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Effects of the Pulsed Electron Avalanche Knife on Retinal Tissue

Daniel. V. Palanker, PhD; Michael F. Marmor, MD; Andre Branco, MD; Philip Huie, MSc; Jason M. Miller, MSc; Steven R. Sanislo, MD; Alexander Vankov, PhD; Mark S. Blumenkranz, MD
Arch Ophthalmol. 2002;120(5):636-640. doi:10.1001/archopht.120.5.636.
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Objectives  To evaluate the precision of retinal tissue dissection by the pulsed electron avalanche knife (PEAK) and to assess possible toxic effects from this device.

Methods  To demonstrate precision of cutting, bovine retina (in vitro) and rabbit retina (in vivo) were incised with the PEAK. Samples were examined by scanning electron microscopy and histologic examination (light microscopy). To evaluate possible toxic effects in rabbit eyes, 30 000 pulses were delivered into the vitreous 1 cm above the retina. Histologic examinations and electroretinography were performed at intervals up to 1 month after exposure.

Results  Cuts in postmortem bovine retina showed extremely sharp edges with no signs of thermal damage. Full-thickness cuts in living attached rabbit retina were similarly sharp and were typically less than 100 µm wide. No signs of retinal toxic effects were detected by histologic examination or electroretinography.

Conclusions  The PEAK is capable of precise cutting through retinal tissue, and there are no demonstrable retinal toxic effects from its use. The precision and tractionless nature of PEAK cutting offers advantages over mechanical tools and laser-based instrumentation. We believe this new device will prove useful in a variety of vitreoretinal surgical applications.

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Figures

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Figure 1.

Diagram of the intraocular pulsed electron avalanche knife probe. Inset is a photograph of the plasma formed in saline in front of the probe.

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Figure 2.

Scanning electron micrograph of the cut in bovine retina produced by pulses of 50 µJ at 20-Hz repetition rate. Bar (black as well as white lines) indicates 0.1 mm (original magnification×503).

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Figure 3.

A full-depth cut in bovine retina resulting from application of 50-µJ pulses at 20 Hz and 1 mm/s scanning rate. The walls of the cut are remarkably sharp, and no signs of coagulation or other thermal damage are observed at the edges (arrows). Bar indicates 0.1 mm.

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Figure 4.

Center of the crater produced in the rabbit retina by a single shot of 17 µJ. The retina was detached from the retinal pigment epithelium and choroid during the sample preparation. Arrows show the edges of the cut; bar indicates 0.1 mm; photograph was taken with ×20 objective.

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Figure 5.

Histologic section of the full-thickness cut in rabbit retina produced at discharge energy of 17 µJ per pulse, repetition rate of 10 Hz, and scanning rate of about 1 mm/s. Arrows show the edges of the cut; bar indicates 0.1 mm; photograph was taken with ×20 objective.

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Figure 6.

Histologic section of the same cut at the site of choroidal bleeding. Note the sharp edges of the cut (arrows) and lack of retinal detachment and of thermal damage at the edges. Bar indicates 0.1 mm; photograph was taken with ×20 objective.

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Figure 7.

Pulsed electron avalanche knife probe photographed on inverted microscope via ×20 objective during the treatment. A, Probe before the irradiation. B, Erosion after 50 000 pulses at 150 µJ per pulse. Bright plasma streamer is seen in front of the tip. C, Erosion after 106 000 pulses. Plasma originates at the surface of metal deeper inside the probe; 13 µm of 25-µm-thick tungsten wire was etched.

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Figure 8.

Diathermy probe after 20 seconds(A) and 100 seconds (B) of treatment in isotonic sodium chloride solution. Photograph was taken with ×10 objective; dashed lines schematically indicate the initial shape of the tip.

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Figure 9.

Electroretinographic measurements before and after (7, 11, and 30 days) treatment of the rabbit eye with 30 000 pulses of 180 µJ. The results from the other 4 animals were essentially identical.

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