A New Technique for 25-g Iridotomy, Iridectomy, and Tumor Biopsy
The Finger Iridectomy Technique may be a flexible and safe way to biopsy tumors.
PAUL T. FINGER, MD
Fine-needle aspiration biopsy (FNAB) has traditionally been performed to diagnose anterior segment tumors and uveitic conditions through a corneal or limbal approach.1-8 Though FNAB will typically yield a few cells for cytology, rarely does the surgeon obtain enough tissue for histopathology or immunopathologic analysis. Additionally, the FNAB also increases the risk of lacerating the lens, iris, and tumor blood vessels. Finally, it has been my experience that up to 35% of patients can develop a significant hyphema after FNAB.
Figure 1. Unlike a needle (right), the 25-g aspiration cutter (left) is blunt at its end and sides.
I have developted a new technique that can be used to biopsy iris and iridociliary tumors and perform iridotomies or iridectomies through a 1-mm (self-sealing) clear corneal incision. The Finger Iridectomy Technique (FIT) utilizes a 25-g aspiration cutter for minimally invasive iris surgery.9,10
The FNAB uses a sharp-needle tip, which stabs and scrapes at cells and maintains less control of suction. The FIT uses an aspiration cutter, which possesses blunter, softer, physical characteristics and nibbles the tumor or iris (Figure 1). I believe that the 25-g aspiration cutter lowers the incidencce of hemorrhage. Also, the use of sodium hyaluronate 1%, (Healon, Advanced Medical Optics) helps prevent blood formation from spreading and developing into media opacity. FNAB uses aqueous without any viscoelastic and blood can quickly spread over the iris.
Typically, surgical iridectomy can be used to obtain larger specimens. However, this procedure requires a relatively large corneal wound, suture-based closure, and subsequent visual rehabilitation.5,8,11-14
The Finger Iridectomy Technique offers the benefits of a small incision like FNAB as well as the large biopsy yield of iridectomy. The FIT also offers a small-incision alternative for patients who require iridotomy and iridectomy. The following is a step-by-step review of the technique for the aforementioned procedures, as well as noted side effects and results.
In the cases I describe (20 total), the FIT procedures were typically performed under conscious sedation, but topical anesthesia can be used. For each patient, the face and eyes were prepped and draped for intraocular surgery. An eyelid speculum was inserted and a 0.3 forcep was used to stabilize the eye. Where necessary, a 25-gauge trocar was used to create a stab incision through clear juxtalimbal cornea, into the anterior chamber.
A clear corneal incision was made to accommodate the 25-g aspiration cutter and to minimize liberation of tumor cells.15 Acetylcholine chloride 10 mg/ml (Miochol-E, Novartis) is introduced into the anterior chamber to induce miosis. Then, sodium hyaluronate 1% was used to maintain the anterior chamber during surgery (and could be used to position the iris for biopsy typically away from the natural lens).
At the end of surgery, an antibiotic-steroid solution was injected beneath the conjunctiva. After 1 drop of timolol maleate 0.5% (Timoptic-XE, Merck) and antibiotic steroid ointment were administered, each eye was patched and shielded. Patients were discharged on the same day and given a regimen of a topical steroid, antibiotic, and pharmacological agents to maintain intraocular pressure control.
For tumor biopsy, patients are not released from the operating room until an adequate specimen is obtained; therefore, for these cases, either procedure (iridotomy or iridectomy) was utilized to achieve tumor biopsy. Only 1 case, a sarcoid granuloma, resulted in the pathologist requesting an open biopsy for tissue after several FIT specimens were biopsed.
TECHNIQUE UTILIZATION FOR TUMOR BIOPSY
|Figure 2. Slit-lamp photo of central tumor crater created with FIT small-incision biopsy (white arrow). Note the dilated iris vessels along the tumor's posterior margin (black arrows).|
The indications for iris and iridociliary tumor biopsy typically include atypical tumor, metastatic tumor with unknown primary, and in cases where histopathologic confirmation of the diagnosis is required prior to treatment. In addition, it is my recommendation that most small iris tumors be watched for growth prior to biopsy or treatment. Because most iris melanomas are associated with a low metastatic rate (related to their small size and isolated location), biopsy must be balanced against the known risks of surgery or radiation therapy.
During the FIT procedures we performed, the use of a corneal entry site ensured that any liberated cancer cells would exit the patient's body (addressing concerns about tumor seeding).15 The entry site for each case was chosen to avoid crossing the pupil and the natural lens. After acetylcholine chloride and sodium hyaluronate, the aspiration-biopsy cannula (25-g aspiration cutter) was inserted into the anterior chamber as to approximate the target tissue (the aspiration portal can be seen along its anterior surface). For tumor biopsy, the aspiration port was rotated 90Þ as to come in contact with the tumor for biopsy. If the tumor could not be engaged at 90Þ, then the portal was progressively rotated posteriorly (toward the iris stroma).
Aspiration cutting was typically started on a suction of 300 mm Hg at 600 cuts per minute. These settings were then adjusted to maximize the efficiency of the process under direct visualization (trying to keep the cut rate as low as possible). Each time the cutter was removed from the eye, the cutter-portal was placed in balanced salt solution and the aspirate flushed (0.5 mL) from the effluent tube utilizing suction from a 3 mL syringe.
Two to 3 biopsies were typically performed in each case.10 Specimens were immediately sent to the pathology department for cytological evaluation. Once the pathologist confirmed that an adequate specimen was obtained, the residual sodium hyaluronate 1% was removed from the eye by manual aspiration and irrigation.
The goal of tumor biopsy was to obtain tumor tissue for cytology, histopathology, and immunohistochemistry. Therefore, only partial thickness of the tumor and iris were sampled (Figure 2).
Figure 3. Left: An FIT iridotomy with its characteristic scalloped edges. Right: A bright transillumination shadow reveals that it is patent.
Iridotomy is typically performed for narrow or closed angle glaucoma. We have performed FIT for this reason, but more commonly when the tumor is within the iris stroma or when a diffuse iris melanoma was suspected.
In these cases, a minimally invasive surgical iridotomy was performed utilizing the FIT "small-incision" technique (Figure 3).9 A juxtalimbal clear corneal incision was made in the superotemporal cornea with a 25-g trocar. Acetylcholine chloride, then sodium hyaluronate, were introduced into the anterior chamber for miosis and chamber stabilization. The 25-g aspiration-cutter was inserted into the anterior chamber through the corneal wound and toward the superonasal peripheral iris. Once engaged with iris tissue, aspiration, cutting, and iridotomy were almost instantaneous.
Tumor excision can be performed utilizing the FIT. I have use this technique on 1 melanoma where the tumor was relatively small, near the pupil, and in a patient with corneal dystrophy. The FIT was also used to remove an epithelial inclusion cyst.
Performing FIT tumor-excision or a large FIT-iridectomy takes more time and requires subsequent injections of sodium hyaluronate, as well as a second 1-mm incision (for an iris manipulator). Obtaining negative FIT tumor margins would require the use of a new aspiration cutter for each margin.
Advantages of FIT iridectomy include: a small incision, rapid rehabilitation, and its ability to spare peripheral iris (Figure 4). This can allow for a more cosmetically acceptable ovoid pupil as compared to a standard "keyhole."
Though FIT yields more cells and relatively large pieces of tissue compared to FNAB, we utilized special cytopathology and immunohistochemistry techniques for tissue-specimen analysis. This includes the cytospin technique to potentiate cytopathology and immunohistochemistry of retrieved tissue.9,10
Cytospin technique. A cytospin technique was used
to optimize the biopsy yield. Cytospin slides were cleaned with alcohol and assembled
with a slide filter card and sample delivery chamber, secured by a metal clip. Approximately
0.5 mL of fluid sample (3–5 drops) were added to the chamber, together with an equal amount of cytospin collection fluid. After spinning at 1800 rpm for 2 minutes, the slides were removed from the cytospin chamber, further fixed in cytology fixative (70% alcohol/formalin), and stained with haematoxylin and eosin.10
Tissue specimens. We have found that up to 0.5 mm chunks of tissue were aspirated and cut utilizing this technology.9,10 This corresponds fairly well to the size of the portal of the 25-g aspiration cutter. If pieces of biopsy specimen could be visualized floating in the 3 mL syringe or cytospin collection fluid, the paraffin embedded cellblock technique allowed for histochemical and immunohistochemical stains.
|Figure 4. A slit-lamp photograph, taken 1 day after FIT iridectomy, reveals a surgically enlarged ovoid pupil. The cornea is clear with minimal subconjunctival hemorrhage.|
Diagnostic material was obtained in 19 of 20 biopsy cases (95%). One rather large sarcoid granuloma was found to be resistant to both FIT and needle biopsy. The diagnosis was made by surgical iridectomy and it resolved with systemic steroid therapy.
In most cases, FIT thinned the tumor, yielding relatively large specimens that were amenable to cytology, histopathology, and immunohistochemical analysis. Diagnoses included iris and iridociliary melanoma (n=12), iridociliary melanocytoma (n=2), suspicious iris nevus (n=3), normal iris (n=1), epithelial inclusion cyst (n=1), and sarcoid granuloma (n=1).
As a result of FIT-biopsy diagnosis, all but 1 iris and all iridociliary melanomas were treated with palladium-103 ophthalmic plaque radiation therapy. Benign iris tumors have been examined less frequently.16-18 One iris melanoma and an epithelial inclusion cyst were resected utilizing the FIT. Iridotomies were found to be both patent and persistent (Figure 3).
Since April of 2003, no patient has lost vision as a result of the FIT procedure.9,16 One patient with a 20-mm iridociliary melanocytoma and melanomalytic glaucoma developed transient ocular hypertension. One patient developed a small (<5%) hyphema that cleared within 1 week and did not induce glaucoma. One patient had elevated IOP, treatable with topical medications. One patient developed a cataract, but only after subsequent external beam radiation therapy.
Postoperative evaluations have revealed no wound leaks, endophthalmitis, cataract, or secondary refractive errors. These findings have largely been attributed to our use of a small incision, lack of irrigation, and the number of patients.
Anterior segment tumors are typically accessible to biopsy through the cornea. Biopsy techniques have included standard iridectomy, iridocyclectomy, transcorneal tumor biopsy, and FNAB.1,12,14
FNAB has been performed with sharp or blunt needles. Most centers use sharp 21- to 25-g needles introduced through clear cornea to poke, slice, or scrape the tumor. Cells are aspirated through the needle, utilizing extension tubing and uncontrolled manual suction from a 5 mL or 10 mL syringe (also used for specimen collection).19 Utilizing FNAB for anterior segment tumors, one can expect a significant hyphema to occur.
In contrast, the relatively small footprint of the active portion of the aspiration-cutter allows the surgeon to place the cutting element in a more precise location. This is particularly important in at the iris root where the tip of a needle would likely be in the ciliary body or into the sclera in order to aspirate tumor. With FIT, the blunt end can rest against the angle while the side portal samples tumor tissue. While FNAB utilizes uncontrolled manual aspiration, FIT aspiration is mechanically controlled and measurable.
The Finger Iridectomy Technique introduces the concept of using a 25-g aspiration-cutter to perform minimally invasive anterior segment biopsies, iridotomy, iridectomy, and tumor excision.9,10 Relatively large specimens were retrieved that allowed for cytology, histopathology, and immunohistochemistry.
Subsequently, benign tumors were treated by observation and malignant lesions by resection or palladium-103 ophthalmic plaque radiation therapy. This technique may also be helpful to determine malignancy prior to enucleation and external beam radiation therapy.16,20 Although we have not performed a prospective comparative study, my experience suggests that as compared to needle-tip FNAB or surgical iridectomy, FIT may be safer and more effective.
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Paul T. Finger, MD, FACS, is director of The New York Eye Cancer Center, New York, NY, Research supported by The EyeCare Foundation, Inc., New York, NY. He can be e-mailed at firstname.lastname@example.org.