viscoelastics

Our Views on viscoelastics

First - Viscoelastics are not absolutely necessary for cataract surgery.

Routine ECCE procedures do not require the use of viscoelastics, if proper oculopression is performed before surgery.

The introduction of Phacoemulsification made the use of viscoelastics mandatory.

We at LA LABS produce both popular types of viscoelastics, the ones containing Sodium Hyaluronate (or Hyaluronic Acid – HA), such as LA LON and also the HPMC (Methyl Cellulose) based solutions, such as LA GEL and LA VISC. We have no interest in positioning, nor promoting one type over the other.

In our opinion, Viscoelastics are liquid surgical instruments, with the following functions during cataract surgery:

- The creation and maintenance of space in the anterior chamber for manipulation
- The protection of cells and tissues during the operation
- The manipulation of tissues
- The lubrication of tissues, instruments and implants

Almost all viscoelastics on the market today are adequate, and perform their function well.

The choice of a viscoelastic is based almost excessively on the personal preference of the surgeon. It is formed primarily during the initial surgical training. This preference can change due to new surgical techniques, new materials and implants, opinions from fellow surgeons, scientific publications, advertisements and price considerations.

Viscoelastics are designed with two customers in mind: the patient and the surgeon. They have to provide a benefit to both.

HA based viscoelastics are cohesive, therefore they do not adhere to the endothelial cells providing little or no protection, resulting in higher levels of post operative corneal edema. However they are easy to remove, and therefore produce smaller post operative pressure spikes.

HPMC based viscoelastics are adhesive, providing a far better protection to the endothelial cells. Due to their adhesivity, they are more difficult to remove. Residual amounts of viscoelastic can cause pressure spikes postoperatively.

There are two types of HPMC based viscoelastics:

- The first generation, low viscosity solutions,like LA VISC, which represent a challenge to surgeons who are used to the high viscosity and cohesivity of HA based materials.

- The second generation, high viscosity HPMC based viscoelastics, like LA GEL are easier to get accustomed to by HA users, since they have a similar viscosity to what they are used to.

The big difference in using HPMC over HA based viscoelastics, is the necessity to completely remove the material from the eye at the end of the surgery. It requires a different technique, since the material adheres to various structures inside the eye.

It seems to be a choice between corneal edema and post operative pressure spikes.

The ideal solution - in our opinion - is to use both materials, combining their advantages, while canceling out their disadvantages. We believe that the optimal method is to combine the two materials in the following way:

- For the opening of the capsule and during the phacoemulsification we recommend a high viscosity, adhesive HPMC solution, like LA GEL. The high viscosity will provide a precise control during capsulorhexis, while the adhesive properties of the material will cause the creation of a protective layer over the endothelial cells, significantly reducing trauma from the microprojectiles launched by the ultrasound and accelerated by the turbulent flow of the irrigating solution in the anterior chamber. By the time the phacoemulsification is complete, most of the viscoelastic will be gone due to the irrigation - aspiration, eliminating the need for removal.

- For the IOL implantation and for the inflation of the capsular bag, we recommend a cohesive, Sodium Hyaluronate based solution, like LA LON. Due to the cohesivity this viscoelastic is easy to remove after the lens is in place.

The above described combination of viscoelastic materials is practiced by quite a few ophthalmologists. It combines the advantages of superior endothelial protection with ease of removal at the end of the surgery, while avoiding the shortfalls of both kind of materials.

We would welcome your comments after trying our recommendation. It would help us in our effort to continually improve our product, and to develop new products, which could further enhance the safety and efficiency of intraocular surgery.

Please send your comments to:

GENERAL INNOVATIONS

7334 Hollister Avenue, Suite i

Goleta, CA 93117 USA

Tel: +1 (805) 685-9991

Fax: +1 (805) 685-1292

E-mail: gimsg@earthlink.net