Emmetropization and optical aberrations in a myopic corneal refractive surgery chick model

Area of Science:

• Ophthalmology
• Animal Models
• Refractive Surgery

Background:

• Myopic corneal refractive laser surgery aims to correct vision but can induce aberrations.
• The role of surgically induced aberrations in myopia development is not fully understood.
• Chick models offer a valuable platform for studying ocular development and refractive error progression.

Purpose of the Study:

• To investigate if photorefractive keratectomy (PRK) induces myopia (axial elongation) in chicks.
• To examine the interaction between surgically induced aberrations and myopia development.
• To determine if high-order aberrations are a risk factor for myopia.

Main Methods:

• Ten chicks underwent unilateral PRK with a nominal -9.9 D change (imposed hyperopia).
• Axial length, corneal curvature, spherical error, and high-order aberrations were measured post-operatively.
• Measurements were taken using ultrasonic biometry, videokeratometry, and Hartmann-Shack aberrometry.

Main Results:

• No significant difference in corneal curvature between treated and control eyes two weeks post-surgery.
• Astigmatism increased by 2.6x and higher-order aberrations by 4.3x after PRK.
• No axial elongation was observed in treated eyes; both eyes emmetropized despite induced aberrations.

Conclusions:

• PRK in chicks did not lead to myopia or axial elongation, possibly due to chick eye biomechanics.
• Induced high-order aberrations significantly decreased contrast but did not cause myopic refractive error or axial elongation.
• Increased aberrations do not appear to be a risk factor for myopia development in this model.