May 2004
Volume 45, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2004
Programmable microdroplet dispenser and ocular surface fluid dynamics
Author Affiliations & Notes
  • J.H. Bertera
    Adaptive Medical Systems, Inc., Milford, MA
  • R.V. Dorjahn
    Adaptive Medical Systems, Inc., Milford, MA
  • Footnotes
    Commercial Relationships  J.H. Bertera, Adaptive Medical Systems, Inc. F, I, E, P; R.V. Dorjahn, Adaptive Medical Systems, Inc. F, E.
  • Footnotes
    Support  in part NIH Grant EY10270
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 3908. doi:
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      J.H. Bertera, R.V. Dorjahn; Programmable microdroplet dispenser and ocular surface fluid dynamics . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3908.

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

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Abstract

Abstract: : Purpose:To describe dosing tradeoffs of an eyeglass frame wearable, non–contacting, microdroplet dispenser for projecting aqueous solutions onto ocular surfaces. Optimum absorption and therapeutic benefit requires programming solution delivery for compatibility with ocular surface fluid dynamics and for minimal disturbance of normal ocular surface functions. Optimizing absorption of active solution components maximizes therapeutic effect and minimizes side effects. The normal ocular surface is dynamic and adaptive and the pre–corneal tear layer renews after each blink. Estimating and modeling the effect of different temporal and spatial dosing programs on ocular fluid dynamics will add to fully utilizing the potential of micro volume projection. Methods: A micro volume projector powered by a programmable microcontroller is described that delivers from 0.5 to 200 nanoliter drops to simulated ocular surfaces. Modeling parameters based on published reports include tear drainage rates, different tear secretion and flow rates, as well as absorption rates of formulations. A series of droplets, at from 1 to 500 Hz, were projected with delays from 20 milliseconds to 100 seconds, corresponding to a wide range of dosing schedules for ocular wetting agents and drugs. Four droplet frequencies and five dosing rates were used along with three droplet–landing positions (nasal and temporal bulbar conjunctiva, and cornea). Results: Aqueous component and drug solutions can be programmed to ocular surfaces at a rate from <1 µl to 20 µl per minute using the programmed dispenser. Overfilling the eye occurs at higher instillation rates. Isolating delivered fluid to a portion of ocular surface is possible. Smallest doses near temporal canthi are subject to individual evaporation rate (controlled by tear layer health) and flow rate. Small doses around 200 nl remain near nasal canthi. Larger volumes spread due to longer drainage period and more blinks and can flow backwards to the cornea and beyond. Absorption of small drug doses will be maximal when droplets are projected to temporal conjunctiva. Conclusions: Micro dosing is adaptable to tear drainage and evaporation rates with combinations of fluid volume, frequency, and ocular surface landing zone. The micro volume projector may be useful for delivering drugs and wetting solutions to ocular surfaces in optimized volumes that may have the benefit of minimizing irritation, and improving therapeutic outcome, while controlling side–effects from over dosing. Optimized, intensive, and sustained drug delivery may be possible compared with conventional topical applications.

Keywords: conjunctiva • cornea: tears/tear film/dry eye • drug toxicity/drug effects 
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