Tip failure occurs more rapidly where the tip begins with flaws, particularly where the optical output of the fiber is distorted. Most instructions for reproducing fiber tips are crude and non-scientific; “stripping and cleaving” instructions found on the internet, within other fiber manufacturers’ websites and IFUs typically yield highly variable and suboptimum results.
The following guide represents best practices in producing fiber working tips and is based upon the science of Fracture Mechanics. It is provided as a supplement to the full ProFlex™ LLF IFU and is intended for use by non-surgical personnel who are routinely charged with reproducing working tips on reusable laser surgical fibers. Refer to the product IFU for full cleaning, reprocessing and sterilization instructions.
Reproducing ProFlex™ LLF Fiber Working Tips
APPROPRIATE FOR REPROCESSING REUSABLE PRODUCTS, ONLY
You must strip the fiber buffer before scoring the fiber in order to produce a safe working tip; controlling the depth of the score is impossible when scoring through the thick fluoropolymer buffer and produces an insufficient length of ‘bare’ fiber for testing the safety of the stripped fiber (see test, below).
Recommended tools for stripping and cleaving fibers may be ordered from your authorized ProFlex™ distributor, or directly from InnovaQuartz (IQ). Check with your IQ sales representative for additional information, e-mail email@example.com or call 1-844-ProFlex (toll free). The following tools are recommended for stripping and cleaving ProFlex™ laser fibers.
IT IS IMPORTANT TO USE THE PROPER TOOL FOR A PARTICULAR FIBER
Verify the stripping tool is appropriate for the fiber size. Tools from other manufacturers and other manufacturers’ fibers may appear quite similar and labeled fiber sizes are often misleading, e.g. many “200 micron” laser fibers are actually 273 micron core and most “400 micron” laser fibers are actually 365 micron core. Even similar sizes of ProFlex™ fibers are difficult to differentiate without reference to the laser inscribed model number on the fiber connector, e.g. ProFlex 200 and ProFlex 273 have very similar total diameters (blue Tefzel®) but require different size stripper blades (see table below). Refer to the table.
For superior results, IQ recommends using Sapphire™ brand scoring wafers (P/N: 5-1001S1MED). Like diamond cleavers, the honed edge of Sapphire wafers produce superior cuts versus standard cleaving stones but both do wear rapidly if misused and both require experience to achieve superior results. If standard scoring wafers are preferred, IQ recommends our double length laser ruled scoring wafer (P/N: 3-8012P) for ease or orientation, tip length determination, smooth scribing action and handy QR CODE link to detailed instructions for stripping and cutting fibers. (Samples included with select ProFlex products.)
Autoclavable Stripping and Cutting Tools
Sapphire Brand Scoring Wafer
STRIPPING THE BUFFER
It is helpful to wear finger cots or rubber (nitrile) gloves when reproducing fiber tips.
Hold the stripper tool in one hand and the fiber in the other.
With the handles fully open, insert the fiber into the fiber guide at the front of the stripper until the fiber tip extends roughly to the 5 cm or 2 inch mark on the ruled handle.
If the fiber cannot be inserted into the fiber guide, the buffer may be melted or ragged, interfering with passage. Remove a short section of fiber and try again. If the problem persists, check that the guide is the proper size. If it is, the presumed fiber buffer diameter may be incorrect. Call the manufacturer for help or measure the buffer diameter and compare to the fiber guide size (guides are sized in inches).
Squeeze the handles closed and keep them closed while twisting the fiber slightly within the blades (twisting is optional and produces a cleaner buffer cut, but it does add to the risk of nicking the fiber so it may be omitted until one has greater familiarity with the tools and techniques).
With the handles still squeezed close, withdrawal the fiber from the tool as straightly as possible. Withdrawal of the fiber at an angle relative to the stripper axis risks scratching the fiber coating (secondary cladding) or nicking the fiber itself.
TEST THE STRIPPED SECTION FOR DAMAGE
(this simple test minimizes tip detachment problems)
While bare fingers are illustrated for clarity, please use some protection in performing this maneuver because the bare fiber tip may be very, very sharp. When sufficient fiber has been stripped to permit flexure about the buffer parting line (bare to buffer), one may use the maneuver illustrated or some other method to flex the fiber about the parting line, simulating surgical stresses in all axes (360 degrees of rotation). If the fiber was nicked, it will break. If it was not nicked, this maneuver causes no damage what-so-ever to the fiber.
There are numerous ways in which a fiber may be damaged in stripping. In addition to those touched upon above, blades become misaligned (reseat them with the white plastic tool provided with the stripper), contaminated, damaged and worn (clean or replace them) or may be mismatched. (Blades come as matched sets and cannot be mixed.) A fiber that is nicked in stripping is at least hundreds of fold more likely to break in use than pristine fiber.
If the fiber breaks, first seat the blades, strip and test again. If the fiber continues to break, replace the blades with a fresh set.
CLEAVING THE FIBER
A diamond or ruby or sapphire scoring blade is perfect for scoring surgical fibers, but they are somewhat expensive and are easily damaged by novices (too much pressure chips the precious gem edge). Scoring wafers are popular because they are inexpensive and, with sufficient practice, reasonable cuts can be produced, but the edges are square so a very wide score line is produced in the glass using these simple tools. Consider using IQ’s Sapphire™ brand scoring wafers with the diamond-honed edge as an alternative to diamonds.
The goal of scoring the fiber is to produce a micrometer-scale flaw in the glass cladding and just a single flaw. This goal is defeated on all fronts by dragging a scoring wafer across a fiber and sharpened scoring instrument will be heavily damaged by dragging. Regardless of the type of edge you choose to use, simply press it onto the fiber with sufficient pressure to part the transparent plastic coating (the thin, clear secondary cladding) and nick the fiber. This is best accomplished if the fiber is on a clean, hard surface and is best practiced several times for each fiber size using scrap fiber material. Illuminating the fiber with a laser aiming beam, or with a tool like IQ’s Scoring Aid™ (SMA-equipped flashlight), aids scoring by lighting-up the score line when it forms within the glass cladding.
Only make a single attempt to score the fiber. Multiple scores will favor multiple fracture origins and fracture planes.
Hold the buffered (blue) fiber in one hand and the stripped portion, beyond the score mark, in the other hand. DO NOT BEND THE FIBER ABOUT THE SCORE LINE; Pull the fiber apart. Fractures propagate at right angles to the applied force. Bending the fiber applies forces at multiple angles whereas pulling the fiber apart applied force solely along the fiber axis, perpendicular to the desired fracture plane.
INSPECT THE NEW TIP
Appropriate magnification is essential when inspecting the working tip. A binocular microscope is ideal but maybe cumbersome, at least at first. A jeweler’s loupe is adequate if it is of appropriate magnification: 30X minimum for small core fibers, e.g. IQ P/N 3-5030A. Video vision systems may function as well. Lighting from an oblique angle that reflects from the fiber face is ideal for visually inspecting the fiber tip.
Inspect the fiber tip for glass protrusions from the cleaved plane known as ‘tangs’ or the inverse of chips. Glass protruding from the fiber tips will scratch or puncture the working channel of your scope and may hang-up in passage. Ideally, the fiber face will be flat and free of chips and score marks that extend into the fiber’s core. The fiber’s glass cladding is 15 μm thick on smaller fibers and up to 45 μm thick on the largest fibers.
Check the fiber output for distortion by connecting the fiber to a laser with an aiming beam (or use our Scoring Aid™). Hold the fiber a few centimeters from a light surface and examine the output pattern. A circular and symmetric spot, without ‘comet tails’, indicates a good cleave. Comet tails occur where there are chips or tangs present that extend into the core. Non-circular or asymmetric brightness indicates a non-planar cleave or multiple cleave planes are present.
Less than perfect cleaves are often accepted as adequate, particularly for small fibers, with the rationalization that the fiber tip will become damaged fairly quickly in use. Damage does occur more rapidly on small core fibers than on large core fibers, but damage from use is favored at flaws and inefficient coupling between the fiber tip and the surgical target due to flaws favors accelerated damage. With a bit of practice you will find production of efficient tips is relatively simple and that efficient fiber tips offer safer initial scope passage and last longer than poorly prepared tips.