Digitally Enhanced Retinal Photography
Turn your fundus camera into a powerful diagnostic tool.
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Dr. Kreda has a medically oriented private practice in Lauderhill, Fla. He has published and lectured on a broad spectrum of optometric topics. He can be reached at eyerx@comcast.net. |
By Sheldon H. Kreda, OD, FAAO
AS STUDENTS, your exposure to retinal photography may have been quite limited. But it’s important to know that retinal photography provides a number of diagnostic benefits that complement traditional ophthalmoscopy. One major benefit is that older images can be compared to current images to detect subtle progressive conditions. This ability to photodocument what we see opthalmoscopically is of great importance, but does the fundus camera really help clinicians see pathology that would go undetected with the ophthalmoscope?
The Evolution of Retinal Photography
As retinal photography has evolved to produce high-definition digital images, the ability to enhance and manipulate these images using powerful software programs has expanded the capability of these instruments beyond simple documentation and demonstration. Enhanced images enable these cameras to become valuable diagnostic aids that can reveal abnormalities which often go undetected during a conventional examination. Below are some tips to enable the examiner to augment fundus photos in various ways to show details that can’t be seen using any other method.
Enhancing and Manipulating Images
I rarely take fundus photos. Pictures are usually taken by a tech who has them ready for me to view when I enter the exam room. From there, I apply any necessary enhancements at the viewing station. Note that enhancement is a viewing technique — not a photographic one. It’s a tool for the user to alter photos in post production to bring out depth, color and perspective — to make visible that which is otherwise unseen. Enhancements don’t have to be permanent (although an enhanced image can be saved).
| Reimbursements? |
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| There is no additional reimbursement for enhancing images. It’s simply a technique to obtain more clinical information from your photos. But note that since insurance reimbursement is only possible when there’s a related medical diagnosis, the more you detect, the greater the chance you have of the images being reimbursed. |
| Photo Storage |
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| I maintain a separate database of photos. The software can recall prior photos by name, date or pathology. Most office systems allow files to be imported or linked to a patient record. |
Most digital cameras come with software that allows images to be manipulated. Non-digital cameras are not excluded from this as images can be scanned or negatives can be digitally printed to disc then altered.
I use a program called Picasa, which is available as a free download (http://picasa.google.com/). Picasa allows me to view patient images in ways that offer powerful diagnostic capabilities. Images can be zoomed, viewed side by side and enhanced. I can also view images off site or on any computer within my office network.
Picasa allows me to fine-tune my retinal photos to highlight features that would otherwise go undetected and salvage less than perfect photographs. For example, augmented images can be viewed under high magnification, dark images can be lightened to provide better contrast, and small pupils, which sometimes limit illumination, can be more easily seen with a bit of enhancement. Additionally, flash intensity can be reduced for improved patient comfort due to the ability to photo-correct images in post production.
Photos of patients who dilate poorly or are limited by capsulotomy can be greatly improved with a number of software tools.
Deciding Which Type of Enhancement to Use
Enhancements can be customized or carried out automatically with a single click. I often review an image using a variety of enhancements, knowing that each will accentuate very specific pathologies. Doing so allows the observer to highlight not only different structures, but also different abnormalities within the same structure. For example, macular blood may be more visible with the infra-red tool while exudates are better seen using the cinemascope tool. Here are a few examples of how I use these powerful features.
Retinal Photography In Action
In Figure 1, the enhanced image (right) sharply reveals macular drusen and geographic atrophy unseen in the original photograph (left). While a particular enhancement may bring out details in one segment of the picture, it may actually obscure the details of other structures.
In Figure 2, right and left optic nerves are viewed under high magnification and compared split screen to diagnose optic cup and disc size asymmetry.
The infrared tool (used in Figure 3) allows an unsurpassed view of choroidal vasculature and sub-retinal pathology. Blood vessels, hemorrhages and exudates pop out of the picture. This is a powerful feature that totally changes the clinician’s perception of the fundus.
In Figure 4, the enhanced image on the right clearly reveals the full extent of retinal traction not visible in the original photo. Note also the small petechial hemorrhages and sharp detail of retinal vessels unseen in the original photo.
Fundus Photography As a Useful Tool
Here I’ve shared just a few examples of how software can turn a fundus camera into a powerful diagnostic tool. Note that enhancements sometimes introduce artifacts that can be misleading if they’re not viewed with respect to the entire clinical picture.
Enhancement serves to highlight areas that may be missed under casual observation and draw attention to regions that require greater scrutiny. Enhanced retinal photos can provide you with “new eyes” to see details that may be indispensable in your diagnosis. nOD
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