Glaucoma Screening Using an iPad-based Visual Field Test: A Feasibility Study
Creators: name: Prince, Jamie
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2018

description: BACKGROUND: Glaucoma, the second leading cause of blindness worldwide, is a progressive neurodegenerative optic neuropathy. Its progression is monitored by documenting morphological changes to the optic nerve head, inner retinal layers, and quantifying the visual field over time. Visual field testing is done using table-top instruments that cannot be used for home self monitoring and are not practical forpopulation-based screening. A tablet-based application, Melbourne Rapid Fields (MRF), was developed recently on the iPad platform to facilitate visual field testing outside the traditional clinical setting, but has not been tested in low-income nations.OBJECTIVE: To test usability of the MRF in a low-resource setting, to compare its results, and to assess the correlation and agreement with those of the Humphrey Field Analyzer 24-2 SITA standard (HFA), considered as clinical standard for testing visual field.METHODS: Thirty-two subjects with and those without glaucoma attending their clinical appointment at the UNC Kittner Eye Center (n= 13) and Tema Eye Center in Ghana (n= 19) were recruited between June and July 2018. All participants underwent visual fieldtesting with the MRF and HFA. They were then administered an Ease of Use Questionnaire to determine perceptions of the new MRF testing. Global (mean deviation, MD; pattern standard deviation, PSD), reliability indices (false positive rate, FPR; false negative rate, FNR; and fixation loss) and testing duration of the two methods were compared. The results were also assessed for correlation and agreement.RESULTS: Twenty-nine patients were included in the final analysis, 11 from UNC Kittner Eye Center (age: 68 ± 8 years old, range: 49-76) and 18 from Tema Eye Center (age: 42 ± 12 years old, range: 18-62). Overall, 48% of participants had glaucoma and 52% were healthy patients. MRF MD was significantly higher than HFA MD at UNC (&lt; 0.01); no difference in MD was observed between the two devices in Tema (p = 0.89). PFR and FNR were comparable between the two methods at both study sites (all p > 0.05). MD and PSD from the two devices were strongly (r = 0.71, p &lt; 0.001) and moderately (r = 0.48, p &lt; 0.001) correlated, respectively. Agreement analysis revealed that MRF tended to generate significantly higher MD (bias: 1.8 ± 0.41 dB, p = 0.03) and PSD (bias: 1.5 dB ± 0.34 dB; p = 0.03) with wide limits of agreements. Subgroup analysis comparing MRF and HFA results in Ghana and UNC separately demonstrated similar mean MD in TEMA (p=0.89), but significantly different at UNC (p&lt;0.01). The MRF was well-tolerated by patients at all sites.CONCLUSIONS: Although, the MRF and HFA global indices correlated strongly for MD and moderately for PSD, the agreement analysis indicated that MRF tended to underestimate MD and PSD values than HFA. In both agreement analysis, the mean differences were significant, suggesting a poor agreement between the two devices. Further studies should investigate this discrepancy and refine the MRF application to maximize results. However, MRF shows great potential for use in a low-income setting.