Link to visual requirements:
http://www.caa.co.uk/srg/med/default.asp?page=538
Mentions normal visual field amongst other requirements. So, if your visual field is abnormal then it sounds like it would rule you out. But, if your visual field is compromised then you may have bigger worries than being able to fly. Once you lose a portion of your sight due to glaucoma, you do not get it back. However, let's not forget that you may not have glaucoma.
You probably want to get touch with the CAA to clarify matters.
Best regards