Emerging Optometry and Visual Prosthetics Study Notes

Emerging Optometry: The Future

  • Date: 28 February 2024
  • Lecture Series: Final Year Emerging Optometry
  • Speaker: Chris Dickinson, Faculty of Biology, Medicine and Health, The University of Manchester

Locations for Electrical Stimulation Delivery

When considering where to deliver electrical stimulation to restore vision, several anatomical sites within the visual pathway are possible, each with specific advantages and characteristics:

  • Cortex:
    • Potential to help the widest range of patients.
    • Functions even if the rest of the visual pathway (retina, optic nerve, LGN) is non-functional or damaged.
  • Lateral Geniculate Nucleus (LGN):
    • Described as a compact, well-defined structure.
    • Possesses a retinotopic structure, which organizes visual information according to its location on the retina.
  • Optic Nerve:
    • Characterized by a looser topographic arrangement compared to the LGN or retina.
  • Retina:
    • The site of the earliest commercial visual prosthesis systems.

Patient Perspectives on Implant Options (Karadima et al. 2023)

While cortical implants offer the benefit of a wider potential population pool, research has investigated what potential recipients actually think about these technological options.

  • The Karadima et al. (2023) Study:

    • The study asked potential recipients to compare three primary options: Retinal, Thalamic (LGN), and Cortical.
    • Methodology: The research involved a multi-stage process:
      • Initial Presentation.
      • Questionnaire 1.
      • Focus Groups.
      • Questionnaire 2.
    • The "Decision Formula": The study utilized a conceptual metric to evaluate preferences based on the perceived trade-off:
      • Value=(Benefit−Risk)\text{Value} = (\text{Benefit} - \text{Risk})

  • Patient Sentiment Findings:

    • Overall data suggests that patients were not particularly keen on any of the proposed approaches.
    • Quantitative Data on "Wants Device":
      • Before Focus Group (n=38n = 38): A high percentage of participants (approximately 50%50\%) responded "no," followed by "unsure" (approximately 45%45\%), and a small minority (approximately 5-10%5\text{-}10\%) responding "yes."
      • After Focus Group (n=27n = 27): The number of "no" responses remained high (above 40%40\%), "unsure" responses remained significant (around 40%40\%), and "yes" responses showed only a slight increase but remained the lowest category (approximately 20%20\%).

Divergent Expectations: Researchers vs. Patients

There is a notable gap between the goals of the scientific community and the desires of the patient population:

  • Researcher Perspective: Researchers often operate under the philosophy that "anything is better than nothing" regarding restored visual input.
  • Patient Perspective: When asked what specific abilities they wanted a prosthesis to deliver, patients prioritized "face perception" as the most important outcome.

Qualitative Patient Feedback and Goals

Direct quotes from potential recipients highlight the emotional and functional requirements they expect from visual prostheses:

  • Desire for Restoration: "I want my vision to be like it was before."
  • Independent Mobility: "To be able to go around on my own."
  • Practical Utility vs. Traditional Aids: "If we get one of these devices, will we still need a white cane?"