Abstract

DO.21.05

Optimizing the quality of digital colour fundus photographs

Tornow R. P., Laemmer R., Mardin C. Y.
Augenklinik mit Poliklinik, Universität Erlangen-Nürnberg, Erlangen

Objective: Due to the spectral distribution of the fundus reflection (high reflection in the red spectral range and low reflection in the blue range) colour fundus photographs show in principle an unequal distribution of the intensity in the 3 colour channels red, green and blue. As the dynamic range of digital cameras is currently lower than that of film emulsions this often results in loss of information due to overexposure in the red channel and underexposure in the blue channel. Thereby, essential information about ocular disease may be overlooked.
Methods: To compensate the unequal intensity distribution of colour fundus images, a special transmission filter for the illuminating beam path of the fundus camera was developed with the following features: The filter has three small transmission bands in the red, green and blue spectral range. The spectral width of the transmission bands decreases from the blue to the red spectral range. Wavelengths outside the 3 transmission bands are blocked. Thereby the unequal fundus reflection is compensated and the contrast of individual fundus features is increased.
Results: Digital colour fundus images taken with the developed filter show equalised intensity distributions in the three channels. This allows qualitative and quantitative analysis of the information of the blue and red channel.
Conclusions: Digital colour fundus images taken with the developed filter show equalised intensity distributions in the three channels. This allows qualitative and quantitative analysis of the information of the blue and red channel.

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