What is Marginal Reflex Distance 1 (MRD1) and why is it important?

Marginal reflex distance 1, or MRD1, is the vertical distance between the corneal light reflex and the upper eyelid margin. Doctors use MRD1 to assess and treat conditions like ptosis, which is when the upper eyelid droops. Measuring MRD1 helps determine the severity of the drooping and guides decisions about potential surgical corrections or other interventions.

What is the Volk Eye Check system, and how does it work for measuring eyelids?

The Volk Eye Check system is a smartphone application designed to measure MRD1 automatically. It aims to provide a more convenient and objective method compared to traditional ruler measurements or more complex digital image analysis techniques. The app uses image processing software to analyze a photograph of the eye and calculate the MRD1 value.

According to the study, how accurate is the Volk Eye Check system compared to traditional measurement methods?

The study indicated that the Volk Eye Check system tended to overestimate MRD1, especially in individuals with ptosis. While it showed strong correlations with clinical and digital measurements, its accuracy varied depending on the condition of the eyelids. Specifically, the app was more likely to overestimate MRD1 in eyes affected by ptosis, while measurements were more consistent with traditional methods in normal eyelids.

What are the potential benefits of using a smartphone app like the Volk Eye Check for eyelid measurements?

The Volk Eye Check system has the potential to improve the efficiency of eyelid measurements. It streamlines the measurement process by reducing reliance on clinical skill and consolidating equipment needs, as it only requires a smartphone, unlike digital measurement methods that need a camera and a computer. It also could reduce variability between different users, making it a useful tool for initial assessments and telemedicine applications. However, its limitations, particularly in cases of ptosis, mean that it cannot completely replace traditional clinical assessments.

What does it mean if the Volk Eye Check system is unsuccessful in obtaining a measurement?

The study found that eyes with unsuccessful Volk Eye Check trials were more likely to demonstrate ptosis. This suggests that the Volk Eye Check system may have limitations in accurately measuring MRD1 in eyes with more severe ptosis, potentially due to challenges in image processing or other factors. It is important to consider that the Volk Eye Check camera successfully obtained MRD1 measurements in only 66% of the eyes.

Digital illustration of an eye being measured by a smartphone app.

Eyelid Measurements: Are Smartphone Apps Accurate?

Lena Voss in Health & Wellness December 2025 • 4 min read.

"A New Study Assesses the Accuracy of the Volk Eye Check System for Eyelid Measurements Compared to Traditional Methods."

Eyelid measurements play a crucial role in diagnosing and planning treatment for various conditions affecting the eyelids, such as ptosis (drooping eyelids). Marginal reflex distance 1 (MRD1), the vertical distance between the corneal light reflex and the upper eyelid margin, is a key measurement used by doctors. Traditionally, MRD1 is measured in the office using a ruler, but this method can be subjective and prone to inaccuracies.

Digital photography and image analysis offer a more precise way to measure MRD1, but this process can be time-consuming and impractical for real-time clinical use. The Volk Eye Check system is a smartphone-based tool designed to bridge the gap between convenience and accuracy, automatically measuring MRD1 using image processing software.

A recent study, published in Ophthalmic Plastic and Reconstructive Surgery, investigated the accuracy of the Volk Eye Check system compared to clinical and digital measurements of MRD1. This article breaks down the study's findings, exploring the potential benefits and limitations of using smartphone technology for assessing eyelid measurements.

Volk Eye Check vs. Traditional Methods: What the Study Found

Digital illustration of an eye being measured by a smartphone app.

The study involved 88 eyes from 44 adult patients with normal eyelids and ptosis. Researchers measured MRD1 using three methods: clinical measurement with a ruler, digital measurement using ImageJ software, and automated measurement with the Volk Eye Check device. The results revealed some key differences between the methods.

Overall, the study found that the Volk Eye Check system tended to overestimate MRD1, especially in patients with ptosis. Here’s a breakdown of the key findings:

Success Rate: The Volk Eye Check camera successfully obtained MRD1 measurements in 66% of the eyes.
Overestimation: In the ptosis subgroup, the Volk Eye Check measured significantly higher MRD1 values compared to both clinical and digital methods.
Normal Eyelids: In participants with normal eyelids, there were no significant differences between the three measurement methods.
Ptosis Detection: Eyes with unsuccessful Volk trials were more likely to demonstrate ptosis.

The study also found strong correlations between all three measurement techniques, suggesting that while the Volk Eye Check may not be perfectly accurate in all cases, it generally provides measurements that are consistent with traditional methods.

The Future of Eyelid Measurement Technology

While the Volk Eye Check system may not be a perfect replacement for traditional methods, it offers several potential advantages. It reduces the dependency on clinical skill, requires only one device (compared to the camera and computer needed for digital measurement), and may reduce interuser variability. Future studies are needed to confirm these benefits and further refine the technology.

The study highlights the importance of validating new technologies before widespread adoption. While smartphone-based tools offer convenience and efficiency, it's crucial to understand their limitations and potential inaccuracies, especially in specific patient populations.

Ultimately, the choice of measurement technique depends on the clinical context and the individual patient. The Volk Eye Check system may be a useful tool for assessing patients with normal or elevated eyelid positions, but clinicians should exercise caution when using it to evaluate patients with ptosis.