Related Experiment Video
Updated: Feb 15, 2026

In Vivo Confocal Microscopy: A Standard Operating Procedure for the Detection of Demodex Mites at the Eyelid Margin
Published on: July 3, 2025
Association of Involutional Lower Eyelid Entropion with Reduced Upper Eyelid Position Relative to the Corneal Light
Paul O Phelps1, Edward J Wladis2,3, Dale R Meyer2
1Division of Ophthalmology, Department of Surgery, NorthShore University HealthSystem, Evanston, Illinois.
Purpose:
To investigate the association between upper eyelid position relative to the corneal light reflex (MRD1) and to delineate an association between eyelid height and involutional lower eyelid entropion.
Methods:
Retrospective study of patients presenting for entropion repair to an academic ophthalmic plastic surgery service. A total of 111 patients were included in the study; 95 had unilateral involutional lower eyelid entropion, and 16 had bilateral lower eyelid entropion. Patients with a history of previous eyelid surgery, trauma, upper eyelid entropion, or cicatricial changes were excluded from the study.
Results:
Of the 95 patients with unilateral involutional lower eyelid entropion, 45 (47.4%) had a lesser MRD1 on the side ipsilateral to the involutional lower eyelid entropion. In this unilateral group, the mean MRD1 (± standard deviation) on the ipsilateral to the involutional lower eyelid entropion was 2.9 (±1.2) mm, while the mean MRD1 on the contralateral side was 3.3 (±1.0) mm. This difference was 0.4 mm and was statistically significant (p < 0.0001). Most patients with unilateral involutional entropion demonstrated a right-sided involutional lower eyelid entropion (56 of 95; 58.9%), although this finding was not statistically significant (p = 0.083). The frequency of true blepharoptosis (MRD1 ≤ 2.0 mm) was 24 of 95 (25.3%) in the unilateral involutional entropion group and was even higher in the bilateral involutional lower eyelid entropion group, with 7 of 16 (43.8%) patients exhibiting bilateral blepharoptosis.
Conclusions:
Patients presenting with involutional lower eyelid entropion tend to have a relatively reduced MRD1 on the ipsilateral (affected) side. When both lower eyelids are affected by involutional entropion, the reduced MRD1 tends to be more pronounced.
Related Concept Videos
Reflex Activity
A reflex exam is a diagnostic procedure performed by a healthcare professional to evaluate the functionality of a patient's...
The Micturition Reflex
The process begins with bladder filling, where the bladder wall stretches as urine accumulates. This stretching activates the urine storage reflex, mediated by the sacral spinal segments and the pontine storage center. Efferent sympathetic impulses stimulate the detrusor muscle to relax and the internal urethral sphincter to contract, facilitating...
Membrane Asymmetry Regulating Transporters
Flippase
Eukaryotic flippases are type-IV P-type ATPases or P4-ATPases belonging to P-type ATPase family proteins that are membrane-bound pumps involved in the ATP-mediated transport of ions and molecules across the membrane. Flippases flip specific phospholipids from the outer to the inner leaflet of a membrane. All P4-ATPases have one...
Position-effect Variegation
Somatic Spinal Reflexes
One of the most well-known somatic spinal reflexes is the stretch reflex, which is activated by the sudden stretching of a muscle. This reflex involves the activation of specialized sensory receptors called muscle spindles, which are located in the muscle tissue and detect changes in the length and speed of muscle contractions. When a muscle is suddenly...
Light Acquisition

