Effect of image compression and resolution on retinal vascular caliber

Area of Science:

• Ophthalmology
• Medical Imaging
• Biometry

Background:

• Retinal vascular caliber measurements from digital fundus photographs are linked to systemic health outcomes.
• The impact of image quality factors like resolution and compression on these measurements remains unevaluated.

Purpose of the Study:

• To investigate how varying levels of digital image compression affect retinal vascular caliber measurements.
• To determine the influence of different spatial resolutions on the accuracy of retinal vascular caliber assessments.

Main Methods:

• 40 high-quality, high-resolution digital fundus images were compressed at ratios up to 147:1.
• Film fundus photographs were scanned at resolutions simulating 1-10 megapixels (MP).
• Semiautomated software measured central retinal arteriole equivalent (CRAE) and central retinal venular equivalent (CRVE) at each alteration; repeated measures ANOVA was used for analysis.

Main Results:

• Increasing compression ratios significantly widened CRAE (approx. 5 μm at 147:1) and CRVE.
• Decreasing resolution narrowed CRVE (approx. 12 μm at 1 MP vs. 7 MP standard) and CRAE.
• Compression and reduced resolution demonstrably skewed vascular caliber measurements.

Conclusions:

• Digital image compression and lower spatial resolution significantly distort retinal vascular caliber measurements.
• These distortions can impact the reliability of epidemiologic studies relying on fundus image analysis.