Conjunctivitis: Conjunctivitis is a general term for inflammation of the conjunctival tissues and is one of the most common conditions seen in ophthalmology clinics. Although conjunctivitis does not usually affect vision, it is often symptomatic and has a variety of causes, so it requires specialized evaluation by an ophthalmologist. Conjunctival congestion: Symptoms of conjunctivitis include foreign body sensation in the eye, burning, itching, photophobia, and tearing. The most common manifestation is conjunctival congestion, or “red eye,” which can be accompanied by various types of discharge: purulent, mucopurulent (sticking to the eyelid in the morning, making it difficult to open the eye), and plasma (increased tearing). In addition, some morphological changes of the conjunctiva, such as papillae and follicles, need to be examined under the slit lamp. Depending on the duration of the disease, less than 3 weeks is considered acute conjunctivitis, while those with more than 4 weeks are considered chronic conjunctivitis. Acute conjunctivitis is mostly caused by bacterial and viral infections, while chronic conjunctivitis has more complex causes, including allergies and contact lens wear in addition to infections, and can also be caused by systemic diseases such as aspergillosis and Steven-Johnson syndrome. The majority of patients currently experiencing clinical discomfort are likely to have conjunctival discomfort due to dry eye rather than conjunctival infection per se. Most conjunctivitis can be diagnosed by history and ocular manifestations. However, in more severe cases or when conventional medications have not been effective in treating conjunctival infections, further testing is required. Conjunctival scrapings, pathogenic microbial cultures, and drug sensitivity testing can help the physician to better target medications. When a combination of systemic diseases is considered, a visit to an internal medicine or dermatology department is also needed for a thorough evaluation. If treated promptly, most patients with conjunctivitis do not develop sequelae. However, severe or prolonged conjunctival inflammation can damage the cornea and intraocular structures due to the spread of inflammation, which can affect vision; conjunctival scarring can also occur, secondary to eyelid deformities and dry eye. Therefore, it is important to visit an ophthalmologist as soon as possible when signs of conjunctivitis appear.