Specvis: Free and open-source software for visual field examination

Validation of a Wearable Virtual Reality Perimeter for Glaucoma Staging, The NOVA Trial: Novel Virtual Reality Field Assessment

Purpose

Compare estimated sensitivities of SITA-Standard to the RATA-Standard algorithm of the Radius virtual reality perimeter (VRP), and measure concordance in glaucoma staging.

Methods

One hundred adult glaucoma patients-half with suspect or mild glaucoma, and half with moderate or severe-from five clinics performed four 24-2 visual field tests during a single visit, two with the Humphrey Field Analyzer (HFA) and two with Radius, in randomized order: HRHR or RHRH. Only one eye was tested per participant. We used the Wilcoxon rank sum test with Bonferroni correction to compare distributions of estimated sensitivities across all 54 test locations over the 15 to 40 dB measurement range of the Radius. Weighted kappa measured concordance in glaucoma staging between two masked glaucoma experts using Medicare definitions of severity.

Results

A total of 62 OD and 38 OS eyes were tested. Estimated sensitivities for SITA-Standard and RATA-Standard were not significantly different for OD, but were for OS-likely because of SITA-Standard OD and OS being significantly different in our sample, but not for RATA-Standard. Low agreement was observed between 15 to 22 dB. Concordance in glaucoma staging was high for both graders: kappa = 0.91 and kappa = 0.93. Average test duration was 298 seconds for RATA-Standard and 341 seconds for SITA-Standard. The correlation in mean deviation was 0.94.

Conclusions

Estimated sensitivities of RATA-Standard are comparable to SITA-Standard between 23 to 40 dB with high concordance in glaucoma staging.

Translational Relevance

Radius VRP is statistically noninferior to HFA when staging glaucoma using Medicare definitions.

Personal Computer-Based Visual Field Testing as an Alternative to Standard Automated Perimetry

Introduction Standard automated perimetry (SAP) is the gold standard of visual field assessment in patients with neuro-ophthalmic conditions. Glaucoma is a progressive optic neuropathy characterized by damage to the ganglion cell complex with corresponding visual field defects and intraocular pressure (IOP) being the only modifiable ocular risk factor. Recent advances in technology have paved the way for remote screening and monitoring of visual field defects with the aid of a computer or tablet-based software. One such personal computer (PC)-based software is 'Specvis', which has shown promising reliability as compared to SAP. The primary objective of this study was to compare Specvis and Humphrey Field Analyzer (HFA) visual field reports in the graphical domain while secondary objectives were to estimate the ease of use of Specvis in comparison to HFA and comparison of test duration between Specvis and HFA.  Materials and methods This was a cross-sectional validation study performed at a tertiary care ophthalmology institute in Rawalpindi, Pakistan. Subjects presenting to the outpatient department were recruited based on consecutive sampling technique and were divided into healthy and diseased groups. Basic data collection instrument after informed consent was filled with demographic data, ophthalmic data, disease condition, and attached with analysis reports of both HFA and Specvis for assessment by three senior ophthalmology consultants independently. A total of 218 eyes of 109 subjects were included in this pilot study. SAP was done on the VF 30-2 program using HFA 3. The same patient then performed the visual field assessment on a PC with Specvis installed and settings adjusted to match the VF 30-2 program of HFA as closely as possible. Visual fields of a subject obtained from HFA and Specvis were then coupled and sent to three different senior ophthalmologists. The assessment was done by comparing the greyscale visual field printouts in the graphical domain and scored based on a 5-point Likert scale which were then analyzed for inter-observer reliability. After each test, all subjects were asked to rate the difficulty level of performing the test on HFA and Specvis based on a 5-point Likert scale. The duration of the test performed on HFA and Specvis was also noted for comparison. Results We observed male preponderance in our study participants (n=128, 58.72%). The majority of the participants were non-diseased (n=170, 77.98%) while advanced glaucoma was the commonest disease in the diseased group (n = 22, 10.09%). The mean age of the participants was 40.71 (SD=15.24). The observations for the HFA test duration had an average of 213.33 seconds (SD=33.49, Min=174.00, Max=314.00) while the Specvis test duration had an average of 267.36 seconds (SD=35.98, Min=228.00, Max=370.00). A significant positive correlation was observed between score 1, score 2, and score 3 given by the three ophthalmologists. A significant negative correlation was observed between ease of using HFA and age, with a correlation of -.28. A significant negative correlation was also observed between ease of using Specvis and age. Conclusion Specvis, a computer-based free open-source software used in our study, can give promising results in diagnosing as well as monitoring the progression of visual field defects. It can act as a significantly cost-effective and readily available bridge between visual field examination by confrontation method and SAP.

The digital Cullen chart: a red colour perimetry aid for visual field examination

BACKGROUND

30 years ago, a paper chart was developed in Edinburgh by Cullen et al. and validated as a swift, supplementary method for perimetric evaluation of visual fields. We have re-developed this concept in digital form (on smartphone screen) and assessed its sensitivity and specificity in detecting visual field loss, by comparison with formal machine-based perimetry.

METHODS

Patients with sellar and parasellar tumours, being managed in a single neurosurgical centre, underwent formal visual field perimetry as part of standard care. They also underwent assessment using the smartphone-based Cullen chart. 37 eye testing episodes were assessed, incorporating pre- and post-treatment assessments for a range of potentially compressive pathologies (non-secretory and secretory pituitary adenoma, craniopharyngioma, and parasellar meningioma). The smartphone-based Cullen chart was compared with formal machine-based perimetry for concordance in detecting visual field loss.

RESULTS

The digital Cullen chart had a sensitivity of 75% and specificity of 98% compared with machine-based perimeters. The positive predictive value was 93% and the negative predictive value was 92%.

CONCLUSIONS

For the visual field assessment of patients with sellar/parasellar tumours, this simple and swift smartphone-based chart shows good concordance with machine-based perimeters. With amendments to the user interface, there may be potential for telemetric patient-led visual field monitoring.

A free and simple computerized screening test for visual field defects

About 30-40% of stroke patients suffer from visual field defects following injury. These can interfere with the standard neuropsychological assessment and complicate the interpretation of tests that use visual materials. However, information about the integrity of a patient's central visual field is often unavailable. We, therefore, designed a screening tool, the computerized visual field test (c-VFT), specifically targeted at providing easily available, but rough, information about patients' central visual field. c-VFT was tested in two samples of stroke patients. Eleven patients were tested on c-VFT and on the Esterman test. Five patients were tested on c-VFT and the Humphrey Visual Field Analyzer (HFA), central 10-2. Criterion validity of the c-VFT was investigated by calculating quadrantwise intraclass correlation for both comparisons. For the HFA comparison, we also calculated point-to-point intraclass correlation, sensitivity, and specificity. Analyses revealed moderately good correspondence between c-VFT and the Esterman test, and between c-VFT and HFA 10-2, respectively. When looking specifically at test points within one degree of visual angle apart in the two tests, intraclass correlation increased. For these points, the sensitivity of c-VFT was 0.89 and specificity was 0.97. While the c-VFT is not designed to be diagnostic nor to replace the detailed visual field analysis, this study shows that it provides a reasonable screening of the central visual field. The test can easily be used and will be made freely available to neuropsychological clinicians and researchers.

Current trends for customized biomedical software tools

In the past, biomedical scientists were solely dependent on expensive commercial software packages for various applications. However, the advent of user-friendly programming languages and open source platforms has revolutionized the development of simple and efficient customized software tools for solving specific biomedical problems. Many of these tools are designed and developed by biomedical scientists independently or with the support of computer experts and often made freely available for the benefit of scientific community. The current trends for customized biomedical software tools are highlighted in this short review.