The advent of Spec­tral Domain Opti­cal Coher­ence Tomog­ra­phy, or SD-OCT, has given us the abil­ity to per­form in vivo ( or “in the body”) his­tol­ogy of the tis­sues of the human eye with a res­o­lu­tion down to just a few microns — a tremen­dous feat that has led to key devel­op­ments in the under­stand­ing of cer­tain ocu­lar dis­eases. This case is that of a young female who pre­sented to our clinic with a shadow in her left eye’s vision. We dis­cov­ered a reti­nal detach­ment in that eye, and we per­formed an OCT to deter­mine how much of her mac­ula (the part of the retina that gives cen­tral vision) was involved. As you can see in the image, her retina is detached just about halfway through her mac­ula, leav­ing the other half flat and attached. Remark­ably, she still had 20/20 vision in that eye! We knew that if the detach­ment had spread just a few more microns, then that 20/20 vision was going to go much fur­ther south, so we arranged for her to have the detach­ment repaired imme­di­ately. She did great in surgery, and, a full year later, still has 20/20 vision.