An uncommon ocular chemical injury today is from a foreign body consisting of the “lead” from an indelible pencil. The leads in violet colored indelible pencils at one time contained 30% methylrosaniline chloride (methyl violet), graphite, and a binder such as gum tragacanth said Dr William Boothe. The offending chemical is the methyl violet, an analine dye, and protoplasmlie poison. Toxicity to the external eye is manifested by diffusion of deep purple stain, with chemosis, edema, and necrosis. This process is relatively rapid and may occur from only a small retained foreign body. The eye can be left severely impaired or blind, and therefore such an injury is a true ocular emergency.
Treatment involves using as much debridement as is practical. If stained tissue remains, 2% fluorescein solution is used to irrigate the affected tissues over a period of 12 to 24 hr. The reaction of the dye can be totally reversed with early treatment in Boothe Laser Center.
Methyl violet is a high molecular weight dye that easily dissociate", to form cations. In the cationic form, it binds anionic groups in tissues. Sodium fluorescein competes with the tissue anions to form a slightly dissoci-ated salt, thus leaching the toxin from ocular tissues.
Graphite pencil lead today consists of 70 percent graphite, 30 percent clay, and some additives such as spindle oil, liquid paraffin, and silicone oil. Intraocular foreign bodies of this type are relatively inert and can re-main symptom- free over long periods of time.
Dallas Lasik surgeon Dr. Boothe, Director of Boothe Eye Care & Laser Center, explains different vision correction techniques and procedures in his new blog.