Abstract
Purpose: :
To compare the diagnostic ability of macular ganglion cell complex (GCC) and peripapillary retinal nerve fiber layer (pRNFL) thickness in patients with high-tension glaucoma (HTG) and low-tension glaucoma (LTG).
Methods: :
We prospectively enrolled consecutive normal subjects, HTG and LTG patients. Glaucoma was defined as glaucomatous optic neuropathy and reproducible visual field (VF) defects. Patients were classified as LTG if untreated intraocular pressure was ≤ 20mmHg on two different occasions.Those with any ocular disease other than glaucoma were excluded and only eyes with early glaucoma [mean deviation (MD) <-6 db] were included. All patients underwent spectral-domain optical coherence tomography (SD-OCT; RTVue-100; Optovue Inc., CA) imaging. Whenever both eyes were eligible, one was randomly selected. Analysis of variance was used to compare different SD-OCT parameters between groups (HTG vs LTG). Areas under the receiver operating characteristic curve (AUROC) were used to compare the discriminating ability of each scan within and between groups (Delong Test).
Results: :
A total of 56 normal subjects (control group), 64 HTG and 35 LTG were enrolled.Patients with LTG were younger (mean age, 52.6± 11.9 years) compared to the others groups (controls, 64.7±13.8 years; HTG, 62.5 ±13.8 years; p<0.05). There was no difference in MD between HTG (-2.6± 1.1 dB) and LTG groups (-2.3±1.9 dB; p=0.51). We found a significant difference in the average, superior and inferior GCC thicknesses between controls and LTG group (p<0.05) and between controls and HTG group (p0.05). There was a significant difference between all 3 groups regarding average, superior and inferior pRNFL (p<0.05). Overall, after adjusting for MD and age, average pRNFL thickness in eyes with LTG was 18.7 µm thinner than in eyes with HTG, (17% difference; p<0.01) . In HTG group, no significant difference was found between AUCs for average GCC and average pRNFL thicknesses (0.77 vs 0.68; p=0.06). In the LTG group, average pRNFL thickness had a significantly larger AUC compared to average GCC thickness (0.95 vs 0.81; p<0.001). Comparing AUCs between HTG and LTG groups, although average GCC had similar AUCs in both groups (p=0.47), average pRNFL had a significant larger AUC in the LTG group (p<0.001).
Conclusions: :
In eyes with early glaucoma and similar functional damage, the pRNFL scan seems to be the most accurate SD-OCT parameter to identify those with LTG. The macular GCC scan seems to perform similarly in eyes with HTG and LTG. Weather this difference could be related to the fact that eyes with LTG usually have a significant proportion of localized RNFL defects at onset deserves further investigation.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • ganglion cells • nerve fiber layer