Keratoconus

Disease Description (Causes and Symptoms)

• Definition summary: Keratoconus is a non-inflammatory, progressive corneal disease that causes decreased vision as the cornea gradually becomes thinner and the central or near-central area protrudes, forming a cone shape. It often occurs asymmetrically in both eyes, usually begins around puberty, and progresses actively in the 20s and 30s. The prevalence has been reported to be approximately 0.15%–0.6%.
• Causes/pathophysiology: A genetic predisposition (family history) is suspected, but no single gene has been confirmed. Atopy, repeated eye rubbing, excessive contact lens use, excessive ultraviolet exposure, and hormonal changes can act as aggravating factors. Structural weakening of the corneal stroma (such as collagen instability) causes increased curvature and thinning, and in severe cases, a Descemet membrane rupture may lead to corneal hydrops (acute keratoconus).
• Main symptoms:
  • Early stage: Changes in eyeglass prescription (increasing myopia and astigmatism), with gradually progressing decreased vision
  • As it progresses: Visual distortion due to irregular astigmatism, glare, halos, double vision, and decreased night vision
  • Complications: Acute corneal hydrops (sudden decrease in vision and pain), permanent visual impairment due to corneal scarring

Treatment Methods

• Conservative/corrective treatment
  • Early stage: Eyeglasses (for mild cases), toric (astigmatism) lenses
  • Advanced astigmatism: RGP (rigid gas-permeable) lenses, scleral lenses, which are more comfortable than hard lenses (covering the ocular surface to provide comfort), and customized specialty contact lenses
• Mechanical and surgical treatment
  • Corneal collagen cross-linking (CXL): Uses riboflavin + UV-A to cross-link corneal collagen and inhibit progression. It is widely performed as a standard treatment for progressive keratoconus. (Indications and contraindications exist, including minimum corneal thickness.)
  • Intracorneal ring (intracorneal ring segments, e.g., Keraring): Partially flattens the corneal curvature to improve refractive error. Used to improve vision in some patients.
  • Epithelium–stroma-sparing surgery: Deep anterior lamellar keratoplasty (DALK) — replaces the corneal epithelium and stroma while preserving the endothelium, thereby reducing the risk of immune rejection.
  • Penetrating keratoplasty (PK): Performed in cases of severe opacity or structural damage. Immune rejection and long-term management are necessary after transplantation.
  • Depending on the case, corneal reshaping (epithelial management) or conservative treatment for acute corneal hydrops (controlled intraocular pressure, hyperosmotic solutions, bandage contact lenses, etc.) may be used; surgical treatment is rarely necessary.
• Other procedures
  • Topography-guided laser (PRK) combined with CXL (selective): The amount of corneal ablation must be considered. LASIK is contraindicated in keratoconus because it can weaken the cornea.
• Self-care and precautions
  • Do not rub the eyes (increases the risk of progression)
  • Manage allergies/atopy (antihistamines, eye drops, etc.)
  • When using contact lenses, visit an ophthalmologist regularly and manage insertion, removal, and wearing time
  • Protect against ultraviolet exposure (sunglasses)
  • Before refractive surgery (such as LASIK), always undergo corneal topography/tomography testing
• Risk of complications
  • Corneal hydrops (Descemet membrane rupture), corneal scarring, rejection after transplantation (especially PK), and lens-related adverse effects (surface damage and infection)

Checklist Before an Outpatient Visit (Including Example Questions)

• Items to prepare/organize in advance
  • A list of all medications currently being taken (including oral medications and eye drops)
  • Records of previous ophthalmic surgeries/tests (LASIK/LASEK, contact lens prescriptions, corneal transplantation, etc.)
  • Existing eyeglass and contact lens prescriptions (and bring the lenses if possible)
  • A record of recent vision changes (when they began and how quickly they changed)
  • History of allergies/atopy and whether there is a habit of rubbing the eyes
  • If available, printed copies or files of previous corneal topography and Pentax/Pentacam (tomography) results
• Precautions for contact lens wearers: Contact lens use must be discontinued before the visit for accurate testing
  • Soft lenses: Usually 1–2 days to 1–2 weeks (follow the hospital's instructions)
  • RGP/hard lenses: Usually 2–4 weeks (follow the medical institution's instructions)
• Common example questions to ask the medical staff during the visit
  • Example symptom questions: "When did your vision start changing?", "Has only one eye gotten worse?", "Are your eyes very itchy, or do you rub them frequently?"

General Example Questions to Ask the Doctor

• Is this condition progressive? Is there a way to stop its progression?
• What are the effects and side effects of corneal cross-linking (CXL), such as pain, vision changes, and infection?
• If my vision can no longer be corrected with lenses (or glasses), when should surgery, including transplantation, be considered?
• I have never had refractive surgery such as LASIK/LASEK. Could I undergo it in the future?

Disease-Specific Example Questions

• Among my corneal tomography (or Pentacam) measurements, what are Kmax (maximum curvature) and minimum corneal thickness (pachymetry), and what do these values mean? What are the criteria for determining progression (e.g., the amount of increase in Kmax and the criteria for thickness reduction)?
• Do I meet the indications for CXL (corneal cross-linking)? If it is performed, what are the minimum corneal thickness requirements and other contraindications (e.g., severe opacity or active infection)?

(Note: The period for discontinuing contact lens use before testing and the surgical indications and prognosis may vary depending on the hospital, equipment, and the patient's condition, so confirm specific instructions with the ophthalmology department you will visit.)