Avoiding Clinical Misinterpretation and Artifacts of Optical Coherence Tomography Analysis of the Optic Nerve, Retinal Nerve Fiber Layer, and Ganglion Cell Layer

Optical coherence tomography retinal ganglion cell complex analysis for the detection of early chiasmal compression

PURPOSE

To report patients with sellar tumors and chiasmal compression with normal visual fields, who demonstrate damage to the retinal nerve fiber layer (RNFL) and ganglion cell complex (GCC) on optical coherence tomography (OCT).

METHODS

Seven patients with sellar tumors causing mass effect on the optic chiasm without definite visual field defect, but abnormal GCC are described. GCC/RNFL analyses using Cirrus-OCT were classified into centiles based on the manufacturer's reference range.

RESULTS

In seven patients with radiologic compression of the chiasm by a sellar tumor, OCT-GCC thickness detected compressive chiasmopathy before visual defects became apparent on standard automated visual field testing. Without OCT, our patients would have been labelled as having normal visual function and no evidence of compressive chiasmopathy. With only OCT-RNFL analysis, 3/7 patients would still have been labelled as having no compression of the anterior visual pathways.

CONCLUSIONS

These patients show that OCT-GCC analysis is more sensitive than visual field testing with standard automated perimetry in the detection of compressive chiasmopathy or optic neuropathy. These cases and previous studies suggest that OCT-GCC analysis may be used in addition to visual field testing to evaluate patients with lesions compressing the chiasm.

Imaging in neuro-ophthalmology in the context of value-based care

PURPOSE OF REVIEW

Neuro-ophthalmic imaging is an invaluable tool for clinical decision-making and has evolved rapidly. At the same time, both imaging utilization and healthcare costs have skyrocketed, and concern for imaging overuse has become a salient topic. This article gives an overview of the current state of neuro-ophthalmic imaging from a value-based medicine lens and discusses recent neuro-ophthalmic advancements in OCT with these considerations in mind.

RECENT FINDINGS

Neuro-ophthalmology is not immune to the waste prevalent in medical imaging. Recent guidelines recommend against routine imaging for ophthalmic conditions without the presence of symptoms. Although neuro-ophthalmic specialty consults and imaging compare favorably against other specialties, the diagnostic yield depending on imaging indication can vary dramatically. For newer developments such as in OCT, it is particularly difficult to assess cost-effectiveness despite the technology's exciting diagnostic potential.

SUMMARY

Familiarity with guidelines to counter misuse, the diagnostic yield of imaging in particular situations, and the limitations of new technology can all help neuro-ophthalmologists make educated tradeoffs and adapt to the new landscape of cost-effective medicine. By helping to decrease costs and efficiently utilize limited resources, the end benefactors will be the increased number of patients who have greater access to affordable care.

Segmentation error in spectral domain optical coherence tomography measures of the retinal nerve fibre layer thickness in idiopathic intracranial hypertension

BACKGROUND

Optical Coherence Tomography (OCT) imaging is being increasingly used in clinical practice for the monitoring of papilloedema. The aim is to characterise the extent and location of the Retinal Nerve Fibre Layer (RNFL) Thickness automated segmentation error (SegE) by manual refinement, in a cohort of Idiopathic Intracranial Hypertension (IIH) patients with papilloedema and compare this to controls.

METHODS

Baseline Spectral Domain OCT (SDOCT) scans from patients with IIH, and controls with no retinal or optic nerve pathology, were examined. The internal limiting membrane and RNFL thickness of the most severely affected eye was examined for SegE and re-segmented. Using ImageJ, the total area of the RNFL thickness was calculated pre and post re-segmentation and the percentage change was determined. The distribution of RNFL thickness error was qualitatively assessed.

RESULTS

Significantly greater SegE (p = 0.009) was present in RNFL thickness total area, assessed using ImageJ, in IIH patients (n = 46, 5% ± 0-58%) compared to controls (n = 14, 1% ± 0-6%). This was particularly evident in moderate to severe optic disc swelling (n = 23, 10% ± 0-58%, p < 0.001). RNFL thickness was unable to be quantified using SDOCT in patients with severe papilloedema.

CONCLUSIONS

SegE remain a concern for clinicians using SDOCT to monitor papilloedema in IIH, particularly in the assessment of eyes with moderate to severe oedema. Systematic assessment and manual refinement of SegE is therefore important to ensure the accuracy in longitudinal monitoring of patients.