keratoconus

Introduction

Progressive thinning & rounding of cornea forming a cone shape.

Etiology

• inherited corneal abnormality (7%)
• eye injury, i.e., excessive eye rubbing or wearing hard contact lenses for many years
• eye diseases
  • retinitis pigmentosa
  • retinopathy of prematurity
  • vernal keratoconjunctivitis
• systemic diseases
  • Leber's congenital amaurosis
  • Ehlers-Danlos syndrome type VI
  • Down syndrome
  • osteogenesis imperfecta
• other
  • ADHD increases risk in males due to excessive eye rubbing

Epidemiology

• most common corneal dystrophy in the U.S.
• prevalence 50-230 per 100,000
• more prevalent in teenagers & adults in their 20s

Pathology

• progressive non-inflammatory thinning of the corneal stroma
• middle of the cornea thins & gradually bulges outward, forming a rounded cone shape
• abnormal curvature changes the cornea's refractive power, producing moderate to severe distortion (astigmatism) & blurriness (nearsightedness) of vision
• 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

• generally affects both eyes
• initially, vision can be corrected with eyeglasses
• as the astigmatism worsens, patient must rely on specially fitted contact lenses to reduce the distortion

Management

• finding a comfortable contact lens can be an extremely f frustrating & difficult process
• poorly fitting lens could further damage the cornea & make wearing a contact lens intolerable
• corneal transplantation
  • 90% succesful in patients with advanced keratoconus
  • 80% patients have 20/40 vision or better
• prognosis
  • in most cases, the cornea will stabilize after a few years without ever causing severe vision problems
  • in 10-20%, the cornea will eventually become too scarred or will not tolerate a contact lens

More general terms

• sign/symptom
• corneal disease (keratopathy)

Patient information

keratoconus patient information

Database

• OMIM: https://mirror.omim.org/entry/148300
• OMIM: https://mirror.omim.org/entry/