Foveal Layer Morphology Detected on Spectral Domain Optical Coherence Tomography and its Correlation with Visual Acuity in Asian Indian Premature Infants in their First Year of Life

Structural consequences of arrested foveal development in preterms with persisting signs of immaturity

Purpose

To 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 methods

Layer 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.

Results

Retardation 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.

Conclusions

A 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.

Spectral Domain Optical Coherence Tomography in Detecting Sub-Clinical Retinal Findings in Asian Indian Children with Down Syndrome

Purpose: Trisomy 21, also known as Down syndrome (DS), is the most common trisomy worldwide. Although ocular associations have been reported, retinal anatomy and pathology remain uninvestigated. We evaluate the role of spectral domain optical coherence tomography (SD-OCT) in analyzing foveal morphology of children with DS. Methods: Nineteen consecutive DS children and eight controls were enrolled under a cross-sectional study in an institutional practice. All subjects underwent SD-OCT imaging on a hand-held device. The morphology and thickness of central fovea, inner retinal layers, outer retina, and photoreceptor layers were measured and compared with age-group sub-analysis. Results: Mean age of the cases was 24 months (3-78 months). All cases and controls had a normal fundus on ophthalmoscopy and foveal thickness was comparable (p = 0.718). Inner retinal fusion was complete in the foveal center in only three eyes (15.8%) of cases compared to all eyes (100%) of controls (p < 0.001). The outer plexiform layer was normal in 10 eyes of cases (52.6%) compared to all eyes (100%) of the controls. Only 10 eyes of DS (52.6%) had a normal external limiting membrane, compared to all eyes of controls (100%, p = 0.01). The interdigitation zone (outer segment) was normal in one (5.3%) case compared to eight (67%) controls (p = 0.001). On subgroup analysis, in older cohorts, cases had a greater proportion of abnormal layers compared to controls. Visual acuity was found to be lower in cases when compared to controls, although not significant (p = 0.19). Conclusion: DS babies have abnormal foveal morphology and persistence of inner retinal layers. This may assist our understanding of their visual development.