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keratoconus
Progressive thinning & rounding of cornea forming a cone shape.
Etiology:
1) inherited corneal abnormality (7%)
2) eye injury, i.e., excessive eye rubbing or wearing hard contact lenses for many years
3) eye diseases
a) retinitis pigmentosa
b) retinopathy of prematurity
c) vernal keratoconjunctivitis
4) systemic diseases
a) Leber's congenital amaurosis
b) Ehlers-Danlos syndrome type VI
c) Down syndrome
d) osteogenesis imperfecta
5) other
- ADHD increases risk in males due to excessive eye rubbing [4]
Epidemiology:
1) most common corneal dystrophy in the U.S.
2) prevalence 50-230 per 100,000
3) more prevalent in teenagers & adults in their 20s
Pathology:
1) progressive non-inflammatory thinning of the corneal stroma
2) middle of the cornea thins & gradually bulges outward, forming a rounded cone shape
3) abnormal curvature changes the cornea's refractive power, producing moderate to severe distortion (astigmatism) & blurriness (nearsightedness) of vision
4) edema & sight-impairing scarring of the tissue
Genetics:
- most often an isolated sporadic condition
- cases of autosomal dominant & autosomal recessive inheritance
- associated with defects in VSX1
- mutations of the TUBA3D gene result in autosomal dominant keratoconus-9
Clinical manifestations:
1) generally affects both eyes
2) initially, vision can be corrected with eyeglasses
3) as the astigmatism worsens, patient must rely on specially fitted contact lenses to reduce the distortion
Management:
1) finding a comfortable contact lens can be an extremely f frustrating & difficult process
2) poorly fitting lens could further damage the cornea & make wearing a contact lens intolerable
3) corneal transplantation
a) 90% succesful in patients with advanced keratoconus
b) 80% patients have 20/40 vision or better
4) prognosis
a) in most cases, the cornea will stabilize after a few years without ever causing severe vision problems
b) in 10-20%, the cornea will eventually become too scarred or will not tolerate a contact lens
General
sign/symptom
corneal disease (keratopathy)
Database Correlations
OMIM 148300
References
- Harrison's Principles of Internal Medicine, 14th ed.
Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 2189
- Keratoconus
http://www.nei.nih.gov/health/cornealdisease/index.asp#h
- NEJM Knowledge+ Ophthalmology
- Dotinga R
ADHD Tied to Keratoconus in Males.
Excessive eye rubbing is often the culprit behind higher rates of this corneal
ectasia.
MedPage Today November 9, 2023
https://www.medpagetoday.com/ophthalmology/generalophthalmology/107243