What phenomenon is responsible for the crowding effect observed in patients with amblyopia?

The crowding effect observed in patients with amblyopia is primarily attributed to simultaneous masking. This phenomenon occurs when the presence of nearby visual stimuli interferes with the perception of a target, making it more difficult to distinguish the target object from its surroundings. In amblyopia, the visual system has an underdeveloped capability to resolve fine details, particularly in the presence of other nearby stimuli. The difficulty in perceiving a letter or object can arise due to other nearby letters or objects that visually mask the target, leading to reduced performance in visual tasks.

Simultaneous masking significantly impacts patients with amblyopia as their visual processing is less efficient compared to individuals with normal vision. The inability to filter out or separate the target from distracting elements results in impaired visual acuity when multiple stimuli are present. This explains why these patients may struggle more in crowded visual environments, thus illustrating the crowding effect attributed to simultaneous masking.