June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Transcleral laser, ciliary muscle shortening & outflow pathway reorganization.
Author Affiliations & Notes
  • Murray A Johnstone
    Ophthalmology, University of Washington , Seattle, Washington, United States
  • Steven Padilla
    Ophthalmology, University of Washington , Seattle, Washington, United States
  • Kimika Wen
    Ophthalmology, University of Washington , Seattle, Washington, United States
  • Footnotes
    Commercial Relationships   Murray Johnstone, None; Steven Padilla, None; Kimika Wen, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 3468. doi:
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      Murray A Johnstone, Steven Padilla, Kimika Wen; Transcleral laser, ciliary muscle shortening & outflow pathway reorganization.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3468.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Aqueous outflow system configuration (OSC) determines aqueous flow and IOP that becomes abnormal in glaucoma. We describe a pilot study with an ex vivo system using visually guided positioning and real time observation of OSC changes (Δs) in response to transcleral µP laser (IridexTM) pulses.

Methods : M. fasc. primates A (PrA) & B (PrB). PrA: microscope, video recordings, calibration micrometer, 1 mm thick radial limbal segments from 4 quadrants (Q). micromanipulator, single pulse of 810 nm µP laser, duty cycle 31.3%. Paired parameters of stepwise power; range: 500-3000 mw, stepwise duration; range: 125-3,000 msec. Energy range: 0.08-2.35 joules. Clinically, ~1.59 J (CEJ) is applied per single location. Video capture during pulse. PrA: Motion quantitated from still frames with ImageJ. PrB: H&E & trichrome in 4 Q after Rx with CEJ.

Results : PrA - Visible µP effects were confined to longitudinal ciliary muscle (CM) near sclera (Fig. 1) Shortening/Contraction (ShCo) & relaxation was detected at ≥ 0.08 J in the IN & SN Q and at ≥ 0.16 J in the IT and ST Q. The CM facing the AC transiently moved inward & posteriorly at ≥ 0.75 Joules in all Q. A pilocarpine-like Δ (PLΔ) in Schlemm’s canal shape occurred when the scleral spur (SS), and trabecular meshwork (TM) moved posteriorly (Fig. 1); (www.youtube.com/user/ibmurray). CM bundles recovered/relaxed to near pre-µP configuration at low energies with progressive reduction in the recovery response as energy increased (Fig. 2). CM bundles experienced ShCo & turned white at 2.35 J (~ 48% > than CEJ) with a persistent Δ in CB, SS & TM configuration. Ciliary epithelial damage was absent with direct observation (PrA & B) & histology (PrB).

Conclusions : Transcleral µP laser induces contraction of the CM, a well-characterized muscle response to uP lasers. CM shortening caused posterior and inward movement of the SS & TM. Our pilot study reports CM, SS, TM & SC PLΔs following transcleral 810 nm µP laser Rx. Clinically used µP parameters induce OSC Δs generally associated with improved aqueous flow. Our preparation permits systematic assessment of effects of probe location, power vs. duration relationships, total energy and focal depth. Systematic lab studies to determine optimized parameters may improve success rates, reduce morbidity and ideally achieve lasting improvement in aqueous flow & IOP.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

 

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