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Updated: Sep 28, 2025
Hand-held Clinical Photoacoustic Imaging System for Real-time Non-invasive Small Animal Imaging
Published on: October 16, 2017
Safety Evaluation of Photoacoustic Tomography System for Intraocular Tumors
Guan Xu1,2, Naheed Khan1, Ahmed Almazroa1,3
1Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, MI, USA.
Purpose:
Photoacoustic tomography (PAT) has demonstrated the ability to characterize molecular components and architectural heterogeneities of intraocular tumors in enucleated human globes and in animals in vivo. Although laser safety levels have been established for illumination through the cornea, the safety limit for PAT illumination through the sclera has not been investigated. The purpose of this study is to examine if the energy level used in intraocular PAT results in ocular damage.
Methods:
Rabbit eyes were exposed to pulsed laser illumination at 20 mJ/cm2 at the scleral surface. Eyes were examined at 1, 7, and 28 days after the laser exposure. Examination procedures included white light and fluorescence fundus imaging, optical coherence tomography (OCT), electroretinography (ERG), and histology with hematoxylin and eosin (H&E) staining as well as terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL staining).
Results:
Fundus imaging and OCT of rabbit eyes at 1, 7, and 28 days following exposure of the laser illumination of the PAT system did not reveal any damage to the retinal structures. ERG showed no significant difference between the experimental and control eyes. Similarly, H&E histology did not show abnormalities in either the scleral tissue where the laser illumination was delivered or in the retinal layers. No sign of apoptosis in the layers of the retina, choroid, or optic nerve was found on TUNEL staining.
Conclusions:
Similar to the application of PAT to other organs, the proposed laser illumination energy level at 20 mJ/cm2 does not impose detectable harm to the ocular tissue.
Translational Relevance:
This study addresses illumination safety issues for PAT.
Insights
Photoacoustic tomography (PAT) laser illumination at 20 mJ/cm2 applied to the sclera does not cause ocular damage. This study establishes safety limits for intraocular PAT, ensuring patient safety during tumor characterization.
Area of Science:
- Ophthalmic imaging
- Biomedical optics
- Laser safety
Background:
- Photoacoustic tomography (PAT) can characterize intraocular tumors.
- Laser safety for corneal PAT is established, but scleral PAT safety is unknown.
- Investigating scleral PAT illumination safety is crucial for clinical translation.
Purpose of the Study:
- To determine if intraocular PAT laser illumination at a specific energy level causes ocular damage.
- To establish safety limits for PAT illumination through the sclera.
Main Methods:
- Rabbit eyes were exposed to 20 mJ/cm2 pulsed laser illumination on the scleral surface.
- Ocular examinations included fundus imaging, OCT, ERG, and histology (H&E, TUNEL staining) at 1, 7, and 28 days post-exposure.
Main Results:
- No retinal structural damage was observed via fundus imaging and OCT.
- Electroretinography (ERG) showed no significant differences between experimental and control eyes.
- Histology and TUNEL staining revealed no scleral or retinal abnormalities or apoptosis.
Conclusions:
- The laser illumination energy level of 20 mJ/cm2 for intraocular PAT is safe for ocular tissues.
- This finding supports the safe application of PAT for intraocular tumor characterization.
