Thanks Sqad although I may not be much help on this as further information would be needed such as history of symptoms, medical history, ophthalmic history etc.
First of all there are several underlying causes of optic neuritis some of which warrant immediate intervention. Optic neuritis often has marked changes to the optic nerve head when looking inside the eye and other times no visible abnormalities like retro bulbar optic neuritis. The main presenting symptoms are reduced vision, eye pain (often with movement) and reduced colour definition noticed when comparing the affected and unaffected eye.
The difficulty with a faxed referral is that the decision about the referral speed would be determined accuracy of the tentative diagnosis and extent of the clinical findings on the report. I would prefer an urgent referral to be via telephone with the patient to take the letter to the appointment.
The hospital eye clinics often have different degrees of urgency with 'immediate' referrals being the same day such as retinal detachment and acute glaucoma. An 'urgent' referral may be to be seen within two weeks at the urgent referral clinic such as wet AMD. Other referrals, like catracts etc, may be classed as routine which in some areas could be 12 weeks