TAKING GOOD PHOTOGRAPHS

PATIENT POSITIONING

To begin, ensure that the patient is positioned correctly. The patient’s head should fit in the cup of the chin-rest and forehead should be touching the forehead rest. The chin rest assembly has an adjustment knob that will align the patient’s eye level with a black band on the column on the chin rest assembly. The patient’s eyes should face forward and the head should not be tilted. In this position, the camera will not need to be further adjusted as images are taken of both eyes.

CAMERA ALIGNMENT

Look on both sides of the camera to align the camera to the eye before looking at the infrared video image. Once the eye is aligned and centered in the video image, move the camera closer to the eye until it registers the retina image mode (where the retinal vessels are visible). The camera will “click” as it changes from external to retina mode. Once the retinal vessels are visible, use the focus knob to sharpen the image. In most cameras there is a focusing mire with two vertical lines. The two vertical lines will line up on top of each other to make a continuous line to properly focus the camera to the patient’s eye. Once that is established, raise and lower the camera to reduce any artifacts.

Another visual tool for correcting the camera distance are two dots on the central horizontal position. In some cameras, the correct eye-to-camera distance is achieved by having the two dots align in the central circle. In some cameras the dots appear as soft large globes on either side of the center point. The proper distance is achieved when the two dots come into focus.

Once the alignments (up and down, side to side), and eye to camera distance is achieved, a picture is taken by pressing down on the top of the joystick control. Immediate feedback is given as the frozen image is displayed shortly after depressing the joystick. Here you can evaluate: • Sharpness • Exposure • Field definition (placement of the macula center and disc)

If any of these are not of acceptable quality, make the adjustments necessary and take additional images.

EXPOSURE VARIATIONS

Sometimes the exposure (flash) does not allow the camera to capture a high-quality image. There is a flash adjustment on the camera base that has a plus sign and minus sign. A dark image, makes it difficult to see the vessels and also makes the image difficult to interpret diagnose. Make proper adjustments to the brightness by increasing or decreasing the flash and take additional images.

PHOTO PROTOCOLS

In the original photo studies on diabetic retinopathy, the Reading Center developed a 7-standard series of images to document retinopathy changes that occurred in patients. It consisted of the following: 1. disccentered, 2. maculacentered, 3. temporal to the macula, 4. superiortemporal, 5. inferiortemporal, 6. superiornasal and 7. inferiornasal