Photo courtesy of National Eye Institute, National Institutes of Health. https://www.flickr.com/photos/nationaleyeinstitute/7544453592/in/photolist-cuFid5-cuFj3Y-8BFByE-iwysKB-zECmk9-cuBBcJ-cuBATG-cuBAD1-28Fd3T2-cuBAHu-cuCyff-zBjbQd-cuCyjw-cuCz1A-cuCyUC-9nuPeK-6jqsDj-cuBARy-cuCyXA-cuFiif-wZ1EMG-cuFi63-cuFi45-cuFiu3-8ZyjyG-29tnx8K-cuFimS-cuBAzJ-A2AAwq-adf7nv-K49nQ5-jyh9S4-2h4FxSH-2eiLd3d-8BCvHk-8EqYsv-8Eu8zd-8EqYkH-4jYcib-zn4kjp-76JCAg-76JCxH-76Nxho-5oiRLb-76NxpY-2eiLe2N-79tkT5-8LMy7R-4bKP2-yGHTXx