ULTRASOUND BIOMICROSCOPY EVALUATION OF OPTIMAL CILIARY SULCUS IOL SUTURE FIXATION SITE

Takeshi Sugiura, MD

The selection of the site of insertion for successful intraocular lens (IOL) suture fixation with the fewest complications and least risk of postoperative IOL decentration has been widely discussed.^1–21 However, it has not been reliably determined how many millimeters from the limbus a needle should be placed to indicate that the needle is accurately inserted through the ciliary sulcus or the pars plana.

The main reason is that the tissue around the ciliary sulcus cannot be inspected directly through a surgical microscope, and posterior observation of the ciliary body via the Miyake-Apple view^22,23 only reveals the radial arrangement of the ciliary processes and fails to provide a clear image of the 3-dimensional shape of the ciliary sulcus in the living eye (Figure 69-1).^22–27 Although the anatomy of the surrounding tissue of the ciliary body in the cadaveric eye has previously been reported, there have been no reports on anatomical findings and measurements of the surrounding tissue of the ciliary body in the living eye.^24–27

Therefore, I measured and demonstrated the shape of the ciliary sulcus and its vicinity using ultrasound biomicroscopy (UBM). Based on those results, I studied mathematically the correct point of needle emergence on the sclera for accurately piercing the ciliary sulcus from the inside of the eye. When I confirmed accurate needle insertion into the ciliary sulcus by endoscope during actual surgery, the point of needle emergence almost exactly matched the point of emergence calculated mathematically based on the UBM results.²⁸ I also studied the optimal point of needle insertion from the outside of the eye in pars plana suture fixation based on UBM measurements and new findings on the 3-dimensional shape of the ciliary sulcus obtained using endoscopy to observe the shape of the ciliary sulcus in living patients.

Shape of the Ciliary Sulcus of Living Eyes Observed by Ultrasound Biomicroscopy

Using UBM, the shape of the surrounding tissue of the ciliary sulcus was measured in 16 eyes of 11 patients (5 men and 6 women; 9 right eyes and 7 left eyes; with a mean age of 78.8 years and standard deviation of 6.93 years) following intracapsular cataract extraction (ICCE).

Measurements were made from 8 directions for each eye at 45-degree intervals from 0 degrees, resulting in 128 (16 x 8) measurement sites. I defined the foot of a perpendicular line drawn from the deepest part of the ciliary sulcus to the sclera as “A,” the point at the intersection of a straight line drawn parallel to the posterior iris surface with the scleral surface as “B,” the deepest part of the ciliary sulcus as “C,” and the tip of the ciliary processes as “D.” I measured the angle of the ciliary sulcus (An), the length between the deepest part of the ciliary sulcus and the tip of the ciliary processes (CD), the length of a perpendicular line drawn from the deepest part of the ciliary sulcus to the sclera (AC), and the length of a straight line drawn parallel to the posterior iris surface from the deepest part of the ciliary sulcus to the scleral surface (BC), and calculated the mean and standard deviation for each of these values. Based on the results obtained, I determined the shape of the ciliary sulcus (Figure 69-2).

Results showed that the angle of the ciliary sulcus (An) was 66.3 degrees ± 20.0 degrees (mean ± standard deviation), the distance from the deepest part of the ciliary sulcus to the tip of the ciliary processes (CD) was 0.535 mm ± 0.137 mm, the length of a perpendicular line drawn from the deepest part of the ciliary sulcus to the sclera (AC) was 1.520 mm ± 0.197 mm, and the length of a line drawn parallel to the posterior iris surface from the deepest part of the ciliary sulcus to the scleral surface (BC) was 2.480 mm ± 0.305 mm (n = 128; see Figure 69-2). Given that ABC in Figure 69-1 is a right triangle, the length of AB is 1.96 mm according to the Pythagorean theorem.²⁸

The ciliary processes are anatomically approximately 1 mm high, 0.5 mm wide, and 2 mm long.^24–27 UBM measurement results showed that the tips of the ciliary processes in the living eye are located 0.535 mm from the deepest part of the ciliary sulcus. The thickness of the region between the deepest part of the ciliary sulcus and the posterior sclera is calculated to be approximately 0.28 mm, using measurements from the UBM image in Figure 69-2. Based on this calculation, the height of the ciliary processes by UBM (distance from the posterior sclera to the tips of the ciliary processes) is 0.535 + 0.28 = 0.815, which seems consistent with anatomical findings.

Optimal Point of Needle Emergence in Ab Interno Ciliary Sulcus Suture Fixation of an IOL

USING A STRAIGHT NEEDLE

It is known that Schlemm’s canal is reachable with a perpendicular incision from the posterior surgical limbus.^26,27 On a UBM image, therefore, the posterior surgical limbus is the point at the intersection on the sclera of a line perpendicular to the sclera, passing through an area that is presumed to be Schlemm’s canal (Figure 69-3). Because the length of AB is 1.96 mm, the distance between the posterior surgical limbus and the perpendicular line drawn from the deepest part of the ciliary sulcus to the sclera (AC) is measured at 0.41 mm on the UBM image (see Figure 69-3).

Thus, assuming that a needle is successfully inserted into the deepest part of the ciliary sulcus horizontal to the posterior iris surface, in ab interno ciliary sulcus suture fixation of an IOL, the distance between the point of needle emergence on the sclera and the posterior surgical limbus is 0.41 mm + 1.96 mm = 2.37 mm (Figure 69-4). In actual surgery of ab interno ciliary sulcus suture fixation of an IOL, a needle piercing from the inside of the eye is inserted in a somewhat downward direction with the iris slightly lifted. Therefore, it is expected that the point of needle emergence on the sclera would be approximately 2.5 mm from the posterior surgical limbus for a straight needle that has been accurately inserted into the deepest part of the ciliary sulcus (see Figure 69-4).

In 117 of 128 eyes with endoscopically confirmed straight needle insertion from the corneal incision on the opposite side of the eye into the ciliary sulcus and through the deepest part of the ciliary sulcus using the Ciliary Sulcus Pad Injector (Duckworth & Kent Ltd), a device the author invented, the needle emerged at a marked point 2.5 mm from the posterior surgical limbus (Figure 69-5). However, when the straight needle emerged through the sclera at a point significantly deviating from the indicator, as in 11 eyes (8.6%), endoscopic observation showed that the straight needle had pierced a site largely deviating from the deepest part of the ciliary sulcus.²⁸ The axis of needle emergence was 45°/225° in the right eye and 135°/315° in the left eye, which was the same for all patients.

USING A WEAKLY CURVED NEEDLE

When a weakly curved needle (eg, Alcon’s PC-9 weakly curved suture needle) is inserted through the ciliary sulcus, taking into account the radius of the curvature of the curved needle, it is expected that the point of needle emergence would be less than 2.37 mm, and probably about 2.0 mm, from the posterior surgical limbus (Figure 69-6).

In 16 of 22 eyes with endoscopically confirmed successful needle insertion through the deepest part of the ciliary sulcus using Alcon’s PC-9 weakly curved suture needle in combination with the Ciliary Sulcus Pad during surgery, the needle emerged at a marked point 2.0 mm from the posterior surgical limbus (Figure 69-7). However, in 6 eyes (27.3%), the weakly curved needle emerged through the sclera at a point significantly deviating from the indicator, and endoscopic observation showed that the needle had pierced a site largely deviating from the deepest part of the ciliary sulcus. The Ciliary Sulcus Pad is a silicone sponge that fits the shape of ciliary sulcus and helps accurately insert the needle into ciliary sulcus. It was the model that preceded the Ciliary Sulcus Pad Injector.²⁸

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