Alpha 2.0
Login Register
» Articles » PMID: 15965160

The Effect of Digital Image Resolution and Compression on Anterior Eye Imaging

Overview
Journal Br J Ophthalmol
Specialty Ophthalmology
Date 2005 Jun 21
PMID 15965160
Authors
R C Peterson
J S Wolffsohn
Affiliations
Soon will be listed here.
Abstract

Aim: To determine the theoretical and clinical minimum image pixel resolution and maximum compression appropriate for anterior eye image storage.

Methods: Clinical images of the bulbar conjunctiva, palpebral conjunctiva, and corneal staining were taken at the maximum resolution of Nikon:CoolPix990 (2048x1360 pixels), DVC:1312C (1280x811), and JAI:CV-S3200 (767x569) single chip cameras and the JVC:KYF58 (767x569) three chip camera. The images were stored in TIFF format and further copies created with reduced resolution or compressed. The images were then ranked for clarity on a 15 inch monitor (resolution 1280 x 1024) by 20 optometrists and analysed by objective image analysis grading. Theoretical calculation of the resolution necessary to detect the smallest objects of clinical interest was also conducted.

Results: Theoretical calculation suggested that the minimum resolution should be > or = 579 horizontal pixels at 25x magnification. Image quality was perceived subjectively as being reduced when the pixel resolution was lower than 767 x 569 (p<0.005) or the image was compressed as a BMP or <50% quality JPEG (p<0.005). Objective image analysis techniques were less susceptible to changes in image quality, particularly when using colour extraction techniques.

Conclusion: It is appropriate to store anterior eye images at between 1280 x 811 and 767 x 569 pixel resolution and at up to 1:70 JPEG compression.

References
1.
Keay L, Jalbert I, Sweeney D, Holden B . Microcysts: clinical significance and differential diagnosis. Optometry. 2001; 72(7):452-60. View
2.
Charman W . Imaging in the 21st century. Ophthalmic Physiol Opt. 1998; 18(2):210-23. View
3.
Newsom R, Clover A, Costen M, Sadler J, Newton J, Luff A . Effect of digital image compression on screening for diabetic retinopathy. Br J Ophthalmol. 2001; 85(7):799-802. PMC: 1724040. DOI: 10.1136/bjo.85.7.799. View
4.
Kocsis O, Costaridou L, Mandellos G, Lymberopoulos D, Panayiotakis G . Compression assessment based on medical image quality concepts using computer-generated test images. Comput Methods Programs Biomed. 2003; 71(2):105-15. DOI: 10.1016/s0169-2607(02)00090-1. View
5.
George L, Leverton C, Young S, Lusty J, Dunstan F, Owens D . Can digitised colour 35 mm transparencies be used to diagnose diabetic retinopathy?. Diabet Med. 1997; 14(11):970-3. DOI: 10.1002/(SICI)1096-9136(199711)14:11<970::AID-DIA484>3.0.CO;2-Y. View