Clinical Studies
Supported by the National Eye Institute
The Contact Lens and Myopia Progression (CLAMP) Study
Purpose
To examine the effects of rigid gas permeable contact lenses on the progression of myopia
(nearsightedness) in children
To determine what changes in the eyes cause certain eyes to progress in nearsightedness
more slowly
Background
Rigid gas permeable (RGP) contact lenses provide clear, comfortable vision with relatively few
ocular health risks and are a standard management option for correcting nearsightedness. While
RGP contact lenses are used to correct myopic refractive error, they may also slow the progression
of myopia. A definitive study that could provide guidance regarding the effects of rigid gas
permeable contact lenses on myopia (nearsightedness) progression may define the standard of care
for slowing the progression of myopia in young children.
An eye care practitioner first reported that hard contact lenses may slow or stop the progression of
nearsightedness in 1956. Other anecdotal clinical reports with similar results soon followed.
Previous review papers have suggested that rigid contact lenses slow the progression of myopia in
children, and several studies have attempted to prove this.
Two studies in the past twenty years have shown that rigid gas permeable contact lenses slow the
progression of nearsightedness in children, however both studies failed to provide proper attention
to many important variables. While these earlier works produced intriguing results for scientists
and clinicians, they contain many problems that challenge the significance of the studies findings.
The faults of the previous studies can be summarized in four categories: 1) high losses to follow-
up, 2) inadequate control group, 3) incomplete ocular component measurements, and 4) inadequate
or poorly selected entry criteria.
Positive results in previous studies also failed to exclude alternate possibilities which may explain
why rigid gas permeable contact lenses may slow t