Optic Nerve and Fundus Evaluation
Visualization and documentation of the optic nerve are crucial in the evaluation and management of pediatric glaucomas. A highly magnified view of the nerve is ideal; this can often be achieved with direct ophthalmoscopy, which may be done in the office or operating room. In patients with small pupils, viewing through a direct ophthalmoscope can be enhanced through a Koeppe lens (Fig 11-11). Alternatively, a stereoscopic view can be achieved by viewing the nerve head through the central lens of a 4-mirror gonioprism with an operating microscope. Indirect ophthalmoscopy can be used, but this method may lead to underestimation of the cup–disc ratio (CDR). Slit-lamp biomicroscopy can be performed in older children with a dilated pupil. Photographs provide the best documentation and help the ophthalmologist evaluate changes over time.
Optic nerve imaging is possible on older, cooperative children and provides useful information that can be followed longitudinally. Normative databases for children do not yet exist in commercially available imaging platforms. However, it has been found that the retinal nerve fiber layer (RNFL) thickness of children over 5 years of age is similar to adult values; therefore, adult normative values can be used for comparison. Optical coherence tomography (OCT) parameters vary with age, axial length, and race, as they do for adults. OCT data for infants cannot be compared to data from adult normative databases. Another barrier to imaging in infants is the lack of commercially available portable handheld OCT machines.
Figure 11-11 photograph of an optic nerve examination with a direct ophthalmoscope using a Koeppe lens for an improved view.
(Courtesy of JoAnn A. Giaconi, MD.)
A typical newborn without glaucoma has a small physiologic cup (CDR less than 0.3) with a pink rim. In individuals with PCG, the optic canal is stretched under high pressure and the lamina cribrosa is bowed backward, causing generalized enlargement of the cup. Enlarged or increasing CDR or CDR asymmetry greater than 0.2 between the 2 eyes is suggestive of glaucomatous cupping. Cupping may be reversible if the IOP is lowered before the child is 3 years old; however, lowering IOP does not reverse any existing atrophy of the optic nerve axons. Studies in which OCT is performed in children with PCG show diffuse RNFL loss rather than loss localized to the superior and inferior poles of the optic disc.
In children without glaucoma, CDR increases slightly from birth until approximately 10 years of age. The CDR of older children without glaucoma is similar to that seen in adults. Racial differences in CDR are present even at birth. Children of African, Middle Eastern, Hispanic, and East Asian descent have larger average CDRs than do children of European descent. Cupping in older children is similar to that seen in adult glaucomas; there are more focal defects and greater loss in the superior and inferior neural rim because their scleral canals do not stretch.
Allingham MJ, Cabrera MT, O’Connell RV, et al. Racial variation in optic nerve head parameters quantified in healthy newborns by handheld spectral domain optical coherence tomography. J AAPOS. 2013;17(5):501–506.
Samarawickrama C, Pai A, Tariq Y, Healey PR, Wong TY, Mitchell P. Characteristics and appearance of the normal optic nerve head in 6-year-old children. Br J Ophthalmol. 2012;96(1):68–72.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.