- Blurry Vision:
Blurry vision is often associated with serious ocular disease. When your doctor checks your vision, even during a routine eye exam, it is a simple, quick way to determine the health of the eye. If a patient can read the 20/20 line on the eye chart with ease, that at least tells the doctor that light is being focused on the retina fairly accurately and the retina is processing the information correctly. However, if your eye is red and your vision is blurry, something significant is going on. If the source of the redness is making your vision blurry, than something is interfering significantly with your visual system. On the other hand, if your vision is blurry without associate redness, then one can determine fairly quickly that the vision may be blurry because your prescription may not be up to date.
- Severe Pain:
Conjunctivitis may produce mild irritation or scratchiness, but not extreme pain. Severe pain is a symptom of keratitis, a corneal ulcer, iridocyclitis, or acute open-angle glaucoma. Severe pain should always be evaluated as soon as possible.
Photophobia, or extreme sensitivity to light, is usually a symptom of iritis. Iritis is an inflammatory disorder of the eye in which the ciliary muscle becomes inflamed and begins to spasm, causing the eye to feel sensitive to light.
- Colored Halos:
Colored halos are a symptom of corneal edema and acute open-angle glaucoma. Usually halos seen around lights are caused by a disruption in the optical system of the eye. The cornea, the clear dome light structure on the front part of the eye, becomes thicker, due to the swelling, or edema. As it thickens, it also becomes cloudy. When this occurs, light scatters and we see halos.
Source: R. Douglasss Cullom, Jr., Benjamin Chang, The Wills Eye Manual Office and Emergency Diagnosis and Treatment of Eye Disease, 2nd edition. Rev. ed. of: Wills Eye Hospital Office and Emergency Room Diagnosis and Treatment of Eye Disease, 1990. ISBN 0-397-51380-1. Chapter Differential Diagnosis of Ocular Symptoms, Pages 1-6 and Differential Diagnosis of Ocular Signs; Pages 7-17.