Keratoconus Updates
Keratoconus
A gradually advancing ocular condition characterized by the progressive thinning of the cornea, leading to its transformation into a conical shape. This pathological alteration in corneal structure is indicative of a condition that evolves over time, resulting in the cornea assuming a cone-like configuration.
Defined as:
Abnormal posterior ectasia
Abnormal corneal thickness distribution
Clinical non-inflammatory corneal thinning
Abnormal topography
Skew deviation, corneal curvatures >48D, and hemi-meridional steepening
Abnormal posterior shape
Diagnosing Keratoconus
Prevalence
Older studies claim 1:2000
Newer studies show: 1:375
Prevalence is increasing with the advancement of diagnostic equipment
Risk factors
Family history has been shown to be #1 in studies
Genetic testing can be performed via buccal swab
Eye rubbing
Recurrent trauma to the cornea causes weakness
Eye rubbing may be due to blepharitis, contact lens use, atopic disease.
Treating these conditions may decrease eye rubbing
Men > women
Ethnicity
Asian, Pacific Islander, Middle eastern
Younger age group
Associated with systemic conditions such as:
Down syndrome
Marfans
Sleep apnea
Connective tissue disorders
Signs / Symptoms
Blurred vision
Shadowing
Poor quality of vision from glare/ haloes
Frequent prescription changes
Increase in myopia, astigmatism, or an oblique axis
Diagnostic Equipment
Corneal topography
Anterior elevation map
Presence of egg shaped mires, skewed radial axis of astigmatism, or a lazy 8 bow tie pattern can indicate signs of keratoconus
Corneal tomography
Anterior and posterior elevation map
Allows for early stage diagnosis
Posterior elevation map usually affected first in keratoconus
Anterior segment OCT
Epithelial thickness mapping
Pachymetry
Corneal thickness less than 500um
Not repeatable or accurate
Corneal hysteresis
Reduced central corneal thickness creates compromised corneal hysteresis
Aberrometry
Higher order aberrations cause glare and haloes that are common in keratoconus
Retinoscopy
Scissoring of light reflex
Treatment options for Keratoconus
“Anyone with progressive ectasia should undergo crosslinking, no matter what age or level of vision”
Progressive Keratoconus Clinical Study Definition
Increase of >/ 1.00D in steepest keratometry value or simK
Increase of >/1.00D in regular astigmatism evaluated by subjective manifest refraction
A myopic shift of >/0.50D on subjective manifest refraction
A decrease >/0.1mm in back optical zone radius in rigid contact lens wearers
Corneal Cross Linking
Stabilizes cornea
Indications:
Progressive keratoconus
Corneal ectasia following refractive surgery
Procedure:
The procedure involves epithelial removal, 30 minutes of riboflavin, and 30 minutes 365nm UVA light exposure
Minimum of 400 microns of intraoperative corneal thickness required
Goal: riboflavin and reactive oxygen species interact in cornea to form crosslinks and stiffens cornea
Not advised during pregnancy or in patients with conditions that may affect corneal healing
Glasses
Reserved for early-stage keratoconus, does not provide the best corrected visual acuity in advanced cases
Contact lenses
Soft contact lenses
Unable to customize these lenses but can be successful in early stages of keratoconus
Hybrid contact lenses
A gas-permeable lens with a soft contact lens skirt
More stable than a traditional GP lens, more comfortable, and lower adaptation period
Gas permeable contact lenses
Better optics than soft contact lenses but are uncomfortable and in some cases can be unstable
Scleral lenses
Improved comfort, stable optics, and customizable
Corneal transplant
Last resort for when contact lenses provide insufficient vision or the patient can no longer tolerate lenses
The information above is a summary of the CE on Demand course "The Continuum of Care for Keratoconus: The OD with the Most Toys Wins." Click here to watch the course and earn 1 hour of free CE!
