Comments and Conclusions

  • Although the majority of clinically encountered optic nerve disorders are due to glaucoma, other etiologies are possible.
  • The GCC is a novel way to document loss of the ganglion cells and their related axons and dendrites.
  • The iWellness Exam furnishes GCC data as well as cross sections of the retina.
  • The VEP is the only available objective test of visual function and is now easy to obtain with the new Diopsys system.
  • Objective tests of structure (such as the GCC) often correlate with the VEP, the objective test of visual function.
  • GCC abnormalities can often be used to predict the visual field deficit.
  • Both GCC and VEPs can be abnormal and confirm an optic nerve disorder even in patients without symptoms, normal VA and a normal appearing fundus.
  • GCC, as well as RNFL defects, can sometimes predict future VF loss.
  • GCC is sometimes more sensitive to optic nerve disorders than is a circumpapillary RNFL measurement since large blood vessels are not present in the macula and do not result in artifacts as in RNFL testing.3
  • Additional reasons for discordance between GCC and Circumpapillary RNFL measurements will be addressed in a future RR.