Refractive Lens Surgery

18
Injectable Polymer
Sverker Norrby
CORE MESSAGES
18.1 Introduction
2 The feasibility of achieving accommodation with an injectable polymer
has been demonstrated in primates.
2 Materials with the required physical, mechanical and biological
properties exist.
2 Although in some cases eyes are clear after several months, lens
epithelial cell proliferation remains an issue.
2 Indirect methods indicate that the optical quality is sufficient, but
this must be verified by direct measurement.
2 Surgical assessment methods that allow surgeons to control the
amount of material to inject must be developed.
2 Long-term stability regarding lens clarity, refraction and accommodative
range must be demonstrated in primates before this technology
is a clinical reality.
If you assume Helmholtz’ theory of accommodation,
it is a natural thought that accommodation
could be restored by replacing the
stiff presbyopic lens with a material mimicking
the young crystalline lens. Such a material
must be soft and transparent,and have a refractive
index close to that of the natural lens.
The material must further be biocompatible,
stable over time and safely confined within
the capsular bag. There must be a surgical
procedure that allows extraction of the crys-
talline lens while preserving the capsular bag.
Following injection into the capsular bag, the
bag must be able to mould the material into a
lens having the right power and sufficient
optical quality.
18.2 The Pioneers
Julius Kessler, a New York ophthalmologist,
was the first to attempt refilling the lens capsule
following endocapsular lens extraction.
In a first paper he describes lens extraction