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Technologies needed to measure, improve functional disability, quality of life in glaucoma patients
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Digital imaging technologies have transformed the diagnostic performance of glaucoma detection and offered new opportunities to decipher the biomechanical and molecular pathways of glaucoma development and progression.
Optical coherence tomography, for example, has taken a huge leap from time-domain to spectral-domain and swept-source OCT, with substantive improvement in scan speed and image resolution over the past 20 years. High-speed imaging facilitates collection of three-dimensional data sets of the optic nerve head (ONH) and retina, and these measurements have been shown to be useful in improving the diagnostic sensitivity in detecting and tracking optic nerve damage in glaucoma patients.
High-resolution imaging has changed the way we examine the optic disc. Visualization of the Bruch’s membrane opening has redefined our understanding of the optic disc margin, and examination of the deep ONH structures, including the lamina cribrosa and prelaminar tissue, has provided important mechanistic insight into the stress and strain response of the ONH in relation to glaucoma development. With adaptive optics OCT and adaptive optics scanning laser ophthalmoscopy, it is now feasible to visualize individual retinal cells.
Imaging technologies also hold promise for evaluating the functional integrity of the retina and retinal cells. Retinal blood flow measured by Doppler spectral-domain OCT, for example, has been shown to be reduced in the hemi-retinal area associated with abnormal retinal nerve fiber layer thickness in patients with glaucoma. With intravenous or topical application of annexin V, apoptosis of retinal ganglion cells can be studied in vivo. Clinical trials are being organized to evaluate how the imaging technology DARC would improve the detection of glaucoma and evaluation of treatment response.
The emerging imaging technologies undoubtedly have advanced our knowledge about the biomechanical, cellular and molecular processes in glaucoma. However, we also need to deliberate how these technologies are going to affect our patient care. How does detection of structural damage influence our treatment plan? In what ways would loss of retinal nerve fiber layer, deformation of the lamina cribrosa and reduced retinal blood flow in glaucoma translate to visual impairment and decrease in quality of life of our patients? While we certainly need better tools to improve structural evaluation and management of glaucoma, developing technologies to measure and improve functional disability and quality of life of our patients is equally important. Active research is ongoing to investigate the impact of glaucoma on driving performance, reading ability and other aspects of activities of daily living, which vary tremendously across different age groups in different regions, even within the same country. Devising and standardizing functional outcome measures in clinical trials for evaluation of visual disability in glaucoma patients are daunting challenges.
References:
Chauhan BC, et al. Am J Ophthalmol. 2013;doi:10.1016/j.ajo.2013.04.016.
Galvao J, et al. Curr Opin Pharmacol. 2013;doi:10.1016/j.coph.2012.08.007.
Leung CK, et al. Ophthalmology. 2009;doi:10.1016/j.ophtha.2009.04.013.
Leung CK, et al. Ophthalmology. 2011;doi:10.1016/j.ophtha.2011.01.026.
Sehi M, et al. Ophthalmology. 2014;doi:10.1016/j.ophtha.2013.10.022.
For more information:
Dennis S.C. Lam, MD, FRCOphth, can be reached at State Key Laboratory in Ophthalmology, Sun Yat-Yen University, 54 South Xianlie Road, Guangzhou 510060, People’s Republic of China; +852-3997-3266; email: dennislam.gm@gmail.com.
Disclosure: Lam has no relevant financial disclosures. Leung has received research support from Carl Zeiss Meditec and Tomey.