Purpose:
The improved visualization of the outer retina and retinal pigment epithelium (RPE) provided by spectral domain optical coherence tomography (SDOCT) technology has sparked interest in the clinical evaluation of these structures. The integrity of the inner and outer segments of the photoreceptors and RPE has been shown to be of visual prognostic significance. In this analysis, we study the thicknesses of these structures in normal eyes and their relationship with age.
Methods:
Raw SDOCT scan data from 53 eyes of 53 subjects without retinal disease were analyzed by trained, certified graders from the Doheny Image Reading Center (DIRC), using previously described 3D-OCTOR grading software. The retinal boundaries including internal limiting membrane (ILM), inner border of outer nuclear layer (ONL), external limiting membrane (ELM), photoreceptor inner and outer segment (IS-OS) junction, photoreceptor outer border, retinal pigment epithelium (RPE) inner and outer border, and Bruchs’ membrane were drawn manually where ever present. Thickness, volume and area of the total retina, ONL, inner segments (IS), outer segments (OS), and RPE layer were calculated for the foveal central subfield using the software. Mean thickness values were computed for the whole cohort as well as for patients below and above the age of 50. Thickness values were also correlated with age.
Results:
Patients ranged in age from 28 to 107 years. Table1 illustrates the mean foveal central subfield thicknesses and standard deviations for the various structures defined by the graded boundaries for the entire cohort as well as the age subgroups. Inner retinal thickness showed the greatest variability between patients. Most structures did not show a significant change with age, except for the RPE, which measured significantly thinner with age (p=0.025, r-0.31).
Conclusions:
Fine outer retinal substructures of clinical relevance may be quantified on SDOCT images using specialized software. While photoreceptor inner segment and outer segment thickness did not change much with age, the RPE measured thinner in older patients.
Keywords: imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina