What the Evidence Says

1Visual acuity: precision that leaves no room for doubt

Multi-centre validation across 28 clinics

In 2025, a multi-centre study was published in the Journal of Optometry, conducted across 28 Spanish optometric clinics with 481 participants and nearly 1,000 eyes assessed. The Clinical and Experimental Optometry Research Group at the University of Murcia compared five digital OVU vision charts: Sloan, British, Numbers, Landolt C, and Broken Ring.

In practice, this means that the OVU offers precision comparable to or better than that reported in the literature for digital vision charts, within the accepted clinical variability of ±1 line. A useful clinical note: the Numbers chart tends to give slightly worse results than Sloan (~1 line) — a further reason to use the same chart consistently when monitoring a patient over time.

Teleconsultation: measuring visual acuity remotely

Two independent studies — one from Glasgow Caledonian University and one from the University of Murcia — evaluated the OVU in teleconsultation mode (Tele-Optonet), comparing it with the printed ETDRS chart as the reference standard.

Tele-Optonet enables visual acuity monitoring with reliability comparable to face-to-face assessment, opening the door to remote follow-up of chronic patients without the need for travel. Any clinically relevant change can subsequently be confirmed in person.

Home monitoring in children with amblyopia

A prospective multi-centre study conducted at three NHS centres in the United Kingdom (Glasgow, Birmingham, and Fife) included 206 children with amblyopia. Orthoptists supervised the home-based test via video call using the Optonet platform.

For paediatric optometry practices, this represents a very concrete practical advantage: the ability to monitor the progress of a child with amblyopia between appointments, without the family needing to travel to the clinic every few weeks.

2Paediatric normative values: knowing what is normal at each age

One of the classic challenges in paediatric practice is the use of a single visual acuity threshold (0.00 logMAR) for all ages, when in reality vision matures throughout childhood. A 4-year-old child with a visual acuity of 0.10 logMAR may be perfectly within the normal range for their age — or may not be. Without reference percentile curves, it is difficult to know with any clinical confidence.

Visual acuity percentile curves (ages 3–12)

A team from the Universidad Europea de Madrid and the Hospital Rey Juan Carlos measured visual acuity in 1,300 children aged 3 to 12 years using the OVU, following a standardised protocol (calibrated monitor, controlled illumination of 400–600 lux, randomised symbol presentation). The results were published in the Journal of Optometry in 2022.

The clinical recommendation arising from the study is clear: consider referral for full assessment when a child's visual acuity falls below the 10th percentile for their age. This provides better clinical guidance than a simple 'does not reach 0.00 logMAR', and reduces both unnecessary referrals and missed cases.

Stereoacuity percentile curves (ages 3–12)

The same team and sample (1,300 children) also generated normative stereoacuity curves using the OVU random dot test. Stereoacuity is key for detecting strabismus, amblyopia, and binocular vision disorders, yet there had previously been little reference data on what to expect at each age in a Spanish population.

Having these curves available allows any stereoacuity measurement to be contextualised in the clinic and referral decisions to be made with greater clinical confidence. A 5-year-old with 60 arcsec may be within normal limits; an 8-year-old with the same value, in all likelihood, is not.

3Contrast sensitivity: detecting what visual acuity misses

Visual acuity measures the finest detail we can discriminate at high contrast. However, many conditions — glaucoma, early cataracts, optic neuropathy — affect contrast sensitivity before they affect strict visual acuity. The OVU includes a digital version of the Pelli-Robson test, whose reliability was evaluated by the Optometry Research Group at the University of Murcia in both healthy subjects and patients with glaucoma.

The OVU digital Pelli-Robson can be incorporated into clinical routine as a practical alternative to the printed test, with advantages in terms of digitalisation, recording, and follow-up. It is especially useful in glaucoma monitoring, where it can detect functional deterioration even when visual acuity remains preserved.

4Digital stereoacuity: sensitive to change, useful for follow-up

A study from the University of Liverpool compared three standard stereoacuity tests — Frisby (real depth), TNO (random dot), and Optonet (digital random dot) — under conditions of simulated monocular blur using Bangerter filters (0.2 and 0.4). The aim was to determine which test is most sensitive for detecting progressive changes in binocular vision.

For clinical follow-up, this has important implications: when seeking to detect subtle changes in a patient's binocular vision over time, the OVU offers greater resolution and sensitivity than conventional tests. The TNO, although highly sensitive, quickly reaches the scale ceiling and becomes unhelpful in moderate-to-severe cases. The OVU maintains discrimination across a wider range.

5Digital visual field: an agile perimeter for the clinic

Automated perimetry (Humphrey HFA) remains the reference standard for the diagnosis and monitoring of glaucoma and other optic nerve conditions. However, its availability is limited to hospital and specialist settings, its cost is high, and the test can be uncomfortable for patients. The OVU includes a digital perimeter that can be used from any computer or tablet.

Validation against the Humphrey HFA (University of Murcia)

The Clinical and Experimental Optometry Research Group at the University of Murcia carried out a comparative validation study in two phases: general population (47 participants) and patients with glaucoma classified by severity according to Hodapp criteria (24 patients with glaucoma, 16 controls).

An important methodological observation: many points identified as abnormal by the OVU do not correspond exactly point-for-point with those on the HFA, but do appear at adjacent points. When this is taken into account in the analysis, sensitivity improves markedly. This suggests that the OVU detects genuine areas of deficit, albeit with a slightly different spatial resolution from that of the HFA.

Clinical evaluation at NHS Forth Valley (Falkirk Community Hospital)

A pilot clinical evaluation at NHS Forth Valley (United Kingdom) assessed the OVU in 11 patients with a variety of neuro-ophthalmic conditions (uveitis, multiple sclerosis, ischaemic optic neuropathy, retinal artery occlusion, and others).

The OVU perimeter is not intended to replace the HFA for definitive diagnosis or formal staging. Its role is different: to provide an agile screening and monitoring tool that is more accessible and better accepted by patients, and that helps determine when a full reference perimetry assessment is needed.

6Online vergence therapy: rapid improvement from home

Visual therapy for binocular vision dysfunction has historically required frequent in-person visits to the clinic, limiting both patient adherence and access to treatment. The OVU enables this therapy to be delivered remotely, from the patient's own home, under the remote supervision of the clinician.

Preliminary results (University Clinic of Valencia – Optom 2026)

The team from the University Clinic at the University of Valencia will present a poster at the Optom 2026 congress with results from patients treated with the OVU for vergence dysfunction. The preliminary data are particularly striking due to the speed of the treatment response.

To put this in context: in clinical practice, positive fusional vergences below 15 PD are considered a functionally significant limitation; exceeding 40 PD implies comfortable binocular capacity for the vast majority of everyday visual demands. If the poster data confirm this trend in a larger sample, they will establish the OVU as a credible tool for the home-based management of vergence dysfunction.