Laser Ophthalmoscopy Provides Full Picture of Eye Disease

For retinal diseases such as diabetic retinopathy (DR), which affect a wide area of the fundus, the interior surface at the back of the eye, it is important for clinicians to be able to examine a broad area of the eye in a single shot.

A research group at Tokyo Medical and Dental University (TMDU) used blue images from widefield scanning laser ophthalmoscopy (SLO) to identify ischemic retinal areas (i.e., areas with low blood flow) in patients with DR. The group used multicolor, widefield SLO to obtain blue images that covered an extensive area of the eye.

In previous research, conventional SLO has been used to show that blue images captured with this technique can identify hyporeflective areas in the eye that indicate DR-related damage.

The TMDU team took these findings a step further with its testing and use of widefield SLO. Multicolor widefield SLO is an advanced version of conventional SLO that uses red, blue, and green lasers to simultaneously capture images of a wide portion of the eye. Unlike fluorescein angiography, it does not require the injection of a fluorescent dye into the eye to examine blood flow.

The researchers’ aim in this retrospective study was to determine whether the hyporeflective areas in the blue images obtained by widefield SLO corresponded to the nonperfused areas seen in the fluorescein angiogram images. They studied 90 patients with diabetes mellitus and compared the hyporeflective areas in the blue widefield SLO images of the patients’ eyes with the nonperfused areas in the images taken with fluorescein angiography. They then used OCT to evaluate the morphology of the patients’ retinas.

(a) Multicolor widefield SLO image of the right fundus of a 65-year-old man with proliferative DR showing multiple hemorrhages in a wide area of the fundus. (b) Blue SLO image showing a hyporeflective area in the mid-periphery to periphery of the fundus. (c) Widefield fluorescein angiogram image shows widespread nonperfused areas in the mid-periphery to periphery. Neovascularization is also seen in the superior pole of the eye. (d) Magnification of image (b) shows hyporeflective areas in the lower temporal quadrant. (e) Magnified fluorescein angiogram image of image (c) shows nonperfused areas in the same quadrant of image (d). (f) The hyporeflective areas in image (d) are outlined by white dots. (g) The nonperfused areas in image (e) are outlined by blue dots. The outline of white dots in image (f) is located inside the outline of blue dots in image (g). Courtesy of the Department of Ophthalmology and Visual Science, TMDU.

Hyporeflective areas in the blue SLO images were observed at a rate of 76.6% in the eyes of the patients with proliferative DR. The researchers further found that the location and appearance of the hyporeflective areas that were identified using SLO corresponded to the nonperfused areas that were found using fluorescein angiography. The rate of correspondence was concordant with a Cohen’s kappa value of 0.675.

“We found that the hyporeflective areas in the blue widefield SLO images appeared to correspond with areas of ischemia in the fluorescein angiogram images of patients with DR,” professor Kyoko Ohno-Matsui said. “We were pleased to find that the rate of concordance was high.”

Further evaluation of patient images showed that ischemic areas appeared to correspond with parts of the retina that were thin and partially disorganized.

“It is possible that the blue wavelength of light can pass more easily through these thinned areas of the retina, which presents as hyporeflective areas in the SLO images,” professor Shintaro Horie said.

The high degree of concordance between the hyporeflective areas in the widefield blue SLO and the nonperfused areas in the fluorescein angiogram images suggests that widefield blue SLO can be used to identify ischemic retinal areas in patients with DR without the intravenous injection of any dye. The study underscores the value of blue widefield SLO as a noninvasive tool for the detection of DR-associated damage in the eye and as a way to screen and monitor disease progression in individuals with DR.

The research was published in the Asia-Pacific Journal of Ophthalmology (www.doi.org/10.1097/APO.0000000000000432).