Background Central corneal thickness (CCT) and its association with intraocular pressure, which is a pivotal parameter in glaucoma management, has previously been reported. In this study, we intended to investigate the long-term change of CCT in terms of rate in eyes with primary angle closure (PAC). Additionally, we aimed to analyze events that could affect CCT.Methods In this retrospective study, 27 patients with PAC who had a follow-up period of more than five years were evaluated. The rate

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... f CCT changes from baseline was evaluated from the serial CCT measurements over the average follow-up period. The pattern of CCT change rate according to modes of treatment and history of angle closure attack was analyzed using the repeated linear mixed model analysis.Results A total of 52 eyes were enrolled. The CCT reduction rate of the entire study population was − 0.72 ± 0.22 µm/yr (P = 0.001) with statistical significance. The CCT thinning rate of the laser peripheral iridotomy (PI) group was − 0.53 ± 0.25 µm/yr (P = 0.034), that of the surgical trabeculectomy group was − 1.32 ± 0.43 µm/yr (P = 0.002), and it was not statistically significant (P = 0.112). The rate of CCT thinning in patients with a history of acute angle closure attack was − 0.81 ± 0.31 µm/yr (P = 0.009) and that in patients without an attack was − 0.63 ± 0.30 µm/yr (P = 0.001), and it was not statistically significant (P = 0.680). Baseline CCT appeared to be the only significant factor affecting the rate of CCT changes (P < 0.001).Conclusions We found a significant reduction in CCT over a long-time observation period in PAC eyes. We also found that the rates of CCT reduction were not affected by different treatment modalities or acute angle closure attack. The analysis of long-term CCT changes in conjunction with baseline CCT would also be helpful in the clinical evaluation of the PAC patients.