P 651Morphometric comparison of high- and low-tension glaucoma optic discs with Laser-Scanning-Tomography
C. Y. Mardin, W. M. Budde, A. G. M. Jünemann, J. B. Jonas
Purpose: The aim this cross-sectional study was to determine, whether there are morphometric differences between glaucomatous optic discs of high (HTOAG, >21 mmHg) and normal-tension open-angle (NTOAG, <22 mmHg) glaucoma patients, measured with the laser scanning technique of the HRT.
Patients and methods: 42 HTOAG (Age 51.7± 12.1a; max. IOP 30.4± 7.9 mmHg) and 42 NTOAG (Age 55.4± 12.3a; max. IOP 20.2± 1.8 mmHg) patients were selected from our Glaucoma Service (Erlanger Glaukomregister) and matched for the size of the optic disc and mean defect of static perimetry. 24h-IOP measurements, Octopus perimetry, gonioscopy, and evaluation of the optic disc on stereographs were used to determine the diagnosis at least two times. Morphometry of the optic disc was performed with the HRT (version 2.01, mean of three pictures). Two-dimensional measurements as area of the neuroretinal rim and cup and three-dimensional measurements as volume of the neuroretinal rim and cup, cup shape measure, cup depth and height of the retinal nerve fiber layer were calculated globally and in four segments. The distribution of refraction and glaucoma stage were equal in both groups. For statistical calculation one eye per patient was selected.
Results: In eyes with NTPOAG the volume of the neuroretinal rim (p=0.01) and the height of the retinal nerve fiber layer (p=0.02) was significantly lower in the inferior sector. In eyes with HTPOAG the maximum depth of the cup was significantly deeper (p=0.03) in the inferior sector with no significant difference in the mean depth of the cup globally and in the four sectors. In all other variables measured by the HRT there was no statisically significant difference between the two groups.
Discussion: Our results support the clinical observation, that eyes with NTPOAG show a higher tendency towards hemorrhages of the neuroretinal rim and subsequent rim loss in the inferior sector of the optic disc, resulting in deeper visual field defects in the superior sector. The clinical observation, that the excavations of glaucomatous discs NTPOAG and HTPOAG appear equally deep and steep, although the maximum IOP in HTPOAG is significantly different has been supported by this study.
Augenklinik mit Poliklinik Universität Erlangen-Nürnberg,
Schwabachanlage 6, D-91054 Erlangen
Supported by DFG (SFB 539)