Allergic conjunctivitis: This condition is characterized by increased itchiness, especially on the inner aspect of the eye, and can present with clear, crusty drainage. It is a common condition and fits well with the symptoms described, particularly the absence of vision changes and the nature of the discharge.

Dry eye syndrome: This condition can cause itchiness and irritation, and while it typically does not present with crusty drainage, it can lead to an increase in the eye's natural discharge. The absence of vision changes and the description of the symptoms make it a plausible diagnosis.
Blepharitis: Although it can sometimes mimic bacterial conjunctivitis, blepharitis can cause itchiness and irritation of the eyelids and can lead to a clear, crusty discharge. It's a common condition that could fit the described symptoms, especially if the patient experiences eyelid margin inflammation.
Vernal keratoconjunctivitis (VKC): This is a severe allergic eye condition that can cause intense itchiness, particularly on the upper inner aspect of the eye, and can be associated with clear, stringy discharge. It's more common in children and young adults and can be seasonal.

Acute angle-closure glaucoma: Although the question specifies no vision changes, this condition can sometimes present with mild symptoms initially, including eye pain, blurred vision, headache, nausea, and vomiting, but also can cause eye redness and discharge. It's a medical emergency that requires immediate attention.
Herpes simplex keratitis: This viral infection can cause eye pain, redness, and discharge, and while it typically affects the cornea, it can lead to significant morbidity if not treated promptly. The presence of clear, crusty drainage and the potential for vision changes (even if not currently present) make it a critical diagnosis not to miss.

Phlyctenular keratoconjunctivitis: This is a rare allergic condition that can cause small, nodular lesions on the conjunctiva or cornea, leading to itchiness and irritation. It's more common in children and can be associated with systemic allergies.
Giant papillary conjunctivitis (GPC): Typically associated with contact lens wear, GPC can cause intense itchiness, especially on the underside of the upper eyelid, and can lead to a clear, stringy discharge. It's less common but should be considered, especially in contact lens wearers.