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Editorial

Optical coherence tomography in the management of congenital glaucoma Mays El-Dairi Primary congenital glaucoma (PCG) is a rare disorder with an incidence of about 0.38–5.4 in 100 0001 2 but it can result in significant visual morbidity.3 PCG is usually diagnosed during infancy and treated with angle surgery; however, patients usually need monitoring for life as up to 57%1 may still need chronic treatment with drops or secondary procedures. The gold standard for monitoring glaucoma in adults and children includes intraocular pressure measurements, monitoring of the optic nerve cup-to-disc ratio and visual fields. Although children have been reported to be able to perform visual fields, the results are not always reliable or reproducible.4 5 It is therefore essential to have a test that can reliably diagnose and monitor for possible progressive vision loss in children and infants with PCG before they are able to perform functional tests such as visual acuity and visual fields, and prior to the development of other ophthalmological signs such as nerve cupping. An objective test that would detect the presence and progression of glaucomatous optic atrophy in the eyes of children with PCG would be desirable. Visual evoked potential (VEP) testing would be equally difficult to obtain at young age, and flash VEP would not correlate well with visual field defects. The development of new imaging devices, such as optical coherence tomography (OCT), has enabled ophthalmologists to view details of ocular anatomy, and quantitate the thickness of specific layers of the retina such as the retinal nerve fibre layer (RNFL) and the macular thickness. RNFL OCT has become widely used in adults, both the diagnosis and monitoring of glaucoma and other optic neuropathies and macular diseases. However, this technology’s application to paediatric posterior segment disorders is still imperfect because of multiple limitations. Paediatric normative values are just recently being published for spectral domain OCT, and have not been integrated into the commercial machines.6–9 We know that normative values for these OCT parameters vary with age, race and axial length.10 Correspondence to Dr Mays El-Dairi, Department of Ophthalmology, Duke university, Durham, NC 27710, USA; [email protected] Br J Ophthalmol February 2014 Vol 98 No 2

Reproducibility studies are scarce11 12 and we still do not know the longitudinal reproducibility of spectral domain OCT values in a growing child.11 12 In this issue of the British Journal of Ophthalmology, Srinivasan et al13 explore the utility of RTVue spectral domain OCT for the detection of the pattern optic atrophy in children who previously were treated as infants for PCG. They prospectively compared OCT measurements of the RNFL, optic disc parameters and ganglion cell complex (GCC) (composite of macular inner plexiform layer, ganglion cell layer and nerve fibre layer) thicknesses in the eyes of 37 older children treated as infants for PCG and 41 healthy controls. They found that children with PCG had statistically significant thinner RNFL and GCC compared with controls. Similar to previous paediatric OCT studies, they showed that there was a correlation between cup-to-disc ratios and OCT measured RNFL,14 and, similar to adult studies, they showed that GCC thickness inversely correlated with the severity of glaucoma.15 Similar to paediatric and adult normative OCT studies, they report that the RNFL is thickest in the inferior, superior and nasal quadrants.6 7 9 10 16 Unlike adult glaucoma, however, they showed that the pattern of RNFL loss is diffuse rather than localised to the inferior and superior quadrant. This finding has been reported before14 17; however, the applicability of these results have been questioned since the cohort of patients with paediatric glaucoma studied may have more significant optic nerve damage. Srinivasan et al13 also showed that eyes with unilateral disease had thinner OCT values probably due to a later presentation. This is the first study in the literature to report the GCC values of normal and glaucomatous eyes of children. The OCT adult literature suggests that the addition of the GCC protocol to the RNFL protocol improved the diagnostic power of OCT in the detection of glaucoma, since it had an improved repeatability,15 a feature that is invaluable in a child. There are still, however, many unanswered questions regarding the utility of OCT in the management of paediatric glaucoma. First, the normative database is still not universal and data from different

institutions differ, albeit slightly, because of racial variations. Second, given that OCT values correlate with axial length, we expect that the longitudinal reproducibility of OCT in the eyes of growing children would be affected by axial growth. One study found that the difference that would be engendered by axial length growth in a growing child is negligible since it would be less than the test–retest variance of the time domain OCT machine.12 However, SD-OCT has been reported to have better reproducibility than time domain OCT in both adults and children,11 so one would expect that a change in axial length will affect SD OCT values. Third, OCTwould be most useful in children under the age of 3, and until now, none of the handheld devices have good analysis software for quantitative use. Doing research on paediatric patients is always a challenge, and this challenge is magnified in the study of rare diseases. Srinivasan et al13 have reiterated that although paediatric diseases resemble their adult counterparts, they have different manifestations; therefore, results from adult studies cannot be simply extrapolated to the paediatric population. More work still needs to be done with the use of ophthalmic imaging in paediatric glaucoma, including imaging of the anterior segment, use of handheld OCT devices for quantitative RNFL and macular measures in children who are too young to sit on a slit lamp, and studying the reproducibility of OCT over time as the axial length of a child increases with growth. In conclusion, Srinivasan et al13 have shown that OCT might be potentially useful for managing young children with PCG who are unable to perform visual acuity or visual field testing. The study did not specifically look at monitoring children with PCG for progression or response to treatment since the data provided are for one point in time and years after these patients’ disease was initially treated. They should, however, be commended for being the first to describe the use of GCC protocol in normal children and those with PCG. More work is still needed to assess the reproducibility of OCT over time as axial length changes and the correlation of OCT with vision and visual fields. Until that time, the clinical examination with intraocular pressure monitoring, detailed examination of the optic nerve head as well as visual fields when feasible, remain the gold standard for the early and late management of children with PCG. Competing interests None. Provenance and peer review Commissioned; internally peer reviewed. 149

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Editorial To cite El-Dairi M. Br J Ophthalmol 2014;98:149–150. 5

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▸ http://dx.doi.org/10.1136/bjophthalmol-2012302486 Br J Ophthalmol 2014;98:149–150. doi:10.1136/bjophthalmol-2013-303723

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REFERENCES

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Papadopoulos M, Cable N, Rahi J, et al. Investigators tBES. The British Infantile and Childhood Glaucoma (BIG) eye study. Invest Ophthalmol Vis Sci 2007;48:4100–6. Aponte EP, Diehl N, Mohney BG. Incidence and clinical characteristics of childhood glaucoma: a population-based study. Arch Ophthalmol 2010;128:478–82. Beck AD. Diagnosis and management of pediatric glaucoma. Ophthalmol Clin North Am 2001;14:501–12. Tschopp C, Safran AB, Viviani P, et al. Automated visual field examination in children aged 5–8 years.

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Part I: experimental validation of a testing procedure. Vision Res 1998;38:2203–10. El-Dairi M, Holgado S, Asrani S, et al. Optical coherence tomography (OCT) measurements in black and white children with large cup-to-disc ratios. Exp Eye Res 2011;93:299–307. Rao A, Sahoo B, Kumar M, et al. Retinal nerve fiber layer thickness in children

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