Additivity of Retinal Damage for Multiple-Pulse Laser Exposures
Abstract
This study has examined the cumulative effects of multiple-pulse laser exposures in contributing to retinal damage via a thermal mechanism. Three sets of experiments have been conducted to determine the variation of multiple- pulse thresholds: With the interval between pulses; with the number of pulses in the pulse train when the interpulse interval is held constant; and with the retinal image size when both number of pulses and interpulse interval are invariant. In addition, thermal model calculations were carried out to compare model predictions with the experimental data. Conclusions from the experimental data are: (1) The threshold for a multiple-pulse train is related to that for an individual pulse in the train by a function of the number of pulses, but is independent of pulse-repetition frequency and pulse train length. This observation is in general accordance both with the thermal model predictions and with previously empirical models. (2) The additivity of multiple pulses is quantitatively similar for collimated and expanded laser beams incident at the eye. (3) The repair or recovery of laser-induced reversible retinal damage (i.e. , sub-threshold with respect to the ophthalmoscopic lesion endpoint) is slow, having a time constant of the order of days. Thus, the cumulative nature of multiple-pulse or repeated exposures within a 24-hr period is relatively unaffected by the ongoing repair process; and only when repeated daily exposures are of concern does the repair process become a factor. Keywords: Laser damage; Retina.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1988
- Accession Number
- ADA206514
Entities
People
- Joseph A. Zuclich
- Michael F. Blankenstein