Biomarkers in the Retina for Prognosticating Mental Health Treatments

Inclusion Criteria: * Veteran of the U.S. Armed Forces * Current diagnosis of PTSD Exclusion Criteria: * Known diagnosis of a primary psychotic or major neurocognitive disorder * Significant bilateral visual loss * History of acute angle closure glaucoma * Known inherited retinal disease * Previous ERG deficits * Known photosensitive epilepsy * Known current pregnancy or lactation * Allergy or previous adverse reaction to sertraline or SSRI * Allergy to Sensor Strip gel * Hepatic failure * Damage to orbit structure or open lesion in soft tissue surrounding the eye * Any use in the time period of at least 6 half-lives prior to baseline of sertraline or other drugs acting on serotonin and/or unwillingness to avoid these medications for the duration of the study.