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Impressum
Derse M., Bräuning J., Völker M., Zierhut M.
Universitätsaugenklinik Tübingen, Abt.I, Schleichstr. 12, 72076 Tübingen (Direktor: Prof. Dr. K.U. Bartz-Schmidt)
Objective: To assess the clinical use of secondary digitalized
video sequences and to determine the maximum compression rate which does
not interfere with clinical judgment. Data compression is necessary in
order to quickly transfer data using standard internet protocols. Biomicroscopical
examinations of the anterior segment as well as scanning laser angiography
(SLO) were used in this study.
Methods: Different pathologic states of the anterior segment (Hyphema
corneal ulcer, rubeosis iridis, corneal endothelial distrophy) as well
as pathologies obtained by SLO angiography (occult / classic membranes,
chorioretinal anastomosis, etc.) were recorded using a standard video
(SVHS) equipment. The Video sequences were digitally compressed (MPE-
1 technique) using a MS-Windows based PC and 4 compression rates (0.4
to 2.0 Mbit/s) subsequently. Four different ophthalmologists compared
the original videotaped sequences to all compressed sequences using a
17 inch PC monitor. Subjective differences in ease of definition of the
clinical diagnosis, pathological details, colour as well as overall quality
were judged in a five point scale.
Results: At 0.4 Mbit/s clinical diagnosis was found good in the
majority of cases. Starting at 0.7 Mbit/s all criteria were judged good
to excellent for anterior segment pathology. SLO angiography was found
to be moderate at 0.7 Mbit/s or good at 1.0 Mbit/s respectively. Using
these compression rates the file size could be reduced up to 1/20 of the
original file size.
Conclusion: The technique presented in this study is useful for
the compression of secondary digitalized video sequences and not interfering
with clinical judgement. File sizes of 3.0 Mb (biomicroscopy) to 5.0 Mb
(SLO angio) per minute enable fast data tranfer using standard PC software
(and hardware). Thus the presented technique is an important tool in the
field of telemedicine.