Fundus photography still a valuable tool in glaucoma care

Although the role of fundus photography as the gold standard for identifying glaucoma-related structural changes has been eroding with the popularity of optical coherence tomography (OCT), photographic assessments still have an important place in glaucoma care, said Robert T. Chang, MD, during his presentation entitled “The Art of Fundus Photo Interpretation.”

Nevertheless, there are well-known problems with using optic disc photography as a diagnostic tool because interpretation of the images can be very subjective and even glaucoma experts in masked studies have only moderate inter-observer correlation. Recognizing these drawbacks, Dr. Chang and colleagues at Stanford University have started to develop an interactive ophthalmology website (www.ophthopedia.org) that they hope will help clinicians improve their disc photograph interpretation skills, especially with anomalous optic nerves.

“Nobody will argue that a quick look at an optic disc photograph can tell the clinician a lot about some patients, but in other cases, it can be difficult to determine if a patient has glaucoma or not,” said Dr. Chang, assistant professor of ophthalmology, Byers Eye Institute, Stanford University, Stanford, CA. “However, it is important that clinicians not just give up on these challenging images, such as high myopes. Teaching the next generation this skill is still important despite the abundance of new automated imaging technology, and practice will only make our assessments better.”

Digital images replacing film

Today, digital images are replacing film photography, and studies have shown good agreement between the two media types.

“While the technology for obtaining photographs has switched to digital, an advantage of photography over OCT is that the photos never go out of date,” Dr. Chang pointed out. “In contrast, OCT results change with each new generation device and are not backwards compatible. Therefore, photos are especially valuable for establishing a baseline.”

However, photographic assessment is not perfect for diagnosing glaucoma, as there are other conditions causing retinal nerve fiber layer thinning that mimic the appearance of glaucoma, and sometimes it is difficult to see the edge of the disc and the cup.

“Fundus photography is generally considered most helpful for diagnosing glaucoma in eyes showing a classic glaucomatous appearance to expert graders,” Dr. Chang explained. “It is when inexperienced clinicians are confronted with anomalous discs that they may disregard the image as being uninterpretable. This is the opportunity where I think we can have an impact by crowd-sourcing digital images to teach others and potentially reach a consensus on the difficult ones.”

Ophthopedia.org is a free resource hosting all types of eye images, including difficult-to-interpret optic disc photographs, and it invites eye-care providers to edit the images online. Users can create their profile, indicating their level of training and leave their interpretations to compare their judgments against those of other participants. The idea for using this technique to teach a standardized method for interpreting disc photographs stems in part from a similar approach used for training residents.

“Presenters at conferences often show optic disc photographs without marking out their interpretations,” he said. “However, we teach our residents by having them trace out the relevant features on an image displayed on a tablet projected in front of the others.

“We believe that by using this same technique online, eye care providers can teach themselves and each other how to interpret challenging images more consistently, akin to examining hundreds of patients during a glaucoma fellowship,” added Dr. Chang. “Once we amass a large set of interpretations, this will become an ideal online teaching tool.”

Efforts of others

Dr. Chang also mentioned the Glaucomatous Optic Nerve Evaluation (GONE) Project, which represents a similar approach towards standardizing optic nerve interpretation and allowing clinicians to self-assess and benchmark their skills. Introduced by a group at the Centre for Eye Research Australia and the University of Melbourne, this program features numerous optic nerve teaching examples that can be accessed online (www.gone-project.com) but without an active drawing component.

Previous attempts to standardize optic nerve interpretation included the Disc Damage Likelihood Scale, introduced by Spaeth et al. in 2002. This method is aimed to standardize estimation of the amount of glaucomatous optic nerve damage based on appearance of the neuroretinal rim relative to optic disc size. However, it has not been widely adopted because of its complexity and the wide variation when applied to normal and diseased eyes.

About five years ago, a group of glaucoma experts came up with the Focusing Ophthalmology on Reframing Glaucoma Evaluation (FORGE) program encouraging all clinicians to look at nerves in the same way during the clinical exam using five rules.

“Experience with the FORGE program reinforced the value of photographs that can be carefully reviewed at a later time to allow greater accuracy and consistency in diagnosis than during a live fundus exam,” said Dr. Chang.

Dr. Chang concluded by noting that while his talk emphasized the importance of optic disc photography in glaucoma care, diagnostic determinations are not usually made based on their assessment alone. Rather clinicians need to use the information in concert with other data, including age, intraocular pressure, and visual fields for optimal glaucoma management.

FYI:

Robert T. Chang, MD, has participated in advisory boards for Alcon, SuCampo, and Allergan.

e. viroptic@gmail.com

TAKE HOME MESSAGE

Fundus photography retains an important role in glaucoma diagnosis and follow-up, but is limited due to subjective interpretation. An educational website is being developed to help standardize optic disc analysis in difficult cases.

Callout:

‘An advantage of photography over OCT is that the photos never go out of date.’

Robert T. Chang, MD

Caption:

Ophthopedia.org, developed by Robert T. Chang, MD, and his colleagues at Stanford University, is an interactive ophthalmology website that helps clinicians improve their disc photograph interpretation skills, especially with anomalous optic nerves. The site also is a free resource hosting all types of eye images.