Testing the Utility of Automatic Retinal Imaging
Are digital images as good as traditional diagnostic fundus photography? This study suggests they may be up to the challenge.
By Thomas Friberg, M.S., M.D., Pittsburgh

How are you documenting your patients' retinal health? Are you still creating detailed drawings with paper and color pencils? Or have you invested in a fundus camera? Before you dilate another eye or snap another photo, ask yourself if you can do better.

The big picture

A retinal imaging system should meet certain criteria. It should:

► Produce quality images. Many diseases initially affect the retinal periphery, so it's important to capture as much of the fundus as possible. Images should be clear, easy to read and useful for determining diagnoses.

► Meet criteria for sensitivity and specificity. An accurate imaging system should reliably document the presence or absence of retinal disease.

► Be easy to use. A well-designed retinal imaging system should be simple, easy to use and minimally invasive.

Unlike other retinal imaging systems, the Optos Optomap Panoramic200 produces clear digital images without mydriatics, direct corneal contact or auxiliary illumination. But can ultra widefield imaging compete with traditional fundus photography? Have we solved the resolution problems that plagued early digital imaging systems? My partner and I decided to find out.

	The nonmydriatic, noncontact Optomap is a valuable tool for screening young patients, as illustrated by this image of a healthy 3-year-old child.

Evaluating the Optomap

To test the accuracy of ultra widefield imaging for evaluating and diagnosing retinal disease, we collected 124 retinal images over 3 months using the Optomap scanning laser ophthalmoscope with Virtual Point™ Technology. After examining each patient with the indirect ophthalmoscope, slit lamp biomicroscope and other traditional evaluation tools, we recorded our diagnoses in the patients' charts along with the suggested time to the next appointment or intervention.

Next, without providing a patient history, we asked two retina specialists to evaluate the Optomap images and present their respective diagnoses. Here's what we found:

► Image quality. We determined that 77 of 124 (62%) Optomap images were good or excellent, thereby suitable for review. Only 6.4% of images were unreadable secondary to vitreous hemorrhage, advanced cataracts or lashes/patient reflexes.

► Sensitivity and specificity. Two retina specialists independently replicated our diagnoses for between 77% and 87% of patients, for an overall sensitivity of 78% (specialist 1) and 74% (specialist 2). Both specialists had a specificity of 78%. Finally, the specificity for detecting peripheral and posterior lesions was 69% and 59%, respectively.

► Recommended follow-up. Using Optomap images only, the independent reviewers matched our recommendations for follow-up in 105 of 125 cases (85%).

The Optomap exam surpasses the criteria for effective, noninvasive retinal imaging. The Optomap images a wide region of the retina (up to 200 degrees) without physically contacting the eye, and more importantly, without dilating the pupil. Easy image storage and retrieval simplifies documenting and comparing retinal pathology from year to year. Several viewing options within the Optos proprietary V² software allow you to zoom in on structures without losing resolution and examine deep or superficial structures separately. In our final analysis, we found the Optomap to be a valuable tool for screening retinal health.

Passing the test

The panoramic Optomap system provides clear, high-resolution images to accurately diagnose most retinal pathologies in most patients, even without the benefit of a clinical history. The Optomap system is effective through a nonmydriatic pupil, providing flexibility for your dilating protocol.

Dr. Friberg is a professor in the department of ophthalmology and chief of the retinal service at the University of Pittsburgh School of Medicine.

The heart of Optomap is an ellipsoidal mirror, which has two focal points. Scanning laser light is focused through one point (F1) while the patient positions his eye coincident with the second focal (virtual) point (F2). The resulting ultra widefield image, which shows about 200 degrees of the retina, is 2,000 x 2,000 pixels with a resolution of about 20 microns on axis and about 40 microns off axis. Because the two scanning lasers have different wavelengths, the final image incorporates information about different retinal structures, which can be viewed separately on the accompanying monitor. Optomap's unique design places the virtual point inside the patient's eye, producing a much broader scan angle and an opportunity to examine the peripheral fundus.

How the Optomap Works

The Optos Optomap Panoramic200 is a noncontact, nonmydriatic, dual scanning­laser-based retinal imaging system designed to record panoramic images of the fundus.