Technology

Laser Light Adds New Details to Fundus Imaging

Once you experience a laser image, you won’t want to go back to white light photography. The SPECTRALIS HRA is a confocal scanning laser ophthalmoscope, enabling a new dimension to angiography and fundus imaging. Laser light enables precision and details not seen in flash photography devices.

Confocal Imaging Blocks the Haze

Confocal imaging is the process of shining light on an object, then capturing reflected light by passing the light through a pinhole. The pinhole blocks light not coming from the plane or layer of interest and blocks scattered light which can “fog” the image. The result is focused, high resolution images without glare. Confocal imaging helps SPECTRALIS create pristine images with all of its fundus imaging modes (infrared, autofluorescence, ICGA, FA and red-free).

Infrared Imaging Penetrates Poor Media

One of the great advantages of using infrared light is its ability to penetrate cataracts and poor media. Traditional fundus cameras use a bright flash of white light to capture images which create a cloudy or foggy image in the presence of cataracts or vitreal opacitities. In addition, since the photographer has a difficult time to see the retina clearly, often the images are out of focus. Infrared light can help overcome these difficulties by imaging through the opacity.

Laser imaging can also be used more easily on non-mydriatic or difficult to dilate patients. This can be especially helpful for obtaining a fluorescein angiogram under difficult conditions.

Fundus Imaging with a Laser vs. White Light Photography

Utilizing specific wavelengths of light enables the Spectralis to maximize the image signal and pick up greater areas of detail than can be accomplished with flash photography. For each application: fluorescein angiography, ICG angiography, autofluorescence, red-free, and infrared imaging the optimal wavelength is used.

For example, to generate high quality, detailed fluorescein images, the system uses the 488nm wavelength to excite the dye. This excitation wavelength generates the optimal emission from the dye which is then easier to detect and record. The other advantage of using a laser is that the image can be continuously recorded, minimizing the chance of the photographer missing the initial uptake phase and providing the clinician with a dynamic view of the bloodflow. The patient is more comfortable because there is no constant bright flash photography, increasing patient cooperation on follow-up examination.

The same principles hold true for autofluorescence images. By selecting the wavelength causing the highest emission of light from RPE lipofuscin, high quality, detailed images can be obtained. Traditional fundus cameras use white light flash photography and then apply filters to try and narrow down to the correct wavelength.

Dual-Beam Imaging Enables Real-Time, Simultaneous Imaging

Laser technology also enables the SPECTRALIS HRA to capture two images at the same time by using two lasers simultaneous. This allows exact registration of the images and knowing that effects in one imaging mode correlate exactly with effects in a second imaging mode. For example, a patient may receive both fluorescein and ICG dye and have the choroidal circulation recorded at the same time as the retinal circulation. This may help the clinician identify where leakage is occurring.