This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glaucoma, Subject name: Ophthalmology
All are true about blackball hyphema EXCEPT 
Select and explain. 
A. AC completely filled with bright red blood is total hyphema, blackball hyphema if dark red blood, B. Also called Eight ball hyphema, C. The black colour is suggestive of impaired aqueous circulation and decreased oxygen, D. Blackball hyphema causes less pupillary block and less angle closure
D: Blackball hyphema causes less pupillary block and less angle closure
Answer: D: Blackball hyphema causes less pupillary block and less angle closure 
Explanation: Post-traumatic hyphema is an ophthalmologic emergency that can result in permanent vision loss. Accumulation of blood in the anterior chamber causes trabecular meshwork obstruction, thereby elevating IOP. Hyphema with increased IOP can result in corneal blood staining, reduced corneal transparency, and vision loss. Hyphemas are graded by the percentage of the anterior chamber (AC) filled with blood, and range from Grade I (blood occupying <1/3 of the AC) to Grade IV (blood occupying 100 % of the AC, or "eight-ball eye").