Krithika Nandakumar

Dyslexia: a review of two theories

Optometrists will frequently see patients, who may have a diagnosis or a suspected diagnosis of dyslexia (specific reading disorder) and will need to manage and counsel such patients. There are many propounded theories on the cause(s) of dyslexia. Although most professionals in this area consider that dyslexia is chiefly a linguistic disorder, the possibility of a visual component is contentious. This article is a selective review of two commonly discussed theories that suggest a visual component in dyslexia; the magnocellular deficit theory and Meares‐Irlen syndrome.

Bifocals in Down Syndrome Study (BiDS): design and baseline visual function.

Purpose. Among children and young people with Down syndrome (DS) there is a high prevalence of reduced accommodation. Prescribing bifocals for these patients has not become fully clinically accepted, although it would be anticipated to improve visual acuity (VA). The aim of this study is to investigate the impact of bifocal correction on VA, visual perceptual skills and early literacy development in children with DS who have reduced accommodation and who are provided with a bifocal correction. This paper describes the study design and the baseline optometric findings. Methods. We have chosen a longitudinal design with frequent measures of subtests of performance to control for progression with time. The main outcome measures are early literacy and visual perception skills. Secondary outcomes are VA and accommodative function. These are measured at baseline, the participant followed for 6 months when bifocals are prescribed if necessary, and the participants were followed for another 6 months with bifocals. Results. Fourteen participants with DS aged 8 to 19 years were enrolled. At baseline 79% required a change in their distance spectacle prescription. One hundred percent had reduced accommodation both before and after new single vision glasses were prescribed. None had an adverse reaction to 0.5 or 1% Cyclopentolate. All the subjects were able to perform either a distance or near crowded Patti-pics symbols test and 93% were able to perform both. There was a significant improvement of near VA with the new single vision spectacles (p = 0.015). The mean binocular distance VA was 0.362 ± 0.17 logMAR whereas binocular near VA was 0.489 ± 0.235. Conclusion. This study confirms previous findings of a high prevalence of reduced accommodation and shows that near VA is reduced compared to distance VA. The present results indicate that all subjects might benefit from bifocals.

Bifocals in children with Down syndrome (BiDS) – visual acuity, accommodation and early literacy skills

Acta Ophthalmol. 2010: 88: e196–e204

Bifocals in Down syndrome study (BiDS): analysis of video recorded sessions of literacy and visual perceptual skills

Purpose:  In this longitudinal study, a group of school children with Down syndrome (DS) and reduced accommodation were prescribed bifocals and followed to investigate the impact of bifocal spectacles on early literacy and visual perceptual skills. The natural progression of early literacy skills in this population along with the changes with bifocals, described by monthly subtest scores and the time taken to complete literacy and visual perceptual tasks, are reported.

Measuring Infant Visual Acuity with Gaze Tracker Monitored Visual Fixation.

PurposeTo validate a method of measuring grating acuity with remote gaze tracking (GT) against a current clinical test of visual acuity (VA), the Teller Acuity Cards (TACs), as part of the development of an automated VA test for infants. MethodsVisual acuity for computer-generated horizontal square-wave gratings was determined from relative fixation time on a grating area compared with the background. In experiment 1, binocular VA was based on eye movements with a GT in 15 uncorrected myopic adults and compared with VA measured with subjective responses with the same stimuli and with the TACs. In experiment 2, binocular VA was determined in 19 typically developing infants aged 3 to 11 months on two visits with both the GT and TACs. ResultsIn adults, the mean difference between VA measured by the GT and TACs was 0.01 log cycles per degree (cpd) and the 95% limits of agreement were 0.11. One hundred percent of GT VA results were within 0.5 octave of the TACs’ VAs. The mean difference between the GT and TACs for infants was 0.17 log cpd on both the first and second visit (95% limits of agreement, 0.42 and 0.47, respectively). The mean difference between test and retest for infant GT VA was 0.06 log cpd, and limits of agreement for repeatability were 0.48 log cpd. In infants, both the TACs and the GT had a reliability of 89% within less than or equal to 1 octave between visits. Gaze tracking VA improved with age and is in agreement with published norms. ConclusionsThe agreement between the TACs and GT in adults and infants validates the method of measuring grating acuity with the remote GT. These results demonstrate its potential for an automated test of infant VA.

Contact lens fitting and training in a child and youth population

PURPOSE To determine the ease with which children and youths without previous soft contact lens (SCL) experience were able to handle, care for, adapt and be fitted with SCLs. METHODS 179 children aged 8-16 were recruited. Study visits included: screening and training visits, 1-week and 3-month follow-ups. During the training visit, the time taken to demonstrate proficiency in lens insertion and removal and care was recorded. A second training visit was scheduled if necessary. RESULTS Nine children did not complete the screening visit and eight discontinued during the study. Of those eight, seven discontinued during the first week and one before the 3-month visit. Of those recruited, 90.5% (162/179) were successfully fitted and completed the study. A majority of children were dispensed with lenses at the first training visit (94.6%, 162/171). The mean training time for all children was 30 min. There were no statistically significant differences in the number of lenses required to fit or instruction time by age group (p > 0.05) or gender (p > 0.05). Nine participants (5.3%, 9/171) required a second training visit with four still unable to handle lenses (2.3%, 4/171). By the 1-week visit 13.2% (22/167) of participants either lost or tore lenses, no subsequent lost or torn lenses occurred. No serious adverse events occurred during the study. CONCLUSION Children and youths with no previous contact lens experience were easily fitted, able to successfully wear and care for lenses. The results of this study should encourage practitioners to recommend SCLs as a vision correction option.

Visual and binocular status in elementary school children with a reading problem

Purpose This descriptive study provides a summary of the binocular anomalies seen in elementary school children identified with reading problems. Methods A retrospective chart review of all children identified with reading problems and seen by the University of Waterloo, Optometry Clinic, from September 2012 to June 2013. Results Files of 121 children (mean age 8.6 years, range 6–14 years) were reviewed. No significant refractive error was found in 81% of children. Five and 8 children were identified as strabismic at distance and near respectively. Phoria test revealed 90% and 65% of patients had normal distance and near phoria. Near point of convergencia (NPC) was <5 cm in 68% of children, and 77% had stereoacuity of ≤40 seconds of arc. More than 50% of the children had normal fusional vergence ranges except for near positive fusional vergencce (base out) break (46%). Tests for accommodation showed 91% of children were normal for binocular facility, and approximately 70% of children had an expected accuracy of accommodation. Conclusion Findings indicate that some children with an identified reading problem also present with abnormal binocular test results compared to published normal values. Further investigation should be performed to investigate the relationship between binocular vision function and reading performance.