Recognizing the critical nature of instrument quality applied to the intraocular surgical environment, Mastel routinely applies ‘sub-micron metallurgy’ to the tip finishes. The metal alloy that is normally used today is titanium with small percentages of aluminum and vanadium (6% and 4% respectively). This material is difficult to machine but more importantly is tenacious in the finishing process with respect to removal of machining burrs and microscopic edge fragments. This is the source of microscopic metallic foreign bodies commonly seen in the iris postoperatively, assuming that an instrument strike has not occurred during the procedure of phacoemulsification.
We began working toward the improvement of phaco and I/A tip finishes in the late 1980’s. However, it was in the early 1990’s that major progress began to develop as we better understood the surgical application as well as how to perfect our finishing processes. This has led to major improvements in safety and efficiency during this critical phase of modern cataract surgery.
In order for our clients to better understand why our tips perform better we have documented using modern metallurgical techniques such as Scanning Electron Microscopy (SEM) and X-Ray Diffraction techniques, amongst others, to both better understand things ourselves to improve our process controls and to communicate these insights to our valued customers.
Essentially, a phaco tip is a high frequency tuning fork, as are crystals in watches or computer chips, albeit oscillating at relatively low frequencies in the 40 KiloHertz (40,000 cycles per second) range. Combining longitudinal phaco energy, where tip excursion is generally approximately 100 microns in extension, along with Ozil or other forms of metal flow and you have a very active crystallographic microstructure. The finish of the tip itself, or bevel as it is commonly called, is the business end of performance. It has often been trivialized by industry because of the ‘disposable’ nature of the product. That is not how Mastel views the picture, rather this is a high performance device that both deserves and requires special attention.
Many theories exist today as to the actual phenomena of phacoemulsification in practice. Does the tip actually have a mechanical cutting effect or is the action in front of the tip or perhaps a combination of both? Quite frankly we do not care. In practical, common sense terms, while a soft lens may appear to emulsify in advance of the tip at times, dense lenses are commonly seen moving during sculpting maneuvers which can and must imply mechanical loading at the tip. Our finishes sculpt far more smoothly and cause far less of this sculpting ‘motion’ which can be extremely beneficial where loose zonules or zonular dehiscence is a consideration.
No matter what the actual mechanism of the removal power of the tip energy, the highly focused energy of the tip movement where applied to the tissue front due to these highly finished (but not radiused) edges concentrates the forces in action far more efficiently. This leads to less energy per procedure which contributes to less heat production, possibly less corneal endothelial damage and thusly, improved safety and efficiency. The resonant frequency of the vibrating metal creates the characteristic sound when phaco power is applied and tends to sound smoother with our finishing technology in place. Another important attribute of perfect finishes is the fact that during aspiration of lens material, material can flow past the tip surfaces and into the lumen with less resistance, contributing to better control of vacuum levels, helping reduce post occlusion surge levels which can be one of the most dangerous aspects of phaco surgery.
The secret to success with our tips remains the fact that they are all hand finished using appropriate fixtures to control angles and geometry. Most companies today rely upon bulk finishing processes and are never touched by an instrument maker. This is simply a mistake and in our opinion and quite a disservice to ophthalmology.