Differential Diagnosis
- Single most likely diagnosis
- A) Afferent pupillary defect: This is the most likely diagnosis because the patient's pupils constrict to 2 mm when light is shone in the left eye, but only to 4 mm when light is shone in the right eye. This indicates a problem with the afferent pathway of the right eye, which is consistent with the patient's complaint of decreased vision in that eye.
- Other Likely diagnoses
- B) Anisocoria: Although the pupils are initially equal, the difference in pupillary constriction to light suggests a possible anisocoria. However, this is not the primary diagnosis, as anisocoria refers to a difference in pupil size, which is not the main issue here.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- None of the options directly point to a life-threatening condition that would be deadly if missed. However, it's essential to consider that an afferent pupillary defect can be a sign of a serious underlying condition, such as a tumor or multiple sclerosis, which would require prompt investigation.
- Rare diagnoses
- C) Argyll Robertson pupil: This condition is characterized by bilateral small pupils that constrict to near vision but not to light. It is not consistent with the patient's presentation, as her pupils are not small, and the issue is unilateral.
- D) Horner syndrome: This condition involves a triad of ptosis, miosis, and anhidrosis, which is not present in this patient.
- E) Tonic pupil: This condition is characterized by a dilated pupil that reacts slowly to light, which is not consistent with the patient's presentation.