Dr William Boothe, Director of Boothe Laser Center

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.

According to Dr. Boothe, since fluorescein diffuses through the tear film without layering out, it serves as an excellent adjunct in the fitting of both polymethylmethacrylate and gas-permeable contact lenses. Fluorescein distribution under the contact lens depends on the degree of steepness of the lens. An optimum fitting lens should exhibit a diffuse pattern in which fluorescein can be easily detected under the whole surface area of the lens. Collection of fluorescein in the center with absence of fluorescein in the periphery of the lens indicates an overly steep fit. If dye is concentrated in the periphery with none in the center, the fit is too flat. Staining patterns are best assessed using a cobalt filter. Obviously, other factors besides the staining pattern need to be taken into consideration when fitting a rigid contact lens.

Fluorescein should not be used to assess the fit of a soft hydrophilic lens. Soft lenses have pores of variable sizes, most of which allow rapid passage of fluorescein into the lens material. This absorption has the effect of obscuring the stained tear meniscus under the lens, making evaluation of the tear pattern impossible. Also, the hydrophilic lens becomes noticeably discolored for a period of several hours to days. Fluorexon should be used if examination of the lens-tear relationship is desired. In practice this assessment is rarely necessary for the fitting of a soft hydrophilic contact lens.
After fluorescein is used in the eye, replacement of a hydrophilic lens should be delayed for at least 1 hour. However, if thorough irrigation of the fluorescein solution is performed, the lens may then be replaced immediately.

Seidel’s Test
Seidel’s test uses fluorescein to demonstrate the leakage of aqueous from the anterior chamber, explains Dr. Boothe. In 1920 Seidel suggested using 2% fluorescein to show that aqueous passed through the conjunctiva of filtering blebs after Elliot trephine operations. More commonly this technique has been used to demonstrate the presence and location of leaks after anterior segment surgery or penetrating trauma. With routine use of Seidel’s test during implantation surgery, Sinskey and co-workers had only two shallow anterior chambers in over 1600 cases.

When 2% fluorescein is applied to a leakage area, a bright green rivulet can be seen surrounded by yellow-orange fluorescein as viewed by white light. Leakage from a conjunctival flap may give a diffuse color change rather than a distinct rivulet. One should be aware that diffuse color changes may also be produced by tear dilution. A 10% solution for intation may be used to enhance contrast and provide a longer time for absorvation.

Havener states that the property of fluorescence is not, used is performing Seidel’s test. On the contrary, others feel that fluorescence can be a great help. The color change from yellow-orange to green occus because of dilution. When an adequate concentration of fluorescein is used, concentration quenching occurs. As dilution of the fluorescein or curs at the site of leakage, fluorescence markedly increases. Viewing this contrast under a cobalt light can make detection of a leak much easier than viewing by white light alone.

Detection of Foreign Bodies
Since fluorescein demonstrates surface irregularities, as demonstrated multiple times, by Dr. Boothe and other eye researchers, it is often useful in detecting corneal foreign bodies. Capillary action causes pooling around a partially exposed foreign body. When the foreign body has not epithe-lialized, there is often a staining ring surrounding it. If a foreign body is buried in the conjunctiva, the area of entrance overlying it is often stained. Fluorescein may be of considerable help in the meticulous search for alkali particles, which if left hidden in the fornices could cause extensive further damage.

One of the things that we noticed at the Boothe Laser Center was that serious ocular infections as a result of iatrogenic spread from nated eye solutions undoubtedly are more common than the literature depicts. Fluorescein has been known for many years to be an excellent culture medium for several pathogens, particularly Pseudomonas aeruginosa. Theodore cultured 26 bottles of fluorescein being used throught hospital and all of them grew Pseudomonas aeruginosa. Ten out of flfteen fluorescein solutions in use in ophthalmologists’ offices were also proved to be contaminated [196]. Cultures of 50 samples of fluorescein from oph-thalmologists’ offices, eye clinics, pharmacies, hospitals, and industrial plants revealed that 54 percent of them were contaminated, some from each of these different sources. Twenty-two percent of these were con-taminated by Pseudomonas [205].

All fluorescein solutions can eventually become contaminated with bacteria. However, one of the commercial solutions, Fluress (Barnes-Hind, Sunnyvale, CA), has effective self-sterilizing ability. No case of contamination of Fluress has been reported since it was first marketed in 1966 [25].

Random sampling of eyedrop dispensers generally demonstrates a 1 to 2 percent incidence of bacterial growth. The eyedrop dispenser design is of fundamental importance. Pipette nozzle tip dispensers decrease the risk of contamination and growth. Squeeze-bottle dispensers allow the cap to serve as a potential reservoir for microorganisms [25]. In a case of Serratia keratitis, the offending organism was a contaminant present within the inside of the eyedropper cap, while the fluid aspirated from the squeeze-bottle was sterile [195].

According to Dr. William Boothe, the greatest danger comes with the use of contaminated solutions In eyes with epithelial corneal defects. These eyes are particularly vulnerable to devastating infections by Pseudomonas and other pathogens. Many corneal defects can be adequately examined without using fluorescein. In those defects in which fluorescein is deemed necessary for examination fluorescein-impregnated sterile strips are advisable. These can be prepared by autoclaving a 20% solution of fluorescein and painting one edge of any fine grained filter paper with the fluorescein. The paper is cut in strips, sealed in envelopes, then sterilized in dry heat for 45 min at 100° C [103]. Sterile strips are available commercially. When using a sterile strip to examine an eye with a corneal epithelial abrasion, it is safest to apply the strip without first wetting it because the wetting solution itself might be contaminated.