Anatomy of an Endoscope

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Endoscope Repair Issues

By Brian Kern


Figure1: Most high quality eyepieces are mounted in place and mounted flush with the eyepiece surface.

The acquisition of a new video endoscopy system usually entails hundreds of clinical evaluation hours by doctors, nurses, and biomedical personnel testing different vendors and equipment. With the clinical capabilities of the hospital at stake, a group consensus must emerge. Yet, when the important decision to repair an endoscope is made, clinical and financial factors are often at odds. Based on a dollar calculation, the endoscope may be sent to a non-OEM (original equipment manufacturer) facility for repair. Frequently, the result is a device that doesn't function like the original, even though it still bears the manufacturer's logo.

This is regrettable, since the endoscope's optics may be compromised. The impact on the surgeon is analogous to being forced to wear eyeglasses with the wrong prescription. Poorly repaired endoscopes can have a crippling effect on the surgeon, staff and patient.

As the Technical Services Manager at a major medical device manufacturer, I work with hospital CS employees who have had their endoscopes repaired by unauthorized personnel. Endoscope lenses fall into patients mid-surgery, sharp tips inadvertently cut patient tissue, and tips burn to a molten mass during electrocautery. These are some of the calls I have fielded from non-OEM repaired endoscopes.

Understanding the functional components of an endoscope and where critical mistakes in its repair may be made -- from eyepiece to distal tip -- enables endoscope users to identify improper repairs and their potential impact on performance, patient outcomes, and hospital liability.

Despite the durable appearance of the outer steel tube, rigid endoscopes are fragile instruments that must be handled with care. Virtually all rigid endoscopes eventually require repair due to the demanding circumstances under which they are used and handled. When the shaft or light fibers become severely damaged, simple repairs become impossible, and the endoscope must be completely replaced.

In today's cost-conscious healthcare environment, it's easy to be led astray by "bargain" repairs performed by unauthorized personnel. Endoscopes may be rebuilt using generic replacement parts, that could include substandard lenses and fibers. Unlike original manufacturer repair technicians, their repair technician may not be factory-certified. As a result, additional damage may occur when trying to access the critical inner components of the endoscope.

The endoscope central services sends to an unauthorized repair facility and the endoscope returned after repair sometimes have little in common. Such "remanufactured" endoscopes often fail to meet the original manufacturer's stringent factory specifications. The warranty may become null and void when an endoscope is sent to an unauthorized firm.

Anatomy of an Endoscope

To perform an endoscope repair, one must have an intimate understanding of how the instrument works; key repair techniques; and, most importantly, access to authentic OEM parts. This is why major endoscope manufacturers encourage a hospital to return damaged endoscopes to them. The OEM has the technical knowledge, proper equipment, techniques and components to repair equipment to meet their stringent standards.

Eyepiece: The most proximal portion of the telescope, the eyepiece is commonly used as a video camera mount. The generic replacement eyepieces commonly used by unauthorized repair firms may be identified by their low-quality materials. In a quality eyepiece performing to specification, the window is flush with the eyepiece cup. Most high-quality OEM eyepieces are milled in place and mounted flush with the surface of the eyepiece (Figure 1). With substandard repairs, a noticeable ledge can be seen where a piece of glass or even Plexiglas has been epoxied to the underside of the eyecup.

In some cases, the entire eyepiece window is removed; the hole is milled out (which will become notably larger) and a generic replacement window is affixed to the underside of the eyecup with epoxy. Again, this is easily identified by the ledge created. Sometimes a visible layer of epoxy can be seen around the edge of the window. Such repairs are less resistant to damage, leaving them prone to seal failure.

If the repair specifications for the eyepiece are not in strict accordance with the manufacturer's specifications, the video camera may freely rotate or even fall off. If the aperture of the generic eyepiece is off-center, the video image will shift to one side of the monitor, leaving only a portion of the actual image in view.

A plastic replacement eyepiece may indicate that additional repairs have been performed and this warrants further inspection of the endoscope.

I.D. Collar: The identification (I.D.) collar is engraved with the endoscope's angle of view and product code. When properly aligned, the label indicating the endoscope's viewing angle is opposite the light post and centered with the block assembly. This ring may be out of alignment following repair.

Even though the I.D. collar is designed for placement on to an endoscope in just one direction, we have seen I.D. collars placed backwards. This places stress on the eyepiece, which can cause the eyepiece to crack. Additionally, if the I.D. collar is damaged during repair, a different I.D. collar may be substituted. As a result, an endoscope originally manufactured as one type may bear the markings of a completely different model. For example, the endoscope may be designed for 30° viewing, but bear an I.D. collar with the markings of a 120° model.

Shaft: The essence of every endoscope, the shaft, contains all of the critical optical and illumination components used in basic endoscopic visualization. Unauthorized repair shops can engage in a process known as "reshafting," where the entire shaft, along with the optical components, are replaced with generic parts--almost always altering the original specifications. During this procedure, some or all of the original optical components may also be replaced. Even though reshafting completely changes the endoscope's specifications, the block assembly bearing the engraved manufacturer name is typically retained. This can be confusing, particularly when a problem arises and the customer does not know which party is responsible, the OEM or the unauthorized repair shop.

Minor shaft dents usually have no deleterious effect on overall endoscope performance. Only dents severe enough to damage the illumination fibers between the inner and outer tubes become a factor. Another possible concern is when the dents themselves preclude the use of the endoscope with other devices such as a telescope bridge or trocar cannula. Dents of this severity are not repairable, and the endoscope should be replaced immediately.

Unauthorized attempts at repairing such dents only increase the risk to patient safety. Cosmetic repairs using non-biocompatible elements is unacceptable.

Another possible concern is elongation of the endoscope shaft as a result of repair, presenting the potential for direct patient harm during electrocautery. An example is during transurethral prostate resection, where the cystoscope shaft must have an exact working length. Quality assurance checks during manufacturing verify precise alignment of the electrodes in close proximity to the cystoscope. An elongated shaft shortens the distance between the active electrode and the cystoscope tip, which allows for arcing to occur. Not only can this harm the patient, but it places the cystoscope operator at risk as well.

To ensure a proper seal between the shaft and body during endoscope manufacturing, the shaft is welded to the body using special procedures. Care is taken to insert the shaft into the body before welding, thereby preventing the light fibers from being burned. In contrast, it is quite common for unauthorized repair shops to use epoxy rather than welding. Even the best epoxy seals will ultimately fail and compromise the endoscope. Additionally, epoxy seals may not be consistent with the hospital's sterilization performance requirements, resulting in leaking and more frequent repairs.

Block Assembly: The block assembly is used primarily as the central connecting piece for the shaft, light post, and eyepiece. It's also the location of the engraved manufacturer's name and logo. Unauthorized facilities might not replace the block assembly following a "reshafting" repair.

Unauthorized facilities may not have access to the OEM parts necessary to perform a repair. As a result, holes are often drilled into the block assembly of smaller endoscopes in an attempt to prevent rotation of the inner tube during repair. This is done to prevent illumination fibers from shearing off during disassembly, resulting in an expensive repair. To hide the damage, unauthorized shops often fill the hole with epoxy. The hole may be placed in an inconspicuous area of the labeling to avoid notice by the customer. The hole creates a potential source for leakage during sterilization and a possible porous reservoir for bioburden.

Code Ring: The color code ring clearly identifies the endoscope's angle of view. The ring may be inadvertently burned during the disassembly process. While the ring itself has no effect on the optical performance of the endoscope, such telltale marks are an indication that the endoscope may have been subjected to unauthorized handling.

Concentrator Light Cone: The concentrator light cone serves to concentrate and transmit light from the fiberoptic light guide to the illumination fibers running between the inner and outer shaft tubes. Unimpeded, the concentrator light cone efficiently transmits light from the light source through the entire endoscope. Protective coatings on the exposed surface guard against exposure to corrosive chemicals during sterilization. Unfortunately, many unauthorized repair facilities offer a polishing service that then removes these protective coatings, making the surface more susceptible to sterilization damage such as pitting. Although there may be a delayed effect, such damage significantly reduces light transmission and impacts visibility. By the time the damage is noticed, it may be falsely attributed to the sterilization system.

Improperly polished light concentrator cones are easily identified by the exposed brass ring (Figure 2) surrounding the light fibers. The pitted or etched surface will be "chalky" to the touch and can be scratched easily with the thumbnail. Proper repair can only be achieved by replacing the entire concentrator light cone.

Occasionally, unauthorized shops will replace the light post with one imprecisely matched to the illumination fibers in the shaft. Not only will the fibers appear out of focus with significantly diminished light transmission, but extreme heat can also become trapped inside the block assembly. Such a repair should be suspected if the surgeon complains of excessive heat in the lightpost or block during use, in some cases, to the point that they cannot even be touched.

Ocular Lens Assembly: Located at the proximal portion of the lens train and mounted inside the block assembly, ocular lenses are used for adjusting fine focus and centering the image after final assembly of the endoscope system. Without access to the actual technical repair specifications, unauthorized repair shops have to guess at fine focus alignment, often resulting in an endoscope that is out of focus or off-center.

The choice of ocular also determines the aperture (f-stop), which in turn determines depth of field. Endoscopes with replacement oculars from unauthorized repair facilities may suffer from a significant loss in both depth of field and edge-to-edge clarity if an incorrect ocular is used. As a result, the surgeon must refocus the camera more often.

Rod Lenses: Rod lens systems use special glass rods with optically finished ends, providing images with higher brightness, contrast and color reproduction than conventional lenses. Replacing or mixing generic lenses with the manufacturer's rod lenses alters the original prescription of the endoscope and has a dramatic impact on the surgeon's ability to view the surgical site.

Spacers: Spacers are pieces of tubing cut to a predetermined length and incorporated in the lens train to precisely set the distance between the rod lenses. The generic spacers used by unauthorized facilities are generally made of highly polished (i.e., reflective) brass, which reduces image contrast by increasing internal reflection. Significant glare is a common complaint arising from the use of unauthorized spacers. Most people tend to assume the camera is at fault. Many times this results in one or more of the video system components being sent to the manufacturer for evaluation and repair. When no problem is found, they are returned to the user, leading to an endless cycle of problems for the biomedical technician who must identify the source.


Figure2. Improperly polished light concentrator cones are easily identified by the exposed brass ring.

Sterilization Seals: The primary solder joint and other important seals in autoclavable endoscopes can become significantly compromised by the use of both improper techniques and materials. This results in a loss of autoclavability--contrary to the original labeling still present on the endoscope. Epoxy seals are also compromised due to the excessive heat generated in the grinding and polishing process, making the endoscope susceptible to flooding and fogging.

Objective Lens Assembly: The objective lens assembly determines the endoscopic field of view. Located at the distal end of the lens train, the objective lens assembly comprises six or more assembled lenses that are epoxied together in a metal sleeve.

Replacement of the objective lens assembly is a common repair performed by unauthorized repair shops and often results in a significantly altered field of view. A secondary problem arises when the distal end of the shaft is shaved down to compensate for the new angle of the objective unit or as the result of damage to the shaft during the repair process. This shortens the shaft length, leaving the telescope incompatible with other devices. For example, shortening the shaft by even a millimeter can cause partial obstruction of the surgeon's view by resectoscope sheaths. Some unauthorized repair facilities attempt to compensate by replacing the objective assembly with one yielding a narrower field of view.

Occassionally, an objective lens will be drawn too far into the shaft. This leaves a protruding thin-walled outer tube with a dangerously sharp edge. The possibility for inadvertent trauma is particularly high in laparoscopes, where it is a common practice for the surgeon to clean the lens by wiping it over the bowel or liver.

Distal Window: The distal window provides the primary seal at the distal end of the endoscope and protects the objective lens assembly. Once a distal window has become marred or scratched, the window should be replaced and resealed.

In endoscope repairs, seemingly minor errors can have dramatic consequences. Indeed, the overall problem with sending endoscopes to non-OEM repair technicians is the customer assumes the endoscope will be repaired properly and returned to original factory specifications. However, this is difficult, if not impossible, without access to original factory specifications and components.

Brian Kern is the Technical Services Manager at Karl Storz Endoscopy-America, Inc. (Culver City, California).

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