PAEDIATRIC IMAGING

Imaging technologies developed for adults and for specialties other than ophthalmology are being adapted for ophthalmic use in children with good results, according to presenters at the annual meeting of the American Academy of Ophthalmology in New Orleans.
The advent of spectral domain OCT (SD-OCT) overcomes one big obstacle to using it with children, said Joel S Schuman MD, FACS, distinguished professor and chairman of ophthalmology at the University of Pittsburgh School of Medicine, US.

Reliability of OCT

SD-OCT machines are fast enough to get good scans even in young children who cannot hold still long. One study of 100 healthy children confirmed the reliability and reproducibility of OCT in paediatric populations, he noted (Atemir et al. J Child Neurol 2012; 27:1517-1523).

Normative databases for children are also beginning to appear, Dr Schuman said. These include data for school-age children including retinal nerve fibre layer thickness (Tsai et al. Jpn J Ophthalmol, 2012. 56(4): 362-70) and mean macular thickness (Atemir et al. Am J Ophthalmol, 2013. 155(1): 171-176). These and other published data can be used clinically for diseases including vitreomacular interface disorders, neuro-ophthalmology, retinal dystrophies and anterior segment conditions.

Other OCT applications include imaging for femtosecond laser-assisted cataract surgery and intraoperative use for pars plana vitrectomy for epiretinal membrane, macular holes, proliferative diabetic retinopathy silicone oil removal and primary rhegmatogenous retinal detachment (Binder. Retina, 2011. 31(7): 1332-6), Dr Schuman said.

However, technical problems such as reflectivity of instruments and OCT-microscope integration limit visualisation of retinal manipulation during surgery. More development of the technology is needed to be clinically useful, Dr Schuman added.

“In the future we will see the use of real-time OCT in the operating microscope.”

Anterior segment imaging

OCT also is being successfully adapted to paediatric anterior segment applications, said Ken K Nischal MD, FRCOphth, director and professor of paediatric ophthalmology, strabismus and adult motility at the University of Pittsburgh, US. He presented a case in which a specially developed mechanical arm was used to hold an OCT probe steady for imaging the anterior chamber.

The scan showed evidence of palisades of Vogt remaining in the limbus of a child with opaque cornea who had been refused transplant due to apparent limbal deficiency. A transplant was done and the patient successfully re-epithelialised, Dr Nischal said.

“Now we have a way of picking those children out who might benefit from surgery because we have this technology.”

With regard to ultrasound, Dr Nischal recommends using linear transducer ultrasound probes rather than the vector probes more commonly used in ophthalmology. The linear probe, which is commonly used to find blood vessels in surgery and is available in any operating suite staffed by anaesthesiologists, uses an array of piezoelectric transducers instead of the single scanning transducer in vector devices, he explained. The result is a much more detailed view.

“I don’t understand why the ophthalmic industry makes vector probes and doesn’t make linear probes. For me the liner probe gives much more information anteriorly and within the globe itself.”

Strabismus

MRI is also useful, but underused, in assessing strabismus, said Joseph L Demer MD, PhD, of the Stein Eye Institute and the Departments of Ophthalmology and Neurology at the University of California – Los Angeles, US.

Clinical information obtainable from imaging, but unavailable from direct examination, includes congenital and other anomalies of the extraocular muscles and ligaments, their length, details of any trauma and changes in anatomy due to surgery and innervation of extraocular muscles.

However, a standard brain protocol MRI does not reveal the orbital detail required, Dr Demer said. He recommended using orbital surface coils, which are now approved for clinical use on most scanners.

“Alternatively, other small clinical surface coils can be easily adapted for ophthalmic use,” Dr Demer said.

Joel Schuman: schumanjs@upmc.edu

Kanwal Nischal: nischalkk@upmc.edu

Joseph L Demer: jld@ucla.edu