Get the Full Picture With Ultra Widefield Retinal Imaging
This clinician shares his insight on the latest generation of imaging technologies
By William L. Jones, O.D.

Eyecare practitioners have been able to capture widefield retinal images using standard imaging techniques with fundus cameras since the 1970s -- albeit with some limitations.

For example, our view with a fundus camera was limited to between 30° and 60° of the retina. To view the periphery, we had to ask our patients to move their eyes into the direction of the fundus area in question. Tilting the camera along the horizontal plane could increase the peripheral field of view in the 3 o'clock and 9 o'clock positions. And some fundus cameras could be tilted along the vertical plane to capture the 12 o'clock to 6 o'clock positions.

Even with these tilting techniques, however, our imaging capabilities were limited because of the camera's optics and some patients' inability to sustain far gaze long enough for us to obtain a good view.

What's more, when the eye is in a far gaze position, the entrance pupil changes from round to oval, which decreases its effective pupillary diameter, making it more difficult to obtain a good image. Obviously, it took a concerted effort to obtain more peripheral images.

First widefield technologies

The early 1980s saw the introduction of the first widefield camera, the Equator Plus, so named because it could obtain images beyond the equator. This was the first time we were able to view truly widefield images of the ocular fundus, and it was exciting to be able to see large fundus lesions in a single view, such as the melanoma shown below.

Although a significant advance, the Equator Plus still had drawbacks. The camera had to touch the patient's cornea, a procedure that's difficult for most patients to tolerate. Another drawback was that the light could not pass through the camera's front lens but had to be delivered to the eye externally through the bulbar conjunctiva, sclera, choroid and retina. To accomplish this, the light passing through the fiber optic system had to be very bright, which created heat on the external eye. The area of the fundus that was being illuminated externally was a very bright and saturated (washed out) region of the image, making it impossible to see lesions in that area of the image.

The greatest drawback to the Equator Plus was that light passing through the choroid with its rich blood vessel supply added considerable red color to the white light. The result was a fuzzy image with a red hue.

Even though it produced truly widefield images, the Equator Plus camera never became popular.

Ultra widefield technology

It wasn't until the late 1990s and early 2000s that we saw imaging systems that could obtain good quality, ultra widefield images. Among the most successful are: Ret Cam, Panoret 1000 and Optomap Retinal Exam. Each of these instruments produce good digital images that show the peripheral fundus anterior to the equator, but there are some differences.

· Ret Cam. The Ret Cam was developed as a pediatric instrument to image infants under anesthesia. With the Ret Cam, light enters and exits through the front optics of a handheld probe. It has a 130° field of view. This camera requires pupillary dilation and contact with the patient's cornea. Thus, patient comfort and compliance are still issues.

· Panoret 1000. This camera is mounted on an arm that can hold the probe just above the eye. It still requires an external light source; however, the more sensitive detector systems and computer-controlled illumination allow for a lower power light source. The image quality is good. It has a 100° field of view, and dilation is not required.

· Optomap Exam. This system, which I use in my practice, uses an ellipsoidal mirror to miniaturize the scanning laser raster of light, producing a virtual scan point of the real scan point just behind the pupil. The virtual scan point allows for an ultra widefield image with the light entering and exiting through the pupil. There's no contact with the eye, and dilation is not required, resulting in better patient cooperation and ease of use.

The Ret Cam and the Panoret 1000 use standard white light sources, whereas the Optomap Exam uses coherent red and green wavelength lasers. An advantage of specific wavelength light sources is that they scatter less than white light. Therefore, they can penetrate cataracts, corneal opacities and vitreous hemorrhages better than white light. Also, the green and red lasers can optically separate the fundus into superficial (green) and deep (red) layers and this aids in making clinical judgments of lesions due to relative location.

The Optomap Exam uses a spinning polygon at 30,000 rpm to produce a scanning laser ophthalmoscope. The high number of laser scans allows for a large amount of data points to be gathered in a fraction of a second.

To expand your field of view with any of these systems, you must either tilt the probe or have the patient move his eye. You may be able to tilt handheld probes slightly. With the Optomap Exam, you can obtain a view of the periphery beyond 200° by having the patient steer his eye toward the area of interest. Therefore, to obtain a view of the fundus comparable to a binocular indirect ophthalmoscope (BIO) view, you must have patients move their eyes toward specific directions. It's the same principle as having your patients move their eyes toward specific fields of gaze with the BIO.

Advantages over manual fundoscopy

Ultra widefield imaging has definite advantages over manual examination techniques. Although you can view the far periphery with a BIO, your view is limited to only one of eight sections at a time. The patient must cooperate by looking to the directed field of gaze long enough for you to obtain an adequate view. Then you must put the fundus views mentally into a composite of what you just saw. Also, the images you see are inverted and reversed, which may lead to some uncertainty about where a lesion is located, its exact shape and its relationship to fundus landmarks.

One advantage of Optomap ultra widefield imaging is that it provides a correctly oriented still image of approximately 200° of the retina. You can study still images for a few seconds, a minute or longer, giving you ample time to write more accurate chart notes. You also can magnify areas of interest on still images to search for small lesions that may be missed with other manual and scanning examination techniques. With the Optomap Exam, you can perform fundoscopy in much less time than it usually takes to do a BIO exam and other fundoscopy techniques.

Compliance through education

One of the great advantages of ultra widefield imaging is that patients can see images of the inside of their eyes. This is a great tool for educating patients. Rather than try to explain a lattice, retinoschisis or other lesion in words that patients may find difficult to grasp, we can show them images that will help them understand the importance of their conditions. Truly, in these cases, "a picture is worth a thousand words." And improved comprehension can bring about better compliance.

What's more, patients often return to work or home eager to tell people about seeing the inside of their eyes. This has an added benefit of branding your practice as a place where patients receive quality, high-tech eye care.

Lattice lesion (arrow) with a hole at the superior end.
Fresh laser marks surround two lattice lesions.

Enhanced detection

Unlike a typical fundus camera, ultra widefield imaging systems can be used to detect and document lesions in the peripheral fundus as well as the posterior pole. I saw this demonstrated at the 2003 Academy of Ophthalmology meeting.

A doctor had his fundus imaged at the Optos booth with the Optomap Exam. After seeing the central 200° of his right eye, the doctor wanted to see if the instrument could capture more of the periphery. He was directed toward the superior field of gaze and another image was taken. This image revealed a lattice lesion with an inferior atrophic retinal hole in the inferior margin of the superior temporal quadrant as shown in the figure at left (top).

The doctor dilated his eye and then went to a booth featuring fundus cameras to see if personnel there could image the lesion; however, they were unable to do so, even though they knew where to look for the pathology.

The next day, the lattice lesion was surrounded by laserpexy and the doctor returned to the Optos booth for a new image of the treated area (bottom figure at left). He later admitted that he was experiencing some symptoms and was amazed at how the instrument could detect his retinal lesions.

Get an edge

Ultra widefield images obtained with today's technology allow for visualization beyond the equator of the globe, giving you a view you've never had before.

Not only will this technology improve your ability to detect and diagnose pathology; it also simplifies documentation and serves as a wonderful patient education tool, which, in turn, improves patient compliance. These are advantages that all practices can realize with this important new technology.

Dr. Jones is in private practice in Albuquerque, N.M. He has written and lectured nationally and internationally. He is the president of the Optometric Retina Society and a consultant to Optos.

 

Ultra Widefield Imaging in Action These cases are examples of how ultra widefield imaging discovered important intraocular findings.
Melanoma detected This 55-year-old woman had been followed for the past 5 years for a suspected melanoma in her right eye. She was being seen by the retinal surgeon in the practice who asked for a widefield image because only the posterior margin could be seen on the fundus camera.	Suspected inferior melanoma (arrow).
Snail-track lesion discovered This 13-year-old girl came to our office for a checkup for eyeglasses. She was a low myope, correctable to 20/20. Before dilation, we took an Optomap image. The inferior region of the image displayed a small gathering of white dots in the right eye. Upon steering her left eye inferiorly, the image revealed a snail-track lesion.	Note inferior white specks (arrow) of sensory retinal degeneration. On inferior gaze, there are 4 snail-track degeneration lesions (arrows).
Childhood injury revealed We saw this 49-year-old man for decreased near vision. He was presbyopic and correctable to 20/20. Before dilation, we took an Optomap image and detected a peripheral retinal chorioretinal degeneration and scarring, a result of being hit with a BB pellet as a child.	Chorioretinal scar from BB injury (arrow).
Effects of eye trauma uncovered We saw this 69-year-old man for a routine examination. His left eye was correctable to 20/25, but his right eye was worse than 20/200. He reported he'd been in a car accident in 1952 just before he went into the military. After he left the military in 1955, he noticed vision loss in his right eye. He was told he had a retinal detachment that needed repair. However, another physician recommended no treatment, and he took that advice. The Optomap Exam revealed an old spontaneously reattached inferior retina with numerous pigmented spots of RPE hyperplasia and a superior curved demarcation line denoting the extent of the original inferior detachment. We also detected an inferior luxated crystalline lens secondary to the original traumatic event of 1952.	Old spontaneous reattached retinal detachment with RPE hyperplasia and luxated lens (arrow).
Watching an operculated retinal tear This 45-year-old woman came to my practice for a routine examination. Her vision was correctable 20/20 OU. The Optomap Exam revealed a micro operculated retinal tear in a patch of RPE hyperplasia and sensory retinal degeneration in the temporal retina of the right eye. Asymptomatic operculated tears in low-risk patients usually are not treated and after consulting with the patient, we decided together to do periodic follow-up examinations.	Operculated retinal tear (white arrow) in patch of degenerating retina.