Evaluation of the Optimal Compression Level for Retinal Video Recording in the setting of Diabetic Retinopathy Screening

1. Daniel Shu Wei Ting^1,2,3
2. Mei Ling Tay-Kearney^1,2
3. Ian Constable¹
4. Janardhan Vignarajan³
5. Yogesan Kanagasingam³

¹Centre for Ophthalmology and Visual Science, University of Western Australia, Lions Eye Institute, Perth, Western Australia
²Royal Perth Hospital, Perth, Western Australia
³Commonwealth Scientific Industrial and Research Organization

Purpose:
To validate the optimal compression level of retinal video recording for diabetic retinopathy screening

Methods:
A total of 20 retinal videos performed on patients with diabetes (10 normal and 10 eyes with diabetic retinopathy) were evaluated in our study. All uncompressed raw retinal videos are compressed to 3 different levels - 10% (Group 1), 3% (Group 2) and 1% (Group 3) of the original file size. The sensitivity, specificity and Pearson's Correlation were calculated for each compression level.

Results:
The mean (±SD) age of participants was 57.7 ± 3.5 years and mean HbA1c was 8.0 ± 2.0%. For group 1 and 2, 75% (n=15) of retinal videos were graded 'acceptable' while 25% (n=5) were 'excellent'. In contrast, 75% of retinal videos in group 3 were graded as 'pixelated but interpretable', 20% (n=4) were 'uninterpretable' and only 5% (n=1) was graded as 'acceptable'. With reference to the raw uncompressed retinal videos, the sensitivity for group 1, 2 and 3 were 100%, 100% and 88.9% respectively while the specificity were 100%, 90.9% and 90.9% respectively. The Pearson correlation based on uncompressed videos for group 1, 2 and 3 were 1.0, 0.985 and 0.966 respectively.

Conclusion:
In conclusion, retinal videos can be compressed from 1 GB (100%) to 30 MB (3%) of its original file size without compromising the retinal videos quality, sensitivity and specificity of diabetic retinopathy grading. By compressing the retinal video file size, this could significantly speed up the retinal videos transmission rate in the setting of tele-retinal video screening for diabetic retinopathy.