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Editors Selection IGR 15-2

Clinical Forms of Glaucoma: sdOCT in congenital glaucoma

Comment by Sharon Freedman on:

53858 Spectral domain optical coherence tomography in children operated for primary congenital glaucoma, Srinivasan S; Addepalli UK; Rao HL et al., British Journal of Ophthalmology, 2014; 98: 162-165

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Both time domain and spectral domain optical coherence tomography (SD-OCT) have proven feasible to perform in children, and several groups have reported on values for retinal nerve fiber layer (RNFL), macular thickness, and optic nerve head analysis in healthy eyes of normal children of various racial and ethnic backgrounds, noting decreases in most parameters in eyes with known pediatric glaucomatous optic neuropathy. In this study, present data on SD-OCT values from older children with primary congenital glaucoma (PCG) controlled by prior trabeculotomy-trabeculectomy (single surgeon, single center), and compare those in a case-control design against the same values for normal controls. The authors utilized a tabletop RTVue and the scans performed included ONH, 3D optic disc, and Ganglion cell complex (GCC) protocols. The study, which included 45 eyes with PCG and 72 control eyes (mean age 10.1 vs.13.6 years, respectively), reports that all SD-OCT parameters were significantly different in the PCG eyes compared with controls. They further noted that all 'global SD-OCT parameters', defined to include rim area, average RNFL, and GCC, correlated with the clinically determined cup-disc ratio in eyes with PCG (median 0.6). A non-statistically significant inverse correlation was also noted between SD-OCT parameter thickness and age at surgery. Mean RNFL thickness was higher in the control than in the PCG eyes (114 vs. 86 mm, respectively), as was optic nerve head rim area (1.39 vs. 0.72 mm², respectively), and GCC (99.9 vs. 85.4 µm, respectively).

Limitations of the study include the significant difference in age between the controls and those with PCG, as well as the refractive difference (PCG eye were more myopic), neither of which likely accounts for the significantly lower RNFL and GCC thickness in eyes with PCG vs. controls. We are not given the clinical cup-disc ratios in the control eyes, nor are we told very much clinical information about the PCG eyes, which presumably have had controlled glaucoma throughout the more than a decade since surgery for their PCG. This study reports, for the first time, SD-OCT parameters specifically in eyes with surgically treated PCG, comparing them to control eyes. The substantial difference between control eyes and those with PCG, in all SD-OCT parameters measured, provides sobering proof of damage to these optic nerves, as well as a means of quantifying that damage in children most of whom remained unable to provide reliable visual field information. It remains to be shown how reproducible these SD-OCT measurements are, and how useful they may prove to be in following children with PCG-related optic neuropathy longitudinally. In addition, normative pediatric data will vary by instrument chosen.

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