95% limits of agreement for the VMIp were -27.11 to 27.34. CONCLUSIONS The 95% limit of agreement for test-retest differences will be useful for determining if the VMI and VMIp have sufficient sensitivity for detecting change with treatment in both clinical and research settings. Further research on test-retest reliability reporting 95% limits of agreement for children across different age ranges is recommended, particularly if the test is to be used to detect changes due to intervention or treatment.

Assessment of grating acuity in infants and toddlers using an electronic acuity card: The Dobson Card

PURPOSE To determine if testing binocular visual acuity in infants and toddlers using the Acuity Card Procedure (ACP) with electronic grating stimuli yields clinically useful data. METHODS Participants were infants and toddlers ages 5 to 36.7 months referred by pediatricians due to failed automated vision screening. The ACP was used to test binocular grating acuity. Stimuli were presented on the Dobson Card. The Dobson Card consists of a handheld matte-black plexiglass frame with two flush-mounted tablet computers and is similar in size and form to commercially available printed grating acuity testing stimuli (Teller Acuity Cards II [TACII]; Stereo Optical, Inc., Chicago, IL). On each trial, one tablet displayed a square-wave grating and the other displayed a luminance-matched uniform gray patch. Stimuli were roughly equivalent to the stimuli available in the printed TACII stimuli. After acuity testing, each child received a cycloplegic eye examination. Based on cycloplegic retinoscopy, patients were categorized as having high or low refractive error per American Association for Pediatric Ophthalmology and Strabismus vision screening referral criteria. Mean acuities for high and low refractive error groups were compared using analysis of covariance, controlling for age. RESULTS Mean visual acuity was significantly poorer in children with high refractive error than in those with low refractive error (P = .015). CONCLUSIONS Electronic stimuli presented using the ACP can yield clinically useful measurements of grating acuity in infants and toddlers. Further research is needed to determine the optimal conditions and procedures for obtaining accurate and clinically useful automated measurements of visual acuity in infants and toddlers.