Endonasal Laser A New

Dacryocystorhinostomy

Approach to Nasolacrimal

Bruce M. Massaro, MD, MPH; Russell S.

Gonnering, MD; Gerald J. Harris, MD

\s=b\ A

ser

high-powered argon blue-green lacoupled to a 300-\g=m\m quartz fiberoptic

used to create intranasal dacryocystorhinostomy fistulas in fresh\x=req-\ frozen cadaver heads. The procedure, which we term endonasal laser dacryocystorhinostomy, is described. Cadaver specimens were examined postoperatively. Laser rhinostomies were found to involve the posteroinferior portion of the lacrimal sac fossa. Tissues surrounding the fistula site showed no signs of damage. We report on the first patient to undergo endonasal laser dacryocystorhinostomy for the treatment of nasolacrimal duct obstruction, with 10 months of follow-up. We believe endonasal laser dacryocystorhinostomy offers the following advantages over standard external dacryocystorhinostomy: (1) Tissue injury is limited to the discrete fistula site. (2) The cutaneous scar and cosmetic blemish of an external dissection are eliminated. (3) Excellent hemostasis is maintained. (4) Minimal operative and catheter

was

postoperative morbidity permits outpatient surgery, with faster resumption of normal daily activities and increased cost-effectiveness. (5) Patients prefer endonasal laser dacryocystorhinostomy to external dacryocystorhinostomy. {Arch Ophthalmol. 1990 ;108:1172-

1176)

1904, Toti1 was the first to describe

external

dacryocystorhinostomy

(DCR) for the treatment of chronic

dacryocystitis.

He used skin sutures

Accepted for publication May 8, 1990. From the Department of Ophthalmology, the Medical College of Wisconsin (Drs Massaro and Harris), and the Department of Ophthalmology, St Luke's Medical Center (Dr Gonnering), Milwaukee.

Reprint requests to Department of OphthalmolEye Institute, The Medical College of Wis-

ogy,

Duct Obstruction

consin, 8700 W Wisconsin Ave, Milwaukee, WI 53226 (Dr Massaro).

alone for wound closure after resecting the adjacent lacrimal sac and nasal mucosa with their intervening bone. In 1921, Dupuyemps and Bourguet2 directly sutured the cut edges of nasal and lacrimal sac mucosal flaps, with improved rates of successful fistulization. Their procedure, with minor modification, has remained the ac¬ cepted method of correction for adult nasolacrimal duct obstruction, yielding success rates of 90% in primary re¬ pairs.3 Even better results have been reported with the addition of silicone stents.4 Intranasal (endonasal) DCR was in¬ troduced by Caldwell" in 1893, with his report of an intranasal trephination of the nasolacrimal duct. Subsequent ad¬ vocates of internal DCR sought to avoid the cutaneous scar of an external dissection and potential damage to structures responsible for normal lacri¬ mal pump function." After choosing the approximate lacrimal sac fossa site from within the nose, resection of nasal mucoperiosteum and underlying bone provided access for lacrimal sac drain¬ age. Endonasal DCR did gain limited

support among some otolaryngologists, but, despite success rates ap¬ proaching those of external DCR,' the procedure was essentially abandoned.

Past and present authorities in both external and internal DCR have pro¬ moted the axiom that a larger bony resection is fundamental to successful fistulization. Most authors'"" recom¬ mend osteotomies 15 to 20 mm in diam¬ eter. Standard bone removal, through a variety of mechanical means, in¬ cludes the anterior lacrimal crest (a portion of the frontal process of the maxilla), superomedial nasolacrimal duct wall, lacrimal bone, and, often, anterior ethmoidal bone. Despite gen-

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erous

berg

bone removal at surgery, Linet al9 discovered an average

healed intranasal ostium size of only 1.80 mm in a series of external DCRs followed up postoperatively with nasal endoscopy. Of particular interest, they found that patients with small healed ostia obtained the same clinical relief from epiphora as those with large os¬ tia. These findings suggested that a smaller initial surgical ostium might be sufficient if it was made in a direct manner,

sparing injury to surrounding

tissues. Recent collaborative work by one of us (B.M.M.), with investigators using a high-powered argon laser to make full-thickness filtration fistulas in eyes with neovascular glaucoma,1" demon¬ strated advantages of the argon sys¬ tem that were directly applicable to our needs in lacrimal outflow surgery. These included a flexible fiberoptic de¬ livery system, the ability to achieve high power densities with excellent hemostasis, and slight tissue shrinkage about the laser fistula that could aid in maintaining its patency. The argon la¬ ser, when used to produce a discrete nasolacrimal fistula from within the nose, would eliminate a cutaneous scar and potential injury to medial canthal structures otherwise involved in an external DCR dissection. Surgical in¬ tervention limited to the actual fistula site would decrease operative and postoperative morbidity and would permit routine outpatient surgical management with improved costeffectiveness. We herein report, to our knowledge, the first use of a high-powered argon laser for the creation of an intranasal nasolacrimal fistula. We describe our surgical method as developed in cadav¬ er studies, and we report the first

clinical case of acquired nasolacrimal duct obstruction successfully treated by the new procedure we have termed endonasal laser dacryocystorhinos¬

tomy (ENL-DCR).

MATERIALS AND METHODS Adult fresh-frozen cadaver heads with normal nasolacrimal anatomy were ob¬ tained from the Department of Anatomy, Medical College of Wisconsin, Milwaukee.

Specimens

brought to room tempera¬ procedure was begun.

were

ture before the

The upper lacrimal punctum of the opera¬ tive site is dilated with a standard gradu¬ ated punctal dilator. To intranasally identi¬ fy the desired site for entry into the lacri¬ mal sac, a specially modified 20-gauge reti¬ nal light pipe (TREK Medical Products, Mukwonago, Wis) is passed via the dilated upper punctum and canaliculus into the lacrimal sac (Fig 1, top left). The fiberoptic light needle, attached to a variable-intensi¬ ty cold light source, is advanced to lie adjacent to the inferomedial aspect of the lacrimal sac, immediately superior to the presumably obstructed nasolacrimal duct. The nasal ala and vestibule are spread vertically with a nasal speculum, permitting visualization of the lateral wall of the nose. Here, the precise location of the light pipe can be identified by transillumination of lacrimal sac wall, nasal mucosa, and inter¬ vening bone (Fig 2). Rotation of the light pipe within the lacrimal sac outlines the desired dimensions of the DCR opening for the intranasal observer. 300-µ quartz fiberoptic laser catheter is coupled to a 16-W argon blue-green laser (model 20, HGM Medical Laser Systems Ine, Salt Lake City, Utah). To position the semiflexible laser catheter tip at the work site and provide immediate laser smoke evacuation, the laser fiber is secured with 0.6-cm sterile adhesive strips alongside a 6F Frazier suction catheter whose distal tip is modified to a 45° angle. The tip of the laser fiber is positioned 3 mm in advance of the suction catheter end. The laser suction catheter is brought into the nose. Its fiber tip is directed at the transillumination site, maintaining a distance of 3 to 5 mm from the nasal mucosal surface during the treat¬ ment (Fig 1, top right). The laser is set to deliver single bursts 0.5 seconds in duration with power settings ranging from 7 to 12 W, depending on the tissue effects desired. Lower power densities are used initially to outline the intended area of resection and to

provide photocoagulation (hemostasis) prior cutting and vaporization. The op¬

to tissue

erative site can be seen during treatment with either the operating microscope, using a 250-mm objective lens, or nasal endo¬ scopes, employing appropriate protective laser filters. Using the laser, an area of nasal mucosa and underlying bone 5 to 7 mm in diameter is removed. Depth of penetration is indicat¬ ed by an increasing degree of transillumination from the light pipe within the lacrimal sac. The light pipe is now used as a probe, indenting the remaining lacrimal sac wall and periorbita via the laser rhinostomy defect into the nose for safe laser ablation.

Fig 1.—Surgical steps in endonasal laser dacryocystorhinostomy. Top left, Light pipe enters lacrimal sac via upper punctum and canaliculus, directed toward posteroinferior portion of lacrimal sac fossa (see Fig 2). Top right, Laser suction catheter resecting tissue overlying light pipe's transilluminating mark. Bottom left, Light pipe enters nose via laser rhinostomy. Bottom right, Completed nasolacrimal fistula with silicone stent in place.

The light pipe enters the nose (Fig 1, bottom left) and is then used to advance additional marginal tissue into view for laser resection until an opening of approxi¬ mately mm is made. When the desired rhinostomy size is achieved, the light pipe is withdrawn. Bicanalicular silicone intubation of the laser fistula is now performed. After they are inserted in the nose, Crawford-style silicone stents (Jedmed Instrument Co, St

Louis, Mo) are passed through a 5-mm section of 503 retinal sponge material (MIRA Ine, Waltham, Mass). The silicone tubes are then tied on themselves and trimmed to provide a proper length within the nose (Fig 1, bottom right). Lacrimal irrigation around the silicone stent while viewing the site intranasally confirms the

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degree of patency operation.

at

completion of the

RESULTS

Six fresh-frozen cadaver heads were used in the development of the proce¬ dure described above. Seventy-five to 150 laser pulses 0.5 seconds in duration at 7 to 12 W were required to effect the desired opening. Despite individual variation in the amount of intervening bone and soft tissue, the intranasal site

of light pipe transillumination was eas¬ ily seen and approached with the suc¬

tion laser catheter in each

case.

Cadaver specimens were dissected postoperatively to evaluate rhinos-

Fig 2. —Intranasal view (cadaver specimen) of the transilluminaled operative site. The light pipe has been passed as shown in Fig 1. A nasal speculum is in the right nostril.

Fig 3.—Sagittal section showing cadaver specimen's right lateral nasal wall after en¬ donasal laser dacryocystorhinostomy. There is a laser nasolacrimal fistula (large curved arrow) lateral to the head of the right middle turbinate (asterisk). A silicone stent passing through a section of retinal sponge (small arrow) traverses the rhinostomy.

Fig 5.—Axial section of the left side (not op¬ erated on) in paraffin through the inferior orbit. Black arrow indicates inferior lacrimal sac in fossa, formed by thick maxillary bone (aster¬ isk) anteriorly and thin lacrimal bone with overlying nasal mucosa (white arrows) poste¬ riorly. Tissue resected in endonasal laser da¬ cryocystorhinostomy is demarcated by white arrows (see Fig 6). Black triangle indicates nasal septum. Fig 6.—Axial section of the right side (operat¬ on) in paraffin through the inferior orbit, corresponding to Fig 5. A laser fistula (white arrows) lies posterior to thick maxillary bone (black asterisk), lateral to the middle turbinate (white asterisk). The remaining lacrimal sac (black arrow) and adjacent orbital tissues are ed

undisturbed. A silicone stent with sponge is seen between the turbinate and ostium.

vaguely

Fig

7. —Patient's appearance 1 dayfollowing left-sided endonasal laser dacryocystorhi¬ nostomy. A silicone tube is in place at the medial canthus (arrow).

Fig 8. —Endoscopie photograph of patient's intranasal ostium (arrow) at the time of sili¬ cone tube removal, 6 months after endonasal laser dacryocystorhinostomy. Fluorescein dye is seen exiting the ostium. Mucosa of the middle turbinate (asterisk) and lateral nasal wall appear normal.

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Fig 4.—Right lateral nasal wall, correspond¬ ing to the cadaver section in Fig 3. The rhinos¬ tomy site (stippled area) is shown in relation¬ ship to the lacrimal outflow tract (broken line) and the surrounding nasal anatomy.

tomy size, position, and surrounding tissue relationships. A representative case was chosen for additional study by cryosection. We performed ENL-DCR on the right nasolacrimal system of this specimen, leaving the left system for internal comparison. The specimen

refrozen after the procedure and bisected in the midsagittal plane. The laser ostium, with a silicone stent in place, is seen adjacent to the head of the right middle turbinate in Fig 3. The position of the laser opening in relationship to the lacrimal sac and nasolacrimal duct is shown in the ac¬ companying diagram of the right later¬ al nasal wall (Fig 4). The two specimen halves were sus¬ pended in paraffin and sectioned in the axial plane. Corresponding axial sec¬ tions were obtained traversing the in¬ ferior portion of both orbits and lacri¬ mal sacs (Figs 5 and 6). A comparison revealed the following: As opposed to standard DCR, ENL-DCR creates an opening limited to the posteroinferior portion of the lacrimal sac. Thin lacri¬ mal bone, usually present at this site, is penetrated with relative ease com¬ pared with the thicker bone of the maxillary bone frontal process that normally makes up the anterior por¬ tion of the lacrimal sac fossa. The site of penetration does not violate anterior ethmoidal air cells or jeopardize drain¬ age pathways of the adjacent paranasal sinuses. Unlike external DCR, me¬ dial canthal tendon structures and nonresected portions of lacrimal sac wall are left in situ and are undis¬ turbed during ENL-DCR. Inspection showed visible laser damage to be lim¬ ited to the resected tissues, with no changes seen in the remaining portions of nasal mucosa, lacrimal sac, or adja¬ cent orbital tissues. was

REPORT OF A CASE A us

29-year-old

woman

presented to one of

(B.M.M.) with symptoms of chronic left

dacryocystic retention for over 1 year. She reported daily morning distention of the left lacrimal sac. Massage caused reflux of mucopurulent material and temporarily re¬

discomfort. Pain was felt throughout the left midface and had prompted several otolaryngology and den¬ tal evaluations. Chronic symptoms were punctuated with several acute episodes of left facial cellulitis. She had recently com¬ pleted taking courses of oral antibiotics and

lieved

her

currently using topical neomycin eye drops. Varying degrees of epiphora were reported between episodes of acute was

infection. On examination, corrected visual acuity was 20/20 in both eyes. The eyelids were normally apposed to the globes. The left lacrimal lake was mildly increased in quan¬ tity. The periorbital soft tissues were not

visibly

distended or erythematous. Mild tenderness in response to palpation was present in the left medial canthus, where massage produced reflux of clear admixed with white mucoid material via the lacrimal puncta. No masses were palpable. When

cultured, coagulase-negative staphylococci

grew from the refluxed material. Results of anterior and posterior segment examina¬ tions were otherwise normal. Lacrimal testing with 2% fluorescein dye placed in the left eye showed no spontane¬ ous passage to the nose and significant conjunctival sac retention 5 minutes after instillation. Irrigation of the left lacrimal system revealed passage of minimal amounts of dye-stained fluid to the nose only with forced irrigation and an otherwise patent upper lacrimal outflow tract. The diagnosis of high-grade acquired nasolacri¬ mal duct obstruction was made. Dacryocystogram confirmed the level and degree of stenosis and did not demonstrate dacryoliths. Results of the nasal examination were judged to be normal.

Dacryocystorhinostomy was recommend¬ ed for treatment. In addition to standard external DCR, the option of ENL-DCR was offered, emphasizing that a failure of laser DCR would require subsequent external surgery. The patient chose ENL-DCR, in¬ dicating her overriding desire to avoid any external facial scar. In May 1989, with the patient under general anesthesia at her request, ENLDCR was performed (Fig 1). The left nos¬ tril was packed with cottonoids soaked with a 4% cocaine solution prior to laser inter¬ vention. A protective scierai shell was placed in the exposed left eye. Sixty laser impactions 0.5 seconds in duration at 7 to 9 W were required to create a 5-mm nasola¬ crimal fistula. The operating microscope was used for visualization. Silicone intuba¬ tion was performed, and irrigation of the tract confirmed its patency. Excellent he¬ mostasis was afforded throughout, and no complications were encountered. No post¬ operative nasal packs or external dressings were required. The patient was discharged on the day of surgery. Postoperative medi¬ cations included oral cephalexin, topical antibiotic-steroid combination eye drops, and saline nasal spray. On the first day after the operation, no external manifestation of surgery could be seen, with the exception of the silicone stent at the left medial canthal angle (Fig 7). The patient reported only mild nasal irritation overnight that did not require pain medication and otherwise had com¬ plete resolution of her previous facial discomfort. Fistula patency was documented at each subsequent examination by the absence of symptoms, fluorescein dye disappearance, lacrimal irrigation, and nasal inspection. Crusts and mucoid debris about the nasal ostium and intranasal silicone tube were gently removed with cotton swabs and bay¬ forceps, leaving normal-appearing mu¬ by the sixth week after surgery. Daily saline nasal spray was continued through¬ out the period of silicone intubation to aid in intranasal hygiene. After 6 months, a previously chosen inonet cosa

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terval, the

silicone stent

was

removed. En¬

doscopie examination documented immedi¬ ate passage of fluorescein dye placed in the left conjunctival sac and a healed ostium approximately 2 mm in diameter (Fig 8). At this writing, the fistula continues to be patent, and the patient was free of symp¬ toms 4 months following stent removal. COMMENT

Membranous occlusion of the surgi¬ cal ostium has been shown to be the most frequent cause of failure of exter¬ nal DCR."12 The most commonly iden¬ tified obstruction results from synechiae between the surgical ostium and adjacent nasal septum or middle turbi¬ nate mucosa.12 These findings suggest that the extensive dissection required in external DCR to generate adequate mucosal flaps for anastomosis can be potentially detrimental to the ultimate goal of patency. As the amount of surgical dissection increases, a con¬ comitant increase in operative morbid¬ ity and postoperative discomfort can be expected. Cerebrospinal fluid leaks have been reported following the rou¬ tine bone resection of external DCR.13 The logic for creating large surgical anastomoses is further questioned in light of the observation of Linberg and colleagues9 that such openings, when healed, averaged only 1.80 mm in diameter yet provided relief from

epiphora.

It was our contention in the develop¬ ment of ENL-DCR that a discrete nasolacrimal fistula of adequate func¬ tional dimensions could be safely and reliably produced using the highpowered argon laser. By avoiding the dissection and displacement of tissues surrounding but not involved in the actual fistula, we anticipated a reduced postoperative inflammatory response, with less chance of fistula closure by wound contracture or synechial ob¬ struction. The intranasal approach eliminates the need for a cutaneous scar, reduces operative morbidity, and allows patients to more rapidly resume their normal daily activities following

outpatient surgery.

The addition of silicone "canalicular"

stents to ENL-DCR offers benefits that outweigh any possible adverse effects and may be essential to the

ultimate patency of its small initial ostium. The use of silicone stents in complicated standard DCR surgery4,8,9 and lacrimal outflow system injury14 is a well-established means of maintain¬ ing fistula patency where an otherwise narrow or traumatized passage might be expected to occlude during healing. Critical to the safe and successful performance of any form of intranasal

DCR is the precise identification of the lacrimal sac lumen while viewing from the nose. The surgeon can then accu¬ rately resect just those tissues overly¬ ing the lumen while avoiding damage to surrounding orbital and nasal tis¬ sues. We have found that the 20-gauge light pipe, used as a transilluminating marker within the lacrimal sac, pro¬ vides this key element of control that was lacking in previous descriptions of intranasal DCR. The preferred site for fistula place¬ ment in ENL-DCR is the posteroinfer¬ ior lacrimal sac fossa, where nasal and lacrimal tissues are in their closest apposition. Unlike the thicker maxil¬ lary bone of the anterior fossa, at the posteroinferior location there is only thin and fragile lacrimal bone1' that is easily penetrated by laser and light pipe (Figs 5 and 6). Penetration at this position enters the middle meatus of the nose without compromise of more posteriorly located sinus duct systems. In addition to its use in other surgi¬ cal specialties, the high-powered argon laser has had rhinologic applications, including the treatment of nasal telan-

giectasis, partial turbinectomy, synechial lysis, and the creation of nasoantral windows through maxillary bone 1 thick."'1' The argon laser emits of two wavelengths (488 and 514.5 nm) found in the blue-green re¬ gion of the visible spectrum. The selec¬ mm

light tive

absorption of these wavelengths by hemoglobin confers coagulative properties that allow the resection of vascular tissues with excellent hemostatic control.1" This feature, combined with a flexible fiberoptic delivery sys¬ tem, makes the high-powered argon laser uniquely suited to our needs in

endonasal DCR. As expected, the argon laser was found to perform more efficiently in our clinical case than was previously noted during laboratory resection of "nonperfused" cadaver tissues. Lower initial wattages were used to coagulate tissue prior to vaporization at high power settings. With this technique, laser resection of the nasolacrimal fis¬ tula proceeded in an essentially blood¬ less field. Study of a clinical series of patients undergoing ENL-DCR for nasolacri¬ mal duct obstruction is now proceed¬ ing. All adult patients who would oth¬ erwise be candidates for external DCR are considered, with some exceptions. The ENL-DCR procedure is contrain¬ dicated if the results of a clinical ex¬ amination suggest a malignant neo¬ plasm in the lacrimal sac. The need for wide surgical access to lacrimal tissues for biopsy or resection would mandate an external approach. The endonasal approach does not, however, preclude routine random biopsy of nasal or lacri¬ mal tissues when used in conjunction with available sinus endoscopy in¬ strumentation. Several other contraindications are related to our current level of sophisti¬ cation in ENL-DCR and may change with expected technical advancements. Confirmed dacryolithiasis, though po¬ tentially treatable with ENL-DCR, may require a wider exposure of the lacrimal sac for stone removal. Pa¬ tients with recurrent acute dacryocystitis that has fistulized to the skin may have abscess cavities that are separate from the main lacrimal sac lumen and need direct incision and drainage. The inclusion of routine pediatrie DCR

cases, we believe, must await further experience and results in the adult population.

For the past 70 years, external DCR has remained the gold standard by which all other procedures for the cor¬ rection of nasolacrimal duct obstruc¬ tion must be judged. Despite its estab¬ external DCR lished success, continues to be approached with reluc¬ tance

by

many

ophthalmic

surgeons

and their patients. Physicians who are uncomfortable with nasal and lacrimal anatomy, unfamiliar with the surgical techniques of bone removal, and wary of bleeding complications tend to treat recurrent dacryocystitis by medical means for extended periods before pursuing a surgical solution. Patients will at times endure chronic lacrimal discharge with annoying epiphora and even episodic pain (as in our case re¬ port) rather than face the potential discomfort and postoperative cosmetic blemish of external DCR. It is perhaps

for these reasons that we have found such enthusiastic support for ENLDCR among both referring physicians and their patients. Based on our initial experience with ENL-DCR, we believe this enthusi¬ asm to be guardedly justified. In¬ creased patient experience and longer follow-up periods will determine whether ENL-DCR is able to provide the reliable and effective therapy of standard external DCR. Funding for this study was provided in part by

unrestricted grant from Research to Prevent Blindness Ine, New York, NY. The authors have no commercial or proprietary interest in any equipment, instruments, or medi¬ cations discussed in this report. an

References 1. Toti A. Nuovo metodo conservatore dicura radicale delle soppurazioni croniche del sacco lacrimale (dacriocistorinostomia). Clin Moderna.

1904;10:385-387.

2. Dupuy-Dutemps, Bourguet. Procede plastique de la dacryocystorhinostomie et ses resultats. Ann Ocul. 1921;158:241-261. 3. Burns JA, Cahill KV. Modified Kinosian dacryocystorhinostomy: a review of 122 cases. Ophthalmic Surg. 1985;16:710-716. 4. Anderson RL, Edwards JJ. Indications, complications, and results with silicone stents. Oph-

thalmology. 1979;86:1474-1487.

5. Caldwell GW. Two new operations for obstructions of the nasal duct with preservation of the canaliculi. Am J Ophthalmol. 1893;10:189. 6. Steadman GM. Transnasal dacryocystorhinostomy. Otolaryngol Clin North Am. 1985;18:107\x=req-\ 111. 7. Jokinen K, Karj\l=a"\J. Endonasal dacryocystorhinostomy. Arch Otolaryngol Head Neck Surg.

1974;100:41-44. 8. Patrinely JR, Anderson RL. A review of lacri-

id

mal

14. Harris GJ, Hunter FH. Lacrimal intubation in the primary repair of midfacial fractures. Oph-

drainage surgery. Ophthalmic Plast Reconstr Surg. 1986;2:97-102. 9. Linberg JV, Anderson RL, Bumsted RM, Barreres R. Study of intranasal ostium external dacryocystorhinostomy. Arch Ophthalmol. 1982;

100:1758-1762. 10. Jaffe GJ, Mieler WF, Radius RL, Kincaid MC, Massaro BM, Abrams GW. Ab interno sclerostomy with a high-powered argon endolaser: clinicopathologic correlation. Arch Ophthalmol. 1989; 107:1183-1185. 11. Welham RN, Henderson PH. Results of dacryocystorhinostomy: analysis of causes for failure. Trans Ophthalmol Soc U K. 1973;93:601-609. 12. Allen KM, Berlin AJ, Levine HL. Intranasal endoscopic analysis of dacryocystorhinostomy failure. Ophthalmic Plast Reconstr Surg. 1988;4:143\x=req-\ 145. 13. Neuhaus RW, Baylis HI. Cerebrospinal flu-

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leakage after dacryocystorhinostomy. Ophthalmology. 1983;90:1091-1095.

thalmology. 1987;94:242-247.

15. Whitnall SE. Anatomy of the Human Orbit. 2nd ed. London, England: Oxford Medical Publications; 1932:70-74. 16. Lenz H, Eichler J. Endonasale chirurgische Technik mit dem Argon Laser. Laryngol Rhinol Otol. 1984;63:534-540. 17. Lenz H, Eichler J, Schaefer G, Salk J. Production of a nasoantral window with an argon laser. J Maxillofac Surg. 1977;5:314-317. 18. Ossoff RH, Duncavage JA. Lasers in otolaryngology-head and neck surgery. In: Apfelberg DB, ed. Evaluation and Installation of Surgical Laser Systems. New York, NY: Springer-Verlag NY Inc; 1987:144-145.

Endonasal laser dacryocystorhinostomy. A new approach to nasolacrimal duct obstruction.

A high-powered argon blue-green laser coupled to a 300-microns quartz fiberoptic catheter was used to create intranasal dacryocystorhinostomy fistulas...
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