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

2/1/99 Chapter 1 Background page 1-11
Table 1-2. Summary of large-scale studies of the characteristics of keratoconus.
Study Source of
patients
%
female
% with
scarring
Conclusions
Kennedy et
al., 1986
Macsai et al.,
1990
Eggink et al.,
1988
Lass et al.,
1990
Swann and
Waldron,
1986
Mayo
Clinic
Cornea
specialty
practice
Academic
and nonacademic
clinical
centers
# of
eyes/
pts
% unilateral
cases
% w/
Vogt’s
striae
% with
Fleischer’s
ring
102/64 20 45 6 2 ?? Incidence and
prevalence, no
increased
mortality
398/199 0 44 ??* ??* ??* If cls first, then
kcn pt is older,
has central cone,
and flatter cornea
?/874 8 45 ?? ?? ?? 6% wore contact
lenses before kcn
diagnosis
Three
corneal
specialty pra
834/417 3.5 45 ??** ??** ??** 74% of patients
fitted with cls;
21% underwent
corneal surgery
Private
optometry p
87/57 9 56 46 25 2 Association of
kcn with atopy,
obesity;
low IOP;
retinoscopic
scissoring,
inferior
steepening
*Data are only available on 106 eyes of 53 patients who wore contact lenses before they were diagnosed
with keratoconus. In this group, 92.5% of eyes had either Vogt’s striae, a Fleischer’s ring, or anterior
stromal scarring.
**In this multicenter, retrospective study, the authors did not analyze these data due to a “lack of ... a
consistent description for each eye regarding ... apical scarring, presence or absence of Fleischer’s ring,
[and] Vogt’s striae.”
None of the studies cited in Table 1-2 have identified the key risk factors and
protective factors that predict whether and how keratoconus progresses. We expect that
utilizing factors that commonly define keratoconus clinically (best corrected high
contrast visual acuity, corneal curvature, corneal scarring, and mode of optical
correction), as well as less commonly described variables that may better characterize
the patient’s symptoms (best corrected and habitual low contrast visual acuity and
visual quality of life) will enable us to identify these key risk and protective factors in
both the cross-sectional and longitudinal phases of the study.
1.5 Surgical Intervention
Keratoconus patients are generally treated with contact lenses by optometrists in