Understanding Primary Polypseudophakia.
Primary polypseudophakia is a relatively recent concept in ophthalmology.
Optically, polypseudophakia would be considered a special intraocular
lens consisting of two rotationally symmetric elements. The first
report of the placement of two intraocular lens implants back-to-back
(piggyback) in a highly hyperopic eye was by Jim Gills, MD in 1993.
With dramatic advances in foldable lens technology allowing for
small, self-sealing incisions, this procedure originally gained
a qualified general acceptance. However, the previous practice
of stacking two acrylic lenses in the capsular bag has since been
abandoned due to occasional problems with interlenticular opacification
and reduced visual acuity.
When the calculated IOL power exceeds that available, and placement
of a single IOL would result in an unacceptable refractive outcome,
it is often worthwhile for the surgeon to place two IOLs in the
eye at the same operative session. This is typically seen in patients
with axial lengths less than 20.00 mm, and often with a hyperopic
spherical equivalent of +8.00, or greater.
With current technology, the preferred approach is to place two
IOLs of different materials in different locations (e.g., a lower
power, thin, biconvex silicone lens in the ciliary sulcus and a
higher power negative shape factor acrylic lens in the capsular
This is commonly referred to as primary
polypseudophakia. With the recent introduction of very high
power, foldable, aspheric, hydrophobic acrylic IOLs available
in powers up to +40.00 D (SA60AT - Alcon Laboratories, Ft. Worth,
Texas), the need for primary polypseudophakia should become less
Secondary polypseudophakia would be something like
a piggyback IOL to correct a refractive surprise months or years
after the original surgery.
Follow this link for an example on how to do IOL
Power Calculations for Polypseudophakia.