The incidence and prevalence of PMD are unknown, and no studies have yet investigated its prevalence or incidence. However, it is generally agreed that PMD is a very rare condition. Some uncertainty regarding the incidence of PMD may be attributed to its confusion with keratoconus. PMD is not linked to race or age, although most cases present early in life, between 20 and 40 years of age. While PMD is usually considered to affect men and women equally, some studies suggest that it may affect men more frequently.

Several diseases have been observed in patients with PMD. However, no causal relationships have been established between any of the associated diseases and the pathogenesis of PMD. Such diseases include: chronic open-angle glaucoma, retinitis pigmentosa, retinal lattice degeneration, scleroderma, kerato-conjunctivitis, eczema, and hyperthyroidism.

A pinguecula is one of the differential diagnoses for a limbal nodule. It may have an increased prevalence in Gaucher's disease.

Episcleritis is a common disease, and its exact prevalence and incidence are unknown. It typically affects young adults, and may be more common in women.

Episcleritis is a benign, self-limiting condition, meaning patients recover without any treatment. Most cases of episcleritis resolve within 7–10 days. The nodular type is more aggressive and takes longer to resolve. Although rare, some cases may progress to scleritis. However, in general, episcleritis does not cause complications in the eye. Smoking tobacco delays the response to treatment in patients with episcleritis.

Visual function declines as a result of the irregular corneal shape, resulting in astigmatism, and causing a distortion in vision. Deterioration can become severe over time.

A limbal nodule is any nodular lesion at the limbus (junction of the cornea and sclera) of the eye.

The differential diagnosis for a limbal nodule can include:

- Pinguecula

- Early Pterygium

- Foreign body / foreign body granuloma

- Phlycten, an inflamed nodule of lymphoid tissue

- Episcleritis

- Scleritis

- Granuloma

- Limbal dermoid, a kind of choristoma (NB: in other organs "dermoid" can refer to a teratoma)

- malignant melanoma

Keratoglobus continues to be a somewhat mysterious disease, but it can be successfully managed with a variety of clinical and surgical techniques. The patient is at risk for globe perforation because the thinned out cornea is extremely weak.

Keratopathy is common in older people. Keratopathy occurs after cataract surgery, its incidence has decreased since the advent of intraoperative viscoelastic agents that protect the endothelium.

It is a much rarer condition than keratoconus, which is the most common of the cornea. Similar to keratoconus it is typically diagnosed in the patient's adolescent years and attains its most severe state in the twenties and thirties.

This is a partial list of human eye diseases and disorders.

The World Health Organization publishes a classification of known diseases and injuries, the International Statistical Classification of Diseases and Related Health Problems, or ICD-10. This list uses that classification.

Treatment options include contact lenses and intrastromal corneal ring segments for correcting refractive errors caused by irregular corneal surface, corneal collagen cross-linking to strengthen a weak and ectatic cornea, or corneal transplant for advanced cases.

A pinguecula is a common type of conjunctival degeneration in the eye.

Corneal ectatic disorders or corneal ectasia are a group of uncommon, noninflammatory, eye disorders characterised by bilateral thinning of the central, paracentral, or peripheral cornea.

- Keratoconus, a progressive, noninflammatory, bilateral, asymmetric disease, characterized by paraxial stromal thinning and weakening that leads to corneal surface distortion.

- Keratoglobus, a rare noninflammatory corneal thinning disorder, characterised by generalised thinning and globular protrusion of the cornea.

- Pellucid marginal degeneration, a bilateral, noninflammatory disorder, characterized by a peripheral band of thinning of the inferior cornea.

- Posterior keratoconus, a rare condition, usually congenital, which causes a nonprogressive thinning of the inner surface of the cornea, while the curvature of the anterior surface remains normal. Usually only a single eye is affected.

- Post-LASIK ectasia, a complication of LASIK eye surgery.

- Terrien's marginal degeneration, a painless, noninflammatory, unilateral or asymmetrically bilateral, slowly progressive thinning of the peripheral corneal stroma.

Few studies have examined the prevalence of FCED on a large scale. First assessed in a clinical setting, Fuchs himself estimated the occurrence of dystrophia epithelialis corneae to be one in every 2000 patients; a rate that is likely reflective of those who progress to advanced disease. Cross-sectional studies suggest a relatively higher prevalence of disease in European countries relative to other areas of the world. Fuchs' dystrophy rarely affects individuals under 50 years of age.

CNV causes may be congenital in nature, such as with Aniridia, or acquired. Frequently, inflammatory, infectious, degenerative, traumatic and iatrogenic (from contact lenses) diseases are responsible for acquired CNV.

Some major associated, acquired inflammatory conditions include graft rejection following keratoplasty, graft or host diseases of the new tissue, atopic conjunctivitis, rosacea, ocular pemphigoid, Lyell's syndrome, and Steven's Johnson syndrome.

Infections responsible for CNV range from bacterial (chlamydia, syphilis, pseduomonas), Viral (herpes simplex and herpes zoster viruses), Fungal (candida, asperigillus, fusarium), and parasistic (onchocerca volvolus).

Degenerative diseases such as pterygiums, and terrien's marginal degeneration may be responsible.

Traumas frequently seen with CNV include ulceration, alkali burns, and stem cell deficiency.

One of the most common causes of corneal neovascularization is iastrogenic pathology from contact lens wear. This is especially true of lenses made with older hydrogel materials such as HEMA (2-hydroxyethyl methacrylate) for both daily and extended wear. Such older hydrogel materials have a relatively low oxygen transmissibility so the cornea becomes starved of oxygen leading to the ingress of blood capillaries into the clear cornea to satisfy that oxygen demand. Older estimates have 128,000 to 470,000 cases of lens-induced CNV each year, but this may be decreasing due to the increasing popularity of daily disposable lenses.

The risk for CNV is elevated in certain instances for patients following penetrating keratoplasty without active inflammation or epithelial defects. CNV is more likely to occur in those with active blepharitis, those who receive sutured knots in their host stromas, and those with a large recipient area.

Xerophthalmia usually affects children under nine years old and "accounts for 20,000-100,000 new cases of childhood blindness each year in the developing countries." The disease is largely found in developing countries like many of those in Africa and Southern Asia. The condition is not congenital and develops over the course of a few months as the lacrimal glands fail to produce tears. Other conditions involved in the progression already stated include the appearance of Bitot's spots, which are clumps of keratin debris that build up inside the conjunctiva and night blindness, which precedes corneal ulceration and total blindness.

As it is associated with excessive sun or wind exposure, wearing protective sunglasses with side shields and/or wide brimmed hats and using artificial tears throughout the day may help prevent their formation or stop further growth. Surfers and other water-sport athletes should wear eye protection that blocks 100% of the UV rays from the water, as is often used by snow-sport athletes. Many of those who are at greatest risk of pterygium from work or play sun exposure do not understand the importance of protection.

Disease begins with vesicles that coalesce. There is severe progressing edema and rupture may occur in 24 hours or less.

DLK is predominantly associated with Lasik, as the creation of a flap creates a potential space for cells to accumulate. Individuals with atopic conditions with pre-existing allergic conjunctivitis, or ocular rosacea, are more prone to developing the condition after surgery. Some authors have reported that moderate to severe eye allergies and chronic allergic conjunctivitis are an absolute contraindication to the LASIK procedure. This is in distinction to findings of earlier studies. Keratitis can also occur after photorefractive keratectomy (PRK), although because it occurs in the setting of infection, it is distinct from the sterile infiltrates of DLK. DLK can also occur following myopic keratomileusis, in which a disc of corneal tissue is removed, shaped and sutured back into place, although this technique is more historical, having been replaced by Lasik and PRK.

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.

Sclerocornea is a congenital anomaly of the eye in which the cornea blends with sclera, having no clear-cut boundary. The extent of the resulting opacity varies from peripheral to total ("sclerocornea totalis"). The severe form is thought to be inherited in an autosomal recessive manner, but there may be another, milder form that is expressed in a dominant fashion. In some cases the patients also have abnormalities beyond the eye (systemic), such as limb deformities and craniofacial and genitourinary defects.

According to one tissue analysis performed after corneal transplantation, the sulfation pattern of keratan sulfate proteoglycans in the affected area is typical for corneal rather than scleral tissue.

Sclerocornea may be concurrent with cornea plana.

Given that episodes tend to occur on awakening and managed by use of good 'wetting agents', approaches to be taken to help prevent episodes include:

- Environmental:

- ensuring that the air is humidified rather than dry, not overheated and without excessive airflow over the face. Also avoiding irritants such as cigarette smoke.

- use of protective glasses especially when gardening or playing with children.

- General personal measures:

- maintaining general hydration levels with adequate fluid intake.

- not sleeping-in late as the cornea tends to dry out the longer the eyelids are closed.

- Pre-bed routine:

- routine use of long-lasting eye ointments applied before going to bed.

- occasional use of the anti-inflammatory eyedrop FML (prescribed by an ophthalmologist or optometrist) before going to bed if the affected eye feels inflamed, dry or gritty

- use of a hyperosmotic (hypertonic) ointment before bed reduces the amount of water in the epithelium, strengthening its structure

- use the pressure patch as mentioned above.

- use surgical tape to keep the eye closed (if Nocturnal Lagophthalmos is a factor)

- Waking options:

- learn to wake with eyes closed and still and keeping artificial tear drops within reach so that they may be squirted under the inner corner of the eyelids if the eyes feel uncomfortable upon waking.

- It has also been suggested that the eyelids should be rubbed gently, or pulled slowly open with your fingers, before trying to open them, or keeping the affected eye closed while "looking" left and right to help spread lubricating tears. If the patient's eyelids feel stuck to the cornea on waking and no intense pain is present, use a fingertip to press firmly on the eyelid to push the eye's natural lubricants onto the affected area. This procedure frees the eyelid from the cornea and prevents tearing of the cornea.

Diffuse lamellar keratitis (DLK) is a sterile inflammation of the cornea which may occur after refractive surgery, such as LASIK. Its incidence has been estimated to be 1 in 500 patients, though this may be as high as 32% in some cases.

In the United States, the incidence of primary congenital glaucoma is about one in 10,000 live births. Worldwide, the incidence ranges from a low of 1:22,000 in Northern Ireland to a high of 1:2,500 in Saudi Arabia and 1:1,250 in Romania. In about two-thirds of cases, it is bilateral. The distribution between males and females varies with geography. In North America and Europe it is more common in boys, whereas in Japan it is more common in girls.

- Congenital glaucoma

- Incidence: one in every 10000-15000 live births.

- Bilateral in up to 80% of cases.

- Most cases are sporadic (90%). However, in the remaining 10% there appears to be a strong familial component.

Punctate epithelial erosions may be seen with different disorders:

- Rosacea

- Dry-eye syndrome

- Blepharitis

- Acute bacterial conjunctivitis

- Trauma

- Exposure keratopathy from poor eyelide closure

- Ultraviolet or chemical burn

- Contact lens-related disorder such as toxicity or tight lens syndrome

- Trichiasis

- Entropion or ectropion

- Floppy eyelid syndrome

- Chemotherapy i.e. cytosine arabinoside

- Thygeson's Superficial Punctate Keratopathy