General considerations in ocular toxicity risk assessment from the toxicologists' viewpoints

Area of Science:

• Ophthalmology
• Toxicology
• Drug Safety

Background:

• Vision is critical for information intake, making visual toxicity a significant concern for new drugs.
• Current guidelines for nonclinical toxicity studies offer limited instruction on ophthalmologic examinations, potentially impacting ocular toxicity risk assessments.
• The eye's complex structure necessitates understanding sub-organ anatomy and physiology to interpret drug-induced changes.

Purpose of the Study:

• To emphasize the importance of comprehensive ophthalmologic examinations in nonclinical toxicity studies.
• To highlight the need for understanding ocular anatomy, physiology, and examination principles for accurate toxicity assessment.
• To provide guidance on differentiating treatment-related ocular findings from spontaneous changes in experimental animals.

Main Methods:

• Thorough ophthalmologic examinations comparing pre- and post-drug treatment findings.
• Consideration of species, strain, age, and lesion location/degree differences.
• Detailed recording of lesion features and integration of histopathological findings with other toxicity data.

Main Results:

• Ocular toxicity risk assessment requires evaluating both "sight-threatening" effects and "quality of vision" impacts.
• Extrapolation to humans necessitates considering species differences, safety margins, reversibility, and risk-benefit balance.
• Effective histopathological examination relies on careful organ sampling, appropriate fixatives, and pre-necropsy communication.

Conclusions:

• Integrated judgments from all nonclinical toxicity study data are essential for accurate ocular toxicity risk assessment.
• Effective risk assessment requires collaboration and data sharing among toxicologists, investigators, and pathologists.
• Comprehensive evaluation, beyond histopathology alone, is vital for reliable extrapolation of ocular toxicity findings to humans.