[Bifocal photography using the HRA -- an optimized method to evaluate tIOL's axial orientation].

BACKGROUND

The assessment of axial orientation of toric IOLs (tIOLs) by monofocal photography can be deteriorated due to intrinsic errors e. g. globe rotation, head inclination or inadequate camera adaption and slide projection.

METHOD: In a 67 years old female a tIOL was implanted after penetrating keratoplasty for correction of high corneal astigmatism. A sequence of two fundus and two tIOL photographs (bifocal photography) was taken in a time interval of 3 months using the HRA II (Heidelberg Retina Angiograph II). A reference at the fundus was defined using two characteristic markers. The axial fundus orientation between the markers was overlaid to the line defined by the tIOL axis markers. The angular offset/distance between the fundus orientation line and the tIOL marker line was analyzed for each bifocal image at different time points.

RESULTS

The comparison of axial tIOL orientation between both different tIOL images revealed a rotation angle of 13 degrees (monofocal photograph). In contrast, using the bifocal photography and digital overlay technique the fundus line as a reference the tIOL rotated 1 degrees and 4 degrees from the first to the second time point of photography. Thus, the real rotation angle of tIOL measured only 3 degrees.

CONCLUSION

The bifocal photography with constant head position has the potential to minimize the intrinsic error in documentation of axial orientation of tIOL.