Image quality characteristics of a novel colour scanning digital ophthalmoscope (SDO) compared with fundus photography.
OBJECTIVE
To establish a set of quality parameters for grading image quality and apply those to evaluate the fundus image quality obtained by a new scanning digital ophthalmoscope (SDO) compared with standard slide photography.


METHODS
On visual analogue scales a total of eight image characteristics were defined: overall quality, contrast, colour brilliance, focus (sharpness), resolution and details, noise, artefacts and validity of clinical assessment. Grading was repeated after 4 months to assess repeatability. Fundus images of 23 patients imaged digitally by SDO and by Zeiss 450FF fundus camera using Kodak film were graded side-by-side by three graders. Lens opacity was quantified with the Interzeag Lens Opacity Meter 701.


RESULTS
For all of the eight scales of image quality, good repeatability within the graders (mean Kendall's W 0.69) was obtained after 4 months. Inter-grader agreement ranged between 0.31 and 0.66. Despite the SDO's limited nominal image resolution of 720 x 576 pixels, the Zeiss FF 450 camera performed better in only two of the subscales - noise (p = 0.001) and artefacts (p = 0.01). Lens opacities significantly influenced only the two subscales 'resolution' and 'details', which deteriorated with increasing media opacities for both imaging systems.


CONCLUSIONS
Distinct scales to grade image characteristics of different origin were developed and validated. Overall SDO digital imaging was found to provide fundus pictures of a similarly high level of quality as expert photography on slides.
Strauss
Rupert W
RW
Department of Ophthalmology, Ludwig-Maximilians-University, Munich, Germany.
Krieglstein
Tina R
TR
Priglinger
Siegfried G
SG
Reis
Werner
W
Ulbig
Michael W
MW
Kampik
Anselm
A
Neubauer
Aljoscha S
AS
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002675:Child, Preschool; D003116:Color; D003952:Diagnostic Imaging / Q000592:standards*; D003941:Diagnostic Techniques, Ophthalmological / Q000592:standards*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000592:standards*; D008297:Male; D008875:Middle Aged; D019721:Ophthalmoscopes / Q000592:standards*; D010781:Photography / Q000592:standards*; D012160:Retina / Q000473:pathology; D012164:Retinal Diseases / Q000175:diagnosis*