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Pujiang Shi, et. al.

Figure 1. Design of bioprinting toolpath for retina equivalent (a); bioprinting of ARPE-19 cells on ultrathin membrane (b1) to obtain
homogenous cell seeding (b2) and the cells finally formed monolayer within two weeks (b3); Y79 cell-laden bioink bioprinting toolpath
to achieve two distinctive cell-seeding densities: high average cell density at the periphery (HP, c1) and high average cell density at the
center (HC, c2).
the smoothly connected constructs maintained consistent diagnose retina-related diseases at their early stages.
morphology in shape and size. The Y79 cells can be For example, AMD is one of the major causes of visual
observed either at the surface or inside the bioprinted loss in elderly people. 5% of population age above 65
construct (Figure 9d, 9e and 9f), and they were in suffers AMD, while the percentage goes up gradually to
“sphere” shape. 12.5% for age 80 and above [17,18] . The AMD according

4. Discussion to its symptoms can be divided into “dry” and “wet”
conditions. Visual loss could happen within months or
Severe retina degeneration due to the malfunction of several years. Majority of AMD initiates as the “dry”
photoreceptor and RPE cells may finally lead to irre- type (80%–90% patients), and it may further deteriorate
versible vision loss. Current treatment methods can in to “wet” type (10%–20% patients) [19] . The early
only delay the disease progression, while it is almost diagnosis of AMD faces many difficulties, and the AMD
impossible to restore the full function of the deteriorated is usually asymptomatic at its early stages; occasionally
sensory retina. More importantly, it is challenging to some patients experience acute symptoms such as vision

International Journal of Bioprinting (2017)–Volume 3, Issue 2 141