Deviation of near vision is conveniently tested by
**Core Concept**
The question is testing the concept of heterophoria, specifically the deviation of near vision, also known as near heterophoria. This refers to the tendency of the eyes to deviate from alignment when viewing near objects, often due to imbalance in the extraocular muscles or other ocular system abnormalities.
**Why the Correct Answer is Right**
Near heterophoria is typically assessed using the near point cover test, which involves covering one eye and asking the patient to fixate on a near object. The examiner then observes the movement of the uncovered eye to determine if it is deviating inward (esophoria), outward (exophoria), or upward/downward (hypertropia/ hypotropia). This test is essential in diagnosing and managing conditions such as strabismus, amblyopia, and convergence insufficiency.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the near point cover test is specifically designed to detect deviations of near vision, not far vision.
**Option B:** This option is incorrect because the cover test for far vision is more relevant to detecting strabismus or other ocular misalignments at distance.
**Option C:** This option is incorrect because the Maddox rod test is used to diagnose conditions such as esotropia or other strabismus types, but not specifically for assessing near heterophoria.
**Clinical Pearl / High-Yield Fact**
When assessing near heterophoria, it's essential to perform the cover test at a distance of 33-40 cm, which is the typical near point for most adults. This ensures accurate detection of deviations and helps in differentiating between esophoria and exophoria.
**Correct Answer: C. Maddox rod test is used to diagnose strabismus, not near heterophoria. However, the correct option for this question should be provided. As this option was not given, I'll give you the correct option.**