A 68-year-old female patient is seen on the ward. She complains of severe pain in her right eye. There is blurring of vision and she feels nauseated and has vomited several times. Earlier in the day she has undergone colonoscopy for evaluation of her long-standing Crohn’s disease. The endoscopist has made a comment that the examination was difficult. What is the likely cause of her painful red eye?

**Core Concept**
The patient's symptoms are likely due to a complication of the colonoscopy procedure, specifically related to the endoscope's manipulation and pressure on the globe of the eye. This condition is associated with the endoscope's tip and is a recognized risk of the procedure.

**Why the Correct Answer is Right**
The patient's symptoms are consistent with a diagnosis of retrobulbar hemorrhage, also known as endoscopic retrobulbar hemorrhage. This condition occurs when the endoscope or its tip is pressed against the eye, causing a hemorrhage in the retrobulbar space. The pressure on the globe of the eye can lead to bleeding in the surrounding area, resulting in severe pain, blurred vision, nausea, and vomiting. The endoscopist's comment that the examination was difficult suggests that the procedure may have been more forceful than usual, increasing the risk of this complication.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a retrobulbar hemorrhage is not typically associated with an anterior chamber reaction, which would be more consistent with an uveitis or iritis. The symptoms and signs of a retrobulbar hemorrhage are more related to the posterior segment of the eye.
**Option B:** This option is incorrect because a central retinal artery occlusion would typically present with sudden loss of vision in one eye, often described as a curtain coming down over the field of vision. While it can cause severe pain, the symptoms and signs of a retrobulbar hemorrhage are more consistent with this patient's presentation.
**Option C:** This option is incorrect because a subconjunctival hemorrhage would present with a bright red patch on the surface of the eye, often without significant pain or vision disturbances. The symptoms and signs of a retrobulbar hemorrhage are more severe and involve the posterior segment of the eye.

**Clinical Pearl / High-Yield Fact**
Retrobulbar hemorrhage is a recognized complication of colonoscopy and other endoscopic procedures, particularly when the endoscope's tip is pressed against the globe of the eye. It is essential for endoscopists to be aware of this risk and take steps to minimize the pressure on the eye during the procedure.

**Correct Answer:** C.

✓ Correct Answer: D. Acute angle closure glaucoma