Purpose: To evaluate whether any parameters of the optic disc and the retinal nerve fibre layer that are measured with the Heidelberg Retinal Tomograph I (HRT I) have a typical diurnal curve and are they related to the itraocular pressure (IOP).
Methods: The optic disc of 34 normals was measured 5 times during the day (8°°, 10°°, 12°°, 14°°, 16°°) with the HRT I as well as the IOP. One eye was randomly chosen to be included in the study.
Results: The mean age of the 34 normals was 59,5 years, 21 women and 13 men. The mean IOP during the day was; 17,30, 16,70, 16,70, 16,20, 15,00 mmHg respectively. Two parameters presented a diurnal curve; cup volume – 0,177, 0,187, 0,186, 0,190, 0,227 mm2 respectively- and mean cup depth - 0,246, 0,246, 0,266, 0,252, 0,280 mm respectively. The correlation between IOP and cup volume and between cup volume and mean cup depth was statistically significant (p<0,05). The correlation between IOP and mean cup depth was almost statistically significant – p=0,06. None of the parameters measured by the HRT I had a typical diurnal curve or correlated with IOP.
Conclusion: The cup volume and mean cup depth have a diurnal curve (maximum at the morning, minimum at the afternoon) that has a positive correlation with the diurnal IOP curve.