Lasers in lacrimal surgery

Introduction

Disorders of the lacrimal drainage system manifest as epiphora and recurrent infection with mucopurulent discharge. Severe lacrimal infections can be very debilitating and cause severe visual and functional disability. In order to select the proper surgical procedure, it is extremely important to know the precise cause and location of the nasolacrimal obstruction. Uncomplicated infections are treated with topical antibiotic drops and irrigation of the lacrimal duct. Postinfectious adhesions, stenosis, or scar tissue formation in the canaliculus are treated with probing and possibly graduated dilatation. Surgery is often required to bypass a nasolacrimal obstruction. Depending on the exact location and severity of the lacrimal blockage, various types of lacrimal procedures are required including dacryocystorhinostomy (DCR), canalicular-DCR, or Jones’ tube surgery.

In order to localize the obstruction prior to surgery, diagnostic techniques such as simultaneous probing and high pressure irrigation, dacrocystography, digital subtraction angiography, and echographic examination have been used for location of the obstruction. Up to now, direct evaluation of lacrimal disorders has been limited to examination of the eyelids and puncta. Lacrimal endoscopes allow direct visualization of the canaliculi, lacrimal sac, nasolacrimal duct, and their mucous membranes. Initially, lacrimal endoscopes were rigid and limited by poor illumination. Newer lacrimal endoscopes with better physical and optical properties can now produce excellent lacrimal images.

Lacrimal irrigation with or without high pressure and dye tests cannot be replaced by endoscopy because they are rapid and easy methods for deter-

mining lacrimal patency. However, endoscopy is the best method for the precise localization and direct evaluation of the lacrimal system, and for the subsequent planning of surgical treatment.

New lacrimal endoscopes have been developed that are thin enough to be placed in the lacrimal puncti and canaliculi in order to enable direct and precise visualization of the lacrimal passages. These miniendoscopes have been used for diagnostic localization of various types of lacrimal disease, such as mucosal deposits, inflammatory membranes, strictures, and scar tissue. The diameter of the punctum ranges between 0.3 mm in children and 0.5 mm in adults, while the canaliculus has a diameter of 0.5 mm, and elastic walls. With miniaturization of integrated endoscopes (outer diameters: 1.1 or 0.7 mm), endoscopic examination is possible in practically all patients. Excellent viewing of the drainage system is possible due to improvement in the optic fibers and in light quality. Pathological changes such as mucosal strictures, scars, and stenosis can be directly visualized and differentiated from partial obstruction, due to mucosal inflammatory changes such as mucosal folds. Stenosis can also be differentiated from debris and mucous secretions, which can easily be removed. When probing a congenital duct obstruction, the stenosis can be dilated visually so that injuries and perforations of the mucous membranes are avoided. Moreover, the precise localization of various types of obstruction enables the lacrimal surgeon to choose the appropriate surgical procedure. Initial difficulties in the handling of the instruments, evaluation of the mucous membranes, and diagnosis of pathological changes, improve with experience and recognition of certain landmarks.

At this time, endoscopy is used to localize lacrimal drainage obstruction and to facilitate the choice

of the appropriate therapeutic procedure. The advantage of endoscopic examination is direct visualization and precise localization of the lacrimal drainage system and its mucous membranes.

The decision regarding whether a DCR, opening the stenosis with a laser, or gradual dilation, is the most appropriate can then be made. Endoscopy can safely be performed in an outpatient setting without adverse effects. With this method, improved diagnostic efficiency can be expected, and a more appropriate choice of surgical procedure. However, endoscopic examinations pave the way for new forms of therapy.

Besides diagnostic improvements, the search for therapeutic uses was of great interest in lacrimal surgery.

Various types of lasers, such as high-energy argon, holmium YAG, carbon dioxide, and KTP, have been used for endonasal endoscopic laser DCR.1-5

Type of laser

The Nd:YAG laser (1064 m) ablates bone through the process of optical breakdown with plasma formation. Minimal thermal effect was noted and may provide a sufficient hemostasis. The holmium:YAG (2.10 m) and Er:YAG (2.94 m) lasers ablate bone by means of a thermal mechanism, with vaporization of the bony tissue. The Er:YAG laser is more efficient for bony ablation and has a decreased thermal effect on the bony structures, due to its absorption in water.

KTP laser

With a wavelength of 523 nm, the KTP laser has the power and ability to penetrate bone and achieves good hemostasis in the soft tissue. Due to its high energy, soft tissue scarring is seen.

Levin and Stormo Gipson6 reported on an anatomical study with a KTP laser used to create a bony opening of up to 4 x 6 mm. He used a 400-600-m blunt-tipped quartz fiberoptic of a KTP (potassium titanyl phosphate) laser (Laserscope, San Francisco, CA) to create the fistula. Ten to 15 pulses were required to produce a 2.5 x 2.5 mm fistula. By raising the energy, the ostia could easily be enlarged to 6 mm.

At the same time, Silkiss et al.7,8 used a chromiumsensitized and thulium and holmium-doped YAG (THC:YAG) laser in four fresh-frozen, bisected human cadavers to create bony ostias. They reached a bony ostium of up to 3 mm, with an energy of between 250 and 900 mJ.

Er:YAG laser

Caversaccio et al.9 used the Er:YAG laser to treat presaccal and postsaccal stenosis. Three of 12 patients required re-stenosis. Despite the small numbers, these authors see a potential advantage in using translacrimal lasers for treating epiphora due to cutaneous

incision and excessive tissue injury being avoided, as well as the short operation time and the precision of the technique.

Emmerich and Meyer-Rüsenberg et al. and Steinhauer et al.1 used a miniaturized Er:YAG laser in combination with lacrimal endoscopy to treat lacrimal disorders. They had a long follow-up of up to six years, with a success rate of 75%, and large patients numbers. The success rate is lower than with conventional external DCR, which is the gold-stan- dard. However, their success was achieved with a method that is less time-consuming, produces no scarring, and is less stressful for the patient.

Kuchar et al.2 reported on the endoscopic laser recanalization of presaccal obstructions using an endoscopic system to localize the stenosis combined with an Er:YAG laser. The success rate of the technique and its advantages are similar to others.

Nd:YAG laser

There are a large number of reports and articles in the literature dealing with the Nd:YAG laser in translacrimal and endonasal surgery. Woo et al.,3 Patel et al.,4 Shapiro and Dan,5 Rosen et al.,13 Pearlman et al.,14 Piaton et al.15 and Saint-Blancat et al.16 all used the Nd:YAG laser to restore the lacrimal pathway via naturalis. The success rate differs from 46%4 to 87.5%.16 The advantages are short operation time, no scars being produced, good hemostasis, and less postoperative complications. Compared to external DCR, the outcome is poor, but has good acceptance among patients and authors.

Holmium:YAG laser

Woog et al.,17 Sadiq et al.18 and Dutton and Holck19 all used a holmium:YAG laser to recreate lacrimal pathways. Woog et al.17 and Sadiq et al.18 performed endonasal DCR with this laser and had good results: long-term patency was 82-84%, which they feel is a good result when dealing with lacrimal disorders. Patient acceptance was high, and surgery was significantly faster and less traumatic.

Dutton and Holck19 used this type of laser for transcanalicular treatment, in cases of complete or almost complete canalicular obstruction. They used a 1000-m optical fiber to cut a 1-mm channel in the lacrimal pathway. In some patients, this method was combined with DCR for concurrent lower nasolacrimal duct obstruction. The success rate was also lower than with conventional DCR. These authors feel that this procedure enhances the success rate by allowing epithelialization along a stent. The procedure is less traumatic and less stressful for the patients.

Argon laser

Massaro et al.20 and Gonnering et al.21 were the first to use a high-powered argon laser under operating microscopic control in order to perform endonasal

DCR. The success and failure rates are similar to all the other lasers mentioned. This is less than conventional DCR, but the technique has good acceptance from the patients and less complications are encountered.

Christenbury22 reported on translacrimal laser dacryocystorhinostomy with an argon laser. The success rate was about 60%, and the main problem was bone penetration and osteotomy formation.

KTP laser

Gonnering et al.21 were the first to use a KTP laser under endoscopic control for endonasal DCR, and noted easy bony osteotomy and good hemostastis with this type of laser. Their primary interest was the evaluation of endoscopic control of endonasal surgery with a laser. They believe that endoscopic laser-assisted operations are effective and are less expensive.

Encouraged by this report, Reifler23 used a KTP laser for endonasal DCR in a retrospective study. The success rate was lower than with conventional DCR, but is coupled to the experience of the surgeon, and has some positive effects, such as the avoidance of skin tissue scarring and reduced postoperative bleeding.

On the strength of Ashenhurst and Hurwitz’s report,24 and on that of our own results using a lacrimal endoscope,25-29 we attempted to find a laser source that was small enough to pass through an endoscope yet powerful enough to cut bone, in order to create a bony window of at least 5 mm in diameter. Our first experience with the Er:YAG laser was not very satisfactory because the power was strong enough to create mucosal scarring or folds, but too weak to cut bone. We had the same experience with the argon and Nd:YAG lasers. Based on the reports of Levin and Stormo Gipson6 and Dutton and Holck,19 we used a KTP laser on four cadaver heads in order to create a bony window. We found that an energy 6-9 W was powerful enough to cut bone in a short time. Based on this experience, since September 1997, we have been treating patients with a combination of lacrimal endoscopy and the KTP laser.

New laser fibers are now thin enough to be transmitted through such mini-endoscopes. Thus, endo lacrimal (transcanalicular or intracanalicular) laser surgery can be performed while also being able to view the surgery simultaneously via the same endoscope.

A modified lacrimal mini-endoscope was used in 103 patients (Waveguide, Laser Systems GmbH, Austria). Light fibers are arranged in a metal canula with an outer diameter of 1.1 mm and an inner diameter of 0.9 mm, which is inside a synthetic covering (Fig. 1). The entire unit consists of a xenon light source (Lisa Basic, Xenon Light Source, Medexxa GmbH, Germany), a video camera (Sony Videocamera, Sony, Japan), with an ocular attachment and a miniature CCD camera system with a monitor (Sony HR Trinitron) and videorecorder (Sony videorecorder,

Fig. 1. The lacrimal endoscope with laser fiber in situ.

SVO 9500 MDP). The KTP laser (Laserscope) consists of a 0.3-mm thick flexible laser fiber surrounded by a synthetic coating (Fig. 2). This laser emits light at 532 nm in a Q-switched mode in either single or continuous pulses. The laser cuts while in the contact mode and coagulates in the near-contact mode. Its maximum energy is 10 W. A modified lacrimal probe with three ports was used. The laser fiber is inserted via the central port, while the mini-endoscope is placed via a side port. Irrigating fluid flows through the other side port.

Patients and methods

One hundred and three patients with endonasally and endolacrimally verified stenosis of the lacrimal sac or nasolacrimal duct were treated with the KTP laser (Figs. 3 and 4). They all complained of epiphora and had thick mucous or purulent discharge coming from the lacrimal sac. Canalicular stenosis was localized with the lacrimal endoscope. The color, condition of the canalicula and lacrimal sac, contour of the submucosa, and extent of the scar tissue or stenosis at the lacrimal duct, were assessed. DCR was performed under general anesthetic. After irrigating and cleansing the lacrimal drainage system, the lacrimal probe was placed with the laser fiber tip and the endoscope was advanced to the lateral wall of the lacrimal sac. Correct positioning of the instruments was verified via endonasal and endosaccal visualization. A bony osteotomy of at least 5 mm in diameter was achieved with 6-10 W of energy. The total amount energy required was 124-432 (average, ±256) W. Surgery lasted for three to ten (average, five) minutes. Bicanalicular silicone intubation was performed and left in place for three to six months (Figs. 5, 6, 7 and 8).

Results

No patients experienced any bleeding or infection. No other complications were noted.

Fig. 2. KTP laser.

During the 12-58 months of follow-up, 85 of the patients treated for lacrimal sac or duct obstruction remained free of symptoms and their lacrimal ducts could easily be irrigated. Five of the 103 patients had greatly improved symptoms, but experienced intermittent tearing in extremely cold weather. Endonasal visualization of these patients revealed a patent bony osteotomy measuring 3-5 mm in diameter. Six patients required conventional DCR for tearing and blurring symptoms. Endoscopic evaluation showed re-steno- sis of the mucosa and bony hole. A further six patients underwent another successful laser-assisted translacrimal DCR with a follow-up of eight months.

We used a KTP laser fiber threaded through the canaliculus with simultaneous lacrimal endoscope visualization in 103 patients. Due to its particular wavelength and energy, the KTP laser can safely create a bony window within a short period of time.

The follow-up has now reached 58 months and the number of relapses is small, so that we are encouraged by our results. The success rates reported here are satisfactory, especially since we were using minimally invasive and rapid outpatient surgery.

It would seem our new experience and modified lacrimal diagnostic tools will be changing further treatment modalities over the next few years. Expensive and time-consuming procedures such scintigraphy and digital substraction scintigraphy are things of the past. Exact diagnoses can be obtained with the new endoscopes, and it is much easier to decide on the correct surgical treatment.

Most specialists who practice laser-assisted DCR do not use translacrimal visualization.3-5,9,13-16,19,24 To us25-29 and to a few other authors,1,2,10-12 endoscopy of the lacrimal system seems to be the main goal in using minimal surgery of the lacrimal pathway. As Emmerich and co-workers,10-12 Kuchar et al.2 and myself believe, if someone uses a laser to operate on lacrimal disorders, the first step should be an endo-

Fig. 3. Laser fiber 5 mm in front of the endoscope.

Fig. 4. A view showing endoscope and laser in situ. View of the monitor.

scopic diagnostic one. After obtaining the correct diagnosis, the correct decision on whether to perform DCR or reconstruction of the original lacrimal pathway can be taken. If there is presaccal stenosis, there is a great variety of lasers to choose from. If someone chooses to carry out translacrimal laser-assisted DCR, only the KTP laser is powerful enough to create a large enough bony window.

Endoscopy and laser-assisted lacrimal surgery is a huge step in the future of lacrimal disorders. The correct diagnosis and a laser as powerful as the KTP provides a new technique with excellent results, less complications, and great patient satisfaction.

Fig. 5. A series of lacrimal views showing lacrimal stenosis.

Fig 6. Submucosal scarring.

Fig. 8. Endonasal view of postoperative translacrimal laser DCR.

Conclusions

Over the past ten years, important steps in the diagnosis and therapeutical management of lacrimal disorders have been taken. The development of mini-endoscopes with excellent picture and light sources has changed the diagnostic lacrimal tools available. Dacryocystography is not longer necessary for making a diagnosis. With the development of these mini-endoscopes, exact diagnosis of the lacrimal pathway, of the mucosa and localization of stenosis can made. The lacrimal sac can be viewed precisely, and scarring or changes in the mucosa, lumen, and size can be seen. With this precise diagnostic instrument, the correct and exact decision on whether to perform DCR or reconstruction of the original lacrimal pathway can be taken.

As well as their diagnostic value, new instruments such as lasers (KTP, CO2, etc.) have been developed for recanalization and translacrimal DCR. The success rates are slightly lower than with transcutaneous DCR, but the complications are also lower. Patient satisfaction is very high and the time taken for the procedure is much lower.

The decision over the best laser still has to be taken. When using applying translacrimal method, the KTP is superior to all the other lasers because of its great power and good hemostasis. With the endonasal approach, the KTP, CO2 or various others appear to be similar, because the laser fiber can be thicker and power becomes stronger.

This method is a new step towards ‘minimal surgery’. All these developments, i.e., mini-endoscopes, lasers, etc., are part of the new generation of lacrimal investigation and therapy modalities.

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