Background: The high prevalence of normal tension glaucoma (NTG) in the Japanese requires special screening tests other than measurements of only the intraocular pressure (IOP). This study was carried out to determine whether there is a significant association between the axial length of the eye and the presence of NTG.
Methods: We reviewed the medical records of all patients who were scheduled to undergo cataract surgery alone or combined with glaucoma surgery at the same time. There were 87 patients with NTG, 137 with POAG, and 978 non-glaucomatous control cases. The axial length, IOP, curvature of the anterior corneal surface, age, and gender were determined at the time of the operation. If both eyes had surgery, data from only the right eyes were analyzed. An association of these parameters with NTG and POAG was analyzed by logistic regression analysis. The three groups were analyzed for differences in the axial length using the Kruskal-Wallis test followed by the Mann-Whitney U test.
Results: The axial length was significantly associated with NTG (odds = 1.24, P = 0.002) and POAG (odds = 1.28, P = 0.001). The incidence of either POAG or NTG was significantly higher in patients with axial lengths >or=25.0 mm (odds = 2.29, P < 0.001, Fisher's exact test). The age at the time of cataract surgery was weakly but significantly correlated negatively with the axial length (r = -0.24, P < 0.001, Pearson's correlation coefficient test). Men had significantly longer axial lengths than women.
Conclusions: Long axial lengths can be considered a risk factor for NTG and POAG, and patients with long axial lengths need to be carefully examined for glaucoma.