1. Comparison of Corneal Rust Ring Removal By Magnetic and Nonmagnetic Tipped Burr Sejal R. Amin, MD Christopher T. Hood, MD Shahzad I. Mian, MD W. K. Kellogg Eye Center University of Michigan The authors have no financial interests to disclose.

2. Purpose Metallic corneal foreign bodies (CFB) remain a frequent problem in urgent care settings. Therapeutic removal of corneal rust rings is advocated to prevent eye pain, corneal inflammation, and scarring. To date corneal rust rings have not been produced in vitro. Study design: –Observational comparison of a standard nonmagnetic ophthalmic burr to a novel magnetic tipped burr for removal of metallic CFB and residual rust rings.

3. Methods In Vitro Rust Ring Formation A 1mm depth corneal pocket was created using a bent 25 gauge needle. A single iron filing was placed within a corneal pocket. Each human cornea contained 6 pockets. The cornea was covered with a gauze soaked in corneal storage medium (Optisol) for a total of 10 days to allow for adequate rust ring formation. Corneal pocket with iron filing Iron filings

4. Methods CFB and Rust Ring Removal Each of the 36 CFB were randomized to removal by either the standard nonmagnetic or novel magnetic tipped burr. The surgeon was masked to the tip identity. CFB and rust ring removal were graded on a subjective 1-10 scale (1 = easy removal, 10 = difficult removal). Nonmagnetic burr tip (left) and magnetic burr tip (right) Corneal rust ring

5. Results Rust rings were successfully formed in vitro in all human corneas. There was no significant difference between the standard nonmagnetic tipped burr and the novel magnetic tipped burr in ease of removal of the metallic CFB (p = 0.159) or residual rust ring (p = 0.840).

6. Ease of Metallic CFB Removal: Nonmagnetic vs. Magnetic Tipped Burr Ease of Removal Scale (Least to Most Difficult) Metallic Corneal Foreign Bodies

7. Ease of Rust Ring Removal: Nonmagnetic vs. Magnetic Tipped Burr Corneal Rust Rings

8. Conclusions In vitro rust ring formation in human corneas is feasible using a protocol involving corneal storage media. A novel magnetized burr tip did not facilitate the ease of removal of CFB or rust rings. Further study is needed to determine whether stronger magnetization is beneficial.

9. References Brock G, Gurekas V. The occasional rust ring removal. Can J Rural Medicine. 2013;18:140-2. Dilly, N. What is a rust ring? Cornea. 2012;31(11):1355-1357. Galin MA, Harris LS, Papariello GJ. Nonsurgical removal of corneal rust stains. Arch Ophthalmol. 1965;74(5):674-8. Liston RL, Olson RJ, Mamalis N. A comparison of rust-ring removal methods in a rabbit model: small-gauge hypodermic needle versus electric drill. Ann Ophthalmol. 1991;23:24-27. Woodburn B. Rust ring removal. Can J Rural Medicine. 2013;18:140-2. Zuckerman BD, Lieberman TW. Corneal rust ring: etiology and histology. Arch Ophthalmol. 1960;63:254-65.

10. Acknowledgements Fuxiang Zhang, M.D. W. K. Kellogg Eye Center University of Michigan Department of Ophthalmology and Visual Sciences Michigan Eye-Bank