Design and clinical application of a series of powerful ophthalmic magnet

Objective To evaluate the magnetic force and clinical efficacy of a series of ophthalmic powerful permanent magnet, which were designed and developed by the authors. Methods According to the requirements of the extraction of the foreign bodies of various location in the eye and the ocular anatomical characteristics, a series of ophthalmic powerful permanent magnet were designed. Including giant ophthalmic magnet, magnet for orbital foreign body and magnet for intraocular foreign body. Six types of magnet were made in those 3 categories. Nd-Fe-B (neodymium iron boron) was used as the magnetic sourc. Those series of magnets were used for the extraction of magnetic ocular foreign body. The procedure of foreign body extraction and surgical complications were observed. Results The ophthalmic powerful permanent magnet series showed strong magnetic force measured by WT10A teslameter. The magnetic force of type I ophthalmic magnet was 900 Tesla (mT, 1 mT=10 Gs), and the force of type Ⅱ was 800 mT. The magnetic forces of the magnet for orbital foreign body, the pen type ocular magnetic head and the needle type magnet were 450 mT, 570 mT and 30 mT respectively. One hundred and forty-five eyes of 137 cases with ocular magnetic foreign bodies were operated using the series of magnets. Foreign bodies were successfully removed from 138 eyes, and the success rate was 95.17%. During the follow-up of 3-6 months, no ocular complication caused by the use of magnets was found. Conclusion The ophthalmic powerful permanent magnet series have strong magnetic force. And they can smoothly extract the magnetic foreign bodies in eyelid, eyeball and orbit, with high success rate and less complications. They are ideal surgical tools for the extraction of ocular magnetic foreign bodies. Key words: Powerful magnet; Nd-Fe-B (neodymium iron boron); Foreign body, ocular, magnetic; Surgery