Hi lybrate-user. Conjunctivitis is usually caused by infection or allergy of the conjunctiva (the white portion that is visible in the eye). Iridocyclitis tends to affect the iris and the ciliary muscle of the eye. Iridocyclitis, as you mentioned, may occur due to trauma or in certain infections. It should be taken seriously. Trauma may cause inflammation in the eye, which in turn could affect the iris (the structure that gives the eye its color). Iridocyclitis may cause pain, blurring of vision, and redness. If it is of traumatic origin, it would usually not affect the other eye. On the other hand, conjunctivitis has more chances of spreading to the other eye if proper hygiene is not maintained. Rubbing both eyes with fingers or using handkerchief to wipe both eyes could result in spread of the conjunctivitis from one eye to the other. Let me know if you require further assistance.