  Significance: Speckle has historically been considered a source of noise in
coherent light imaging. However, a number of works in optical coherence
tomography (OCT) imaging have shown that speckle patterns may contain relevant
information regarding sub-resolution and structural properties of the tissues
from which it is originated.
  Aim: The objective of this work is to provide a comprehensive overview of the
methods developed for retrieving speckle information in biomedical OCT
applications.
  Approach: PubMed and Scopus databases were used to perform a systematic
review on studies published until April 2021. From 134-screened studies, 37
were eligible for this review.
  Results: The studies have been clustered according to the nature of their
analysis, namely static or dynamic, and all features were described and
analysed. The results show that features retrieved from speckle can be used
successfully in different applications, such as classification and
segmentation. However, the results also show that speckle analysis is highly
application-dependant, and the best approach varies between applications.
  Conclusions: Several of the reviewed analysis were only performed in a
theoretical context or using phantoms, showing that signal-carrying speckle
analysis in OCT imaging is still in its early stage, and further work is needed
to validate its applicability and reproducibility in a clinical context.
