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

2/1/99 Chapter 1 Background page 1-13
occur at a rate of 8 to 39% (Keates and Falkenstein, 1972; Chandler and Kaufman, 1974;
Sayegh et al., 1988; Sharif and Casey, 1991). Recent evidence has shown endothelial cell
loss five years after corneal transplant (Bourne et al., 1994). Less frequent, but visionthreatening
complications include wound dehiscence, endophthalmitis, iris injury,
synechia formation, glaucoma, cataract formation, and operative suprachoroidal
hemorrhage (Brown and Tragakis, 1971; Binder et al., 1975; Sharif and Casey, 1991).
Because of these significant risks and the protracted recovery rate, keratoplasty is one of
the last steps considered in the management of keratoconus.
Contact lens intolerance and/or poor vision are the primary indications for
surgery (Dana et al., 1990), whether epikeratoplasty or penetrating keratoplasty.
However, several studies have demonstrated that a substantial proportion of patients
(68%) with moderate to advanced keratoconus (corneal curvature of 50 to 60 D) who
were referred because of poor vision or contact lens intolerance can be successfully fit
with contact lenses. Smiddy et al. (1988) report that 87% of 115 consecutive keratoconus
patients could be fit with contact lenses. Forty-four percent of eyes that eventually had
keratoplasties needed three or fewer contact lens changes over a 5 year period prior to
surgery. Sixty percent of 88 postoperative eyes needed contact lenses for best vision.
Keratoplasty was delayed or avoided by using contact lenses in 69% of the selected
patients of Smiddy et al. (1988) followed for an average of 5 years and in 95% of 64
patients of Kastl et al. (1987) followed for up to 20 years. Moreover, Belin et al. (1988)
have noted that 47 of 61 eyes of 33 patients with keratoconus that had been previously
diagnosed as contact lens intolerant could be successfully fitted. Smiddy et al. (1988)
conclude that while “successful [contact lens] wear requires significant commitment on
the part of the patients and contact lens fitter, ... those undergoing keratoplasty require
at least a similar degree of care and commitment.” Moreover, although the costs of
numerous follow-up visits and a large number of contact lens fittings over a long period
of time are not negligible, they compare favorably with the costs of even an
uncomplicated surgical procedure. Furthermore, potential surgical complications can be
avoided altogether.
Those patients who go on to penetrating keratoplasty spend almost a year
engaged in the surgery and tedious attendant follow-up care, typically sacrificing
functional vision for a period of 3-12 months, depending on the course of the
postoperative period. Even optically clear grafts still have refractive problems, such as
high or irregular astigmatism or anisometropia, and corneal transplantation does not
guarantee the keratoconus patient freedom from contact lens wear. After keratoplasty,
many patients continue to need to wear contact lenses for best vision (Genvert et al.,
1985; Mannis et al., 1986; Zadnik, 1988).
1.6 Treatment With Contact Lenses
Prior to the availability of modern contact lenses, keratoconus could not be