Abstract

P 118

Influence of axial length and spherical equivalent on the optic nerve head planimetry using scanning laser ophthalmoskopy and optical coherence tomography

Matthias Klamann1, Arne Viestenz2, Achim Langenbucher3, Wolfgang Behrens-Baumann4
1Universitäts-Augenklinik Düsseldorf, 2Augenklinik mit Poliklinik, Otto-von-Guericke-Universität, Magdeburg, 3Medizinische Physik, Institut für Medizinische Physik, 4Universitätsklinikum Erlangen, Erlangen

Objective
To evaluate the optic nerve head (ONH) planimetry with two different methods, and to investigate the influence of axial length and spherical equivalent.
Evaluation of optic nerve head plays a decisive role in the diagnostic of glaucoma. While small cups can be already glaucoma suspicious (CDR 0.2) large cups in macro optic nerve heads can be physiologicaly. This study is proposed to show the influence of biometric parameters on the optice nerve head planimetry using HRT and OCT and to give some clinical decision support.
Methods
Prospective examination of 106 consecutive eyes with OCT Stratus and HRT II. After a complete ophthalmological examination fundus photographs were taken and axial length (AL, Zeiss IOLMaster) and spherical equivalent (SEQ) were measured.
Results
A good correlation was found between the mean ONH size (r=0,686; p<0,001) measured with OCT 3 and HRT II and the mean ONH excavation (r=0,604; p<0,001) measured with the same devices. A good correlation of the axial length with the difference of ONH size was found (OCT 3 - HRT II, r=-0,415, p<0,001). By trend, OCT 3 measures higher ONH size with lower axial length then HRT II, whereas HRT II measures higher ONH size with higher axial length. Within a mean axial length range between 23 mm to 24 mm, both devies give comparable values.
Further more a good correlation of the spherical equivalent with the difference of the ONH size was found (OCT 3 - HRT II, r=0,409, p<0,001). By trend, HRT II measures higher ONH size with lower SEQ then OCT 3, whereas OCT 3 measures higher ONH size with higher SEQ. Within a mean SEQ range between -1 D to +1 D, both devices give comparable values.
Conclusions
Axial length and spherical equivalent have a significant impact on the papillary planimetry. In the future, biometric parameters should be integrated more carefully in the evaluation of the optic nerve head planimetry.

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