Long-Term Follow-Up of Scanning Laser Polarimetry and Confocal Scanning Laser Ophthalmoscopy in Normal Tension Glaucoma

Background: To investigate the potential of optic nerve head measurements using confocal scanning laser ophthalmoscopy (CSLO) and nerve fiber layer images by means of scanning laser polarimetry (SLP) in the longterm follow-up of normal tension glaucoma (NTG). Methods: Retrospective study of 49 NTG patients with an average age of 65.5 years that have been followed for about 5 years. The long-term change of various parameters of perimetry, CSLO and SLP was examined for all patients. In addition patients were classified according to their Aulhorn glaucoma classification score as beginning (AGS<3) or advanced (AGS ≥ 3) and progressive and non-progressive NTG trying to reveal differences of the parameters in stage and time. Results: Intraocular pressure (IOP), mean defect (perimetry), neuroretinal rim and CDR (CSLO) did not show significant changes over the time. In CSLO, average depth and cupping shape were significantly different over the time and between progressive and non-progressive NTG. SLP revealed significant decrease especially in the superior retinal nerve fiber layer (66.1 vs 57.3 μm), but only relative parameters such as NFI, superior ratio and ellipse modulation were different between beginning and advanced NTG. Discussion: Our study points out that especially relative parameters in SLP such as ellipse modulation or NFI and CSLO-values of optic disc steepness and depth might be helpful in the follow-up of glaucoma patients. They show a better correlation to progression of the disease than classical parameters such as MD, IOP, neuroretinal rim or CDR.