Near Point of Convergence || NPC || Direct test for vergence

The near point of convergence (NPC) is a visual measurement used to assess the ability of both eyes to converge and maintain focus on a close object. It represents the closest point at which an individual can maintain single, binocular vision without experiencing double vision or eye strain.

When looking at an object up close, such as a book or a computer screen, the eyes need to converge inwardly to bring the object into focus. The NPC is the distance between the object and the eyes when the convergence is maximized and the object is still clearly seen as a single image.

Typically, the NPC is measured in centimeters (cm) or inches (in). The measurement is obtained by slowly bringing an object, like a pen or a target, towards the individual's nose until they experience double vision or the object becomes blurred. At this point, the examiner notes the distance between the object and the individual's nose as the NPC.

The NPC is an important diagnostic tool in assessing binocular vision disorders, particularly convergence insufficiency. Convergence insufficiency is a common condition in which the eyes have difficulty converging accurately, leading to symptoms like eye strain, headaches, blurred or double vision, and difficulty reading or performing close-up tasks.

By measuring the NPC, eye care professionals can evaluate the efficiency and coordination of the eye muscles, identify any abnormalities or weaknesses in the convergence system, and determine the appropriate treatment plan. Vision therapy exercises, prism lenses, or other interventions may be prescribed to improve the near point of convergence and alleviate symptoms associated with convergence insufficiency or related vision disorders.