Raccoon eye/eyes (also known in the United Kingdom and Ireland as panda eyes) or periorbital ecchymosis is a sign of basal skull fracture or subgaleal hematoma, a craniotomy that ruptured the meninges, or (rarely) certain cancers. Bilateral hemorrhage occurs when damage at the time of a facial fracture tears the meninges and causes the venous sinuses to bleed into the arachnoid villi and the cranial sinuses. In layman's terms, blood from skull fracture seeps into the soft tissue around the eyes. Raccoon eyes may be accompanied by Battle's sign, an ecchymosis behind the ear. These signs may be the only sign of a skull fracture, as it may not show on an X-ray. They may not appear until up 2–3 days after the injury. It is recommended that the patient not blow their nose, cough vigorously, or strain to prevent further tearing of the meninges.

Raccoon eyes may be bilateral or unilateral. If bilateral, it is highly suggestive of basilar skull fracture, with a positive predictive value of 85%. They are most often associated with fractures of the anterior cranial fossa.

Raccoon eyes may also be a sign of disseminated neuroblastoma or of amyloidosis (multiple myeloma).

Depending on cause, raccoon eyes always require urgent consultation and management, that is surgical (facial fracture or post-craniotomy) or medical (neuroblastoma or amyloidosis).

Some of the adverse outcomes associated with intra-operative injuries include:

- Increased length of stay. This is due to ophthalmology consults required, associated infections and treatment.

- Increased costs. This is due to increased length of stay, cost of treating the complications.

- Pain and discomfort for the patient. Corneal abrasions are extremely painful for the patient and the treatment consists of drops and ointments applied in the eye which may cause further discomfort for the patient.

It is usually caused by allergies or viral infections, often inciting excessive eye rubbing. Chemosis is also included in the Chandler Classification system of orbital infections.

If chemosis has occurred due to excessive rubbing of the eye, the first aid to be given is a cold water wash for eyes.

Other causes of chemosis include:

- Superior vena cava obstruction, accompanied by facial oedema

- Hyperthyroidism, associated with exophthalmos, periorbital puffiness, lid retraction, and lid lag

- Cavernous sinus thrombosis, associated with infection of the paranasal sinuses, proptosis, periorbital oedema, retinal haemorrhages, papilledema, extraocular movement abnormalities, and trigeminal nerve sensory loss

- Carotid-cavernous fistula - classic triad of chemosis, pulsatile proptosis, and ocular bruit

- Cluster headache

- Trichinellosis

- Systemic lupus erythematosus (SLE)

- Angioedema

- Acute glaucoma

- Panophthalmitis

- Orbital cellulitis

- Gonorrheal conjunctivitis

- Dacryocystitis

- Spitting cobra venom to the eye

- High concentrations of phenacyl chloride in chemical mace spray

- Urticaria

- Trauma

- Post surgical

- Rhabdomyosarcoma of the orbit

Corneal abrasions are the most common injury; they are caused by direct trauma, exposure keratopathy/keratitis

or chemical injury.

An open eye increases the vulnerability of the cornea to direct trauma from objects such as face masks, laryngoscopes, identification badges, stethoscopes, surgical instruments, anaesthetic circuits, and drapes.

Exposure keratopathy/keratitis refers to the drying of the cornea with subsequent epithelial breakdown.

When the cornea dries out it may stick to the eyelid and cause an abrasion when the eye reopens.

Chemical injury can occur if cleaning solutions such as povidone-iodine (Betadine), chlorhexidine or alcohol are inadvertently spilt into the eye, for example when the face, neck or shoulder is being prepped for surgery.

Therefore, the anaesthetist ensures that the eyes are fully closed and remain closed throughout the procedure. Seemingly trivial contact can result in corneal abrasions and the risk of this occurring is markedly increased if exposure keratopathy is already present.

Corneal abrasions can be excruciatingly painful in the postoperative period, may hamper postoperative rehabilitation and may require ongoing ophthalmological review and after care. In extreme cases there may be partial or complete visual loss.

Iatrogenic injury of the eyelids is also common. Bruising (frequently) and tearing (rarely) of the eyelid can occur when the adhesive dressing used to hold the eye closed is removed. Removal of eyelashes can also occur.

A study in Austria found over the course of the testing, a total of 154 cases of "Acanthamoeba" keratitis. The age of the positive tests ranged from 8 to 82 years old and 58% of the people were female. The data showed that 89% of the infected patients were contact lens wearers and 19% required a corneal transplant.

Chemosis is the swelling (or edema) of the conjunctiva. It is due to the oozing of exudate from abnormally permeable capillaries. In general, chemosis is a nonspecific sign of eye irritation. The outer surface covering appears to have fluid in it. The conjunctiva becomes swollen and gelatinous in appearance. Often, the eye area swells so much that the eyes become difficult or impossible to close fully. Sometimes, it may also appear as if the eyeball has moved slightly backwards from the white part of the eye due to the fluid filled in the conjunctiva all over the eyes except the iris. The iris is not covered by this fluid and so it appears to be moved slightly inwards.

A determination of the prevalence of anisometropia has several difficulties. First of all, the measurement of refractive error may vary from one measurement to the next. Secondly, different criteria have been employed to define anisometropia, and the boundary between anisometropia and isometropia depend on their definition.

Several studies have found that anisometropia occurs more frequently and tends to be more severe for persons with high ametropia, and that this is particularly true for myopes. Anisometropia follows a U-shape distribution according to age: it is frequent in infants aged only a few weeks, is more rare in young children, comparatively more frequent in teenagers and young adults, and more prevalent after presbyopia sets in, progressively increasing into old age.

One study estimated that 6% of those between the ages of 6 and 18 have anisometropia.

Notwithstanding research performed on the biomechanical, structural and optical characteristics of anisometropic eyes, the underlying reasons for anisometropia are still poorly understood.

Anisometropic persons who have strabismus are mostly far-sighted, and almost all of these have (or have had) esotropia. However, there are indications that anisometropia influences the long-term outcome of a surgical correction of an inward squint, and vice versa. More specifically, for patients with esotropia who undergo strabismus surgery, anisometropia may be one of the risk factors for developing consecutive exotropia and poor binocular function may be a risk factor for anisometropia to develop or increase.

Hypertropia may be either congenital or acquired, and misalignment is due to imbalance in extraocular muscle function. The superior rectus, inferior rectus, superior oblique, and inferior oblique muscles affect the vertical movement of the eyes. These muscles may be either paretic, restrictive (fibrosis) or overactive effect of the muscles. Congenital cases may have developmental abnormality due to abnormal muscle structure, usually muscle atrophy / hypertrophy or rarely, absence of the muscle and incorrect placement.

Specific & common causes include:

- Superior oblique Palsy / Congenital fourth nerve palsy

- Inferior oblique overaction

- Brown's syndrome

- Duane's retraction syndrome

- Double elevator palsy

- Fibrosis of rectus muscle in Graves Disease (most commonly inferior rectus is involved)

- Surgical trauma to the vertical muscles (e.g. during scleral buckling surgery or cataract surgery causing iatrogenic trauma to the vertical muscles).

Sudden onset hypertropia in a middle aged or elderly adult may be due to compression of the trochlear nerve and mass effect from a tumor, requiring urgent brain imaging using MRI to localise any space occupying lesion. It could also be due to infarction of blood vessels supplying the nerve, due to diabetes and atherosclerosis. In other instances it may be due to an abnormality of neuromuscular transmission, i.e., Myasthenia Gravis.

Keratoconjunctivitis sicca is relatively common within the United States, especially so in older patients. Specifically, the persons most likely to be affected by dry eyes are those aged 40 or older. 10-20% of adults experience Keratoconjunctivitis sicca. Approximately 1 to 4 million adults (age 65-84) in the USA are effected.

While persons with autoimmune diseases have a high likelihood of having dry eyes, most persons with dry eyes do not have an autoimmune disease. Instances of Sjögren syndrome and keratoconjunctivitis sicca associated with it are present much more commonly in women, with a ratio of 9:1. In addition, milder forms of keratoconjunctivitis sicca also are more common in women. This is partly because hormonal changes, such as those that occur in pregnancy, menstruation, and menopause, can decrease tear production.

In areas of the world where malnutrition is common, vitamin A deficiency is a common cause. This is rare in the United States.

Racial predilections do not exist for this disease.

Exophoria is a form of heterophoria in which there is a tendency of the eyes to deviate outward. During examination, when the eyes are dissociated, the visual axes will appear to diverge away from one another.

The axis deviation in exophoria is usually mild compared with that of exotropia.

Exophoria can be caused by several factors, which include:

- Refractive errors - distance and near deviation approximately equal.

- Divergence excess - exodeviation is more than 15 dioptres greater for distance than near deviation.

- Convergence insufficiency - near exodeviation greater than distance deviation.

These can be due to nerve, muscle, or congenital problems, or due to mechanical anomalies. Unlike exotropia, fusion is possible in this condition, causing diplopia to be uncommon.

Any intense exposure to UV light can lead to photokeratitis. Common causes include welders who have failed to use adequate eye protection such as an appropriate welding helmet or welding goggles. This is termed "arc eye", while photokeratitis caused by exposure to sunlight reflected from ice and snow, particularly at elevation, is commonly called "snow blindness". It can also occur due to using tanning beds without proper eyewear. Natural sources include bright sunlight reflected from snow or ice or, less commonly, from sea or sand. Fresh snow reflects about 80% of the UV radiation compared to a dry, sandy beach (15%) or sea foam (25%). This is especially a problem in polar regions and at high altitudes, as with every thousand feet (approximately 305 meters) of elevation (above sea level), the intensity of UV rays increases by four percent.

Neurological causes for photophobia include:

- Autism spectrum disorders

- Chiari malformation

- Occipital Neuralgia

- Dyslexia

- Encephalitis including Myalgic encephalomyelitis aka Chronic fatigue syndrome

- Meningitis

- Trigeminal disturbance causes central sensitization (hence, multiple other associated hypersensitivities. Causes can be bad bite, infected tooth, etc.

- Subarachnoid haemorrhage

- Tumor of the posterior cranial fossa

Causes of photophobia relating directly to the eye itself include:

- Achromatopsia

- Aniridia

- Anticholinergic drugs may cause photophobia by paralyzing the iris sphincter muscle.

- Aphakia (absence of the lens of the eye)

- Blepharitis

- Buphthalmos (abnormally narrow angle between the cornea and iris)

- Cataracts

- Coloboma

- Cone dystrophy

- Congenital abnormalities of the eye

- Viral conjunctivitis ("pink eye")

- Corneal abrasion

- Corneal dystrophy

- Corneal ulcer

- Disruption of the corneal epithelium, such as that caused by a corneal foreign body or keratitis

- Ectopia lentis

- Endophthalmitis

- Eye trauma caused by disease, injury, or infection such as chalazion, episcleritis, glaucoma, keratoconus, or optic nerve hypoplasia

- Hydrophthalmos, or congenital glaucoma

- Iritis

- The drug isotretinoin (Accutane/Roaccutane) has been associated with photophobia

- Optic neuritis

- Pigment dispersion syndrome

- Pupillary dilation (naturally or chemically induced)

- Retinal detachment

- Scarring of the cornea or sclera

- Uveitis

Photokeratitis can be prevented by using sunglasses or eye protection that transmits 5–10% of visible light and absorbs almost all UV rays. Additionally, these glasses should have large lenses and side shields to avoid incidental light exposure. Sunglasses should always be worn, even when the sky is overcast, as UV rays can pass through clouds.

The Inuit, Yupik, and other Arctic peoples carved snow goggles from materials such as driftwood or caribou antlers to help prevent snow blindness. Curved to fit the user's face with a large groove cut in the back to allow for the nose, the goggles allowed in a small amount of light through a long thin slit cut along their length. The goggles were held to the head by a cord made of caribou sinew.

In the event of missing sunglass lenses, emergency lenses can be made by cutting slits in dark fabric or tape folded back onto itself. The "SAS Survival Guide" recommends blackening the skin underneath the eyes with charcoal (as the ancient Egyptians did) to avoid any further reflection.

The causes of TSPK are currently not yet well known.

However, there seem to be indications that dysfunctioning of the Meibomian gland can cause the condition. Inflammation of the meibomian glands (also known as meibomitis, meibomian gland dysfunction, or posterior blepharitis) causes the glands to be obstructed by thick waxy secretions. Besides leading to dry eyes, the obstructions can be degraded by bacterial lipases, resulting in the formation of free fatty acids, which irritate the eyes and sometimes cause punctate keratopathy.

Strabismus can be seen in Down syndrome, Loeys-Dietz syndrome, cerebral palsy, and Edwards syndrome. The risk is increased among those with a family history of the condition.

Keratoconjunctivitis sicca is uncommon in cats. Most cases seem to be caused by chronic conjunctivitis, especially secondary to feline herpesvirus. Diagnosis, symptoms, and treatment are similar to those for dogs.

Refractive errors such as hyperopia and Anisometropia may be associated abnormalities found in patients with vertical strabismus.

The vertical miscoordination between the two eyes may lead to

- Strabismic amblyopia, (due to deprivation / suppression of the deviating eye)

- cosmetic defect (most noticed by parents of a young child and in photographs)

- Face turn, depending on presence of binocular vision in a particular gaze

- diplopia or double vision - more seen in adults (maturity / plasticity of neural pathways) and suppression mechanisms of the brain in sorting out the images from the two eyes.

- cyclotropia, a cyclotorsional deviation of the eyes (rotation around the visual axis), particularly when the root cause is an oblique muscle paresis causing the hypertropia.

Thygeson's superficial punctate keratopathy (TSPK; also "Thygeson Superficial Punctate Keratitis") is a disease of the eyes. The causes of TSPK are not currently known, but details of the disease were first published in the Journal of the American Medical Association in 1950 by the renowned American Ophthalmologist, Phillips Thygeson (1903–2002) - after whom it is named.

According to the US National Institute for Occupational Safety and Health, computer vision syndrome affects about 90% of the people who spend three hours or more a day at a computer.

Another study in Malaysia was conducted on 795 university students aged between 18 and 25. The students experienced headaches along with eyestrain, with 89.9% of the students surveyed feeling any type of symptom of CVS. Americans spend an average of 8 hours a day in front of a screen, whether that be a television screen, phone/tablet, or a computer screen. This has increased the prevalence of individuals affected by computer vision syndrome.

Congenital heterochromia is usually inherited as an autosomal dominant trait.

In segmental heterochromia, sometimes referred to as sectoral heterochromia, areas of the same iris contains two completely different colors.

Segmental heterochromia is rare in humans; it is estimated that only about 1% of the population have it.

Diplopia has a diverse range of ophthalmologic, infectious, autoimmune, neurological, and neoplastic causes.

People of all ages who have noticeable strabismus may experience psychosocial difficulties. Attention has also been drawn to potential socioeconomic impact resulting from cases of detectable strabismus. A socioeconomic consideration exists as well in the context of decisions regarding strabismus treatment, including efforts to re-establish binocular vision and the possibility of stereopsis recovery.

One study has shown that strabismic children commonly exhibit behaviors marked by higher degrees of inhibition, anxiety, and emotional distress, often leading to outright emotional disorders. These disorders are often related to a negative perception of the child by peers. This is due not only to an altered aesthetic appearance, but also because of the inherent symbolic nature of the eye and gaze, and the vitally important role they play in an individual's life as social components. For some, these issues improved dramatically following strabismus surgery. Notably, strabismus interferes with normal eye contact, often causing embarrassment, anger, and feelings of awkwardness, thereby affecting social communication in a fundamental way, with a possible negative effect on self esteem.

Children with strabismus, particularly those with exotropia (an outward turn), may be more likely to develop a mental health disorder than normal-sighted children. Researchers have theorized that esotropia (an inward turn) was not found to be linked to a higher propensity for mental illness due to the age range of the participants, as well as the shorter follow-up time period; esotropic children were monitored to a mean age of 15.8 years, compared with 20.3 years for the exotropic group. A subsequent study with participants from the same area monitored congenital esotropia patients for a longer time period; results indicated that esotropic patients "were" also more likely to develop mental illness of some sort upon reaching early adulthood, similar to those with constant exotropia, intermittent exotropia, or convergence insufficiency. The likelihood was 2.6 times that of controls. No apparent association with premature birth was observed, and no evidence was found linking later onset of mental illness to psychosocial stressors frequently encountered by those with strabismus.

Investigations have highlighted the impact that strabismus may typically have on quality of life. Studies in which subjects were shown images of strabismic and non-strabismic persons showed a strong negative bias towards those visibly displaying the condition, clearly demonstrating the potential for future socioeconomic implications with regard to employability, as well as other psychosocial effects related to an individual's overall happiness.

Adult and child observers perceived a right heterotropia as more disturbing than a left heterotropia, and child observers perceived an esotropia as "worse" than an exotropia. Successful surgical correction of strabismus—for adult patients as well as children—has been shown to have a significantly positive effect on psychological well-being.

Very little research exists regarding coping strategies employed by adult strabismics. One study categorized coping methods into three subcategories: avoidance (refraining from participation an activity), distraction (deflecting attention from the condition), and adjustment (approaching an activity differently). The authors of the study suggested that individuals with strabismus may benefit from psychosocial support such as interpersonal skills training.

No studies have evaluated whether psychosocial interventions have had any benefits on individuals undergoing strabismus surgery.