Purpose  To evaluate the relationship between genetic polymorphisms of the adrenergic receptor (ADR) and diurnal intraocular pressure (IOP) curve in Normal-tension glaucoma (NTG) patients.

Design  Prospective comparative case series

Participants: Eighty-six untreated patients with NTG were recruited in this study.

Methods: The IOP of both eyes was measured with a Goldmann applanation tonometer in the sitting position at 3 hour intervals from 0600 to 2400 hours for two consecutive days. IOP data from the eye with the greater visual field defect was used for statistical analysis. The mean IOP over two days was used for each time point. Genetic polymorphisms in α1A-, α2A-, α2B-, α2C-, β1-, β2- and β3-ADR were determined mainly by direct DNA sequencing. The relationship between IOP and genetic polymorphisms was statistically analyzed.

Main Outcome Measurements: IOP and genotypes of genetic polymorphisms

Results  Diurnal mean IOP of the subjects was 14.0 ± 1.9 mmHg (mean ± standard deviation). The peak IOP (15.2±2.2 mmHg) occurred at 1200, while the trough IOP (13.5±2.3 mmHg) occurred at 2400. There was a significant effect of time on diurnal IOP levels shown by repeated measures ANOVA (P<0.001), which indicated the presence of diurnal IOP fluctuations. Diurnal IOP levels were significantly different between the major homozygotes and minor carriers of Del 301-303 in α2B-ADR (P=0.017), Del 322-325 in α2C-ADR (P=0.040) and S49G in β1-ADR (P=0.024), but that the interaction of genotype of these 3 polymorphisms and time was not significant. These results indicated that the major homozygotes and minor carriers had parallel diurnal IOP curves but significantly different diurnal IOP levels. For other polymorphisms, diurnal IOP levels showed no significant differences between the major homozygotes and minor carriers.

Conclusion  Genetic polymorphisms of ADR may alter the untreated IOP level of NTG patients.