Inhibition of retinal ON/OFF systems differentially affects refractive compensation to defocus

Area of Science:

• Ophthalmology
• Neuroscience
• Developmental Biology

Background:

• Hatchling chicks exhibit remarkable visual plasticity, compensating for induced refractive errors through eye growth and refractive changes within a week.
• The retinal ON and OFF pathways are crucial for visual processing, but their specific roles in emmetropization remain incompletely understood.

Purpose of the Study:

• To investigate the distinct roles of retinal ON and OFF pathways in mediating refractive compensation during emmetropization.
• To determine if pharmacological inhibition of these pathways interferes with the compensatory eye growth and refractive adjustments in response to defocus.

Main Methods:

• Chicks were exposed to negative and positive lens defocus.
• Intravitreal injections of L-alpha-aminoadipic acid (inhibiting ON response) and D-alpha-aminoadipic acid (inhibiting OFF response) were administered.
• Electroretinography (ERG) was used to assess the functional integrity of ON and OFF responses.
• Refractive state and eye growth were monitored to evaluate compensation.

Main Results:

• L-alpha-aminoadipic acid selectively inhibited refractive compensation to negative lens defocus, correlating with suppressed ERG ON responses.
• D-alpha-aminoadipic acid selectively inhibited refractive compensation to positive lens defocus, correlating with suppressed retinal OFF responses.
• Neither isomer affected compensation to zero power lens defocus.

Conclusions:

• The retinal ON and OFF subsystems play independent, sign-dependent roles in the emmetropization process.
• Pharmacological evidence supports a model where distinct retinal pathways differentially regulate eye growth and refractive adaptation.
• These findings provide critical insights into the neural mechanisms underlying visual development and refractive error correction.