Optic Nerve Head Structural Response to IOP Elevation in Patients With Keratoconus

Inclusion Criteria: Candidates must meet the following inclusion criteria in order to participate in the study. * Ability to provide informed consent and to understand the study procedures Keratoconus: * Clinical diagnosis of keratoconus * Central thinning of the cornea * Abnormal posterior ectasia. Glaucoma: * Glaucomatous ONH abnormality: rim thinning, notching, undermining (excavation) or diffuse or localized RNFL defects that are characteristic of glaucoma. * Two consecutive abnormal SITA standard perimetry tests with GHT outside normal limits. Exclusion Criteria: Candidates that meet any of the exclusion criteria at baseline will be excluded from study participation. * Media opacity (e.g. lens, vitreous, cornea). * Strabismus, nystagmus or a condition that would prevent fixation. * Diabetes with evidence of retinopathy. * Previous intraocular surgery or ocular trauma (with the exception of laser procedures and subjects that have undergone uneventful cataract surgery more than 6 months from enrollment date). * Neurological and non-glaucomatous causes for visual field damage. * Any intraocular non-glaucomatous ocular disorders.