Ординатура / Офтальмология / Учебные материалы / Atlas of Glaucoma Second Edition Choplin Lundy 2007

flap is being developed in such a patient, careful

bridle suture, and also avoids bleeding at the supe-

and patient dissection is often required to extend the

rior rectus and postoperative ptosis that may occur

dissection anteriorly enough for appropriate place-

rarely with the superior rectus bridle suture. How-

ment of the filtration site.

ever, the corneal traction suture has the disadvan-

After initial suturing of the scleral flap, the sur-

tage that dissection through the Tenon’s capsule is

geon should re-form the anterior chamber to a nor-

more laborious. Also, the other disadvantage of the

mal depth and pressure and then always evaluate

corneal traction suture is the possibility, especially

the amount of filtration obtained prior to closing the

in myopes with pliable sclera, that when the eye

conjunctiva. As described in the following text,

is forcibly infraducted near the end of the surgery

further manipulation can be done to adjust filtra-

for closure of the limbus-based conjunctival flap,

tion to a specific level of outflow, rather than sim-

the traction at the superior limbus will distort the

ply placing a predetermined number of sutures in

anatomy enough at the filtration site that the wound

the scleral flap for every case. This intraoperative

cleft will gape with outflow of aqueous and inabil-

adjustment is crucial for obtaining a consistently

ity to maintain a formed chamber during conjunc-

successful result.

tival wound closure. In general, we prefer a superior

rectus bridle suture for limbus-based conjunctival

flaps and a corneal traction suture, if needed, for

TECHNIQUES

fornix-based flaps.

Placement of a corneal traction suture is best

Preparation

done with a 6-0 or 7-0 Vicryl suture on an S-29

needle through superior peripheral clear cornea

After sterile prepping and draping, the lid speculum

(Figure 17.1b). Care should be taken not to enter

should be inserted with care so that the speculum

the anterior chamber. If the filtration site is to be

does not cause pressure on the globe. A traction

off-set either superonasally or superotemporally,

suture should be placed in such a way as to maxi-

then the traction suture should be centered in the

mally infraduct the globe, exposing conjunctiva as

quadrant to be used. The globe needs minimal

far superiorly and posteriorly as possible, especially

stabilization during passage of this suture, with a

if a limbus-based conjunctival flap is being used.

cellulose sponge being sufficient to hold the globe

This is crucial for making the conjunctival incision

steady for needle passage. With either suture tech-

as far posterior as possible, preferably 10 mm poste-

nique, the surgeon should remember at all times to

rior to the limbus, so that the area of the postoper-

resist the tendency to grasp conjunctiva on the

ative filtering bleb will not be limited by scar tissue

superior bulbar portion of the globe anywhere near

from the conjunctival incision. Either a corneal trac-

the planned filtration site.

tion suture or a superior rectus bridle suture may be

A superior rectus bridle suture is best done

used. The corneal traction suture has the advantage

with a 4-0 silk suture on a taper-point needle. The

of avoiding the rare instance of scleral perforation

superior rectus muscle can be grasped with a

which may occur with the larger needle and less

toothed forceps by either infraducting the globe

well visualized needle pass of the superior rectus

with a muscle hook pressing into the inferior fornix

(a)

(b)

may be too thick for the dissection to be completed

popularized by Peng Khaw, MD. We now recom-

with the cellulose sponge and therefore the final

mend dissecting enough of a conjunctival flap to

remaining fibers must be dissected with a 67 blade

permit much of the superior quadrant to serve a

tip oriented perpendicularly to the scleral surface and

bleb. It may also be helpful to dissect posteriorly

‘scraped’ circumferentially along the base of the

enough to puncture the posterior Tenon’s insertion

Tenon’s attachments. The remaining tissue can then

near the superior rectus insertion. This large dis-

be pushed forward into the sulcus as desired. Patient

section, combined with a broad application of

and complete anterior dissection of the conjuncti-

antimetabolite and posteriorly directed flow from

val flap is crucial to allow sufficient exposure to

the scleral flap promotes a low, diffuse bleb that is

perform the proper scleral flap dissection.

much less likely to break down over time and pose

If a superior rectus bridle suture is used, the

an infection risk.

only difference from the technique just described

is with the conjunctival and Tenon’s incision.

Scleral flap dissection

With the bridle suture, the surgeon should grasp

conjunctiva only with the non-toothed forceps just

The size and shape of the scleral flap is of some

anterior to the bridle suture and pull the conjunc-

significance. Most surgeons prefer either a square,

tiva toward the patient’s feet to put the tissue on

rectangular or triangular flap with the anterior base

stretch and then incise it with the blunt Westcott

of the flap being 2–4 mm with the length likewise

scissors. The Tenon’s is grasped in a like manner

ranging from 2 to 4 mm. Depending on the place-

but without the need for an assistant to also grasp

ment of the underlying scleral punch, rectangular

this tissue since it is, in effect, already held by the

and triangular flaps can promote sideways flow or

bridle suture. As this Tenon’s incision is done over

posterior flow. Khaw’s theory holds that sideways

the superior rectus, care should be taken not to cut

flow more commonly leads to eventual bleb break-

into muscle. The incision is then extended as pre-

down at the limbus and so, with his technique, the

viously described.

goal is to create posteriorly directed flow through

If a fornix-based conjunctival flap approach is

the flap to form a low, diffuse bleb. To achieve this,

elected, a limbal conjunctival incision of about

a large rectangular flap with a central punch is

6–8 mm is initiated by tenting the conjunctiva near

needed. Prior to dissection of the flap, the surgeon

the limbus with non-toothed forceps and the inci-

should confirm its appropriate placement anteri-

sion is begun with the Westcott scissors (Figure

orly at the limbus and then, if desired, outline the

17.2b). This is carefully extended along the limbus

desired dimensions with the needle-point cautery

for the full length of the peritomy. The Tenon’s is

(Figure 17.3a). A 67 blade should then be used to

incised in a like manner. Blunt dissection with the

outline the scleral flap with a scleral incision of one-

blunt Westcott scissors should be done posteriorly

half to two-thirds scleral thickness (Figure 17.3b).

underneath the Tenon’s, along the length of the

The posterior-most aspect of the scleral flap is then

limbal incision, to allow for good posterior exposure,

grasped with non-toothed forceps and the flap is

to encourage larger posterior bleb development, and

dissected forward with the blade held almost flat

to allow posterior placement of antimetabolites, if

against the sclera (Figure 17.4). During this dissec-

necessary (Figure 17.2b). We have had good success

tion, the scleral flap should be pulled continually

using a fornix-based trabeculectomy technique

anteriorly with the forceps so that the dissection is

(a)

(b)

Figure 17.3 Scleral flap.

(a) Cautery is used to outline the scleral flap. (b) A 67 blade is used to outline a partial-thickness

scleral flap.

Once the eventual desired postoperative intra-

Rather than using cautery to increase outflow,

ocular pressure has been set with the initial sutures,

the surgeon may wish to simply remove the sutures

externalized, releasable scleral-flap sutures may be

already placed, replacing them with looser sutures.

placed as described later in this chapter. This will

The number of sutures required to obtain the

temporarily cause less flow in the immediate post-

desired level of outflow may be highly variable

operative period, will help protect against hypotony

from patient to patient, depending on many factors

and, upon postoperative removal, will permit a fur-

including the amount of flow desired (which will

ther reduction in intracular pressure when desired.

depend upon the type of glaucoma and the charac-

The three steps of suture placement, anterior cham-

teristics of the patient), the thickness of the scleral

ber re-formation, and evaluation of aqueous out-

flap, and the proximity of the corneoscleral opening

flow and level of intraocular pressure (assessed by

to the edge of the flap. In some cases, the posterior

palpation or amount of pressure needed to deform

corner or apex sutures may be all that is required,

the corneal light reflex with a 30-gauge cannula) are

while in other cases 6–8 sutures may be necessary

patiently and continually repeated after each new

for control of the amount of aqueous egress. For a

suture is placed until the anterior chamber remains

rectangular flap using a central punch, we rarely

deep after re-formation with the desired intra-

use more than one suture at each flap corner and

ocular pressure and with a continual but slow and

one releasable suture in the center of the posterior

controlled egress of aqueous from the edge of the

lip of the flap. The tension on the two corner sutures

flap (Figure 17.11a).

is set to permit the desired long-term intraocular

In some cases, such as patients with a shallow

pressure and the tension on the releasable suture is

anterior chamber and chronic angle closure (who

set to regulate the initial postoperative intraocular

are at risk for flat chamber), or young adults with

pressure. The intraoperative evaluation and mani-

significant myopia and thin sclera who are at risk

pulation of the amount of aqueous egress is crucial

for hypotony maculopathy (especially if mitomycin

for obtaining consistently good results, minimizing

is used) the surgeon may wish to have minimal or

early postoperative complications, and avoiding

no egress of aqueous visible and use suture lysis to

unwanted surprises which may occur if the sur-

regulate the intraocular pressure in the postopera-

geon simply places a predetermined, standard

tive period. However, the surgeon should make

number of sutures without evaluating or adjusting

certain that outflow can be induced by applying

the flow rate intraoperatively (Figure 17.13). The

light pressure with the cellulose sponge on the

judgment of the correct amount of aqueous egress

scleral-bed side of the edge of the flap. In cases in

requires experience. This aspect of the surgery is a

which the egress of aqueous is less than the surgeon

large part of the ‘art’ of glaucoma filtering surgery,

believes necessary, short bursts of cautery with the

and the glaucoma surgeon should strive to develop

needle-point cautery can be applied into the cleft

a ‘feel’ for the correct amount of outflow for each

at the edge of the flap in order to make the edges

particular case.

gape and allow aqueous outflow (Figure 17.12).

Special care should be taken to initially apply

Conjunctival flap closure

this cautery in a very short burst, since excessive

retraction of tissue may occur, making it difficult to

If a fornix-based conjunctival flap has been created,

suture the edges close enough to prevent over-

the limbal incision site should be de-epithelialized

filtration.

by scraping with a 67 blade or by cautery. Conjun-

ctiva should then be stretched anteriorly with the

goal of suturing both Tenon’s and the conjunctiva

back into position at the limbus. For short limbal

incisions the closure can be as simple as suturing

either end of the peritomy with an anterior anchor-

ing suture of 10-0 nylon through peripheral clear

cornea. A small running or purse-string-type suture

will probably be required to close any gaping of

conjunctiva beyond the anchoring suture. The other

end of the conjunctival flap is then very tightly

stretched and also sutured anteriorly with an

anchoring suture. As at the other end of the wound,

a small running closure may be required to prevent

leakage distal to the anchoring suture, especially if

a posterior relaxing incision had initially been

Figure 17.12 If the block is not close enough to the edge of

made at that end of the conjunctival incision.

the flap, cautery can be used to shrink the sclera to lessen

Longer conjunctival peritomies often will not be

overlap.

watertight unless the entire peritomy is sutured in