Purpose:
Acute phototoxic damage by short wavelength light may occur as an unwanted side-effect when visualizing the retina for therapeutic purposes, such as during prolonged vitreoretinal surgery. Furthermore, phototoxic damage is believed to be a risk factor for the development of age-related macular degeneration (AMD). The purpose of the present study was to examine the dosage-response relationship of blue light on the extent of acute phototoxic injury to the retina of pigmented rats.
Methods:
Male Brown Norway rats were exposed to a blue diode-laser emitting at 445 nm on both eyes for between 1 and 20 minutes. The intensity of the laser was varied between 2.3, 4.5, and 8.4 mW. The combination of these factors resulted in a received dose ranging from 30 to 750 J/cm2. Immediately after irradiation, the extent of phototoxic injury was evaluated macroscopically by funduscopy using a surgical light microscope, which was equipped with a digital camera. Lesion size was assessed using graphical measurement software.
Results:
Gross morphological changes were evident immediately after irradiation in all eyes receiving a dose equal to or exceeding 110 J/cm2. However, gross morphological changes were also observed in some eyes receiving doses down to 67 J/cm2. The results showed a correlation between the dosage and the size of the observed damage for each of the three intensities. The dosage-response relationship and the threshold for damage were comparable for all three intensities.
Conclusions:
Our results show that phototoxic retinal damage above threshold levels can be detected by visual inspection immediately after exposure. Furthermore, our results indicate that for the intensities used, the size of the retinal lesion in response to the insult is not dependent on the intensity of the incoming light per se, but rather on the received dose.
Keywords: retina • lesion study • laser