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Slow Binocular Reading in Children With Amblyopia is a Fellow Eye Deficit
abstract
This abstract is available on the publisher's site.
Access this abstract nowSIGNIFICANCE
Amblyopic children read 25% slower than their peers during binocular silent reading.
PURPOSE
We compared binocular reading to fellow eye reading to determine whether slow reading in amblyopic children is due to binocular inhibition i.e., the amblyopic eye is interfering during binocular reading.
METHODS
In a cross-sectional study, 38 children with amblyopia and 36 age-similar control children who completed grades one to six were enrolled. Children silently read grade-appropriate paragraphs during binocular reading and fellow eye reading while wearing ReadAlyzer eye-tracking goggles. Reading rate, number of forward saccades, number of regressive saccades, and fixation duration were analyzed between groups and between viewing conditions. We also examined whether sensory factors (amblyopia severity, stereoacuity, suppression) were related to slow reading.
RESULTS
For amblyopic children, binocular reading versus fellow eye reading did not differ for reading rate (176 ± 60 wpm vs 173 ± 53 wpm, p = .69), number of forward saccades (104 ± 35 saccades/100 words vs 97 ± 33 saccades/100 words, p = .18), number of regressive saccades (21 ± 15 saccades/100 words vs 22 ± 13 saccades/100 words, p = .75), or fixation duration (0.31 ± 0.06 sec vs 0.32 ± 0.07 sec, p = .44). As expected, amblyopic children had a slower reading rate and more forward saccades than control children during binocular reading and fellow eye reading. Slow reading was not related to any sensory factors.
CONCLUSIONS
Binocular reading did not differ from fellow eye reading in amblyopic children. Thus, binocular inhibition is unlikely to play a role in slow binocular reading, and is instead a fellow eye deficit that emerges from a disruption in binocular visual experience during development.
Additional Info
Slow Binocular Reading in Amblyopic Children is a Fellow Eye Deficit
Optom Vis Sci 2023 Jan 31;[EPub Ahead of Print], KR Kelly, RM Jost, LA Hudgins, DR Stager, JS Hunter, CL Beauchamp, LM Dao, EE BirchFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
The authors previously conducted two studies in which they found that children with amblyopia tended to read more slowly than those without a history of amblyopia. In the present study, they now investigated whether the slower reading speed among children with amblyopia could be attributed to binocular inhibition or a deficit in the fellow (non-amblyopic) eye. This was accomplished by comparing the reading rates during silent reading of 100-word passages using the ReadAlyzer computer-assisted infrared eye tracking system between children with anisometropic or strabismic amblyopia and age-matched controls and further comparing the reading rates of the amblyopic children when reading binocularly versus when reading with the amblyopic eye occluded.
The study participants were children aged 7 to 13 years; those with strabismus >4 prism diopters were excluded owing to ReadAlyzer's technical limitations. Amblyopia was defined by an interocular difference in visual acuity of ≥0.2 logMAR, with the amblyopic eye having a best-corrected visual acuity of ≥0.2 logMAR and the fellow eye having a best-corrected visual acuity of ≤0.1 logMAR. Age-matched controls without a history of visual disorders and with normal visual acuity and stereoacuity were also recruited. All participants had English as their primary language. The amblyopic and non-amblyopic pools were matched for socioeconomic status and reading comprehension. The analyzed samples included 38 children with amblyopia (mean age, 10.0 ± 1.5 years) and 36 control children (10.3 ± 1.7 years). There were no significant differences between the two groups in terms of the last grade completed or binocular or fellow-eye reading comprehension.
As in their previous research, the authors found that children with amblyopia read more slowly, with average binocular reading rates of 176 ± 60 words per minute (wpm) versus 217 ± 83 wpm for non-amblyopic children. Additionally, they found that amblyopic children read more slowly than their age-matched peers when the amblyopic eye was occluded, at 173 ± 53 wpm. To directly compare this monocular situation for non-amblyopic children, the control group was evaluated with their left eyes occluded, resulting in a mean reading rate of 213 ± 75 wpm. The authors also examined other key metrics of reading eye movements measured using the ReadAlyzer, including the number of forward saccades, regressive saccades, and fixation duration. The amblyopic group exhibited more forward saccades than the control group, indicating that the amblyopic children in this study had smaller spans of recognition and had to make more saccades to complete the 100-word passages than the non-amblyopic children. This finding was consistent whether the amblyopic children were reading with both eyes open or with the amblyopic eye occluded. Interestingly, there were no differences in fixation duration; thus, the slower reading speed for amblyopic children appears to be a direct result of them having to make more saccades, not taking longer for each fixation.
This study and the prior studies published by Kelly and co-authors are important because they demonstrate that, on average, children with amblyopia have visual deficits that exist and impact major life activities, such as reading, regardless of whether the amblyopic individual is reading with both eyes open or when the amblyopic eye is occluded. Therefore, it is incumbent on all eye care practitioners to carefully evaluate visual functioning that may have an impact on reading or other occupational or academic activities in all individuals with amblyopia. If an individual with amblyopia objectively demonstrates slower reading speed, as is shown to be possible in this study and the authors’ prior studies, accommodations for test taking and other reading-related tasks should be considered.