Evaluation of the optic nerve head in healthy children with the Heidelberg Retina Tomograph.

The optic disc, the most anterior part of the optic nerve, is the target of a
number of ocular diseases possibly leading to serious visual impairment or
blindness. Probably the most important of such disorders is glaucoma, one of
the leading blinding diseases in the world. Glaucoma is defined as a
progressive optic neuropathy with characteristic optic disc cupping and
subsequent visual field loss. In childhood, a number of additional diseases may
involve the optic nerve head, such as increased intracranial pressure,
inflammatory optic neuropathies and optic nerve dystrophies.

The Heidelberg Retina Tomograph (HRT, Heidelberg Engineering, Heidelberg,
Germany) is a non-invasive imaging device, originally developed for topographic
optic nerve head evaluation in glaucoma. For this purpose, a low-energy,
monochromatic, red light beam is projected on the posterior pole of the eye. To
receive reflectance information from surface points of diverse depths, a number
of subsequent scans are made through a variable confocal aperture. Doing so, a
series of images, all from a different focal plane, is received and a
three-dimensional reconstruction of the optic nerve head and the surrounding
retina can then be computed. Their non-invasiveness, patient comfort and high
levels of repeatability and reliability characterize measurements by HRT.

Exact knowledge about the range of normal values is important for correct
interpretation of HRT results in patients with a possible optic disc disorder.
As a consequence, a number of studies have thus reported on normal values of
healthy adults and small numbers of adolescents measured by HRT. However,
rigorous literature exploration did not reveal any useful data about reference
intervals of HRT measurements in children, even though some investigators
reported on optic disc disorders in childhood as measured by HRT.
Interpretation of such measurements, however, remains rather uncertain without
knowledge of the appropriate normal values.

Because reference intervals are essential to interpret HRT in children with
presumed optic disc abnormalities properly, we aim to build up a normal value
database of HRT optic disc measurements in young children.

Prospective, observational case series

There are no risks associated with participation. The The Heidelberg Retina
Tomograph is a non-invasive imaging device for topographic optic nerve head
evaluation. It uses a low-energy, monochromatic, red light beam which is not
harmful to the patient at all.