Keratoconus

Keratoconus
Keratoconus-with-Munsons-sign-USA-1965.jpg
The "cone shaped cornea" that is characteristic of keratoconus
Synonyms	KC, KCN, conical cornea
Pronunciation	KEHR-uh- toh-KOH-nus
Specialty	Ophthalmology, optometry
Symptoms	Blurry vision, nearsightedness, light sensitivity
Usual onset	Early adulthood
Causes	Unknown
Diagnosis	Slit lamp exam
Treatment	Glasses, contacts, surgery
Frequency	~1 in 2,000 people

File:Kc simulation.jpg

Simulation of the multiple images

File:Kc simulation2.png

Multiple images made by extremely high contrast light sources as seen by a person with keratoconus

File:David G Cogan case 245 keratoconus thin stroma wrinkled endothelium.png

A specimen of keratoconic cornea taken out six years after diagnosis: thin stroma, wrinkled posterior surface

File:Mini Asymmetric Radial Keratotomy - MARK.jpg

Diagram of MARK incisions

File:David G Cogan collection Case 244 photo 2 keratoconus Descemet rupture.png

A small rupture of Descemet's membrane (magnified view)

Keratoconus (KC) is an ocular disorder characterized by progressive thinning of the cornea, which may lead to various vision-related complications. Notably, the condition typically affects both eyes and tends to manifest during late childhood or early adulthood. Although the exact cause remains unknown, a blend of genetic, environmental, and hormonal factors are believed to contribute to its occurrence.

Clinical Presentation

Keratoconus induces changes in the cornea's shape, transforming it into a cone-like structure. This modification in the corneal form may result in various visual disturbances, including blurry vision, double vision, nearsightedness, astigmatism, and light sensitivity. In more severe cases, corneal scarring or a visible circle within the cornea may develop.

Etiology and Risk Factors

The exact cause of keratoconus remains elusive, but the condition appears to result from a mix of genetic, environmental, and hormonal factors. Around 7% of keratoconus patients have a family history of the condition, suggesting a genetic predisposition. Proposed environmental factors that may contribute to the development of the disease include eye rubbing and allergies.

Diagnosis

Diagnosis of keratoconus typically involves examination with a slit lamp, a tool that allows for detailed inspection of the eyes' structures. Other diagnostic tests may include corneal topography and tomography, which provide a detailed view of the cornea's shape and thickness.

Management and Prognosis

The initial stages of keratoconus can often be managed with glasses or soft contact lenses, which help correct vision changes induced by the cornea's deformation. As the condition advances, special contact lenses, such as rigid gas-permeable lenses or scleral lenses, may be required.

In most patients, the disease stabilizes after a few years, preventing severe vision problems. However, a minority of individuals with keratoconus experience corneal scarring, necessitating a corneal transplantation.

Epidemiology

Keratoconus has a global distribution and affects approximately 1 in 2,000 individuals. Although it occurs across all populations, certain ethnic groups, such as those of Asian descent, may exhibit a higher prevalence. The disorder most commonly develops in late childhood or early adulthood.

Etymology

The term "keratoconus" derives from the Greek word "kéras," meaning cornea, and the Latin word "cōnus," indicating a cone — reflecting the characteristic cone-shaped deformation of the cornea in this condition.

References

• Rabinowitz YS. Keratoconus. Surv Ophthalmol. 1998 Jan-Feb;42(4):297-319. doi: 10.1016/s0039-6257(97)00119-7. PMID: 9493273.
• Krachmer JH, Feder RS, Belin MW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol. 1984 Jan-Feb;28(4):293-322. doi: 10.1016/0039-6257(84)90164-7. PMID: 6230741.
• Godefrooij DA, de Wit GA, Uiterwaal CS, Imhof SM, Wisse RP. Age-specific Incidence and Prevalence of Keratoconus: A Nationwide Registration Study. Am J Ophthalmol. 2017 Mar;175:169-172. doi: 10.1016/j.ajo.2016.12.015. Epub 2016 Dec 29.