Functional outcome in subretinal electronic implants depends on foveal eccentricity

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Neuroscience

Background:

• Hereditary retinal degenerations cause progressive vision loss.
• Current treatments are limited for end-stage retinal degeneration.
• Active microelectronic subretinal implants aim to restore photoreceptive function.

Purpose of the Study:

• To evaluate the efficacy of an active microelectronic subretinal implant in patients with end-stage retinal degeneration.
• To compare visual outcomes based on implant placement (subfoveal vs. parafoveal).

Main Methods:

• A pilot and clinical study involving 20 blind patients with hereditary retinal diseases.
• Surgical implantation of active visual devices in the subretinal space (8 subfoveal, 12 parafoveal).
• Masked, randomized testing of visual functions (light perception, localization, motion detection, grating acuity, Landolt C-rings) with implant ON and OFF.

Main Results:

• Three patients were excluded due to surgical/technical issues.
• Parafoveal placement: 80% light perception, 10% light localization, 10% grating acuity (0.33 cycles/degree). No motion or Landolt C-ring test success.
• Subfoveal placement: 100% light perception/localization, 75% motion detection (35°/s), 88% grating acuity (3.3 cycles/degree), 38% Landolt C-ring test success (20/546 visual acuity).

Conclusions:

• Subfoveal placement of active subretinal visual implants demonstrates superior functional outcomes.
• Implant location is critical for maximizing visual restoration in retinal degeneration patients.