Functional Vision in the Real-World Environment With a Second-Generation (44-Channel) Suprachoroidal Retinal Prosthesis

Abstract

Purpose: In a clinical trial (NCT03406416) of a second-generation (44-channel) suprachoroidal retinal prosthesis implanted in subjects with late-stage retinitis pigmentosa (RP), we assessed performance in real-world functional visual tasks and emotional well-being.

Methods: The Functional Low-Vision Observer Rated Assessment (FLORA) and Impact of Vision Impairment-Very Low Vision (IVI-VLV) instruments were administered to four subjects before implantation and after device fitting. The FLORA contains 13 self-reported and 35 observer-reported items ranked for ease of conducting task (impossible-easy, central tendency given as mode). The IVI-VLV instrument quantified the impact of low vision on daily activities and emotional well-being.

Results: Three subjects completed the FLORA for two years after device fitting; the fourth subject ceased participation in the FLORA after fitting for reasons unrelated to the device. For all subjects at each post-fitting visit, the mode ease of task with device ON was better or equal to device OFF. Ease of task improved over the first six months with device ON, then remained stable. Subjects reported improvements in mobility, functional vision, and quality of life with device ON. The IVI-VLV suggested self-assessed vision-related quality of life was not impacted by device implantation or usage.

Conclusions: Subjects demonstrated sustained improved ease of task scores with device ON compared to OFF, indicating the device has a positive impact in the real-world setting.

Translational relevance: Our suprachoroidal retinal prosthesis shows potential utility in everyday life, by enabling an increased environmental awareness and improving access to sensory information for people with end-stage RP.

Figure 1.

Timeline of key events relative to device fitting (week 0). ^*Presurgical baseline FLORA measured with no device. ^✝Post-device fitting baseline FLORA at week 17. ^‡Subject 4 ceased FLORA measurements at week 20 for reasons unrelated to the device. ^§Only subject 3 had FLORA and IVI-VLV performed at weeks 80 and 92 because of the impacts of the COVID-19 pandemic in 2020. ^||Endpoint is defined as the last time point in the study where FLORA and IVI-VLV were performed for subjects 1, 2, and 3, which were at 110, 109, and 136 weeks (approximately two years) post-device fitting, respectively. The timing of the endpoint for subject 3 was extended because of the COVID-19 pandemic in 2020. ^#The gray zone marks the time range where subjects began using the device unsupervised at home (subject 1 = week 21.0, subject 2 = week 20.3, subject 3 = week 23.3, subject 4 = week 27.6).

Figure 2.

Ease of task scores for functional vision tasks in the “Visual Orientation,” “Visual Mobility” and “Interaction with Others” domains with the device ON (A) and OFF (B) at each visit presented as cumulative (stacked) counts. Gaps indicate that a task was not able to be completed by all 3 subjects at that time point. Presurgery Device OFF results are duplicated in A for ease of reference.

Figure 3.

Ease of task scores of subjects for functional vision tasks in the “Daily Life” domain with the device ON (A) and OFF (B) at each visit presented as cumulative (stacked) counts. Gaps indicate that a task was not able to be completed by all three subjects at that time point. Presurgery Device OFF results are duplicated in A for ease of reference.

Figure 4.

Mode ease of task scores for all tasks for subjects 1, 2, and 3 with the device switched ON and OFF up to two years (109–136 weeks) post-device fitting. ^*If bi-modal, higher mode presented.

Figure 5.

IVI-VLV results relating to emotional well-being (A) and activities of daily living (B). Data shows that emotional well-being and activities of daily living scores remain stable over the two-year clinical trial for subjects 1, 2, and 3. For subject 4, emotional well-being decreased over time because of psychosocial stressors unrelated to the study.