Abstract
PurposeTo evaluate the impact of structural changes in a limited sample of adult preterms with foveal immaturity from optical coherence tomography (OCT) B-scan images and to estimate layer displacement and changes in areal and volume magnification within the inner fovea.Subjects and methodsLayer thickness was measured in conventional and directional OCT scans from eight preterms with different degrees of foveal immaturity (24–33 weeks of gestation, 22–33 years of age) and five controls (20–33 years of age). We obtained reflectivity profiles of the outer plexiform layer (OPL) and manual segmentation data of the inner nuclear layer (INL) and the combined ganglion cell layer (GCL) and inner plexiform layer (IPL) at specified eccentricities from 300 to 900 µm. Displacement of cumulative thickness curves of preterms compared with that of the controls was used to estimate retardation of layer displacement. Changes in areal magnification and layer thickness were used to construct a structural model of redistribution within the fovea of preterms.ResultsRetardation of centrifugal layer displacement of OPL and all inner retinal layers (IRL) was marked in both preterm groups with foveal immaturity, whereas retardation was marginal in the preterm group without clinical signs of immaturity. Retarded displacement within the IRL and OPL had a major impact on available space within the central fovea.ConclusionsA marked retardation of displacement was demonstrated for all IRL within the immature fovea of preterms with decreased areal and volume magnification and reduced space available for synaptic communication coupled to the degree of immaturity.
Highlights
Marked changes occur in the human fovea during normal development
An increased inner retinal layers (IRL) thickness associated with a decreased foveal depth (FD) is still observed at adult age in most preterms born before 28 weeks of gestation [10, 13]
The foveal development arrest (FDA) index expressed as a ratio of the Henle fibre layer (HFL) + outer nuclear layer (ONL) thickness and IRL + outer plexiform layer (OPL) thickness (Table 1) was related to the magnitude of retardation, with a mean ratio of ≤5 in both groups with foveal immaturity (PG2 and PG3)
Summary
Marked changes occur in the human fovea during normal development. Histological studies show that towards the latter part of gestation the foveal pit deepens and that neurons within the ganglion cell layer (GCL) and inner nuclear layer (INL) start to disappear from the foveal centre (FC) [1,2,3]. Characteristic persisting signs of immaturity in preterms are increased thickness of the different layers of the inner retina together with presence of a sheet of outer plexiform layer (OPL) covering FC in combination with a reduced foveal depression [11]. An increased IRL thickness associated with a decreased foveal depth (FD) is still observed at adult age in most preterms born before 28 weeks of gestation [10, 13]. This lack of extrusion of the inner part of the fovea has been explained as an arrest of normal maturation. Since normal foveal development of the inner retina has been proposed to involve centrifugal migration of cells out from FC before and after
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