Molecular background of endothelial cell loss in patients with phakic intraocular lenses (MoBack-ECL): a tear and aqueous humour analysis study

The number of highly myopic patients is increasing. Especially in East and
Southeast Asia, up to 90% of adolescents are currently myopic. Long-term
treatment of high myopia can be obtained by three types of surgery: laser
refractive surgery, phakic intraocular lens (pIOL) implantation, and refractive
lens exchange Implantation with a pIOL is the preferred treatment for high
myopes, resulting in increasing patient numbers implanted due to the increasing
numbers of patients with high myopia.
Long-term results show that implantation of a pIOL induces an accelerated
decrease in corneal endothelial cells (EC). Although some risk factors for
increase EC loss have been identified, the underlying mechanism is currently
unknown. It is hypothesized that the aqueous flow in the anterior segment of
the eye (i.e. anterior chamber) is disturbed, causing an altered nutritional
flow in the anterior chamber. Another hypothesis is that the pIOL causes
chronic subclinical inflammation in the anterior chamber resulting in increased
EC loss. Currently there is insufficient proof to confirm or reject either
hypothesis. If one of these hypotheses can be confirmed, it is likely to
induces significant changes in clinical practice.

The primary objective of the study is to explore the role of inflammation in
the anterior chamber on endothelial cell loss in patients implanted with
iris-fixated pIOLs. The secondary objective is to identify whether there is a
correlation between biomarkers in aqueous humour and biomarkers in tears, both
related to the accelerated progression of EC loss.

Two strategies are incorporated in the design of this study. The first part
will retrospectively evaluate EC loss in patients with iris-fixated (IF) phakic
intraocular lenses (pIOLs). The second part is prospective and will compare EC
measurements, cytokines in aqueous humour and in tears from patients scheduled
for IF-pIOLs explantation and compare them to patients with routine cataract
surgery.

In both groups preoperatively, tears will be collected using a Schirmer strip.
Schirmer strips are small paper strips which are placed behind the lower
eyelid, in the inferior fornix of the eye to absorb tear fluid. Tear collection
is non-invasive without risk for complications. During surgery, aqueous humour,
the phakic intraocular lens, and the lens capsule, will be collected, which
will not increase the burden for the patient, nor the risk of an infection.