Tag Archives: autofluorescence

Book Review

Optical Coherence Tomography and OCT Angiography: Clinical Reference And Case Studies

Darrin A. Landry, CRA, OCT-C
Amir H. Kashani, MD, PhD

Bryson Taylor Publishing, 2016

In the early days of retinal angiography, photographers often worked very closely with ophthalmologists, learning together as they explored the diagnostic uses of fluorescein angiography and unraveled the complexities of interpreting the fascinating images they were capturing. This spirit of scholarly collaboration between imager and physician continues today in a new book: Optical Coherence Tomography and OCT Angiography, Clinical Reference And Case Studies by Darrin Landry and Amir Kashani. These authors are both well respected in their respective fields as educators and authors. Together they have created a timely textbook that will appeal to members of both professions.

Before receiving an advance copy of this book for review, I anticipated that the content would focus almost exclusively on OCT angiography.  I was pleasantly surprised to find that although the book features OCT-A prominently, it is much more than a text on this new state-of-the-art technology. It appropriately places OCT-A in the context of multiple imaging modalities to assist in diagnosis of a variety of retinal conditions.

The authors have produced a book that is part tutorial, part clinical atlas, and a collection of over forty cases that “puts it all together” using multiple imaging modalities with clinical descriptions. The book is divided into three sections:

Section 1. OCT and OCT Angiography

The introductory section will be particularly useful to imagers as it includes a basic overview of OCT and OCT-A technology, followed by a discussion on pattern recognition, normal anatomy and layers of the retina, how to move the scan pattern, recognizing artifacts, EDI/FDI and a basic primer on OCT-A. The OCT-A primer explains how this technology scans through the z-axis and detects motion to identify the retinal vasculature including the deep retinal plexus.  It includes a discussion of artifacts specific to OCT-A . This section will be especially helpful to those new to OCT and OCT-A, and anyone preparing for certification as an OCT-C.

Section 2. Atlas of Images and Disease Pathology

This section is an atlas of retinal OCT findings organized in anatomical order from the vitreous to the choroid. For each condition, the text includes a brief discussion of the disease process, clinical findings, and appearance in multiple modalities. For each condition, there are multiple image examples providing a full spectrum of potential findings for that disease. For instance, there are over twenty different examples of epiretinal membrane. Novice imagers will find this variety especially helpful in learning to recognize different manifestations of a single condition. In addition to common retinal findings the book also includes good examples of less recognized conditions such as outer retinal tubulation (ORT) and reticular pseudodrusen. As expected, retinal vascular diseases include OCT-A examples along with SD-OCT and other imaging modalities including fluorescein and ICG angiography. Experienced imagers will recognize many of these conditions, but the addition of OCT-A will give them another viewpoint and expand their understanding of each disease.

Section 3. Case Studies

The final section of the book is a series of over forty cases where the authors combine a brief medical summary with appropriate imaging modalities for clinical correlation. This format fits well with the current trend of “case-based-learning” in medical education. In many of these cases, OCT-A dovetails nicely with other imaging modalities to increase our understanding of a disease process or help confirm a diagnosis. This quote from the book’s Preface describes the format well “These images are presented in the context of additional imaging modalities to aide the reader in making useful correlations.”

In conclusion, this timely book is well organized and thorough, without becoming unwieldy. It is easy to navigate between sections if you want a quick reference on OCT anatomy or to look for examples of specific retinal conditions and how they may appear on OCT, OCTA and other imaging modalities. With over a thousand images and forty cases, to say that this book is generously illustrated would be an understatement. It is an impressive collaboration between an ophthalmic imager and a retinal specialist that should appeal to a wide audience that would include ophthalmic imagers, retinal technicians, residents in training, and clinicians wanting a reference for clinical correlation between modalities.

From a personal standpoint, I think it’s great to have an ophthalmic imager making a significant contribution to the ophthalmic literature. Darrin’s collaboration with Dr Kashani serves as a model for what imagers can accomplish when we collaborate with physicians on a professional level.  The spirit of collaboration between professions is echoed several times in the book including this statement from the Introduction, “Constant and close communication between the physician and imager is very essential.”

Reviews like this often end with a cliché that suggests that everyone in the profession should “add this book to your collection” or “keep a copy on your bookshelf”. I’ve tried to avoid those clichés, but honestly, I am happy to have this book in my collection and plan to keep it handy in clinic for reference, especially as we integrate OCT-A into our own diagnostic armamentarium.


Ocular Autofluorescence – More Than Just the Fundus

Over the past decade, fundus autofluorescence imaging has become a commonly used diagnostic technique to document the presence of fluorescent structures in the eye.1-2 The term “autofluorescence” is used to differentiate fluorescence that may occur naturally from fluorescence that is derived from application of dyes such as fluorescein or indocyanine green.

Autofluorescence is most commonly used to document fluorescence of lipofuscin, a fluorescent pigment that accumulates in the retinal pigment epithelium (RPE) as a normal byproduct of cell function.3 Lipofuscin deposition normally increases with age, but may also intensify in certain retinal abnormalities. It is used to document progression of macular degeneration, central serous chorioretinopathy, Stargardt disease, drug toxicities, and several hereditary retinal dystrophies.

In addition to the documentation of lipofuscin in the RPE, there are other fluorescent findings that may occur in the eye. One of the initial uses of autofluorescence was documenting optic disc drusen and astrocytic hamartomas as early as the 1970’s.4 Both of these entities are calcified lesions that are highly fluorescent and can be documented with standard fluorescein excitation and barrier filters.

Fig 1 small
Left: optic disc drusen. Right: astrocytic hamartoma, a calcific tomor associated with tuberous sclerosis

The aging crystalline lens is also known to be fluorescent. In fact, lens autofluorescence was the inspiration for the development of fluorescein angiography by Novotny and Alvis.

LENS faf2
Dense cataract that fluoresces with the standard fluorescein excitation and barrier filter combination in a fundus camera. This image illustrates how fluoresence from the lens can compromise the qulaity of a fluorescein angiogram by adding unwanted fluorescence.

In addition to these well-known entities, there are some additional autofluorescent findings you may encounter in the eye. In 2009, Utine et al reported autofluorescence of pingueculae on the ocular surface.5 This finding may interfere with photo-documentation of topical fluorescein staining patterns in patients with conjunctival lesions.

Autofluorescence image of a pinguela taken with a fundus camera in external mode. Note that the crystalline lens of this eye also fluoresces.

Certain emboli, presumably calcific, exhibit fluorescence.

Patient with a branch retinal artery occlusion. Left image demonstrates classic retinal whitening from the occlusion. Right image identifies the fluorescent calcific plaque associated with the arterial blockage.

We’ve also had a case of corneal blood staining that fluoresced. As it turns out, hemoglobin and hemosiderin are known to be fluorescent and that’s what fluoresced in this case.

A case of corneal blood staining after a long standing hyphema. Autofluorescence is presumably from either hemoglobin or hemosiderin.
Another case where blood is hyperfluorescent in a patient with angioid streaks.

There may be other ocular findings that exhibit autofluorescence when excited with light of specific wavelengths. Have you noticed anything else that fluoresces? If so, I encourage you to share them.

  1. von Ruckman A, Fitzke FW, Bird AC. Distribution of fundus autofluorescence with a scanning laser ophthalmoscope. Br J Ophthalmol 1995;79:407-412.
  2. Spaide RF. Fundus autofluorescence and age-related macular degeneration.
    Ophthalmology 2003;110:392-9.
  3. Delori FC, CK Dorey CK, G Staurenghi G, et al. In vivo fluorescence of the ocular fundus exhibits retinal pigment epithelium lipofuscin characteristics. Invest Ophthalmol Vis Sci 1995;36:718-729.
  4. Kelly JS. Autofluorescence of drusen of the optic nerve head. ArchOphthalmol 1974;92: 263-264.
  5. Utine CA, Tatlipinar S, Altunsoy M, et al. Autofluorescence imaging of pingueculae. Br J Ophthalmol 2009;93:396–399.