- Rigid gas permeable (RGP) contact lens wear
- Chronic eye rubbing
- Down syndrome
- Atopic disease
- Leber congenital amaurosis
- Connective tissue disease
- Tapetoretinal degeneration
- Family history
Initial presentation typically occurs during adolescence followed by 10–20 years of progression before a stable phase is reached in the third or fourth decade of life. In general, the progression of KC is very heterogeneous but ultimately 15–20% of patients will require a corneal transplant.
- Significant and variable reduction in visual acuity ((having to change glasses frequently due to changes in refractive error)
- Image distortion
- Increased sensitivity to glare & light
Significant asymmetry reduces the ability of spherocylindrical spectacle lenses to adequately correct vision.
KC should be suspected in patients with higher degrees of astigmatism, astigmatism with oblique axis, as well as when progression in astigmatism and/or spherical refraction occurs. Steep corneal curvature and a lack of 20/20 visual acuity in a non-amblyopic eye with optimal refraction, should also raise suspicion.
Slit lamp examination:Absence of slit lamp signs of KC does not exclude absence of the disease
- Stromal thinning at cone apex
- Munson’s sign: V-shaped conformation of the lower eyelid produced by the ectatic cornea in downgaze
- Paracentral stromal scars
- Fleischer’s ring: iron deposits partially/completely surrounding the corneal cone
- Vogt’s striae: Fine vertical lines in deep stroma and Descemet’s membrane that parallel the axis of the cone
- Rizzuti’s sign: Conical reflection on the nasal cornea when a penlight is shone from the temporal side
- Corneal hydrops (severe cases): Breaks in Descemet’s membrane with stromal permeation of aqueous through these breaks
- Irregular myopic astigmatism
- Scissoring reflex
- Charleux sign: “Oil-droplet” reflex
Anterior segment optical coherence tomography (OCT):3D re-creation of the anterior segment including: anterior and posterior cornea surfaces, corneal thickness analysis, anterior iris and len
Corneal topography:Restricted to measuring only the anterior corneal surface
- Manual keratometry: Steep cornea, high astigmatism, and/or distorted mires in keratoconus
- Computerized videokeratography: Zone of increased corneal power surrounded by zones of decreasing corneal power, inferior-superior asymmetry in corneal power, and skewing of the steepest radial axes above and below the horizontal meridian
The treatment of KC depends on the severity and the rate of progression.
Spectacles (initial treatment):With progressive disease spectacles rapidly become insufficient.
Contact lenses:Right choice and correct fitting contact lenses can often provide good visual acuity in the early stages before central scarring
- Rigid Gas-Permeable (RGP) contact lenses (M/C)
- Hybrid contact lenses (rigid center and a softer periphery)
- Scleral contact lenses
- Soft contact lenses designed specifically for KC
Intracorneal ring segments (ICRS):ICRS consists of one or two semi-circle segments, operated into a surgically created tunnel in the mid corneal stroma. The ICRS are typically placed at the site of the steepest curvature and are designed to take up space in the stroma, thereby contributing to a decrease in curvature
Topography Supported Custom Ablation Photo-refractive keratotectomy (TOSCA PRK)Used in contact lenses intolerant patients, TOSCA PRK has been successfully combined with collagen cross-linking (CXL) to treat both progression and refractive error
Collagen cross-linking (CXL):Photochemical treatment of KC, consisting of loading of the corneal tissue with the photosensitizer riboflavin followed by irradiation with UVA-light. CXL has been shown to stiffen the cornea and halt the progression of KC.
Keratoplasty:Generally accepted indications for keratoplasty in kerato-conus are poor visual acuity with contact lenses, contact lens intolerance or inability to fit/wear contact lenses, and nonresolving corneal hydrops.
- Deep anterior lamellar keratoplasty (DALK)
- Penetrating keratoplasty (PK)