The effect of compression on clinical diagnosis of glaucoma based on non-analyzed confocal scanning laser ophthalmoscopy images.
OBJECTIVE
To evaluate the effect of different image compression formats of non-analyzed Heidelberg Retina Tomography (HRT; Heidelberg Engineering, Heidelberg, Germany) images on the diagnosis of glaucoma by ophthalmologists.


METHODS
Thirty-three topographic and reflectance images taken with the HRT representing different levels of disease were transformed using nine different compression formats. Three independent ophthalmologists, masked as to contour line and stereometric parameters, classified the original and compressed HRT images as normal, suspected glaucoma, or glaucoma, and Kappa agreement coefficients were calculated.


RESULTS
The Tagged Image File Format had the largest file size and the Joint Photographic Experts Group (JPEG) 2000 format had the smallest size. The highest Kappa coefficient value was 1.00 for all ophthalmologists using the Tagged Image File Format. Kappa values for JPEG formats were all in the range of good to excellent agreement. Kappa values were lower for Portable Network Graphic and Graphics Interchange Format compression formats.


CONCLUSIONS
Image compression with JPEG 2000 at a ratio of 20:1 provided sufficient quality for glaucoma analysis in conjunction with a relatively small image size format, and may prove to be attractive for HRT telemedicine applications. Further clinical studies validating the usefulness of interpreting non-analyzed HRT images are required.
Bélair
Marie-Lyne
ML
Guy-Bernier Research Center, Hôpital Maisonneuve-Rosemont, Université de Montréal, Montréal, Canada.
Fansi
Alvine Kamdeu
AK
Descovich
Denise
D
Leblanc
A R
AR
Harasymowycz
Paul
P
D044962:Data Compression / Q000379:methods*; D005902:Glaucoma, Open-Angle / Q000175:diagnosis*; D006801:Humans; D007834:Lasers; D009798:Ocular Hypertension / Q000175:diagnosis; D009887:Ophthalmoscopy / Q000379:methods*; D010781:Photography / Q000379:methods; D014054:Tomography