The changes of retinal nerve fiber layer thickness with GDx-VCC were analyzed to assess the use of this instrument for longitudinal follow-up of retinal nerve fiber layers.

From July 2004 to July 2007, patients suspected of glaucoma were measured with GDx-VCC at baseline and measurements were repeated at a minimum interval of 12 months. The medical records of 150 patients were reviewed and 42 patients that showed glaucomatous visual field progression in 36 months were classified into a "progression group" and 108 patients with no visual field loss were classified into a "nonprogression group".

In the nonprogression group, the temporal superior-nasal-inferior-temporal (TSNIT) average and theinferior average showed statistically significant changes for the follow up periods. However, in theprogression group, there were no parameters with significant changes even though glaucomatous visual field loss was found. The visual field progressed at a rate of 0.1dB/year in the progression group but the relationship between MD, PSD and GDx-VCC parameters could not be established.

GDx-VCC may not be sufficient for longitudinal assessment of the RNFL, especially during the early glaucomatous visual field changes. The progression of glaucoma only with GDx-VCC should be cautiously evaluated, and confirmation with the visual field which elucidates early glaucomatous changes is necessary. Further study is needed before GDx-VCC can be recommended as the instrument for longitudinal assessment.