Abstract
Several parameters on optical coherence tomography (OCT) have been suggested as biomarkers for photoreceptor degeneration in retinitis pigmentosa (RP). This study is to compare the spatial distribution of the changes of OCT biomarkers in RP patients. OCT line scans of the horizontal meridian were conducted in 22eyes of 22 RP patients and 30 eyes of 30 healthy controls. Longitudinal reflectance profiles were obtained using ImageJ at every 5 pixels. The following parameters on OCT were quantitatively measured: (1) relative optical intensity (ROI) of ellipsoid zone (EZ) and interdigitation zone (IZ); (2) thickness of outer nuclear layer (ONLT), photoreceptor (PRT), inner segment (IST) and outer segment (OST). The variations of these parameters across different regions were analyzed. From fovea to perifoveal region, all the OCT biomarkers declined before disappeared, except IST and IZ-ROI. There was no identifiable declining zone for the IST and IZ-ROI between the normal and disappeared zones in some patients. The most central biomarker was the reduction of OST and IZ-ROI, followed by the PRT, EZ-ROI, then IST and finally ONLT. All these biomarkers had significant correlations with best-corrected visual acuity, except ONLT. In retinitis pigmentosa, EZ-ROI, IZ-ROI, PRT, OST, IST and ONLT are valuable biomarkers of photoreceptor degeneration. Changes of OST and IZ-ROI are located most centrally and may be the early biomarkers.
Highlights
Photoreceptor degeneration is an important cause of visual impairment in many diseases, such as inherited retinal degeneration, retinal detachment, diabetic retinopathy and age-related macular degeneration.[1,2,3,4,5] Optical coherence tomography (OCT) provides high-resolution visualization of the cross-sectional morphology of the retina.[6]
The earliest biomarker was the shortening of outer segment thickness (OST) and reduced interdigitation zone (IZ)-relative optical intensity (ROI), followed by the shortening of photoreceptor thickness (PRT), ellipsoid zone (EZ)-ROI, inner segment thickness (IST), and ONLT
OST and IZ-ROI may serve as the earliest biomarkers
Summary
Photoreceptor degeneration is an important cause of visual impairment in many diseases, such as inherited retinal degeneration, retinal detachment, diabetic retinopathy and age-related macular degeneration.[1,2,3,4,5] Optical coherence tomography (OCT) provides high-resolution visualization of the cross-sectional morphology of the retina.[6] There are four hyperreflective bands on OCT images of a normal retina, including external limiting membrane (ELM), photoreceptor inner segment ellipsoid zone (EZ), interdigitation zone (IZ) and retinal pigment epithelium (RPE). In patients with photoreceptor degeneration secondary to various causes, disruption of EZ and IZ are important biomarkers.[7,8,9] With advanced image analysis techniques, some parameters of the photoreceptors can be measured. It remained unknown which is the earliest identifiable biomarker for photoreceptor degeneration
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