# Could a hand-held, visual electrophysiology device theoretically reduce diagnostic waiting times for complex eye conditions in the NHS? A Discrete Event Simulation (DES) modelling study

## TL;DR

A portable eye test device could reduce waiting times for complex eye conditions in the NHS by screening patients before lab testing.

## Contribution

This study uses discrete event simulation to evaluate a hand-held device's potential to reduce waiting times for eye diagnostics.

## Key findings

- The RETeval® device could avoid lab-based testing for up to 45% of patients.
- Waiting time reductions are resilient to changes in referral rates and device accuracy.
- DES modeling is a useful tool for assessing diagnostic pathway changes.

## Abstract

Visual Electro-Diagnostic Testing (EDTs) are a highly specialised service in the NHS. The high cost of tests and a paucity of trained visual electrophysiologists has resulted in very few services across the UK and, when combined with increasing patient backlogs, has caused significant travel burden and variable waiting times. Here, we study the potential for impact on patients and services by adding a screening step to traditional referral pathways using an Electroretinogram (ERG) test from a relatively inexpensive, portable, hand-held EDT device; the RETeval® (LKC technologies, Gaithersburg, MD, USA).

We model a large regional-referral EDT service using Discrete Event Simulation (DES) modelling based on retrospective patient data and published best evidence for the device. We evaluate the potential impact that adding the screening step in referral pathways could have on patient waiting times should the device prove to be safe and useable in clinical practice.

We demonstrate that should the RETeval® ERG be safe and useable in real-world clinical practice, it has the potential to significantly reduce patient waiting times by avoiding lab-based EDT assessment for up to 45% of patients. We also show that the impact on services and patients is likely to be resilient to realistic changes in referral numbers, sensitivity/specificity of the device and changes in clinical capacity.

This work demonstrates that a RETeval® ERG screening step, performed at the point of referral, has the potential to result in significantly reduced EDT waiting lists through fewer patients requiring lab-based EDT assessment and that DES modelling is a useful tool in making this assessment. However, many questions remain about using the device in the real-world setting for this purpose. Future studies are needed to assess its sensitivity/specificity, test/retest variability, changes in referral patterns due to the device, useability, acceptability to patients and importantly, the consequences of screening errors. Our work, using only retrospective data and a DES model, shows that using the device as an ERG screening tool warrants further investigation due to the potential impact on both patients and clinical services.