Which threshold is associated with isometropia myopia amblyogenic factor in BOTH eyes?

• A. -6.00D
• B. -8.00D
• C. -4.00D
• D. -9.00D

Answer: (B)

Isometropic myopia amblyopia risk occurs when both eyes are highly myopic, so the visual input to each eye is degraded enough during development that the brain doesn’t learn to create sharp vision from either eye. The threshold at which bilateral myopia becomes amblyogenic—meaning likely to cause amblyopia if not corrected during the critical period—is about minus 8 diopters. At or beyond this level, even with best possible correction, the image quality is so poor that normal visual development is unlikely, making bilateral (in both eyes) deprivation more probable.

Lower levels of bilateral myopia, such as around minus 4 or minus 6 diopters, typically do not cross this amblyogenic threshold; with appropriate correction or other visual stimulation, normal development can often proceed. A much higher level like minus 9 diopters is certainly severe, but the standard threshold used in testing to flag isometropic amblyopia risk is around minus 8 diopters, which is why that value is selected.