Pain in the back of the head with eye pain considers elevated intraocular pressure, visual fatigue, or inadequate blood supply to the brain as the cause.
High intraocular pressure, such as glaucoma, will present with headache with orbital pain and may be accompanied by blurred vision.
Visual fatigue is mostly due to lack of sleep and excessive eye use, and may manifest as headache with eye pain and weakness.
Inadequate blood supply to the brain such as cervical spondylosis, cerebral atherosclerosis, etc.