From Paper to Clinic, Episode 6: The Window to the Brain: OCT and OCTA

Welcome to From Paper to Clinic, a podcast focused on evidence-based eye care and real-world clinical decision-making, hosted by Hamza Shah, OD, MS, FAAO, a faculty member at the University of Houston College of Optometry. His work spans clinical patient care, education, and mentoring, and his clinical interests include ocular disease, dry eye, perioperative care, and—above all—the challenge of translating information into meaningful patient outcomes.

In Episode 6 of From Paper to Clinic, “The Window to the Brain: OCT and OCTA,” host Hamza Shah, OD, sits down with Andrew Rixon, OD, FAAO, to unpack a systematic review on retinal biomarkers for early Alzheimer disease detection and what it means for everyday optometric care. Rixon starts by cleaning up our language regarding dementia as a broad clinical syndrome versus Alzheimer disease as a specific pathologic subtype characterized by beta-amyloid deposition and phosphorylated tau. From there, the pair explore why catching patients at the preclinical or very early symptomatic stage matters—when biomarkers may be detectable 10-15 years before overt decline, but current therapies remain only modestly effective. This naturally leads to the “retina as a window to the brain.” Shah and Rixon walk through the shared neuroectodermal origin of the retina and CNS, parallels in vascular and barrier systems, and emerging data showing amyloid and tau in ocular tissues, including retinal ganglion cells and even aqueous humor at levels comparable to CSF.

The discussion then shifts from theory to OCT and OCT angiography (OCTA) at the slit lamp. Shah and Rickson review the paper’s heterogeneous OCT/OCTA findings—some studies showing thickening and increased vascular density, others thinning and rarefaction—and explain how early inflammatory or vascular changes could precede later neurodegeneration, making simple “thick vs thin” heuristics unreliable in isolation. Rickson outlines how OCTA actually works in clinic, why it does not replace dye-based angiography, and where it shines today: detecting quiescent, non-exudative macular neovascular membranes in AMD and complementing ultra-widefield imaging rather than supplanting it. They also touch on the still-evolving role of OCTA in glaucoma—particularly in suspected normal-tension glaucoma phenotypes—while underscoring the current lack of robust normative vessel-density databases. Throughout, Shah pushes the conversation toward what clinicians can do now: using OCT/OCTA judiciously rather than reflexively, avoiding overpromising on Alzheimer “screening” from a single scan, and preparing for a future where higher-resolution imaging and AI may finally bring that sci-fi-style, noninvasive neurodegeneration assessment closer to reality.

The paper inspiring this discussion is "Retinal biomarkers for early Alzheimer's detection: a systematic review of optical coherence tomography (OCT) findings," by Lepoittevin and colleagues, published in BMJ Open Ophthalmology.

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Episode 7 is coming on Monday, September 7, 2026, at 8 AM ET

The sixth episode of From Paper to Clinic will debut in early August and will feature Leonard Messner, OD, focusing on the effect of GLP-1RA exenatide on idiopathic intracranial hypertension. Listeners are invited to join the conversation as the series explores how evidence moves… from paper to clinic.