Participants completed protocol NTMT-01. All participants received surgery to implant NT-501. All participants received ciliary neurotrophic factor (CNTF).

Participants completed protocol NTMT-02. Participants for cohort 2 arm were either:

• NT-501 group: included subjects who each had 1 study-eligible eye that had NT-501 implanted and a fellow eye that did not undergo any study intervention.
• Sham group: included subjects who each had 1 study-eligible eye that underwent sham surgery and a fellow eye that did not undergo any study intervention.
• Sham+NT-501 group: included subjects who had both eyes that were study-eligible, and had NT-501 implanted in 1 eye and underwent sham surgery in the contralateral eye.

The investigational product is the NT-501 encapsulated cell system, which consists of cells encapsulated within a semi-permeable polymer membrane and supportive matrices. NT-501 contains NTC-201 cells that secrete recombinant human CNTF, which were derived from genetically modified NTC-200 cells.

Change from baseline to 72, 84, 96 and 108 months post-surgery (based on participants' original implant date during precursor study) by SD-OCT for Cohort 1

Change in EZ from baseline to 36, 48, 60 and 72 Months post-surgery (based on participants' original implant date during precursor study). Cohort 2 sham surgery arm includes 16 participants (16 eyes) that received an NT-501 following their Month 36 follow-up

Baseline to 72 Months - analyses also presented for additional times: 36, 48, and 60 Months post-surgery (based on participants' original implant date during precursor study) . Cohort 2 sham surgery arm includes 16 participants (16 eyes) that received an NT-501 following their Month 36 follow-up in this study.