A randomised, subject-masked evaluation of introcular lens stability after implantation of two different lens models: FEMTIS-study

Cataract is a clouding of the crystalline lens which causes vision loss and
blindness if untreated. Cataract surgery is the most frequently performed
surgical intervention in medicine with an incidence of 880 surgeries per
100.000 population in 2010 amounting to a total number of over 160.000
surgeries per year in the Netherlands.1,3 The number of individuals with
cataracts is predicted to reach 30 million by the year 2020.2 Due to aging of
the general population this number of cataracts will only grow in the future.
For the last decade conventional phacoemulsification cataract surgery
(CPCS) is the dominant form of cataract surgery in developed countries,
accounting for over 90 percent of these procedures.4 The basic
phacoemulsification procedure has remained largely unchanged over the past 20
years, including a series of steps: creating corneal incision, capsulorhexis
and lensfragmentation.4 Although highly successful, each of the steps mentioned
above are created manually which affects the safety and effectiveness of the
procedure.
Since the first human eye was treated by femtosecond laser cataract
surgery in 2008, the femtosecond-laser assisted cataract surgery (FLACS) became
an innovative growing new technology in the world of cataract surgery.4-7
Femtosecond-lasers are capable of performing some of the most delicate and
essential key steps during cataract surgery: capsulotomy, lens fragmentation,
and corneal incisions. *Automating* these steps and performing them with
increased precision could lead to an improved quality of capsulotomy, easier
lens fragmentation, and more precisely positioned corneal incisions, which in
turn, lead to improved visual and refractive outcomes, a decrease in intra- and
postoperative complication rates, and increased quality of life.
In order to remove the crystallized human lens, a circular opening in
the capsular lens bag, capsulotomy, needs to be created. After removing the
lens an intraocular lens (IOL) can be inserted in the empty capsule bag.
However, one of the factors affecting postoperative achieved visual acuity and
refraction, is the behaviour of this IOL in the capsular bag. Preoperative
measurements need to be obtained in order to calculate the required IOL. One of
the challenges of these IOL calculations is determining exactly where in the
eye the IOL will end up, the effective lens position (ELP). The position of the
IOL is crucial for the IOL*s general performance because it influences the
postoperative IOL tilt, decentration, and posterior capsule opacification
(PCO). Considering the anatomical variety between patients, the predictability
of an individual*s ELP remains an educated guess.
The ELP, and therefore the amount of IOL tilt, decentration and PCO, of
an IOL is mainly influenced by the interaction between the IOL and the lens
capsule, especially during the time of capsule shrinkage. Theoretically, the
positive optical effect of an IOL is lost when there is more than 7 degrees of
tilt or more than 0.4 mm of decentration.8 Furthermore, many studies have shown
the effect of axial displacement of an IOL on refractive error. There is
approximately 1.25 D change per millimetre of the IOL*s longitudinal
displacement.9 This reflects the importance of a stable and predictable ELP.
As mentioned above, the anatomy of an individual*s eye is unique and
therefore, each ELP will be different when placing the IOL in the capsular bag.
Therefore, a new lens type has been developed: the FEMTIS® FB-313 laser lens
(FEMTIS-IOL, Oculentis). This IOL has a special haptic system and is designed
to be clasped in the capsular bag opening and therefore, the ELP of this IOL is
theoretically more stable and predictable, resulting in a higher predictability
of refractive and visual outcomes. However, in order to provide as much
stability as possible a (nearly) perfect capsulotomy is needed. Several
comparative studies have shown that femtosecond-lasers produce a more precise,
circular, reproducible, and better centered capsulotomy compared to
conventional manual capsulorhexis.6-7 The combination between the
femtosecond-assisted capsulotomy and the implantation of a FEMTIS-IOL in the
capsular opening, could definitely contribute to the search of perfection in
cataract surgery.
In this study we will investigate the stability of lens position and
the visual outcome after implantation of the new FEMTIS-IOL using FLACS
capsulotomy compared to conventional placement of the IOL in the capsular bag.
So far, there are no published studies using the FEMTIS-IOL. Therefore, we will
perform this randomized control trial

Primary Objective:
The primary objective of this study is to compare postoperative decentration of
the FEMTIS-IOL versus a standard monofocal IOL (Acrysof monofocal IOL)

Secondary Objective(s):
The secondary objectives of this study are to compare:
- Rotation-stability
- Tilt
- UDVA
- Postoperative subjective refraction
- BCVA
- Complication profile

The study design is a single-centre randomized clinical study. The study will
be conducted at the Maastricht University Medical Centre (MUMC), the
Netherlands.

Cataract surgery with implantatie of either a FEMTIS-IOL or an Acrysof
Monofocal IOL

The pre- and postoperatively examinations to be performed in this study are
part of the regular medical treatment of patients who need cataract surgery.
Postoperatively, there will be one extra postoperative visit, compared to
standard cataract surgery follow-up.
Both the FEMTIS Laser Lens and Acrysof monofocal IOL are CE marked and
commercially available in the countries in which the study will be conducted.
The cataract surgery that will be performed in both groups is a standard
femtosecond-laser assisted phacoemulsification procedure. As with any type of
intraocular surgery, there is a possibility of complications due to
anaesthesia, drug reactions, and surgical problems. An IOP increase may occur
from the surgical procedure, residual viscoelastic in the eye, or a steroid
response to post-operative medications. Raised IOP may be controlled with
medication or non-intraocular treatment (e.g. pressure release at an existing
wound edge).
There is no additional burden or risk for the patients compared to routine
FLACS cataract surgery with implantation of a standard IOL. As mentioned above,
the early results from Holland et al. show a comparable complication profile to
standard IOL implantation.12
The possible benefits of FEMTIS-IOL implantation are a better refractive
outcome, due to less decentration, tilt, and rotation postoperative.
Furthermore, a highly predictable effective lens position provides better
refractive outcome. Centering the capsulorhexis on the visual axis might
decrease higher order aberrations, resulting in an increased postoperative
patient satisfaction.13