The influence of luminous intensity on the eyelid aperture and measurement of the margin reflex distance

ABSTRACT

Purpose

To evaluate whether the flashlight feature of smartphones can be used to replace the traditional flashlight for measuring MRD and investigate the relation between increasing light intensities and MRD measurements.

Methods

A prospective clinical study was conducted with 40 individuals from Hospital de Clínicas de Porto Alegre. Outcome measures: MRD1, MRD2, and palpebral fissure height (PFH) were analyzed by photographic record using different intensity light sources.

Results

Flashlight (10 lux): MRD1 mean: 3.97 mm ±1.16; PFH mean: 9.87 mm ±1.53; Smartphone (100 lux) MRD1 mean: 4.02 mm ±1.17; and PFH mean: 9.62 mm ± 1.45 (p > .05). Using a dimmable source of light resulted in a mean reduction of the PFH of 0.75 mm with the highest light intensity (1200 lux). There was no statistically significant association between MRD changes and the iris color, age, and gender of the subjects.

Conclusions

There was no statistically significant difference between the MRD measurements using traditional flashlights compared to higher intensity smartphone flashlight. Using a dimmable source of light, there is a statistically significant reduction in palpebral fissure with higher light intensity, which occurs mostly by upper eyelid lowering, probably due to orbicularis oculi muscle contraction. A smartphone with a built-in flashlight can be used to replace the traditional flashlight in clinical practice without prejudice to the evaluation of the MRD.

KEYWORDS:

• Eyelid
• flashlight
• margin reflex distance
• palpebral fissure
• smartphone

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.