The biometric properties of the infant human eye are significantly different in comparison to those of adults, with shorter axial lengths, steeper corneal curvatures, and greater astigmatism and refractive errors.
4 Preterm infants are predominately myopic, the degree of which decreases with increasing age until there is a shift to hyperopia by approximately 40 to 52 weeks.
13,14 Age-specific adjustments in the OCT imaging protocol need to be established in order to ensure optimal image acquisition in young children. Normally, an OCT scan of the retina is obtained by pivoting the OCT beam in the iris plane. In the shorter infant eye, the OCT scanning pivot position is anterior to the iris plane, resulting in clipping of the peripheral portion of the image by the iris.
4 The shorter axial length may be corrected for by shortening the OCT reference arm position such that the pivot point is positioned in the iris plane.
4 The image is further optimized by adjusting the focus of the handheld probe (range, −10 to +12 diopters) to correct for any refractive errors.
4 In addition, the shorter axial length of the infant human eye results in a magnified retinal image, which alters the scan position on the retina relative to an eye with a longer axial length.
15 In order to facilitate comparisons at specific locations across different age groups, the lateral scales for the OCT data need to be adjusted based on age-specific axial length estimates.
4
Images obtained using the handheld probe may also contain movement artifacts caused by the examiner and/or the child.
8,16 Therefore, HH-SDOCT imaging is limited by its lack of automatic registration for serial measurements, and it may be prudent to consider conventional table-based SDOCT imaging in older children who are sufficiently cooperative. The importance of a child-friendly environment in maximizing cooperation from infants and young children undergoing HH-SDOCT imaging should not be underestimated. Children are much more at ease in a private, spacious, and imaginatively decorated environment that is easy to navigate and in which there is control over noise and lighting. Access to information and communications technology is also suggested.
17 In our experience, we have found that a variety of techniques can be used in order to keep children calm and cooperative for OCT examination. Optical coherence tomography scanning of young infants was most often successful if acquired when the child was seated on a parent's lap while bottle feeding or breastfeeding. Optical coherence tomography imaging could also be successfully carried out with an infant lying supine in his or her own pram or stroller, particularly if infants were drowsy at the time of imaging. Less than 10% of children younger than 12 months of age were imaged lying supine. Children older than 12 months of age responded well to animated fixation targets, for example, age-appropriate cartoons that were employed using a portable laptop computer, which was positioned behind the examiner (
Fig. 1A).