A Study of the Structure and Function of the Retina in Adult Patients With Refractory Complex Partial Seizures Treated With Vigabatrin (Sabril®)

Important Inclusion Criteria: 1. The patient speaks English or Spanish. 2. The patient has had no prior exposure to Sabril. 3. To begin Sabril therapy for the treatment of CPS. 4. Male or female ≥18 years of age. 5. The patient has refractory CPS: 1. The patient has complex partial epilepsy of more than 1 year duration and no other seizure type within the past year except for partial seizures secondarily generalized. 2. The patient has failed because of lack of efficacy 3 or more prior or concurrent treatment trials including 3 or more anti-epileptic drugs (AEDs) of differing pharmacologic mechanisms administered as monotherapy or polytherapy. 3. The patient is taking at least 1 AED. A vagal nerve stimulator is not counted as an AED. 4. The patient reports an average of 2 or more seizures per month averaged over the prior 3 months. 6. The patient is deemed by the treating neurologist and ophthalmologist to be able to reliably complete perimetry testing. 7. The initial (Visit 1) SD-OCT and static perimetry readings tests must be performed and assessed for technical adequacy by the SD-OCT and perimetry central readers prior to the first dose of Sabril. The initial (Visit 1) tangent corner test must be performed prior to the first dose of Sabril. Exclusion Criteria: 1. Prior exposure to Sabril. 2. Pre-existing ocular or neurological disease that might affect bilateral visual fields or interfere with perimetry (e.g., aphakia, visually significant cataract, glaucoma, diabetes mellitus, ischemic optic neuropathy, multiple sclerosis). Patients with stable visual field defects from CNS lesions (e.g., epilepsy surgery more than 6 months prior to receiving Sabril) may be enrolled. 3. Concurrent exposure to medications with known or suspected retinal or optic nerve toxicity. 4. Concurrent use of an investigational agent or device or such use within 30 days of entering the study. 5. Concurrent use of the ketogenic or similar diet. 6. For any reason, the patient is considered by the investigator to be an unsuitable candidate for the study.