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Corneal Trabeculectomy Ayman Nassar, Abdalla Al Sawi, Mohamed Al Deeh, Hani Salem, and Mohamed Abd Rabo. Puropse: To evaluate a modified trabeculectomy technique for glaucoma filtering surgery through a clear corneal flap without performing a conjunctival incision. Methods: The procedure was performed on 27 glaucomatous eyes with uncontrolled TOP. A corneal flap 2 x 3 mm was raised and a sclera! pocket was dissected 2 to 3 mm posteriorly . The subconjunctival space was entered with a cystitome and a fragment of the floor of the scleral pocket was excised using a Kelly Descemet s membrane punch. The anterior chamber was entered at a limbal incision and iridectomy was performed. Corneal flap was closed with two separate 10-0 nylon sutures. Results: At 6 month the mean TOP decreased from 32.65mm Hg preoperatively to 12.93 mmHg. 88% of the eyes had an TOP less than or equal to 18 mm Hg without medication. Conclusion: Corneal trabeculectomy showed as a relatively as a traumatic filteration procedure producing diffuse persistent conjunctival blebs and adequate control of TOP. BULL. OPHTHALMOL. SOC. EGYPT, 1999; VOL. 92, NUMBER 3, 657-660 Success of glaucoma filtering surgery depends on the maintenance of a patent fistula connecting the anterior chamber of the eye and the subconjunctival space. Scarring at the conjunctiva-episclera interface represents the most common cause of filteration failure and subsequent elevation of the TOP . Minimizing surgical trauma is believed to decrease postoperative scarring . Cairns in 1985 described a trabeculectomy technique through a clear corneal incision avoiding the conjunctiva and Tenon s capsule. Inspite of reporting initially good results, poor results have been obtained by other authors who used his technique ( Keiler and Moltino, 1985, Ali et al., 1990 , and Taha, 1990 ). The technique did not entail a direct communication between the created internal fistula and the conjunctival space but relied upon the ostia of the scleral perforating vessels to provide access to subconjunctival space . Van Buskirk, (1992) and later Cioffi and Van Buskirk, (1993) described a modification to Cairns technique by creating an external fistula that communicates directly to the subconjunctival space. In this article, we review the results of 27 glaucoma eyes who were operated upon by the modified technique for corneal trabeculectomy. 657 Subject and methods The study was conducted on 27 eyes of 18 glaucoma patients ( 8 men and 10 women) who were submitted for glaucoma surgery due to uncontrolled TOP or deteriorating visual field loss despite maximal tolerated medical treatment. As regards the type of glaucoma, 14 eyes had chronic angle closure glaucoma, 11 eyes had chronic open angle glaucoma and 2 eyes had pseudoexfoliation s yndrome associated with glaucoma. Mean age of the patients was 54.13 years (range 29 to 73 years). Technique : Fixation suture was taken through superior rectus muscle to rotate the eye downwards, the upper nasal or upper temporal quadrant was chosen for surgery, only in two cases the operation site was at 6 o'clock meridian. A partial-thickness trapezoidal flap 2 mm in wide at the corneal side and 3 mm at the limbal base was made using a super blade. A spatula blade was then used to dissect the flap at approximately 1/3-1/2 corneal thickness. Dissection was continued Corneal Trabeculectomy, Ayman Nassar et al posteriorly 2-3 mm beyond the cornea-scleral junction to fashion an intrastromal scleral pocket . An irrigating cystitome formed by a 27-gauge needle bent over its tip and mounted on a syringe containing normal saline was introduced into the intrascleral pocket till it reaches its posterior end, then rotated 90° superiorly so that the bevelled tip pierces the roof of the sclera] pocket and enters the subconjunctival space. Saline was then injected to raise the conjunctiva and form a subconjunctival bleb. The incision was then enlarged by a horizontal side-to side movement of the cystitome. At the anterior end of the scleral pocket, a fragment approximately 1.5 x 1.0 mm of the its floor was excised using the Kelley Descemet membrane punch, this creates an external fistula from the subconjunctival space to the intrascleral pocket. An ab-externo stab incision, 2 mm in length, was made to enter the anterior chamber at the anterior extent of the surgical blue zone under the corneal flap. Two bites were taken from the posterior lip of the incision using the Kelly Descemet membrane punch to create the inner part of the fistula. Peripheral iridectorny was then performed and the corneal flap closed by two 10-0 nylon sutures at its anterior end. Sometimes two additional sutures were needed to secure the flap at its base. The anterior chamber was formed by injecting saline through a previously made limbal stab incision. Postoperatively the patients were given a combination of neomycin, polymyxin, and dexamethasone (Maxitrol eye drop four times daily, and cycloplegic two times daily . Topical steroids were continued for approximately six weeks during which the dose was tapered gradually Examinations were carrided on the immediate postoperative day and for the next two days to evaluate the inflammatory reaction of the eye, anterior chamber depth, filteration bleb, lop, and fundus examination . Visual acuity was measured at later follow-up visits . Further examinations were done at weekly intervals during first month postoperatively , and monthly intervals later. Results All cases received a minimum follow-up of 3 months, 15 cases showed up to 6 months. The surgery was considered successful if the TOP was 18 mm Hg or less at 3 month visit without antiglaucoma medication The mean [OP preoperatively was 32.65±7.24 mmHg. At one week lOP ranged from 414 trim Hg with a mean of 7.51±2.9 mmHg. At 2 weeks, the mean TOP was 10.29±2.41 mmHg. At 1,3 and 6 months the mean lOP remained almost stable at approximately 12 mmHg . Table (1) shows the mean TOP at the successive follow-up visits . Eighty-eight percent of the eyes had 10P less than or equal to 18 mmHg without medication at the end of three month postoperatively. Three cases (3/27) failed to achieve the desired TOP level throughout the follow-up period . Table (1) : Comparing preoperative and postoperative lOP KW 10P Range (mmHg) Mean ± SD No. of eyes Preoper. [OP 27 22-64 32.65 ± 7.25 One week 27 0-14 7.51 ± 2.94 2 weeks 27 4-16 10.29 ± 2.41 1 month 27 9-27 12.16 ± 2.11 3 month 27 10-22 12.26 ± 2.43 6 month 15 10-16 12.93 ± 1.91 One case was controlled medically with single topical medication (Timolol) and 10P was reduced to approximately 15 mmHg and remained so thereafter. The other case did not respond to reinstitution of medical therapy and digital pressure, and underwent a revision of the corneal trabeculectomy at the same site, by removing adequate episcleral tissue to enhance filteration through the originally made 658 fistula. The TOP after two months was 10 mmHg without medication. The third case was complicated by an infected bleb 4 months after surgery. Clinically the filteration blebs were typically low and diffuse covering one to two quadrants. The blebs were seen well formed throughout follow-up period with occasionally apparent cystic changes. No BULL. OPHTHALMOL. SOC. EGYPT, 1999; VOL. 92, NUMBER 3 Table (2) : Summerizes the operative and postoperative complications. Complication Number Perecent Operative : 2 8 1- Tandvertent injury to corneal flap. 2 8 1- Hypherna . 7 26 2- Shallow A.C. 16 59 3- Flat A.C. 2 8 4- Hypotony. 2 8 5- Choroidal effusion. 2 8 6- Anterior uveitis. 3 11 7- Wound leak . - 0 8- TOP increase. 2 8 1- Infected bleb 1 4 2- TOP increase . 3- Persistent hypotony 1 4 1 4 2- Iandequate excision of sclera] tissue . Early postoperative : Late postoperative : encapsulated blebs have developed. Transient corneal edema, at the site of the corneal flap was commonly seen in the early postoperative period and tend to resolve subsequently. Epithelial defect over the corneal flap was noticed in one case which was complicated with inadvertant damage to the corneal flap during surgical manipulations. As regards the encountered complications, bleeding from the sclera] bed at the time of dissecting the sclera] pocket or when rotating the cystitome was the main distressing problem during surgery, this was managed by gentle compression. Mild hyphema seen in the first day following surgery occurred in seven cases and resolved spontaneously over few days. Shallow anterior chamber on the first postoperative day was commonly observed in nearly all cases and reformed within 2-3 days with simple patching and routine postoperative treatment. Two cases, however, remained shallow for 3-4 weeks due to visible choroidal detachment. The latter managed conservatively and disappeared after 4 weeks. No wound leak was observed in any case. Persistant hypotony was encountered in one case and was attributed to an over functioning bleb that encircled the entire limbus, causing bogginess of the bulbar conjunctiva and ocular discomfort. This case, despite persistent low TOP had a final visual acuity of 6/12, unchanged from his preoperative examination. In 659 general, keratometric readings obtained for all cases before and after surgery did not show significant changes. Discussion Corneal trabeculectomy, using Van Buskirk technique, showed in our study a successful control of TOP in 88.8% at the end of the 3 and 6 months follow-up. The reported success rate for conventional trabeculectomy when performed as initial surgery range from 50-98% (Watson et al., 1981). Van Buskirk (1992) in his series of 5 glaucoma patients at high risk for failure of glaucoma filtering surgery achieved a 100% control of TOP, three of this cases, however, were treated postoperatively with subconjunctival 5-FU in divided doses. Cioffi and V a n B u s k i r k , ( 1 9 9 3 ) p e r fo r m e d c o r n e a l trabeculectomy on 20 eyes and reported success rate of 85% (17 of 20 eyes) at 3 month follow-up examination. The mean TOP at 3 month was 13.9 mmHg compared to 12.26 mmHg in our series, whereas at 6 months the mean IOP was 11,0 mmHg compared to 12.93 mmHg in our study . Lerner, (1997) described a modified trabeculectomy technique different from that of Corneal Trabeculectomy, Ayman Nassar et al Cairns, (1985) and Van Buskirk (1992) in that he did not dissect a corneal flap, instead he preformed a 2.5 mm conjunctival periotomy without cutting the Tenon s capsule, followed by partial thickness limbal incision and then dissected a sclera) pocket for 2 -3 mm posteriorly. As in the Buskirk technique, the subconjunctival space was entered with a cystitome passed through the scleral pocket. He reported a 90% success rate (27 of 30 eyes) in his series at 6 month postoperatively without medication . Filtering blebs were typically low and diffuse and were seen formed in all successful case throught the follow-up period. They developed a hypovascular appearance with multiple microcystic changes of filteration. No encapsulated blebs were seen. Similar findings were reported by Cioffi and Van Buskirk (1993) and Lerner (1997) . Hypotony with flat anterior chamber was ob s e r ve d in 2 c a s e s c omp lic a te d b y c hor oid a l detachment in our study. Both cases regaind normal d e p th c ha mb e r a nd s how e d a b s or p tion of the suprachoroidal fluid within 4-6 weeks postoperatively without specific treatment apart from usual postoperative regimen . However, pers istent hyp otony w ith a n over functioning bleb was noticed in one case without adverse sequelae. Van Buskirk, (1992) reported flat a nte r i or c ha mb e r in one c a s e a s s oc ia ted w i th choroidal detachment. This patient had received 5 FU postoperatively. Cioffi andVan Buskirk (1993) reported one case of shallow AC that, persisted for 3 months a nd thr e e ca se s with vis ib le c hor oid a l detachment that resolved spontaneously . Under manipulation of the corneal flap may lead to epithelial defects. Transient corneal epithelial defect over the corneal flap was observed in one case in the present study and it healed during the first week postoperatively. Corneal edema from manipulation of the corneal flap lead to transient e p ithe lia l d e fe c t. Va n Buskir k (1992) rep or ted transient corneal epithelial defects in all five patients in his first study . The epithelial defects healed promptly in four of the five patients but persisted for two weeks in one patient who was treated adjunctively with 5-FU that necessitated the use of a bandage soft contact lens. • Bleb infection was encounteres in a single case four months p ostoper ative ly in our study. T his particular case was one of two cas es who were operated upon at 6 o clock position. The latter site has the disadvantage of an unprotected bleb that is continuously irritated by the lower lid movements. The procedure however, is technically easier to perform at 6 o clock since the instruments are hold 660 conforming with the usual position, unlike the upper meridian where the instruments are hold facing the surgeon, opposite to the usual position. Corneal trabeculectomy presents no doubt a significant modification of the original trabeculectomy technique, since it offers the great advantage of sparing the conjunctiva intact avoiding excessive surgical trauma that stimulates postoperative conjunctival scarring. The clinical appear ance of the oper ated eyes w i th minima l infla mma tor y r eac tion, together w ith p r evious histological studies on rabbit eyes (Cioffi et al., 1993), suggest that corneal trabeculectomy incites less subconjunctival inflammation than conventional trabeculectomy. Meanwhile, the technique has the disadvantage of dissecting a corneal flap, working in a small surgical field and difficulty in obtaining adequate exposure. References 1. Cairns JE: Trabeculectomy . Preliminary report of a new method. Am J. Ophthalmol. 1965, 66: 6739 2. Cairns JE: Clear-cornea trabeculectomy. Trans. Ophthalmol. Soc. UK. 1985. 3. C i o f f i G A a n d V a n B u s k i r k E M : C o r n e a l trabeculectomy without conjunctival incision. Extended follow-up and histological findings. Ophthalmology 1993; 100:1077-82. 4. Fahmy [A, Ali MA, and Spaeth GL: Long-term follow-up of clear cornea trabeculetomy. Ophthal. Surg. 1990; 21 (4): 294-5. 5. Keiller RB and Molten() ACB: Twenty -two cases o f c l e a r c o r n ea t r a b ec u le c t o m y. A us t. N ZJ Ophthalmol. 1986; 14: 334-42. 6. Lerner SF: Small incision trabeculectomy avoiding Tenon s capsule. Ophthalmology 1997;104:123741 7. Taha AM: Clear ornea versus subscleral trabeculectomy for uncontrolled primary open angle glaucoma. Bull. Oppthalmol. Soc. Egypt 1990;83:145. 8. V a n B u s k i r k M : T r a b e c u l e c t o m y w i t h o u t conjunctival incision . AM.J. Ophthalmol. 1992, 113: 145-53. 9. Watson PG and Grierson 1: The place of trabeculectomy in the treatment of glaucoma. Ophthalmology 1981; 88: 175-96.