Using two preferred retinal loci for different lighting conditions in patients with central scotomas

Area of Science:

• Ophthalmology
• Neuroscience
• Visual Science

Background:

• Macular diseases can cause central vision loss, leading to the development of preferred retinal loci (PRLs) for fixation.
• Patients with scotomas may utilize different fixation points depending on stimulus conditions.

Purpose of the Study:

• To investigate the adaptation of preferred retinal loci (PRLs) in patients with macular diseases under varying stimulus illuminances.
• To describe how changes in stimulus brightness affect scotoma size and PRL usage.

Main Methods:

• Utilized a scanning laser ophthalmoscope to map macular scotoma borders in 28 patients with macular diseases.
• Defined and assessed high-illuminance PRL (PRLhi) and low-illuminance PRL (PRLlo) based on fixation behavior at different light levels.
• Evaluated visual task performance, including fixation stability, pursuit, and saccadic abilities, for both PRLhi and PRLlo.

Main Results:

• A consistent shift between PRLhi and PRLlo was observed as stimulus illuminance changed.
• The visual system preferentially uses PRLhi for better fixation stability when lighting conditions permit.
• PRLhi was typically located within or near the scotoma, while PRLlo was found in healthier retinal areas.

Conclusions:

• The visual system can develop two distinct PRLs in response to maculopathy, with usage dependent on object brightness.
• The existence of multiple PRLs should be considered in the development of vision rehabilitation and treatment strategies for patients with visual impairment.