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Correspondence to:
P T Finger
MD, The New York Eye Cancer Center, 115 East 61st Street, New York City, NY 10021, USA; pfinger@eyecancer.com
Accepted for publication 1 October 2004
Cryoprobes are used to grasp, provide traction, and facilitate orbital tumour removal.1–4 Standard ophthalmic cryoprobe tips are typically rounded and offer small surface areas for cryo-adhesion. I describe a new spatulated cryotherapy probe with a large oval and uniform surface area for adhesion and subsequent traction. This report uses photography to document the use of this probe and describes its manufacture and effectiveness during orbital surgery.
Methods
Three spatulated probes were manufactured (Mira, Inc, "Finger-tip probe," Uxbridge, MA, USA) under Good Manufacturing Practice (GMP), International Standards Organization (ISO), and Food and Drug Administration (FDA) guidelines (fig 1).
Figure 1 Top, the 25.2 mm2 surface area large "Finger-tip" cryotherapy probe set to show its spatulated active surface. Bottom, computed tomography shows a well defined, 1.8 cm lobular tumour in the superonasal orbit.
The medium sized probe has an active surface of 25.2 mm2. Its design allows for preferential cooling of the active surface of the applicator. Mira tested this probe to cool to up to –85°C on nitrous oxide (as governed by the Joule-Thompson principle).
Results
A 77 year old patient was found to have a superonasal orbital tumour (by clinical examination and radiographic imaging). The tumour was 18 mm in largest diameter and found to be contiguous with both the orbital portion of the frontal bone and optic nerve. Ultrasonography revealed intrinsic tumour vascularity (low flow). Cavernous haemangioma was suspected and an anterior orbitotomy performed. A combination of sharp and blunt dissection was required to expose the tumour. Then, a medium sized "Finger-tip" cryoprobe was used to create an adhesion to the tumour’s surface (fig 2). This relatively large cryo-adhesion allowed for easier handling of the tumour and improved traction (fig 2). The tumour remained adherent to the cryoprobe for 60 seconds after the nitrous oxide was discontinued. Freezing induced no change in the appearance of the tumour on gross examination. Histopathology revealed cavernous haemangioma. No clinical side effects (related to cryo-extraction) were noted.
Figure 2 Top left, the tumour (arrow) can be seen deep within the superonasal orbit. Top right, the cryoprobe is introduced such that the spatulated tip is placed flush with the tumour and not touching adjacent orbital tissues. Bottom left, the tumour is delivered from the orbit utilising the cryo-adhesion. Bottom right; the tumour is visualised outside the orbit. Note the freeze within the tissue with minimal ice formation on the shaft of the probe.
Comment
Cryo-extraction works best with tumours and cysts that contain fluids (for example, blood, tears), as opposed to solid tumours and those containing lipid or keratin (for example, dermoid). Thus, cavernous haemangiomas are particularly good candidates because freezing occurs on both the tumour’s surface (capsule) and within the tumour stroma. With a well formed fibrous capsule, the outer and inner ice balls provide a strong attachment to the probe.
The fingertip cryoprobes differ from previously available applicators in that they offer relatively large, spatulated tips. This allows for more homogeneous cryo-adhesion over a larger surface area. The larger surface area of application also increases tissue penetration, resulting in a stronger adhesion.
This study examines a new type of cryoprobe used to assist orbital surgery during tumour extraction. It was found capable of adhering to the tumour. Held by the surgeon, tumour traction could be induced with one hand, while the other hand wielded instruments used to sever residual tumour attachments.5 Fingertip cryoprobes offer an alternative to current devices used for cryo-extraction of orbital tumours.
References
Maroon JC, Onik G, Quigley MR, et al. Cryosurgery re-visited for the removal and destruction of brain, spinal and orbital tumours. Neurol Res 1992;14:294–302.
Henderson JW, Neault RW. The use of the cryoprobe in the removal of posterior orbital tumors. Ophthalmic Surg 1976;7:45–7.
Loewenstein A, Geyer O, Lazar M. Cavernous haemangioma of the orbit: treatment by transconjunctival cryoextraction. Eye 1993;7 (Pt 4) :597–8.
Gdal-On M, Gelfand YA. Surgical outcome of transconjunctival cryosurgical extraction of orbital cavernous hemangioma. Ophthalmic Surg Lasers 1998;29:969–73.
Finger PT. "Finger-tip" cryoprobe assisted enucleation. Am J Ophthalmol. (in press).