(An interview with Assistant Professor Dr. Johannes Steinberg and Professor Dr. Stephan Linke, Hamburg, hamburgvisionclinic – eyeclinic at the university hospital hamburg.

What is a „Cataract“?

Cataract is a medical term used to describe a opacity of the natural lens inside the eye. If the lens remains inside the eye, the opacity increases until the entire lens become grey or even white.
Unfortunately, the cataract is still the worlds leading cause for blindness because every human will develop a cataract but not all people are able to get the necessary medical treatment due to poverty or poor medical care especially in emerging countries.

What causes the Cataract?

The cataract can develop in every age group and can be caused by different reasons. The most frequent reason is the aging eye. In Germany, this entity usually develops after the age of 60, but it can occur prematurely in especially in countries with a lower development status for example due to an unbalanced nutrition.

How to treat the Cataract?

Currently, the only treatment is the surgical removal of the opac lens and replacing the natural lens with a clear artificial intraocular lens. In Germany, over 400.000 cataract – surgeries are conducted every year. Thereby, the cataract surgery is the most frequently performed medical surgery in Germany.

Since when Cataract surgeries are performed?

In 1949, Sir Harold Ridley implanted the first artificial intraocular lens (IOL) in London, Great Britain. Since then, the way ophthalmologists perform cataract surgery changed distinctly. Milestones were the introduction of the phacoemulsification technique whereby the lens get fragmented within the eye by using ultrasound energy and the development of foldable intraocular lenses.
Nowadays, cataract surgery is performed as microincisional surgery with incisions < 2.5mm, intraocular lens-fragmentation, – removal and implantation of a foldable intraocular lens. The incisions are self-sealing and usually need no additional sutures.


How long does the classical cataract surgery/ Femto-cataract surgery take and how safe is the procedure?

The cataract surgery takes with or without femtosecond laser assistance about 15 minutes and is usually performed in local anasthesia (eyedrops).  Applying the current standards of care, the complication rate is very low. The implementation of modern technical achievements combined with the experience over the last centuries make cataract surgery to one of the most safe surgical procedures in ophthalmic surgery.

What happens during the cataract surgery?

Currently, different methods to perform cataract surgery exist. In modern cataract surgery the most frequently used technique is a manual approach using local anesthesia (eyedrops or injections), micro-incisions (< 2.5mm) to enter the eye, a forceps to open the bag of the natural lens (capsule) and an ultrasound device to fragment and aspirate the lens inside the capsule. Following the removal of the natural lens, an artificial foldable lens is inserted into the eye and fixated within the remaining (empty) capsule of the natural lens.

You often use the femtosecond-Laser for your cataract surgeries. What is a Femto-Laser and why decided to incorporate the Femto-Laser into your surgical routine? 

The femtosecond Laser or Femto-Laser is a device, which emits light impulses for a very short (femtosecond-) fraction of time onto a exactly defined target (LASER = Light Amplification by Stimulated Emission of Radiation“). This leads to a very precise alteration of the tissue without collateral disruption of the surrounding tissue. Modern femtosecond Laser vary regarding the frequency of the laserpulses and the energy per puls. We purposely decided to use the Z8 femtosecond Laser (Ziemer Ophthalmic Systems, Switzerland). The Z8 currently uses light pulses of the highest  frequency. Thereby the Z8 can work with an extremely low energy per puls leading to unsurpassed tissue protection and precision.
The high frequency – low energy principle using femtosecond laser systems was awarded with the Nobel Price for Physics in 2018 (for more information use this link).

In Hamburg, we implemented the Femto-Laser into our cataract procedures to improve the safety of the surgery and the predicatability and precision of our outcomes. This is not only apprechiated by our patients, but also delights us in our day to day work.
Another importent circumstance is, that the implementation of the Femto-Laser doesn’t suspend the procedure: we don’t need additional anesthesia, the Laser doesn’t irritate the patient and we don’t increase the total surgery time.

The video below demonstrates the surgical steps of the femto-cataract-surgery as performed in our clinic in Hamburg.
In summary, the Laser prepares the self-sealing incisions through the cornea, opens the capsula bag more precise and more safe then any surgeon would be able to do and subsequently, fragments the often dense, opaque and hard intraocular lens within the capsula bag which also significantly reduces the (potentially) additional amount of applied ultrasound energy. The usage of ultrasound energie is the hallmark of the „classical“ phakoemulsification – cataract surgery. The technique of using ultrasound energy to fragment the intraocular lens is a very effective and precise approach. However, a distinct disadvantage of using ultrasound energy is the higher risk of damaging intraocular tissue like the iris, the capsula bag an especially, the innermost layer of the cornea. Due to reflecting ultrasound-waves during the usage of the device, every cornea looses endothelial cells during the procedure. These cells can’t regenerate or regrow. Therefore, saving intraocular fragile structures is one of the main reasons for the attempts of constantly improving cataract surgery.
Another reason to improve the safety of the procedure is the increasing desire of the patients to achieve a good uncorrected visual acuity after the surgery. This can be enabled by implanting ‚premium‘ lenses like multifocal and/or toric and/or EDOF-lenses (see more here). These lenses should only be implanted, if an intact capsula bag exists. Further, the lens should be perfectly centered and a longtime staple position should be warranted to enable a good and stable visual quality.  and the number of implanted ‚premium lenses‘ t efforts to  of the reasons for constant improvement of the procedure.
Last but not least, in patients with a small amount of corneal astigmatism, we use the Femto-Laser to reduce this refractive disorder by performing arcuate laser-incision directly within the corneal tissue to enable the cornea to reshape into a more symmetrical morphology.

How realistic is a good visual acuity without glasses after cataract surgery?

It’s absolute realistic. To achieve this goal, three things are important:

I) A thorough examination of the eye and an in-depth evaluation of the expectations and requirements of the patient in her/ his day-to-day life.
II) An exact pre-surgical biometry (measurement/ scan of the eye) to select the optimal IOL power and assess potential pre-surgical refractive errors.
III) A technically precise and medically complication-free cataract surgery.

To lay the foundation for an on the one hand realistic and on the other hand technically optimal result, we conduct a thorough pre-surgical assessment (patient – doctor consultation), scan the eyes with a highly precise device using different technical approaches (Scheimpflug-Scan, Placido-Scan, OCT-Scan) by using Galilei G6 biometry (Ziemer Ophthalmic Systems, Switzerland) and perform the cataract surgery with the addition of the Z8 femtosecond laser system (Ziemer Ophthalmic Systems).

What are the differences regarding the lens material and what are the criteria to decide which lens to implant? 

Nowadays, several different lenses exist to customize the refractive outcome of the cataract surgery.
One basic criteria are material related aspects, meaning technical properties of the lens which only indirectly influence the refractive outcome, the other important criteria is the choice of the refractive characteristics of the lens which directly influence the visual acuity and quality after the cataract surgery.

First the material related characteristics:
In this respect, we don’t make any compromises when performing cataract surgery in our clinic. If we replace the natural lens with an artificial one, we always implant lenses of the highest quality in regard to their material properties based on the current scientific data and our personal assessment.

All of the lenses implanted in our clinic display the following characteristics :

-foldable acrylic lenses: This material features a high biocompatibility, is highly elastic so it can be implanted through selfsealing corneal microinsisions of less then 2.4 mm and presents a very high stability ensuring a steady position after the surgery.

-aspheric lens design: The optical surface of an apspheric lens differs from a spheric lens in regard of its ability to focus the passing light on one precise spot. If the lens has a spherical surface, the outermost parts of the optic refract passing parallel light rays stronger then the more central parts. Thereby the overall-focus of the lens becomes diffuse/ blurred. In aspheric lens designs, the outermost parts of the lenses are designed in a way, that the entire light passing the lens gets refracted in one precise focus.
We further optimize the visual quality by precisely measuring refractive errors of the cornea before the surgery. Thereby we can choose the best aspheric lens design for every patient (i.e. the asperic lenses are not only able to compensate for their own refractive errors as explained above, but are also able to negate corneal refractive abberations). The benefit for the patient is a higher quality of vision with a better contrast vision and less glare and halo at night.

-strong ultraviolet (UV) filter:  The natural lens acts as a strong UV-filter. The liftetime-cumulative dosage of UV-light is a known risc factor for retinal/ macula diseases like the age related macula degeneration (AMD).
All of the lenses implanted at the hamburgvisionclinic feature specilized UV-filter systems to avoid an unnecessary UV exposure of the retina.

-optimized capsula opacification protection: The intraocular lens (IOL) gets implanted into the capsula bag. In all eyes after cataract surgery, the capsula bag develops a partially dens opacification. To decrease the risc of a central opacification, we only implant lenses with a special „edge-design“ at the back-surface, which impedes cells from migrating into and thereby reducing the clarity of the optical zone.

And what are the differences regarding the refractive lens designs?

Nowadays several options regarding the lens design exist which directly impact the visual acuity without glasses after the surgery. These choices should be adressed during the patient – doctor conversation before the day of surgery.

Available refractive lens designs/ principles are:

-Monofocal lenses: Monofocal lenses provide the highes possible visual quality with the least possible amount of unwanted halos and contrast sensitivity reduction. The downside of this lens technology is the necessarily of glasses to shift the focus/ area of sharp vision. They designed to provide high quality of vision in one distance. Usually they are calculated for best far-vision which means the patient needs glasses for near and intermediate distance (reading + PC-distance).

-EDOF lenses: EDOF stands for „extended depth of focus“. Different to the monofocal lenses, these IOLs provide very good visual quality and acuity without glasses in far and intermediate (PC-) distance. Whenever the depth of focus increases (more areas of sharp vision), also the scatter of light increases leading to more halos/ glare when looking at artificial light sources („lamps“) when it’s dark (big pupils). The EDOF lens combines a high range of high visual acuity without glasses (far to pc-distance) with only slightly increased night-time halos. These lenses are perfect for patients who love to drive their car (good visual acuity in far- and dashboard-distance) or work a lot on the PC. But, in situations where good near distance visual acuity is wanted, reading glasses has to be used. To achieve perfect visual acuity, 20% of the patients need corneal laser vision correction (like LASIK treatment) after the cataract surgery to eliminate small amount of refractive error. At the hamburgvisionclinc we implant high-quality EDOF IOL manufactured by Zeiss.

-Multifocal lenses (MIOL): The MIOL are EDOFs with the addition of good near visual acuity without glasses, i.e. good visual acuity without glasses in every distance. This enables the patient to enjoy her/ his day-to-day life without glasses. The downside are increased halos/glare at night and a slightly decreases contrast sensitivity when the surrounding light intensity decreases. Therefore they are a very good choice for people who like to be completely free of glasses during their everyday life, but not ideal for people who loves to drive at night (glare) or want to go hunting in the woods after the sunset. To achieve perfect visual acuity, 20% of the patients need corneal laser vision correction (like LASIK treatment) after the cataract surgery to eliminate small amount of refractive error. At the hamburgvisionclinc we implant high-quality MIOL manufactured by Zeiss.

-Toric lenses: Toric lenses are designed to reduce the toric (=asticmatic) refractive errors of the cornea. Both monofocal and EDOF, as well as MIOL can be manufactured as toric lenses. Therefore, toric lenses are not an own lens-‚identity‘ but more a technical addition to the refractive IOL designs explained above.
In toric, as well as in EDOF and MIOL lenses, a precisely centered and stable implantation of the IOL is  of outermost importance. Therefore we implant these ‚premium‘-lenses only as part of a femto-cataract surgery (–> the manual approach leads to a nonavoidable decreased precision of the surgery/ outcome).
If the corneal astigmatism befor cataract surgery is only small (between 0.75 and 1.25 diopters), we routinely use the Femto-Laser to reduce this refractive disorder by performing arcuate laser-incision directly within the corneal tissue to enable the cornea to reshape into a more symmetrical morphology. If the corneal astigmatism is > 1.25 diopters, the implantation of a toric IOL results in a superior predictability of the refractive result.