OM t of c.iii - Vision Research Coordinating Center - Washington ...

2/1/99 Chapter 2 Study Design page 2-5
Eye Council stated,
Council believes that relatively little is known about the natural progression of
keratoconus and that focusing on an observational study looking at the general
experience of individuals with this disorder is perhaps of greater scientific merit
than that of the proposed clinical trial. A study designed to obtain information on
progression may provide the most valuable information on keratoconus. The
investigators are likely to be able to retain many scientific aspects of the current
application and incorporate these into a more general observational study. Council
recognizes the outstanding team of investigators and the well developed manual of
operations.
2.4 Patient Eligibility
2.4.1 Inclusion Criteria
If all of the following conditions are satisfied, the patient is eligible for the study:
• Age: At least 12 years old
• Irregular corneal surface in either eye determined by distortion of keratometric mires,
of the retinoscopic reflex, or of the red reflex.
• Either Vogt’s striae in the deep stroma or Fleischer’s ring of at least 2 mm of arc or
corneal scarring characteristic of keratoconus in either eye.
• Able to complete at least 3 years of follow-up.
2.4.2 Exclusion Criteria
If a patient has the following s/he is excluded from the CLEK Study:
• Bilateral corneal transplants
• Non-keratoconic ocular disease in both eyes: cataract, intraocular lens implant,
macular disease, optic nerve disease other than glaucoma (eg, optic neuritis, optic
atrophy)
2.4.3 Rationale for Inclusion and Exclusion Criteria
2.4.3a Age
To be eligible a patient must be at least 12 years old.
The age of onset of keratoconus is typically cited as the second or third decade of
life (Krachmer, 1984). It is rare to see the disease in children under the age of 10 years.
2.4.3b Corneal Irregularity