Optical Coherence Tomography utilizes infrared light that renders an in vivo cross sectional view of the retina. Therefore, anything that affects the light pathway WILL affect your image. Common artifact issues can be attributed to cataracts, vitreous opacities, and corneal media interference.
The act of performing application tonometry and the drying effect of some eyedrops, such as anesthetic and dilating drops, may disrupt the tear film and epithelium. This will scatter light entering the eye, and more importantly, reduce the focused light coming out of the eye and back to the sensor on the OCT. The resulting image will have a “snowy” or “static” appearance throughout the vitreous, and the layers of the retina will not be as evident.
One way to reduce this problem is to scan the patient prior to the technical workup. This will allow the imager to scan through a cornea that has not been subjected to drying effects.
Here is an example of a patient that was scanned prior to begin worked up and after being worked up.
Before work up
After work up