Signs and symptoms of corneal abrasion include pain, trouble with bright lights, a foreign-body sensation, excessive squinting, and reflex production of tears. Signs include epithelial defects and edema, and often redness of the eye. The vision may be blurred, both from any swelling of the cornea and from excess tears. Crusty buildup from excess tears may also be present.

Corneal abrasion is a scratch to the surface of the cornea of the eye. Symptoms include pain, redness, light sensitivity, and a feeling like a foreign body is in the eye. Most people recover completely within three days.

Most cases are due to minor trauma to the eye such as that which can occur with contact lens use or from fingernails. About 25% of cases occur at work. Diagnosis is often by slit lamp examination after fluorescein dye has been applied. More significant injuries like a corneal ulcer, globe rupture, recurrent erosion syndrome, and a foreign body within the eye should be ruled out.

Prevention includes the use of eye protection. Treatment is typically with antibiotic ointment. In those who wear contact lenses a fluoroquinolone antibiotic is often recommended. Paracetamol (acetaminophen), NSAIDs, and eye drops such as cyclopentolate that paralysis the pupil can help with pain. Evidence does not support the usefulness of eye patching for those with simple abrasions.

About 3 per 1,000 people are affected a year in the United States. Males are more often affected than females. The typical age group affected is those in their 20s and 30s. Complications can include bacterial keratitis, corneal ulcer, and iritis. Complications may occur in up to 8% of people.

Symptoms include recurring attacks of severe acute ocular pain, foreign-body sensation, photophobia (i.e. sensitivity to bright lights), and tearing often at the time of awakening or during sleep when the eyelids are rubbed or opened. Signs of the condition include corneal abrasion or localized roughening of the corneal epithelium, sometimes with map-like lines, epithelial dots or microcysts, or fingerprint patterns. An epithelial defect may be present, usually in the inferior interpalpebral zone.

Corneal ulcers are extremely painful due to nerve exposure, and can cause tearing, squinting, and vision loss of the eye. There may also be signs of anterior uveitis, such as miosis (small pupil), aqueous flare (protein in the aqueous humour), and redness of the eye. An axon reflex may be responsible for uveitis formation—stimulation of pain receptors in the cornea results in release inflammatory mediators such as prostaglandins, histamine, and acetylcholine.

Sensitivity to light (photophobia) is also a common symptom of corneal ulcer.

Most cases of recurrent corneal erosion are acquired. There is often a history of recent corneal injury (corneal abrasion or ulcer), but also may be due to corneal dystrophy or corneal disease. In other words, one may suffer from corneal erosions as a result of another disorder, such as map-dot fingerprint dystrophy. Familial corneal erosions occur in dominantly inherited recurrent corneal erosion dystrophy (ERED) in which COL17A1 gene is mutated..

A reduction in visual acuity in a 'red eye' is indicative of serious ocular disease, such as keratitis, iridocyclitis, and glaucoma, and never occurs in simple conjunctivitis without accompanying corneal involvement.

Of the many causes, conjunctivitis is the most common. Others include:

"Usually nonurgent"

- blepharitis - a usually chronic inflammation of the eyelids with scaling, sometimes resolving spontaneously

- subconjunctival hemorrhage - a sometimes dramatic, but usually harmless, bleeding underneath the conjunctiva most often from spontaneous rupture of the small, fragile blood vessels, commonly from a cough or sneeze

- inflamed pterygium - a benign, triangular, horizontal growth of the conjunctiva, arising from the inner side, at the level of contact of the upper and lower eyelids, associated with exposure to sunlight, low humidity and dust. It may be more common in occupations such as farming and welding.

- inflamed pinguecula - a yellow-white deposit close to the junction between the cornea and sclera, on the conjunctiva. It is most prevalent in tropical climates with much UV exposure. Although harmless, it can occasionally become inflamed.

- dry eye syndrome - caused by either decreased tear production or increased tear film evaporation which may lead to irritation and redness

- airborne contaminants or irritants

- tiredness

- drug use including cannabis

"Usually urgent"

- acute angle closure glaucoma - implies injury to the optic nerve with the potential for irreversible vision loss which may be permanent unless treated quickly, as a result of increased pressure within the eyeball. Not all forms of glaucoma are acute, and not all are associated with increased 'intra-ocular' pressure.

- injury

- keratitis - a potentially serious inflammation or injury to the cornea (window), often associated with significant pain, light intolerance, and deterioration in vision. Numerous causes include virus infection. Injury from contact lenses can lead to keratitis.

- iritis - together with the ciliary body and choroid, the iris makes up the uvea, part of the middle, pigmented, structures of the eye. Inflammation of this layer (uveitis) requires urgent control and is estimated to be responsible for 10% of blindness in the United States.

- scleritis - a serious inflammatory condition, often painful, that can result in permanent vision loss, and without an identifiable cause in half of those presenting with it. About 30-40% have an underlying systemic autoimmune condition.

- episcleritis - most often a mild, inflammatory disorder of the 'white' of the eye unassociated with eye complications in contrast to scleritis, and responding to topical medications such as anti-inflammatory drops.

- tick borne illnesses like Rocky Mountain spotted fever - the eye is not primarily involved, but the presence of conjunctivitis, along with fever and rash, may help with the diagnosis in appropriate circumstances.

Corneal perforation is an anomaly in the cornea resulting from damage to the corneal surface. A corneal perforation means that the cornea has been penetrated, thus leaving the cornea damaged.

The cornea is a clear part of the eye which controls and focuses the entry of light into the eye. Damage to the cornea due to corneal perforation can cause decreased visual acuity.

The person experiences pain and a sudden severe clouding of vision, with the cornea taking on a translucent milky-white appearance known as a corneal hydrops.

Corneal ulcers are a common human eye disease. They are caused by trauma, particularly with vegetable matter, as well as chemical injury, contact lenses and infections. Other eye conditions can cause corneal ulcers, such as entropion, distichiasis, corneal dystrophy, and keratoconjunctivitis sicca (dry eye).

Many micro-organisms cause infective corneal ulcer. Among them are bacteria, fungi, viruses, protozoa, and chlamydia:

- Bacterial keratitis is caused by "Staphylococcus aureus", "Streptococcus viridans", "Escherichia coli", "Enterococci", "Pseudomonas", "Nocardia", "N. Gonorrhoea" and many other bacteria.

- Fungal keratitis causes deep and severe corneal ulcer. It is caused by "Aspergillus" sp., "Fusarium" sp., "Candida" sp., as also "Rhizopus", "Mucor", and other fungi. The typical feature of fungal keratitis is slow onset and gradual progression, where signs are much more than the symptoms. Small satellite lesions around the ulcer are a common feature of fungal keratitis and hypopyon is usually seen.

- Viral keratitis causes corneal ulceration. It is caused most commonly by Herpes simplex, Herpes zoster and Adenoviruses. Also it can be caused by coronaviruses & many other viruses. Herpes virus cause a dendritic ulcer, which can recur and relapse over the lifetime of an individual.

- Protozoa infection like "Acanthamoeba keratitis" is characterized by severe pain and is associated with contact lens users swimming in pools.

- "Chlamydia trachomatis" can also contribute to development of corneal ulcer.

Superficial ulcers involve a loss of part of the epithelium. Deep ulcers extend into or through the stroma and can result in severe scarring and corneal perforation. Descemetoceles occur when the ulcer extends through the stroma. This type of ulcer is especially dangerous and can rapidly result in corneal perforation, if not treated in time.

The location of the ulcer depends somewhat on the cause. Central ulcers are typically caused by trauma, dry eye, or exposure from facial nerve paralysis or exophthalmos. Entropion, severe dry eye and trichiasis (inturning of eyelashes) may cause ulceration of the peripheral cornea. Immune-mediated eye disease can cause ulcers at the border of the cornea and sclera. These include Rheumatoid arthritis, rosacea, systemic sclerosis which lead to a special type of corneal ulcer called Mooren's ulcer. It has a circumferential crater like depression of the cornea, just inside the limbus, usually with an overhanging edge.

Acutely or at the early sign includes painful, photophobic, red and watery eye. This is due to active corneal inflammation resulting in vascular invasion and stromal necrosis which can be diffuse or localized. This cause the pinkish discoloration of what was a clear transparent normal corneal tissue (called "Salmon patch of Hutchinson").

Chronically or the end result will cause blurring of vision secondary to corneal stromal scarring, presence of ghost vessel and thinning of the cornea especially if it involves the visual axis.

Neurotrophic keratitis (NK) is a degenerative disease of the cornea caused by damage of the trigeminal nerve, which results in impairment of corneal sensitivity, spontaneous corneal epithelium breakdown, poor corneal healing and development of corneal ulceration, melting and perforation.

Neurotrophic keratitis is classified as a rare disease, with an estimated prevalence of less than 5 in 10,000 people in Europe. It has been recorded that on average, 6% of herpetic keratitis cases may evolve to this disease, with a peak of 12.8% of cases of keratitis due to herpes zoster virus.

The diagnosis, and particularly the treatment of neurotrophic keratitis are the most complex and challenging aspects of this disease, as a satisfactory therapeutic approach is not yet available.

Conjunctival concretions are generally asymptomatic. Common symptoms include eye discomfort, eye irritation, and foreign body sensation. Sometimes, the larger, harder or multiple concretions make the rubbing off of the superficial layers of the conjunctiva or eyelids to cause conjunctival abrasion, especially prominent when upon blinking. In severe cases, dysfunction or inflammation of the Meibomian (Meibomianitis, an inflammation of the tarsal glands) glands may occur.

Corneal hydrops or corneal rupture is an uncommon complication seen in people with advanced keratoconus or other corneal ectatic disorders, and is characterized by stromal edema due to leakage of aqueous humor through a tear in Descemet's membrane. Although a hydrops usually causes increased scarring of the cornea, occasionally it will benefit a patient by creating a flatter cone, aiding the fitting of contact lenses. Corneal transplantation is not usually indicated during corneal hydrops.

Corneal neovascularization (CNV) is the in-growth of new blood vessels from the pericorneal plexus into avascular corneal tissue as a result of oxygen deprivation. Maintaining avascularity of the corneal stroma is an important aspect of corneal pathophysiology as it is required for corneal transparency and optimal vision. A decrease in corneal transparency causes visual acuity deterioration. Corneal tissue is avascular in nature and the presence of vascularization, which can be deep or superficial, is always pathologically related.

Corneal neovascularization is a sight-threatening condition that can be caused by inflammation related to infection, chemical injury, autoimmune conditions, post-corneal transplantation, and traumatic conditions among other ocular pathologies. Common causes of CNV within the cornea include trachoma, corneal ulcers, phylctenular keratoconjunctivitis, rosacea keratitis, interstitial keratitis, sclerosing keratitis, chemical burns, and wearing contact lenses for over-extended periods of time. Superficial presentations of CNV are usually associated with contact lens wear, while deep presentations may be caused by chronic inflammatory and anterior segment ocular diseases.

Corneal neovascularization is becoming increasingly common worldwide with an estimated incidence rate of 1.4 million cases per year, according to a 1998 study by the Massachusetts Eye and Ear Infirmary. The same study found that the tissue from twenty percent of corneas examined during corneal transplantations had some degree of neovascularization, negatively impacting the prognosis for individuals undergoing keratoplasty procedures.

Conjunctival concretions can be single, also multiple, less confluent. There is no difference between the site of the occurrence on the upper and lower eyelid, nor right or left eye. The vast majority of concretions are in the conjunctival surface rather than deep. There is no difference in age for predilection or incidence of concretions, due to the causes of conjunctivitis, aging, and even congenital factor.

Physical or chemical injuries of the eye can be a serious threat to vision if not treated appropriately and in a timely fashion. The most obvious presentation of ocular (eye) injuries is redness and pain of the affected eyes. This is not, however, universally true, as tiny metallic projectiles may cause neither symptom. Tiny metallic projectiles should be suspected when a patient reports "metal on metal" contact, such as with hammering a metal surface. Intraocular foreign bodies do not cause pain because of the lack of nerve endings in the vitreous humour and retina that can transmit pain sensations. As such, general or emergency room doctors should refer cases involving the posterior segment of the eye or intraocular foreign bodies to an ophthalmologist. Ideally, ointment would not be used when referring to an ophthalmologist, since it diminishes the ability to carry out a thorough eye examination.

Flicking sand, flying pieces of wood, metal, glass, stone and other material are notorious for causing much of the eye trauma. Sporting balls such as cricket ball, lawn tennis ball, squash ball, shuttlecock, and other high speed flying objects can strike the eye. The eye is also susceptible to blunt trauma in a fistfight. The games of young children such as bow-and-arrows, bb guns and firecrackers can lead to eye trauma. Road traffic accidents (RTAs) with head and facial trauma may also have an eye injury - these are usually severe in nature with multiple lacerations, shards of glasses embedded in tissues, orbital fractures, severe hematoma and penetrating open-globe injuries with prolapse of eye contents. Other causes of intraocular trauma may arise from workplace tools or even common household implements.

About 5.3 million cases of foreign bodies in the eyes occurred in 2013.

According to Mackie's classification, neurotrophic keratitis can be divided into three stages based on severity:

1. "Stage I:" characterized by alterations of the corneal epithelium, which is dry and opaque, with superficial punctate keratopathy and corneal oedema. Long-lasting neurotrophic keratitis may also cause hyperplasia of the epithelium, stromal scarring and neovascularization of the cornea.

2. "Stage II:" characterized by development of epithelial defects, often in the area near the centre of the cornea.

3. "Stage III:" characterized by ulcers of the cornea accompanied by stromal oedema and/or melting that may result in corneal perforation.

Corneal perforation can be diagnosed by using the Seidel test. Any aqueous leakage is revealed during the Seidel test confirms corneal perforation. A fluorescence strip is wiped over the wound. If the clear aqueous humor from the eye runs through the yellow stain, the patient tests positive for corneal perforation.

Interstitial keratitis (IK) is corneal scarring due to chronic inflammation of the corneal stroma. Interstitial means space between cells i.e. corneal stroma which lies between the epithelium and the endothelium. Keratitis means corneal inflammation.

Post-LASIK ectasia is a condition similar to keratoconus where the cornea starts to bulge forwards at a variable time after LASIK eye surgery.

Eye care during general anaesthesia is an important part of anaesthesia care. Eye injuries are reasonably common if care is not taken to prevent them.

Hypopyon is a medical condition involving inflammatory cells in the anterior chamber of the eye.

It is a leukocytic exudate, seen in the anterior chamber, usually accompanied by redness of the conjunctiva and the underlying episclera. It is a sign of inflammation of the anterior uvea and iris, i.e. iritis, which is a form of anterior uveitis. The exudate settles at the dependent aspect of the eye due to gravity. It can be sterile (in bacterial corneal ulcer) or not sterile (fungal corneal ulcer).

Before LASIK surgery, people must be examined for possible risk factors such as keratoconus.

Abnormal corneal topography compromises of keratoconus, pellucid marginal degeneration, or forme fruste keratoconus with an I-S value of 1.4 or more is the most significant risk factor. Low age, low residual stromal bed (RSB) thickness, low preoperative corneal thickness, and high myopia are other important risk factors.

People with early keratoconus typically notice a minor blurring of their vision and come to their clinician seeking corrective lenses for reading or driving. At early stages, the symptoms of keratoconus may be no different from those of any other refractive defect of the eye. As the disease progresses, vision deteriorates, sometimes rapidly. Visual acuity becomes impaired at all distances, and night vision is often poor. Some individuals have vision in one eye that is markedly worse than that in the other. The disease is often bilateral, though asymmetrical. Some develop photophobia (sensitivity to bright light), eye strain from squinting in order to read, or itching in the eye, but there is normally little or no sensation of pain. It may cause luminous objects to appear as cylindrical pipes with the same intensity at all points.

The classic symptom of keratoconus is the perception of multiple "ghost" images, known as monocular polyopia. This effect is most clearly seen with a high contrast field, such as a point of light on a dark background. Instead of seeing just one point, a person with keratoconus sees many images of the point, spread out in a chaotic pattern. This pattern does not typically change from day to day, but over time, it often takes on new forms. People also commonly notice streaking and flaring distortion around light sources. Some even notice the images moving relative to one another in time with their heart beat.

The predominant optical aberration of the eye in keratoconus is coma. The visual distortion experienced by the person comes from two sources, one being the irregular deformation of the surface of the cornea, and the other being scarring that occurs on its exposed highpoints. These factors act to form regions on the cornea that map an image to different locations on the retina. The effect can worsen in low light conditions, as the dark-adapted pupil dilates to expose more of the irregular surface of the cornea.