Preferred retinal locus--hand coordination in a maze-tracing task

Area of Science:

• Ophthalmology
• Neuroscience
• Human Motor Control

Background:

• Fine manual tasks demand precise integration of visual input, eye movements, and motor output.
• Age-related macular degeneration (AMD) can cause macular scotomas, potentially disrupting this visual-motor coordination.
• The role of the preferred retina locus for fixation (fPRL) in guiding manual tasks, especially in individuals with AMD, is not fully understood.

Purpose of the Study:

• To investigate if the fPRL directs hand movements during fine manual tasks.
• To examine the interplay between the fPRL, fingertip position, and scotomas in AMD patients during task performance.
• To compare visuomotor control in individuals with AMD and normally sighted controls.

Main Methods:

• Participants with AMD-induced macular scotomas and healthy controls performed a maze-tracing task using their index finger.
• The task was conducted within a scanning laser ophthalmoscope (SLO) to simultaneously view the hand and maze on the retina.
• Retinal images were analyzed to map scotoma locations, fPRL positions, and fingertip trajectories.

Main Results:

• Fingertip retinal positions were centered around the fPRL, indicating fPRL-guided hand movements.
• The size of the fingertip retinal ellipse correlated with the fPRL ellipse size.
• For scotoma subjects, maze-tracing accuracy was positively associated with saccade rate.

Conclusions:

• The fPRL, similar to the fovea in normally sighted individuals, guides the fingertip during visuomotor tasks like maze tracing.
• While fPRL guides the hand, other factors likely contribute to the reduced maze-tracing performance observed in individuals with AMD.
• Findings highlight the adaptive role of the fPRL in visuomotor control despite central vision loss.