There are many causes for a red eye and most people get very alarmed on seeing a very red eye. This article hopes to share some information about the common causes for a red eye and what one should do after developing a red eye. Before we go into the causes and the a development of a red eye, lets briefly look at the anatomy of the eye in the picture below.
The eye is like a ball made of the tough sclera (white part of the eye) all around except in the very front of the eye where the transparent cornea is attached. The front part of the sclera is covered by the protective conjunctiva which folds under the eyelids. The conjunctiva has a rich supply of blood vessels and they open up whenever there is an irritation and make the eye red.
The cornea is the transparent window that allows the light inside the eye. The amount of light allowed in is controlled by the iris and its central opening called the pupil. The lens of the eye which is biconvex focuses the light on to the fovea , an area on the retina where light is transduced into electric impulses that are carried by the optic nerves for interpretation in the brain.The retina is the inner most layer (of nerves) inside of the sclera and is separated from the sclera by the vascular choroid layer.
The eye is an extremely sensitive organ and the body does everything to protect it. Therefore any irritation which may be due to injury, abrasions, allergy, infection immediately stimulates an increase in the blood flow into the eye to help contain and repair the damage sustained. So a red eye is an indicator that all is not well with the eye.
So when should you go immediately to an Ophthalmologist or to a Eye hospital?
You need to go immediately to an eye hospital if you have severe pain in the eye or if your vision is impaired or if your pupils are irregular. There are 6 conditions that should make you seek help immediately.
1. Severe conjunctivitis : the eyes would be red, painful and with a lot of pus like discharge from the affected eyes.
2. Corneal ulcer is an extremely painful condition and can happen due to accidentally touching the eye, rubbing the eye or due to some caustic fluid splash on the eye or due to herpetic infection. The eye will be red with excessive tearing and patient would find it difficult to open eye and look at light.
3. Uveitis – is when the iris and the ciliary body are inflamed due to an infection or any other condition. The eye will be red, painful with visual loss and inability to look into the light (Photophobia). On examination the pupils could be small and irregular and pus collection inside the eye may be made out (Hypopyon)
4. Acute angle closure glaucoma – can happen with those with farsightedness.The eye is filled with fluid that must be circulated. For many reasons when the drainage of this fluid is blocked the pressure increase inside the eye leading to the condition. The eye of such a person is red, very painful, vision is blurry, and nausea and vomiting may happen. On examination the cornea may be hazy and the pupil is dilated.
5. Herpes Zoster ophthalmicus- is a condition when the ophthalmic division is affected by the Varicella zoster virus (which causes chicken pox). Much after the initial chicken pox is overcome, the virus comes out of hiding along certain nerves to produce small vesicles on the skin. When this process affects the eye, it is a ophthalmic emergency.
6. Scleritis – also shows up with red painful eye with visual loss.
The way to approach a red eye when there are no worry signs is as follows-
1.Look out for discharge from the eye-if there is no discharge it could be sure to a sub conjunctival bleed which is usually seen in an elderly patients who may be on blood thinners and might have strained hard recently (or even after a bout of violent coughing or sneezing) This can
happen suddenly and may be noticed after a overnights sleep leading to severe anxiety.
2. If the discharge happens only intermittently- it could because of dry eyes, again something that is common in the elderly. Dry eyes can happen after prolonged screen times and in conditions such as Sjögren’s syndrome. Using artificial tears eye drops will make things much better.
3. If the discharge is continuous – to see if the discharge is watery or purulent (pus like).Pus like discharge always indicates infection and will get better with antibiotics (eye drops and tablets). If the watery eye discharge is associate with mild itching, it could be due to viral conjunctivits and if the itching is severe, it could be due to allergic conjunctivitis.
Take home message:
1. If the red eye is very painful, with visual loss and irregular pupil – rush to the Eye doctor/hospital.
2. If the red eye is not or minimally painful, with clear vision, mild irritation and discharge – you can probably wait till the next day before going to see an ophthalmologist.
3. If you are very anxious or in doubt – see the ophthalmologist immediately.