Abstract
Purpose: :
To evaluate the use of an advanced retinal imaging technique, SD-OCT, to examine in vivo the retinal disruption caused by near-damage-threshold laser exposures.
Methods: :
We have incorporated the use of a high-resolution SD-OCT system into an experiment to measure the laser-induced retinal damage threshold. The retinas of non-human primates were exposed to 100 ns pulses from a frequency-double Nd:YAG laser (532 nm wavelength). The energy of the pulse was measured and recorded for each exposure, and is therefore a known quantity. Nominally one-hour and 24-hours after exposure, the retinas were examined via direct ophthalmoscope and digital fundus photography to look for visible alteration to the retina. Generally, this takes the form of a small white lesion. Immediately after the visual examination, SD-OCT images of the retina were acquired. The SD-OCT images were correlated with the fundus images to examine the nature of the disruption caused to the retina by near-threshold laser exposure. Further retinal imaging was performed several weeks after exposure.
Results: :
The SD-OCT images showed disruption of the retina extending from the retinal pigmented epithelium (RPE) through the photoreceptor layer for laser pulse energies several times the threshold energy. Smaller disruptions, localized closer to the RPE, are seen for pulse energies slightly greater that the damage threshold. The disrupted area was observed to changed over time, indicating some retinal healing following near-threshold laser exposure.
Conclusions: :
The SD-OCT imaging system allowed us to observe over time the development of laser-induced retinal disruption in a non-disruptive manner, within the retina of a single subject animal. It is important to be able to make such observations without the need to sacrifice any animals.
Keywords: lesion study • retina • imaging/image analysis: non-clinical