Comparison of a New Head Mount Virtual Reality Perimeter (C3 Field Analyzer) With Automated Field Analyzer in Neuro-Ophthalmic Disorders.

BACKGROUND: Automated perimetry in neurologically disabled patients is a challenge. We have devised a patient-friendly virtual reality perimeter, the C3 field analyzer (CFA). We aim to assess the utility of this as a visual field-testing device in neuro-ophthalmic patients for screening and monitoring. METHODS: Neuro-ophthalmic patients and controls were selected to participate in the study between September and December 2018. They randomly underwent either the CFA or automated field analyzer (HFA) first followed by the other in an undilated state. The CFA results were compared with the HFA, and the correlation of the pattern of the field defect was assessed by an independent masked physician. RESULTS: In total, 59 eyes of 33 neuro-ophthalmic patients (cases) and another 95 normal individuals (controls) were enrolled. CFA was found to have greater proportion of reliable fields (81.4%) than HFA (59.3%) ( P = 0.009). There were less false negatives ( P < 0.001) and more false positives in CFA ( P < 0.001) among neuro-ophthalmic patients compared with controls. Among neuro-ophthalmology patients, the number of fixation losses was greater with CFA ( P < 0.001), whereas false negatives were greater in HFA ( P < 0.001). On assessing the pattern of the field defects, we found that there was almost 70% correlation of CFA with HFA. Moreover, in classical neurological fields such as hemianopia, the correlation was 87.5%. CONCLUSIONS: The CFA seems to correlate well with HFA in classic neurological fields such as hemianopias and may serve as an alternative in patients unable to perform a standard automated perimetry. Further developments are currently underway to incorporate threshold testing.

Validation of a Head-mounted Virtual Reality Visual Field Screening Device.

PRéCIS:: The C3 fields analyzer (CFA) is a moderately reliable perimeter preferred by patients to standard perimetry. While it does not approximate the gold standard, it was sensitive and specific for clinically defined glaucoma (area under the receiving operator characteristic curve=0.77 to 0.86). PURPOSE: Testing the visual field is a vital sign for diagnosing and managing glaucoma. The current gold standard, the Humphrey visual field analyzer (HFA), is large, expensive and can be uncomfortable for some patients. The current study investigated the CFA, a virtual reality head-mounted visual field testing device, as a possible subjective field test for glaucoma screening and eventually glaucoma monitoring. PATIENTS AND METHODS: The CFA presented stimuli in the same 54 positions as the HFA 24-2 SITA Standard test using a suprathreshold algorithm approximating an 18 dB deficit. A total of 157 patients (both controls and glaucoma patients) at the Aravind Eye Hospital, Pondicherry, India, were tested with both devices. RESULTS: The number of stimuli missed on the CFA correlated with HFA mean deviation (r=0.62, P<0.001), and with pattern standard deviation (r=0.36, P<0.001). The area under the receiving operator characteristic curve was 0.77±0.06 for mild glaucoma (HFA mean deviation ≥-6 dB) and 0.86±0.04 for moderate-advanced glaucoma (HFA mean deviation <-6 dB). Patients with an 18 dB or worse deficit at a point in the visual field on the HFA failed to see the CFA stimulus at the same position 38% of the time. CONCLUSIONS: While the CFA did not reliably identify deficits that matched the HFA, it was moderately effective at identifying glaucoma subjects. Further refinements to the device will be required to improve point by point testing performance and screening performance.