Assessment of optic disc and retinal nerve fiber layer in normal-tension glaucoma and high-tension glaucoma patients

Purpose To evaluate differences in the pattern of optic disc and retinal nerve fiber layer (RNFL) damage in normal tension glaucoma (NTG) and high tension glaucoma (HTG) patients. Methods We enrolled 49 eyes of 49 patients:30 NTG (IOP≤21 mm Hg,1 mm Hg=0.133 kPa), 19 HTG(IOP≥25 mm Hg). Mean age was 59.2±12.3 (range, 36-75) for HTG patients, and 59.6±8.6(range, 39-71) for NTG patients. All patients underwent complete ophthalmic examination, achromatic automated perimetry (AAP), scanning laser ophthalmoscopy (SLO), scanning laser polarimetry (SLP), optical coherence tomography (OCT) and Heidelberg retinal tomography (HRT). All patients had glaucomatous optic nerve damage and abnormal AAP. Results There were no differences in mean deviation on AAP between NTG and HTG eyes ( P =0.37), while the corrected pattern standard deviation was larger in NTG than in HTG eyes ( P =0.014). Cup∶disc area ratios in global ( P =0.03) and three sectors ( P 0 05) except nasal sector were significantly larger in the NTG group, whereas rim area in global ( P =0.03) and three sectors ( P 0.05) except nasal quadrant obtained by SLO were smaller in NTG than in HTG eyes. The other numerical parameters obtained by three imaging technologies could not detect differences in the optic disc or RNFL anatomy between the two groups. Conclusions Cup∶disc area ratio was larger in patients with NTG than in those with HTG, whereas significant thinning of rim was associated with NTG eyes. The measurement of retinal nerve layer thickness in global and each quadrant was similar between two groups. More focal or segmental analysis of the data contained within SLO, SLP and OCT images are needed to detect localized differences in eyes with varying levels of IOP.