**10. Anterior chamber intraocular lens**

Baron was the first to implant an anterior chamber IOL in 1952 [33]. Several other ACIOLs followed during the 1950s but were limited by their design and anterior vault that led to high rates of corneal decompensation. Closed loop ACIOLs gained popularity in the 1970s due to their various flexible designs that were thought to alleviate problems with sizing. However, the sharp edges of the closedloop ACIOL haptic eroded uveal tissue, released inflammatory mediators, and led to multiple complications including uveitis-glaucoma-hyphema syndrome, corneal decompensation, and cystoid macular edema [34–37]. Open-loop ACIOL designs were introduced in the 1980s and their design continued to be improved with its use peaking in the 1990s. These modern open-loop ACIOL designs appear to have less associated complications.

A peripheral iridectomy is required as ACIOLs can cause pupillary block glaucoma. Compared to other IOL techniques, the ACIOL requires a larger six-millimeter incision. Typically, a scleral tunnel is formed in order to minimize astigmatism from a clear corneal incision. Contraindications for anterior chamber intraocular lens include corneal decompensation, angle abnormalities with or without glaucoma, and lack of iris support. Complications associated with ACIOL implantation include endothelial failure with corneal edema, chronic intraocular inflammation,

and/or uveitis glaucoma hyphema. The angle to angle measurement measured by a UBM or OCT is the most accurate option for fitting an ACIOL. More commonly however the white-to-white distance is measured intraoperatively with calipers and 1 mm is added to size the ACIOL. The white-to-white distance is not always a reliable equivalent to the actual angle to angle distance.

Many of the complications of ACIOL implantation can be prevented with an appropriately-sized lens, however, limited sizes are available. An overly small lens can be mobile and cause damage to the corneal endothelium leading to corneal decompensation. A small lens can also cause trauma to iris tissue leading to inflammation and cystoid macular edema. Similarly, an overly large lens can cause inflammation, cystoid macular edema and corneal endothelial failure. A large lens can be noted if the iris is distorted or ovalized during placement. This is due to the footplates not being seated well in the angle. Since the vertical and horizontal angle to angle dimensions are different the lens can be rotated to see if it fits better at a different meridian.

### **10.1 Anterior chamber intraocular lens implantation technique**

A scleral tunnel is created in either a frown or linear configuration. This can be placed temporally or superiorly based on surgeon preference. A corneal incision is avoided to minimize astigmatism however can be used if needed. The benefits of a corneal incision include preserving conjunctiva/sclera for potential glaucoma interventions. Miosis is induced and viscoelastic is then injected. The ACIOL is then inserted with or without a use of a lens glide. The purpose of the lens glide to secure placement of the ACIOL across the pupil so as not to get the lens or haptic caught on the iris at the pupillary margin. The ACIOL is then positioned such that the footplates of the IOL are well-seated in the angle and the pupillary margin is round. Gonioscopy can be performed to confirm appropriate placement of the ACIOL footplates. Once the ACIOL is positioned, a peripheral iridectomy is created and the scleral or corneal incision is closed.
