## Core Concept
The question assesses knowledge of evaluating diplopia, particularly in the context of maxillofacial trauma. Diplopia, or double vision, can result from various injuries affecting the orbit, extraocular muscles, or the nerves controlling eye movements. Accurate assessment and documentation of diplopia are crucial for diagnosis, treatment planning, and monitoring recovery.

## Why the Correct Answer is Right
The Hess chart, also known as the Hess screen or Lancaster red-green chart, is a tool specifically designed to quantify and document the field of binocular single vision and the extent of diplopia. It works by having the patient wear red-green glasses and then point to where they see a light source on a screen with their eyes open. The results are plotted on a chart, providing a precise map of the patient's binocular vision field and accurately recording the degree and extent of diplopia. This method is particularly useful in assessing the impact of maxillofacial trauma on eye movements and in monitoring recovery.

## Why Each Wrong Option is Incorrect
- **Option A:** While a cover test can help identify strabismus (crossed eyes) and some causes of diplopia, it does not accurately record the degree of diplopia or provide a detailed assessment of the field of binocular single vision.
- **Option B:** A simple questionnaire might gather information on symptoms but lacks the specificity and sensitivity needed to accurately record the degree of diplopia, especially in cases of maxillofacial trauma where precise measurements are critical for treatment planning.
- **Option C:** Although orthoptic exercises and assessments can evaluate eye movements and binocular vision, they are not as precise as the Hess chart for accurately recording the degree of diplopia in the context of trauma.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the Hess chart is particularly valuable in clinical settings for its ability to objectively measure and document diplopia. This can be crucial not only for initial assessments but also for tracking changes over time, guiding rehabilitation, and in medico-legal documentation.

## Correct Answer Line
**Correct Answer: D. Hess chart.**