Recently, the retinal nerve fiber layer (RNFL) thickness measurement using the optical coherence tomography (OCT) becomes very useful to detect such a glaucomatous damage. However, there are some difficult cases including parapapillary atrophy to perform this measurement. Because the RNFL thickness is so sensitive to the position of measurement and the measurement of RNFL thickness on parapapillary atrophy is incorrect, it is difficult to determine exact RNFL thickness in patients with a large parapapillary atrophy. In the present study, we want to find the proper method to analyze the RNFL thickness on parapapillary atrophy. The previous OCT used a fixed circle to measure the RNFL thickness, but the new spectral domain OCT, the Cirrus HD OCT, uses a movable one. Therefore, we may suggest a new analysis strategy for the parapapillary atrophy.