Duke Neuro-ophthalmologist Mays Dairi, MD and her work on OCT presented during the American Academy of Ophthalmlogy (AAO) annual meeting was recently featured in Ophthalmology Management Show Daily.
OCT is non-invasive, it uses optical waves and interferometry, and gives in vivo high resolution tomograms of tissues. When discussing childhood glaucoma many doctors think first of the retinal nerve fiber layer scan. Dr. Dairi believes that should be expanded to include the rest of the retina scan as well. These retina scans can be single line scans which are easy to obtain, and will show the retina pathology.
The authors have previously shown that multiple patients had outer retinal changes. They assumed the pathology for vision was caused by the glaucoma but actually it was retinal pathology. In that same paper the authors looked at non-glaucomatous optic atrophy and these patients were unlikely to have those outer retinal changes but many had inner nuclear layer cysts that are very unlikely to be seen in pediatric glaucoma. Another protocol discussed is a macular map. This is a customizable feature that can be generated by integrating multiple single-line macular scans. This provides a topographical map centered on the foveal center that respects the ETDRS macular map. These macular maps can be segmented with the proper equipment to get a map of each layer of the retina, to see which are involved. The next scan discussed was the retinal nerve fiber layer (RNFL) scan. This is a circular scan of 3.4-3.5mm (machine-dependent) that is centered on the optic nerve head, and is an indirect measure of all the retrobulbar optic nerve axons. These were shown to correlate with the severity of glaucoma. The optic nerve head map is similar to the macular map, but is instead centered on the optic nerve. It is useful for qualitatively assessing the peripapillary area if a lesion is suspected. There are multiple methods of acquiring the RNFL scan, and different machines have different advantages.
The authors concluded that a limited scan could give more information than a poor quality extensive scan. They say to pay attention to the axial length change and macula, and that reversal of cupping is accompanied by stability or thinning of the RNFL with time and changes in the Bruch membrane position.