Several models have been used to study the drug delivery mechanisms [5–7]. Recently, a review of barriers to posterior eye drug delivery and the challenges and opportunities were discussed by Thrimawithana et al. [8]. Table 1 summarizes various drugs, their diffusion coefficients, the average dosage, and

the frequency to treat AMD diseases. Fick’s second law of diffusion can be used to describe the transport of drug into the eye using microchannels. As the drug delivery device is implanted in the vitreous body of the eye, usually the diffusion depends on the local concentration rate between a drug reservoir and an aqueous humor. The Fick’s second law Inhibitors,research,lifescience,medical of diffusion model can predict the diffusion time of the local tissue concentration in the eye following a variety of microchannel geometries for ocular implantable delivery. The diffusion coefficient of drugs may vary based on the chemical properties Inhibitors,research,lifescience,medical and internal structure as well as

the molecular weight of the drug. Table 1 Diffusion Inhibitors,research,lifescience,medical coefficient of drugs for the AMD. Several Micro Electro-Mechanical System (MEMS) devices, such as, microreservoirs and micropumps have been fabricated to address the spatial constraints posed by ocular drug delivery [1, 4]. Microreservoirs Inhibitors,research,lifescience,medical offer maximum control of drug delivery but cannot be refilled or reused, thereby ruling out suitability for treating chronic eye conditions. Peristaltic micropumps provide targeted drug delivery through active pumping but require considerable space to achieve a desired volume of flow per minute. To overcome these limitations, Lo et al. [9] recently developed a first generation prototype polymer MEMS delivery device with a refillable drug reservoir for treating ocular diseases. In addition to the refillable drug reservoir, the device consists of a transcleral cannula, check valve, and suture

Inhibitors,research,lifescience,medical tabs. The device LY450139 order requires surgical implantation underneath the conjunctiva and the specified dose of medication is dispensed from the device when the reservoir is mechanically activated by the patient’s finger. This device has several advantages when compared to existing systems including the following: through the device is refillable, requires only a single surgical intervention, and is suitable for treating chronic ocular conditions; it is compact and fits within the dimensions imposed by the ocular orbit (<2mm thick). However, the device requires patient’s intervention in dispersion of the drug. In order to cater to multiple scenarios in terms of amount of drug delivery and constraints, alternate MEMS devices might be of interest for treating ocular diseases.