New imaging techniques shed light on RPE role in AMD

Advances in imaging technologies such as spectral domain optical coherence tomography (SD-OCT) and polarization-sensitive OCT (PS-OCT) have significantly enhanced understanding of the anatomy and function of retinal pigment epithelium (RPE) and its role in degenerative diseases such as age-related macular degeneration (AMD), Ursula Schmidt-Erfurth MD told the 14th EURETINA Congress.

“In-vivo high-resolution imaging using a multimodal OCT system allows identification of photoreceptors and RPE disease and highlights pathophysiologic mechanisms in a quantitative and qualitative manner in all subtypes and stages of AMD,” she said.

Dr Schmidt-Erfurth noted that the RPE is a key structure in AMD pathology, with a number of structural changes occurring with increasing age.

“With age, human RPE accumulates two complex granules containing melanin – melanolipofuscin and melanolysosomes – which are polarized by laser light,” she said.

Dr Schmidt-Erfurth explained that melanosomes, melanolipofuscin and lipofuscin are the principal intracellular organelles of RPE.

“Biosynthetic enzymes localise to the organelle surface suggesting that RPE melanosomes have a dynamic turnover process,” she said.

SD-OCT allows clinicians to see depolarizing structures transformed to a quantity called Degree of Polarization Uniformity (DOPU), while polarization-sensitive OCT is capable of measuring an intrinsic tissue property known as the polarization scrambling effect, she said.

The PS-OCT in drusen allows for individual prognosis versus genetic risk calculation using a standard tool, said Dr Schmidt-Erfurth. 

“It offers a method offering quantitative data sets and reliable automated algorithms. Qualitative identification of drusen morphology gives us valuable insight into mechanisms of RPE pathology and disease progression,” she said.