The comparative analysis of changes in optic disc morphology after trabeculectomy, measured by scanning laser tomography

Purpose:
The aim of this study was to investigate and estimate quantitative changes in optic nerve morphology after glaucoma surgery using the Heidelberg Retina Tomograph (Heidelberg Engineering, HRT Software 2.01).

Material and methods
The eyes of 42 consecutive patients (34 women and 8 men) undergoing trabeculectomy at the Department of Ophthalmology, Wroclaw Medical University, were enrolled into the study. Quantitative analysis of the optic nerve head parameters by scanning laser tomography were performed, as well as automated perimetry, before and after surgery. Post operative HRT images were obtained at 2-3 weeks, 4-6 months, 9-12 months and >12 months after surgery.

Results:
: Forty one patients (97,6%) have obtained postoperatively IOP reduction greater than 30%. Two weeks after trabeculectomy seven HRT parameters showed statistically significant improvement: CA, CV, RA, RV, mean cup depth, CSM. Approximately 5 months after surgery only 2 parameters (mean cup depth & CSM) were statistically changed, as well as 12 months after surgery (mean and max cup depth), which cannot be explained by postoperative disc edema. A corresponding change was also noted in the visual field. There was no statistically significant association between optic disc morphology as measured by HRT and the degree of intraocular pressure reduction.

Conclusions:
All patients showing a 30% lowering of IOP after glaucoma surgery show improved optic nerve morphology as measured by the HRT. Further studies are required to provide information, to what extent the change in optic disc topography is dependent on the duration of elevated intraocular pressure or advanced stage of glaucomatous optic neuropathy.