Optical Coherence Tomography Opens a New Era in the Afferent Visual System Evaluation

For decades, thinning of the retinal nerve fiber layer in optic neuropathy could only be observed ophthalmoscopically or using red-free fundus photography. These days are over. Subsequently, different techniques to image the optic nerve and the retina have been developed. Optical coherence tomography (OCT) has gained the most attention and has opened a new area of revolutionary diagnostic possibilities.

OCT is a noncontact diagnostic imaging technique that provides detailed, cross-sectional images of the retina and the optic disc in vivo.

It was first used in 1991 to visualize the eye.[1] Image capture is noninvasive, painless, and fast. The technology is analogous to obtaining images with an ultrasound B scan, except that instead of using acoustic waves it uses nearinfrared light reflections to acquire images.

Early models of OCT using time-domain technology generated two-dimensional images and were limited by a relatively slow acquisition time and minor axial resolution. Spectral domain OCT entered clinical practice in 2003.[2] Major advancements are the faster image acquisition, the increased axial resolution, generation of three-dimensional images, and the reduction of artifact from ocular movements.

OCT was first used in the diagnosis of macular pathology and glaucoma.[3] [4] In the meanwhile, it has been more widely used in other ophthalmic subspecialties too. In neuro-ophthalmology OCT is particularly useful for the structural documentation of the peripapillary retinal nerve fiber layer (RNFL) thickness and optic disc morphology.[5] [6] [7] Hence, OCT has been considered for diverse potential applications in the field of clinical neuroscience. RNFL thinning as measured by OCT represents an objective biomarker of optic atrophy,[8] [9] it can confirm trans-synaptic retrograde degeneration of retinal ganglion cells following retrogeniculate visual pathway lesions[10] and even can predict the potential of visual recovery after surgery for parachiasmal tumors.[11] Recently, OCT has been used to evaluate diseases of the central nervous system that affect the afferent visual system. Both, RNFL and macular thickness are significantly reduced in patients with Parkinson disease and Alzheimer disease.[12] [13]

In this issue, Avery et al report the broad spectrum of potential applications of OCT in pediatric clinical neuroscience.[14] They convincingly present the current OCT hot topics Optic Nerve Swelling and Optic Neuritis. Less known application which may attract more attention soon are discussed as well. OCT might become a follow-up parameter in patients receiving Vigabatrin and seems promising in several neurodegenerative conditions such as X-linked adrenoleukodystrophy, Friedreich ataxia, and late infantile neuronal ceroid lipofuscinosis.[14]

Latest OCT developments allowing segmentation of specific retinal layers have brought the ganglion cell layer (GCL) investigation into focus. It has been suggested that macular GCL thickness analysis might be more sensitive to detect damage in optic neuropathy and might be reduced earlier than RNFL analysis.[15] [16]

The OCT applications in the field of pediatric clinical neuroscience are a truly emerging market. It may be used to aid diagnosis, assess disease progression, and even give prognostic information about optic neuropathies and diseases that affect the central nervous system. It also might influence nystagmus and amblyopia management by disclosing underlying retinal pathologies.

Since its introduction 25 years ago, OCT has revolutionized the whole field of ophthalmology and has also become a powerful tool in the diagnostic armamentarium of pediatric neuro-ophthalmic practice. Its usefulness in managing pediatric patients was facilitated by a hand-held device.[15] The ongoing advancements in OCT technology will continuously widen the spectrum of potential diagnostic applications.

This article is an editorial on “Applications of Optical Coherence Tomography in Pediatric Clinical Neuroscience” by Avery et al (Neuropediatrics 2015;46(2):88–97, doi: 10.1055/s-0035-1549098).

• References

• 1 Huang D, Swanson EA, Lin CP , et al. Optical coherence tomography. Science 1991; 254 (5035) 1178-1181
• 2 Drexler W, Sattmann H, Hermann B , et al. Enhanced visualization of macular pathology with the use of ultrahigh-resolution optical coherence tomography. Arch Ophthalmol 2003; 121 (5) 695-706
• 3 Puliafito CA, Hee MR, Lin CP , et al. Imaging of macular diseases with optical coherence tomography. Ophthalmology 1995; 102 (2) 217-229
• 4 Schuman JS, Hee MR, Arya AV , et al. Optical coherence tomography: a new tool for glaucoma diagnosis. Curr Opin Ophthalmol 1995; 6 (2) 89-95
• 5 Subei AM, Eggenberger ER. Optical coherence tomography: another useful tool in a neuro-ophthalmologist's armamentarium. Curr Opin Ophthalmol 2009; 20 (6) 462-466
• 6 Pasol J. Neuro-ophthalmic disease and optical coherence tomography: glaucoma look-alikes. Curr Opin Ophthalmol 2011; 22 (2) 124-132
• 7 Rebolleda G, Diez-Alvarez L, Casado A , et al. OCT: New perspectives in neuro-ophthalmology. Saudi J Ophthalmol 2015; 29 (1) 9-25
• 8 Bock M, Brandt AU, Dörr J , et al. Patterns of retinal nerve fiber layer loss in multiple sclerosis patients with or without optic neuritis and glaucoma patients. Clin Neurol Neurosurg 2010; 112 (8) 647-652
• 9 Horowitz J, Fishelzon-Arev T, Rath EZ, Segev E, Geyer O. Comparison of optic nerve head topography findings in eyes with non-arteritic anterior ischemic optic neuropathy and eyes with glaucoma. Graefes Arch Clin Exp Ophthalmol 2010; 248 (6) 845-851
• 10 Jindahra P, Petrie A, Plant GT. Retrograde trans-synaptic retinal ganglion cell loss identified by optical coherence tomography. Brain 2009; 132 (Pt 3) 628-634
• 11 Danesh-Meyer HV, Papchenko T, Savino PJ, Law A, Evans J, Gamble GD. In vivo retinal nerve fiber layer thickness measured by optical coherence tomography predicts visual recovery after surgery for parachiasmal tumors. Invest Ophthalmol Vis Sci 2008; 49 (5) 1879-1885
• 12 Satue M, Seral M, Otin S , et al. Retinal thinning and correlation with functional disability in patients with Parkinson's disease. Br J Ophthalmol 2014; 98 (3) 350-355
• 13 Marziani E, Pomati S, Ramolfo P , et al. Evaluation of retinal nerve fiber layer and ganglion cell layer thickness in Alzheimer's disease using spectral-domain optical coherence tomography. Invest Ophthalmol Vis Sci 2013; 54 (9) 5953-5958
• 14 Avery RA, Rajjoub RD, Trimboli-Heidler C, Waldman AT. Applications of optical coherence tomography in pediatric clinical neuroscience. Neuropediatrics 2015; 46 (2) 88-97
• 15 Garcia-Martin E, Polo V, Larrosa JM , et al. Retinal layer segmentation in patients with multiple sclerosis using spectral domain optical coherence tomography. Ophthalmology 2014; 121 (2) 573-579
• 16 Gonul S, Koktekir BE, Bakbak B, Gedik S. Comparison of the ganglion cell complex and retinal nerve fibre layer measurements using Fourier domain optical coherence tomography to detect ganglion cell loss in non-arteritic anterior ischaemic optic neuropathy. Br J Ophthalmol 2013; 97 (8) 1045-1050