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Refractive error and preferential looking visual acuity in infants 12-24 months of age: year 2 of a longitudinal
Insights
Infant vision rapidly improves from 12 to 24 months, with visual acuity increasing significantly. Refractive error remains stable in low hyperopia, and stereopsis develops by 24 months.
Area of Science:
- Ophthalmology
- Developmental Pediatrics
- Infant Vision Science
Background:
- Normal visual development is crucial for cognitive and motor skill acquisition.
- Understanding visual changes in infants informs early detection of potential visual impairments.
- Previous research has established typical visual development milestones from birth to 12 months.
Purpose of the Study:
- To assess changes in visual acuity and refractive error in healthy infants from 12 to 24 months of age.
- To document the development of stereopsis (3D vision) during this period.
- To evaluate the feasibility of standard vision testing methods in older infants.
Main Methods:
- Longitudinal study tracking 18 healthy infants from 12 to 24 months.
- Bimonthly measurements of visual acuity using the acuity card preferential looking procedure.
- Bimonthly assessment of refractive error via Mohindra's near retinoscopy.
- Observation of stereoacuity development using the Stereo Fly test.
Main Results:
- Mean visual acuity improved from 6.4 cycles per degree (cpd) at 12 months to 20.5 cpd at 24 months.
- Refractive error remained stable, showing low hyperopia (mean X = 0.4D).
- Stereopsis improved significantly, with Stereo Fly response increasing from 0% at 12 months to 87% at 24 months.
- Astigmatism remained largely unchanged in amount and frequency.
- Acuity card testing became more challenging in the 12-24 month age range compared to younger infants.
Conclusions:
- Healthy infants demonstrate substantial visual acuity gains between 12 and 24 months.
- Infant refractive error typically stabilizes in low hyperopia during this period.
- Stereopsis develops significantly between 12 and 24 months, indicating maturing binocular vision.
- While feasible, vision testing in older infants requires careful consideration of developmental stage.
Abstract:
This paper presents data from year 2 of a study assessing changes in visual acuity and refractive error in normal, healthy infants between birth and 24 months of age. Visual acuity and refractive error measurements were taken at 2-month intervals on 18 infants, 12-24 months of age. The acuity card preferential looking procedure and Mohindra's near retinoscopy were used for acuity and refractive error measurement. Response to the Stereo Fly was also observed. Mean acuity improved from 6.4 cycles per degree (cpd) (20/93) at 12 months to 20.5 cpd (20/29) at 24 months (SD = 0.5 octave). Refractive error remained in low hyperopia (X = 0.4D, SD = 0.5D). Amount and frequency of astigmatism showed little change. Response to the Stereo Fly improved from 0% at 12 months to 87% at 24 months. The acuity card procedure was easily accomplished, but more difficult with these children at 12-24 months of age than when previously tested between 0-12 months of age.