Optical coherence tomography (OCTOptical Coherence Tomography (OCT)) has emerged as an important tool for quantifying retinal neural loss in many different optic nerveOptic nerve diseases including compressive optic neuropathiesOptic neuropathy. As in other optic neuropathiesOptic neuropathy OCTOptical Coherence Tomography (OCT) can be useful for diagnosisDiagnosis and follow-up of both optic nerveOptic nerve and chiasmal compressive diseases. Axonal loss can be assessed both through peripapillary retinal nerve fiber layerPeripapillary retinal nerve fiber layer measurements as well as using macular thickness measurementsMacular thickness measurements, especially when analyzing segmented layers of the retinaRetina. By analyzing the amount of axonal loss OCTOptical Coherence Tomography (OCT) can also be of help in estimating the possibility of visual improvement in such conditions. Additionally, OCTOptical Coherence Tomography (OCT) can provide data to analyze structural optic disc characteristics such as cupping that may occur in compressive optic neuropathiesOptic neuropathy, by evaluating the minimum rim with of the optic disc. Furthermore, OCT angiographyOCT angiography (OCTA) enables the assessment of retinal vesselRetinal vessels density in these cases. In this chapter, we discuss the main use of OCTOptical Coherence Tomography (OCT) in compressive optic neuropathiesOptic neuropathy including primary optic nerve tumorsOptic nerve tumor, extrinsic optic nerve compressionOptic nerve compression by tumors or other orbital lesions and the important group of diseases causing chiasmal compression.