Synechiae are adhesions of the iris to ocular structures which can cause issues of aqueous blockage, pupil dilation, and more. Anterior synechaie are at the angle of the eye where the peripheral iris impedes aqueous drainage and can lead to angle closure glaucoma. Posterior synechiae are at the pupil margin where the iris is adherent to the anterior lens capsule which prevents dilation and makes cataract surgery more challenging. Cataract surgery is a good time to manage these synechiae and help restore ocular anatomy and function,
The cause of synechiae is typically a result of inflammation in the eye, such as from uveitis or as a result of trauma. For posterior synechiae, the adherence of the iris and fibrotic tissue to the anterior lens capsule can limit the patient’s vision, particularly if these fibrotic membranes or lens opacities are in the visual axis. In many cases, use of strong mydriatic topical medications can induce sufficient dilation to pull these synechiae off the surface of the lens capsule.
Using a blunt instrument such as a 27-gauge cannula or a spatula, find a gap between the iris and the lens and carefully insert the tip. Now sweep side to side to gently break these adhesions to free the iris from the anterior lens capsule. This can be done in multiple directions until the iris is completely free for the full 360 degrees. We can perform this maneuver with an anterior chamber inflated with balanced salt solution or moderately filled with viscoelastic.
Fibrotic membranes will impede dilation and despite freeing the adhesions, the pupil will still be miotic. Using two chopping instruments to hook the pupil margin, we then stretch the pupil by pulling it toward the limbus. This gently and slow stretch helps to break the fibrotic membranes and it is common to see small spots of hemorrhage at the iris margin. This stretching maneuver can be done just once in a single direction or repeated 90 degrees away from the first stretch.
Now we can inject more viscoelastic to perform visco-mydriasis by pushing the pupil margin toward the angle of the eye. The capsulorhexis forceps are used to peel away the fibrotic membranes from the pupil margin, using a circumferential direction more than a radial approach. This is done slowly and gently so as to not damage the iris. At this point we have achieved a 5-mm pupil size which is sufficient for performing cataract surgery.
Cataract surgery in an eye with a shallow anterior chamber has the added benefit of widening the angle and flattening the iris. When removing the cataract, which has a thickness of 4 mm or more, and then replacing it with a 1 mm thin IOL, we create more space in the eye and allow the anterior chamber to deepen. This is useful in an eye with narrow angles and a history of prior angle closure glaucoma.
During the cataract surgery, make a sufficiently large capsulorhexis since the iris tends to stick to the lens capsule more than the hydrophobic acrylic IOL optic. This will help prevent future posterior synechiae from forming again. The patient in these figures received a +29.5 D toric monofocal IOL, held in place with a 5.5-mm capsulorhexis.
Once the IOL is implanted in the eye, we can make sure that the pre-existing peripheral iridotomy is patent and flowing. We can also use the forceps to gently grab the iris root and pull centrally to help release anterior synechiae from the angle. Due to the iris manipulation in the case, we can expect more post-operative inflammation. We can help to control this by injecting a small amount of preservative-free triamcinolone into the anterior chamber at the end of the case. We also keep the patient on topical steroids and NSAIDs for a longer post-operative course.
For patients with synechiae, cataract surgery can provide many benefits. We can break the adhesions, peel off fibrotic membranes, restore a normal pupil size, remove impediments to aqueous flow, deepen a shallow anterior chamber, and correct the cataract and refractive error.
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