II. SCISSORS METHOD.

We will now return to the consideration of the second school in which scissors were introduced through a previously made corneal section and a free incision was made in the iris-membrane, or a portion of the membrane excised.

Fig. 17.—Wenzel’s cataract knife, and method of incision (after Mackenzie).

Janin,[11] in 1768, having abandoned the procedure of Cheselden, proposed a new method. He incised the cornea below as for cataract extraction, and raised the corneal lip with a spatula while he introduced a pair of curved scissors, the lower blade of which was pointed. He plunged this sharp blade through the iris-membrane, and with a single vertical cut made a crescentic pupil which gaped sufficiently for visual purposes. As this is the first known description of iridotomy by the scissors method it is probable that Janin was the originator of this procedure.

Wenzel,[23] in 1786, employed a different method. With a lance-shaped cataract knife he entered the cornea, dipped through the iris-membrane, returned to the anterior chamber, and continuing to cut made a counter-puncture on the opposite side of the cornea, following which he completed his cataract incision. This gave a semilunar flap of iris tissue which could easily be excised by scissors passed through the large corneal opening (Fig. [17]).

Fig. 18.—Maunoir’s scissors.

Fig. 19.—V-shaped iridotomy with scissors (Maunoir).

Fig. 20.—Parallelogram pupil (Maunoir).

Maunoir,[24] in 1802, took up the method of Janin, with the object of improving it. He made an incision near the corneal margin, through which he introduced a pair of long, thin, angular scissors of his own design (Fig. [18]), one blade of which was sharp-pointed like a lancet, and the other button-pointed like a probe. The iris-membrane was then punctured by the sharp blade at about the natural location of the pupil, and an incision executed toward the ciliary margin of the iris. Finding that this single incision did not always succeed,[25] he subsequently improved this method by making a second incision from the pupillary area toward the iris margin, in the line of the radiating iris fibers, thus making a divergent V (Fig. [19]). This triangular flap was then allowed to shrink back, or if too stiff, was drawn out and excised. The resultant pupil assumed the shape either of a triangle, a parallelogram (Fig. [20]), or a crescent (Fig. [21]). He always made his incision parallel with the radiating fibers of the iris and across the circular fibers.

Fig. 21.—Crescent pupil (Maunoir).

Scarpa,[16] in 1818, having abandoned his own method of iridodialysis as wholly unsatisfactory, adopted Maunoir’s procedure with enthusiasm, chiefly because he had by a friendly correspondence[25] personally encouraged Maunoir with advice and suggestion during its development. He indorsed Maunoir’s plan of a double incision when he stated his conviction that “experience has proved that in order to obtain, with the most absolute certainty, a permanent artificial pupil, it is necessary to make two incisions in the iris so as to form a triangular flap in the membrane, in the form of a letter V, the apex being precisely in the center of the iris and the base near the great margin.” Some have claimed that Scarpa himself originated the V-shaped incision, but he gives Maunoir full credit for its successful accomplishment, although he does suggest some additional indications for its practical application.

His opposition to the knife-needle incision of Cheselden arose from the fact that the pupil either did not open, or if it did open would not remain permanent, chiefly because of the single iris incision. His antagonism to the more successful procedure of Adams was the result of a caustic personal controversy[17] with that skilful surgeon, who ably parried his charges.[15] His great influence with the profession of that day, however, served to check the sentiment in favor of Adams’ procedure, and when the weight of his indorsement was cast in favor of Maunoir’s operation the scales were decisively turned toward the side of the scissors method.

Mackenzie,[26] in 1840, practiced Maunoir’s operation with considerable success, but in certain cases found it necessary to employ a slight modification of this procedure. He reversed Maunoir’s incision by making the same divergent V across the radiating fibers of the iris instead of parallel with them (Fig. [22]), thus securing a triangular pupil (Fig. [23]), which Lawrence[27] thought might succeed in some cases where Maunoir’s method would not be available.

Fig. 22.—Mackenzie’s incision in cornea and iris-membrane (Mackenzie).

Fig. 23.—Resulting triangular pupil from Mackenzie’s incision (Mackenzie).

Bowman,[28] in 1872, proposed a method which, though surgically difficult to execute, was quite ingenious, and may have been the initial suggestion that stimulated DeWecker to write his monograph in the following year. I will quote his description as follows: “We make a double opening simultaneously on opposite sides of the cornea. It is more convenient, of course, to make these two openings in a horizontal than in a vertical direction. I then run a pair of scissors in two diverging lines (V) from each incision, thus enclosing between the incisions a large square or rhomboidal portion of the iridial region including the pupil, and all the structures there. You then withdraw the portion thus cut out. There is no drag on the ciliary region; whatever is withdrawn has been cut away from its connections beforehand” (Figs. 24, 25 and 26).

Fig 24.—Plan of Bowman’s first iris in­ci­sion. Divergent V.

Fig. 25.—First in­ci­sion completed. Plan of sec­ond, showing double V.

Fig. 26.—Rhomboidal pupil, resulting from Bowman’s iridotomy.

This method is simply an elaboration of the one proposed by Maunoir, in which, instead of forming one divergent V, Bowman has made a duplicate incision on the opposite side, and by joining the bases of these two resultant triangles has caused them to take the shape of a rhomboid, thus <>.

Fig. 27.—Stop keratomes, straight and angular (De Wecker).

Fig. 28.—Forceps-scissors (pinces-ciseaux) (DeWecker).

DeWecker,[29] in 1873, published his admirable monograph on iridotomy, in which he proposed the operation which bears his name, and which has long stood as the best recognized method of this procedure. He advocated two different ways of performing this: 1, simple iridotomy, and 2, double iridotomy.

1. Simple Iridotomy.—This is practically the same operation as Critchett’s sphincterotomy and Bowman’s visual iridotomy, although differently executed. It has been supplanted in our day by iridectomy, and does not, therefore, come within the purview of this discussion.

2. Double Iridotomy.—He rightly claimed that this was both antiphlogistic and optical in its purpose. He employed two distinct methods, which he designated as (a) iritoectomie, and (b) iridodialysis. The instruments he used were a small stop-keratome (Fig. [27]) and a pair of specially devised fine iris scissors (pinces-ciseaux) (Fig. [28]), one blade being sharp pointed and the other blunt. These scissors were a great mechanical advance over all previous instruments of this kind, and undoubtedly proved to be a most important element in the success of his procedure.

Fig. 29.—Iritoectomie. Convergent V (DeWecker).

Fig. 30.—Iridodialysis. Divergent V (DeWecker).

(a) Iritoectomie.—He entered the stop-keratome through the cornea, made an exact 4 millimeter incision, and then partly withdrew it while letting the aqueous slowly escape. As soon as the iris-membrane floated up against the knife, he pressed forward, making a 2 millimeter incision in the iris. Slowly withdrawing the knife, he introduced the sharp point of the scissors through the iris buttonhole and cut obliquely from either extremity of the incision toward the apex of a triangle, thus making a convergent V (Fig. [29]). He then grasped the resulting triangular flap with the forceps and removed it, leaving an open central pupil.

(b) Iridodialysis.—His second method was a counterpart of Maunoir’s earlier operation, with the addition of iridodialysis. He made the corneal and iris incision with the stop-knife, as in the previous method. Slipping in his scissors he cut from the center of the iris-membrane toward the periphery, and duplicated this incision at an oblique angle to the first, thus making a divergent V (Fig. [30]). This formed a triangular flap which he grasped with forceps and tore from its ciliary attachment by iridodialysis.

DeWecker’s procedure was planned by a skilled operator, and required great dexterity in its execution. When successful, however, the result was most brilliant. Nevertheless, it was impossible to eliminate the danger of hemorrhage and loss of fluid vitreous in iritoectomie, while in iridodialysis there was the added danger of a torn ciliary surface and traction on the ciliary body. His strict injunction to have a trained assistant hold up the speculum blades in order to avoid the loss of fluid vitreous, showed how much he feared this disastrous contretemps. The success of his method of incision is well shown in the illustration of his two cases (Figs. [31] and 32).

Fig. 31.—Pupil by iritoectomie. Two incisions. Convergent V (DeWecker).

Fig. 32.—Stenopaic pupil. Single iris incision (DeWecker).

I have already suggested the possibility of Bowman’s paper before the London Congress of 1872 having given origin to DeWecker’s monograph in 1873. This seems quite reasonable when we consider that Bowman proposed two methods of iridotomy, one his double V operation with a rhomboidal pupil (previously quoted), and the other a visual iridotomy or sphincterotomy, by cutting through the pupillary margin with a blunt corneal knife. These two methods are exact prototypes of DeWecker’s proposals. Furthermore, DeWecker was present at the London Congress where he heard Bowman’s paper, and took part in its discussion. In fact, thirteen years later DeWecker acknowledged[30] that after considering the objections to Bowman’s method of iridotomy “I addressed myself at that time to the search for an instrument which allows the avoidance of all traction on the iris, and which can be handled through a narrow opening, while exerting its cutting action in a plane parallel to the surface of the cornea, against which the diaphragm of the iris applies itself, after the escape of the aqueous humor. The forceps-scissors having been discovered, it was easy for me to cause to be revived the procedure of Janin, and to make it decisively take rank in modern ocular surgery.”

DeWecker makes only a casual reference to Maunoir’s method, but credits Janin with the original suggestion of the method which he has thus elaborated. Nevertheless, it is quite evident that DeWecker’s method was simply a modification of the one outlined by Maunoir seventy years before. Furthermore, he lays down the same rule that Maunoir first offered: “Always cut parallel to the radiating fibers and perpendicularly to the circular fibers of the iris.”