Outer retinal thickness refers to the combined thickness of the layers from the outer plexiform layer through to the photoreceptor outer segments and retinal pigment epithelium interface, depending on the measurement definition. It reflects the health of the photoreceptors and supporting structures.
Measurement
Optical coherence tomography is used to segment macular scans and calculate thickness within these outer layers. Maps and numerical values are generated for different regions and compared with normative data.
- Requires high-quality scans and accurate layer segmentation
- Can show focal thinning, thickening, or disruption
- Changes often correlate with alterations in visual acuity and symptoms
- Serial measurements help track disease progression or treatment response
Clinical Significance
Outer retinal thickness is particularly relevant in macular degeneration, inherited retinal diseases, and conditions causing photoreceptor damage. Thinning or loss in these layers usually indicates irreversible structural damage.
- Useful in assessing efficacy of therapies aimed at preserving photoreceptors
- Helps distinguish outer retinal from inner retinal pathology
- Important in clinical trials as an objective structural endpoint
- Interpretation must consider coexisting fluid or scarring that can alter apparent thickness
