Symptoms of increased intraocular pressure. Increased intraocular pressure can irritate the optic nerve and lead to optic nerve papilla edema. The main symptom is swelling and pain in the eye because once the intraocular pressure is increased it will irritate the area around the wall of the eye and it will feel like the eye is very swollen. Increased intraocular pressure can lead to headache because it compresses the optic nerve and causes pain in the trigeminal innervation area, and also stimulates the excitability of the vagus nerve, causing nausea and vomiting. Increased intraocular pressure can lead to iris, with the outer ring being red, the inner ring being violet and the middle being green, which means corneal edema and increased intraocular pressure.