Reprints:Daljit Singh, MD, Dr. Daljit Singh Eye Hospital, 1-Radha Soami Road, Amritsar-143001, India.

The authors are from Dr. Daljit Singh Eye Hospital, Amritsar, India.

The authors have stated that they do not have a significant financial interest or otherrelationship with any product manufacturer or provider of services discussed in thisarticle.

O R I G I N A L A R T I C L E

The ability to control and stabilize eye pressure hasbeen the cornerstone of glaucoma therapy over the

last century. Pharmaceutical companies have devel-oped excellent advances in glaucoma medications overthe last 20 years. On the other hand, clinical ophthal-mologists have been slow to improve on the surgicalfiltration procedures that are the last line of defense inprotecting the eye from the ravages of glaucoma.

A novel technique is presented herein that reducessurgical filtration time to approximately 5 minutes induration, eliminates the need for peripheral irido-tomies, and effectively eliminates postoperative flatanterior chambers. Furthermore, the surgical revisionrate for this procedure is less than 5% at 3 monthspostoperatively, and a surgical revision with thisapproach is both safe and much easier than with pre-vious glaucoma filtration surgeries. This novel tech-nique is called transciliary filtration (TCF).1 In theUnited States, ophthalmologists have referred to thisprocedure as Singh filtration.

Materials & MethodsThe procedure employed a modified Fugo Blade™(Plasma Blade) capsulotomy unit.2 A blunt 1-mmdiameter probe was employed to ablate a 1-mm pore inthe sclera (Fig 1). This 1-mm pore was placed 1 mmbehind the limbus, and the ablation was performedfull thickness through sclera. Once ablation was com-pleted, the outer surface of the ciliary body wasexposed. At this point, a second probe was used. The

Daljit Singh, MD, & Kiranjit Singh, MD

Transciliary FiltrationUsing the Fugo Blade™

Transciliary filtration is an approach to manage glaucoma that

departs from classic filtration surgery. This approach uses the tis-

sue ablation and noncauterizing, hemostatic capabilities of the Fugo

Blade™ (Plasma Blade). A nonbleeding micropore is created, which

drains aqueous from behind the iris and into subconjunctival lym-

phatics. No peripheral iridectomy is needed. Mitomycin and excess

cautery are contraindicated. Surgical time for this procedure is

approximately 5 minutes.

A B S T R A C T

ANN OPHTHALMOL. 2002;34(3):183–187 183

ANN OPHTHALMOL. 2002;34(3)184

second probe had a hair-thin, long incising filament,which produced a plasma column 100 µm in diameter.Once the outer surface of the ciliary body wasobserved, this second tip was employed to make a full-thickness penetration through the ciliary body. Tobegin this procedure, a 1-cm wide conjunctival flapwas incised along the limbus. This flap was pulledbackward, thereby exposing sclera. This was in thepre-Tenon area. In actuality, a thin layer of Tenon tis-sue may be present; however, the thin nature of thistissue allows the sclera to be easily and quicklyexposed with minor abrasion and cleaning of the scle-ral surface.

At this point, the area was prepared. If bleeding wasobserved from vessels in the scleral surface, discretepinpoint cautery was placed precisely over the area ofvessel leakage, rather than application of massiveamounts of cautery to the surface. This was performedin this manner to minimize trauma to the sclera and tothe scleral lymphatic system.

After preparation of the sclera, the blunt modifiedFugo Blade tip was employed to penetrate throughsclera and thereby expose ciliary body. Following this,the long, thin, modified Fugo Blade tip was employedto place a 100-µm pore through the full thickness ofthe ciliary body. When this was accomplished, the sur-geon checked for a slow ooze of aqueous fluid throughthe pore (Fig 2). Once that was established, the con-junctiva was repositioned with a suture placedthrough sclera and conjunctiva along the limbus.

Appropriate antibiotic and steroid drops wereapplied to the eye 5 times a day. The eye was alsopatched for approximately 4 hours postoperatively.

In the event that the filter failed, revision wasaccomplished by the following technique. The con-junctiva flap was again loosened. The surface of thesclera was cleaned. The area was checked for over-growth of Tenon capsule. If this was the case, theentire area of Tenon overgrowth was excised and the

surface of the sclera was meticulously cleaned. Onemay observe a flow of aqueous from the originalmicropore. If the micropore was established byremoval of overgrowth of Tenon capsule, the conjunc-tival flap was replaced to its original position and theoperation was complete. In those cases in which aTenon overgrowth was not the cause for lack of filtra-tion, the area was cleaned and the second modifiedFugo Blade tip was used to re-form the 100-µm-diame-ter pore opening. It was necessary to identify a dis-crete ooze of aqueous fluid to be sure that the filterwas patent. If the flow was not reestablished with thismeans, a second primary procedure was performed, asdescribed above, in another location along the limbus.A complete primary procedure required approximate-ly 5 minutes in duration and traumatized a minimalarea along the scleral surface.

For all glaucomatous eyes that underwent TCF, IOPdata were subjected to statistical analysis based on thepreoperative IOP vs the postoperative IOP, to evaluateif the pressure decrease due to TCF was statisticallysignificant. The data were evaluated with the Wilcox-on signed rank test. The preoperative IOP was the lastIOP reading before TCF surgery. The postoperativeIOP was the IOP registered at the last postoperativeexamination after surgery.

ResultsTo date, we have performed 147 TCF cases, with thelongest follow-up lasting 6 months. Seven casesrequired surgical revisions at 3 months postoperative-ly. No patient had flat anterior chambers postopera-tively. There were 2 cases of choroidal effusions, andboth resolved by 1 month postoperatively.

The preoperative intraocular pressure (IOP) rangedfrom 28 to 62 mm Hg. The maximal acceptable post-operative pressure without medication was 21 mm Hg,and only 15 of 147 eyes had IOP above this level at 6months. The statistical analysis of IOP for TCF-treat-

Fig 1.—Creation of transciliary filtration (TCF) ostomy. 1 indicates limbus, withcornea above and sclera below; 2, margin of small (1-cm-wide) fornix-based con-junctival flap; 3, thin, long incising filament projecting at a right angle from FugoBlade cannula below; and 4, small round ball of plasma at junction of incising fila-ment and eye. This small ball of plasma ablates or “erases” sclera and ciliary bodysimilar to action of an excimer laser, thereby creating TCF micropore.

Fig 2.—Patent TCF ostomy. 1 indicates limbus, with cornea above and sclera below;2, insertion of Tenon capsule into sclera as seen inside of conjunctival flap raised withconjunctival incision along limbus. Tenon tissue has been darkened with trypan blue;3, small conjunctival flap being reflected back with forceps; and 4, TCF ostomybetween limbus above and Tenon insertion below. Conjunctiva will be reflected backinto place and secured with one suture.

ANN OPHTHALMOL. 2002;34(3) 185

ed patients demonstrated a preoperative to postopera-tive drop in pressure, which was statistically signifi-cant (P<.2%).

DiscussionSince 1957, the senior author has performed 6000-plusglaucoma operations, using every available technique,including the diode, erbium, and excimer lasers. In1979, D. Singh initially described TCF for intractableglaucoma.3 Since then, he has used this technique forthe original indication—intractable glaucomas thatare not amenable to other available modalities. He hasperformed nearly 200 such operations in the past 23years before beginning TCF with Fugo Blade technol-ogy. Many patients have benefited from this proce-dure, but we are unable to present any objective datadue to incomplete follow-up.

Our institution has done more than 3500 kerato-prosthesis operations since 1979. Most of thesepatients had faulty filtration channels and the circum-corneal tissues were fibrosed by the extensive dissec-tion that keratoprosthesis surgery involved. It is notpossible to check the IOP by any instrument, sincethese patients have no cornea. We check the oculartension digitally and prescribe antiglaucoma medica-tion based on clinical judgment.

A year ago, we saw a patient who had only 1 eye andhad good vision 1 year after receiving a keratopros-thesis. However, her ocular tension was not under con-trol despite receiving oral acetazolamide therapy.Topical drops were too expensive for this patient.After considering all options, we decided to performTCF with the Fugo Blade.4 The operation was easy andbloodless, and the aqueous fluid came out effortlessly.Since that time, this keratoprosthesis patient has hada good bleb, and the IOP is digitally acceptable.

We decided to use the Fugo blade technology basedon the capability of this technology. It does not cut,but rather ablates tissue, much like an excimer laser.5

It breaks the large molecular lattice of tissue and con-verts it into small aromatic molecular fragments.These fragments act to plug up or pack the top of theblood vessels, thereby promoting platelet plug forma-tion and coagulation. This factor is very important inthis procedure, since the ciliary body is highly vascu-lar and prior techniques used in TCF inevitably result-ed in extensive uveal bleeding.

The operative and immediate postoperative resultsare encouraging to a glaucoma surgeon. The tech-nique involves making a limbus-based conjunctivalflap, clearing the sclera of Tenon capsule and makinga transciliary filtering pore. The Fugo Blade (a mere100-µm activated filament) produces instant microab-lation wherever it touches.6,7 A 1-mm-diameter roundablation pit is made in the sclera. Very soon, the uvealtissue becomes visible. The uveal tissue is clearedvery cautiously, gaining depth at a slow pace. A suc-cessful micropore is signaled by the outward flow of afew pigment particles along with a “seepage” of theaqueous. Seepage is the correct term, since the fluid

seeps and does not gush out. This is the most desir-able feature of drainage, since there is a slow fall inIOP, which reduces the chances of choroidal hemor-rhage. Furthermore, there is no shallowing of the ante-rior chamber. In fact, the anterior chamber deepens incases of angle-closure glaucoma. No iridectomy is per-formed, as it is unnecessary. This prevents iris-relatedanterior chamber complications. As the conjunctivalflap is sutured in place, a small bleb is already inplace, without an undesirable change in the depth ofthe anterior chamber. The dressing is removed after 4hours, and the patient is placed on a regimen ofsteroid and antibiotic drops 5 times a day.

The first 20 or so cases that we performed with theFugo Blade included primary open-angle glaucoma,pseudoexfoliation glaucoma, pseudophakic pupillaryblock glaucoma, aphakic glaucoma, failed surgerycases of glaucoma, neovascular glaucoma, phacomor-phic glaucoma, buphthalmos, and a case of perforatinginjury in which pars plana vitrectomy had been done.In 3 cases, there was a droplet of vitreous presentation,which was repeatedly cut until only aqueous was seep-ing. This observation made us move the opening ante-riorly to as close as 1.0 mm from the limbus.

Important observations in the initial patients includ-ed the following. The postoperative period was quietwithout the worry of shallow anterior chamber or pro-nounced hypotony. The anterior chamber was not flat ina single case. The anterior chamber actually deepenedin cases of angle closure and phacomorphic glaucoma,which was a pleasant unexpected finding. In addition,the filtration blebs were shallow and functional.

However, some complications developed. Threepatients developed encapsulated blebs within a monthof operation. In all 3 cases, the Tenon cyst had prolif-erated, wherein underneath this Tenon layer we founda patent filtering track.

We thought the formation of an encapsulated blebwas a great obstacle, and it had to be prevented beforereal progress could be made. A great deal of thoughtwas focused on this problem. Since 1984, one of theauthors (D.S.) had been performing a form of filtrationsurgery called microtrephine and presented the find-ings at the International Congress of Ophthalmologyin 1986 (unpublished data). During all these years, amodified technique had been used, but the leadauthor had never seen a case of encysted bleb. We sur-mised that this was so because his technique ofmicrotrephine involved detaching the conjunctivafrom the limbus for approximately 2 mm, applying apoint of cautery on the limbus, and placing a 0.7-mmhole formation in the pre-Tenon area with a handheldmotorized microtrephine, through which a peripheraliridectomy was done. Then the detached conjunctivawas put back in place with a single 40-µm suture. Allsurgery was pre-Tenon. We concluded that encapsulat-ed blebs were forming since we were cutting theTenon capsule, cauterizing it, and inciting it with mit-omycin C, thus producing all forms of maladies,including the encapsulated bleb formation.

ANN OPHTHALMOL. 2002;34(3)186

We decided to shift anteriorly and perform pre-TenonTCF. Before making a conjunctival flap, we alwaysinject 2% subconjunctival lidocaine so that the subcon-junctival Tenon capsule swells up, which makes it easyto dissect. When we decided to dissect anteriorly, wechose to inject in the pre-Tenon subconjunctival spaceinstead of the post-Tenon subconjunctival space. Wetook a 1-mL syringe with a 30-gauge needle and inject-ed in the limbal subconjunctival tissue. It was a tightspace and took fluid slowly. As soon as the surgeon(D.S.) applied pressure on the piston of the syringe,from the corner of his eye he got a momentary glimpseof a swollen lymphatic vessel about 1 cm away. Theappearance was that of a lymphangiectasis, a familiarsight. We were impressed by this chance observationand thought further investigation was necessary. In thenext case, we injected fluorescein and found it immedi-ately pooled far away from the site of injection. Wefound photography of fluorescein not very demonstra-tive; therefore, we decided to use trypan blue, the samedye that is used to stain the anterior capsule. We usedtrypan blue on 3 cases, which gave us much insight intothe pathophysiology of the conjunctiva.

At a presentation at the 2002 American College ofEye Surgeons meeting, the senior author emphasizedthat we perhaps have not understood the physiologyand pathology of the surgical filtration procedures(unpublished data). While we are content with the for-mation of an avascular bleb and refer to it as an idealbleb, the reality is far from correct. While we credit theabsorption of the drained aqueous by veins and lym-phatics, it is merely lip service to the lymphatics. Thereason is that we have never seen the lymphatics and,therefore, we take no steps to preserve them. Lym-phatics are storm drains, as we found out. They arevery good in their function. If you balloon the con-junctiva with saline or local anesthetic, you will findall this extra fluid removed in a matter of minutes.The veins do not have the power to remove all of thisfluid. The lymphatics open their flood inlets for quickdrainage of excess interstitial fluid.

We came to term the avascular filtration bleb a typeof elephantiasis of the eye. When interstitial fluid allover the body is being removed by the lymphatics, itis inconceivable that the same process is not operatingin the case of the eye. The absence or damage of thelymphatics should mean that a filtration procedurehas a propensity to fail.

We amply confirmed this theory in failed glaucomasurgery cases. They all showed absence of lymphaticsin the area where the filtration surgery had been done.These areas showed scar tissue and excessive promi-nence of blood vessels. We performed a dye drainagetest using trypan blue in normal and abnormal (failedglaucoma surgery) cases. We found that whereas innormal patients the injected dye disappears in a mat-ter of 1 hour, in the absence of lymphatics the dyestayed for 3 to 5 days. In difficult perilimbus-scarredcases undergoing repeated surgery, we preoperativelyperformed a dye drainage test around the limbus to

find out the most suitable spot for performing filtra-tion, that is, the area that harbored healthy lymphaticsthat were connected to drainage channels. The prog-nosis, according to us, will depend on the position anddensity of healthy lymphatics.

At the end of the surgery, each case showed a near-normal anterior chamber. In angle-closure cases, thechamber depth has been seen to increase. The irisbombé became vastly reduced and the anterior cham-ber seemed to get a deep breath (ie, it deepened). Thebleb started forming under the conjunctival flap assoon as it was sutured back to the limbus.

Since we became aware of the delicate structurecalled lymphatics, we have stopped giving subconjunc-tival injection of antibiotic and steroid at the end of theoperation. We just drop the mixture on the conjunctiva.

The first examination is done 4 hours after surgery.The anterior chamber is always well formed, and so isthe bleb. If trypan blue dye was injected under theconjunctiva at the beginning of the surgery, it getstotally removed in 4 hours. However, in patients inwhom we are unable to demonstrate the lymphatics,the dye remains for many days. In 2 patients, wenoticed a trace of blood in the anterior chamber. It wasthe same blood seen oozing in from Schlemm canal atthe end of the surgery. One of the patients had neo-vascular glaucoma and the other had inflammatoryglaucoma.

In the follow-up examinations after 15 days, 1month, 2 months, and 3 months, we found that most ofthe patients had very shallow diffuse blebs, with avariable amount of scarring. The scarring was moremarked in the younger patients. All these patients hadbeen operated on with a limbus-based flap and hadreceived a tiny application of mitomycin C. We arenow afraid to use even a tiny antimitotic application,since there is every possibility of this agent gettinginto the lymphatics and causing damage to the fewcells that these vessels possess.

Two cases of phacomorphic glaucoma that were con-trolled by TCF underwent cataract surgery 2 monthslater. In both of these patients, the blebs were unaf-fected. This was quite natural, since the particulatematter that is released at the time of cataract surgerywould not move posteriorly to reach the internal open-ing of the filtration track. We believe that it is an impor-tant consideration for the glaucoma surgical cases.

There was no case of severe hypotony and minimalrisk of choroidal detachment. About 90% of thepatients had well-controlled IOP without medication.About 10% of patients were advised to massage theeye to keep the filtration track functional, with orwithout local medication. There were both high andlow risk factors for pathology among the cases in ourseries. In sum, these patients represented some of themost complicated abnormalities seen in our hospital.

Because a small part of the limbus was used to per-form the filtration surgery, it was possible to repeatthe operation at other places on the limbus in cases offailure.

ANN OPHTHALMOL. 2002;34(3) 187

In summary, transciliary filtration works like otherfiltration surgeries. However, the route of filtration isdifferent. The lymphatic channels need to be betterunderstood. They may hold the key to many success-es and failures in this technique. We intend to contin-ue the study for the simple reason that the surgery iseasy to perform and is attended with few problems.This new surgical approach has become a reality onlyafter the introduction of a new fundamental technolo-gy, plasma energy,8 as harnessed by the Fugo Blade.9

References 1. Winn CW. Broad applications seen for electrosurgical instrument.

Ocular Surg News. 2001;19(11):45–46.

2. Fugo RJ, Delcampo DM. The Fugo Blade™: the next step after cap-sulorhexis. Ann Ophthalmol. 2001;33(1):12–20.

3. Singh D, Verma A, Singh M. Transciliary filtration for intractableglaucoma. Trans Ophthalmol Soc UK. 1979;99:92–95.

4. Winn MC. Broad applications seen for plasma blade [Asia-Pacificed]. Ocular Surg News. 2001;12(8):1–5.

5. Sabbagh LB. The leading edge: harnessing electrons for a faster,smarter incision. Eyeworld. 1998;3(4):88.

6. Roy FH. Course for Fugo Blade is enlightening, surgeon says.Ocular Surg News. 2001;19(17):35–38.

7. Sabbagh LB. The never ending quest: creating a better way toremove the lens. Eyeworld. 1998;3(4):50–53.

8. Kronemyer B. Fugo Blade uses low-level energy to create anteriorcapsulotomy. Ocular Surg News. 2000;18(21):45–46.

9. Singh IR, Singh D, Singh R, Singh K, Kaur H, Jit Singh RS. Vit-reoretinal surgery with plasma knife may be a new frontier. Ocu-lar Surg News. 2001;19(19):80–83.