A recent study published in Cornea assessed the clinical value of upper eyelid meibographic imaging in the early detection of ocular diseases and their correlation with systemic conditions.
Give me some background on meibomian glands.
Meibomian gland dysfunction (MGD) remains the leading cause of evaporative dry eye disease (DED)—accounting for 65-86% of cases—and commonly presents with an increased degree of meibomian gland (MG) dropout, particularly in the lower lid.
The following morphological changes in MGs are key indicators of MGD:
- Gland shortening
- Tortuosity
- Atrophic tissue loss
- Bifurcation
- Gland dropout
Now bring in meibography.
Meibography has been established as a fundamental component in managing MGD and DED that provides deeper insights into the role of the MGs in ocular and systemic conditions that contribute to ocular surface disease.
How do the MGs in upper and lower eyelids differ?
Typically the upper eyelid contains 24-40 glands (compared to 20-30 in the lower lid), and glands in the upper eyelid are longer and thinner, with central measurements of approximately 5.5 mm, compared with 2 mm in the lower eyelid.
- Moreover: The shape of the MGs in the upper eyelid makes them especially susceptible to early structural changes such as tortuosity and dropout, which may precede symptomatic disease.
Of note: The upper eyelid is more difficult to evert than the lower eyelid, and inadequate eversion may distort perceptions of MG health, while excessive eversion may cause glands to seem shorter than their actual length.
Now, talk about the study.
In this study, investigators conducted a narrative review of the PubMed database from the years 2005 to 2023 and added relevant papers from cited references on studies referencing MGs and MGD.
And the findings?
Upper eyelid tortuosity has been associated with increased odds of contact lens dropout, and studies have shown that the odds of contact lens dropout significantly increased with each worsening grade of:
- Upper eyelid meibum quality
- Gland tortuosity
- Upper or lower eyelid gland plugging
Another study found that contact lens wearers had significantly worse MG thickening scores on their upper eyelids than on their lower eyelids, while both upper and lower eyelids of contact lens wearers had worse MG thickening scores than those in noncontact lens wearers.
Why perform upper eyelid meibography before cataract surgery?
One study found that monitoring of the upper eyelid meibography before cataract surgery may help identify patients at high risk for dry eye symptoms induced by surgery.
- Further: Involvement of the upper eyelid is perhaps an earlier finding than the involvement of the lower eyelid glands in patients with DED.
As such: Surgeons can proactively mitigate surgery-induced dry eye symptoms by incorporating meibography for both upper and lower eyelids into precataract surgery evaluations alongside therapeutic interventions where necessary.
How can upper eyelid MGs detect ocular diseases related to systemic conditions?
In patients with SS: MG dropout in the upper eyelid was significantly greater in patients with SS than in other patients with dry eye—suggesting the potential diagnostic value of upper eyelid meibography.
In terms of TED: Dry eye is the most common cause of ocular discomfort in TED patients and relates to their perception of disease severity.
- Moreover:
- Incomplete blinking due to proptosis and eyelid retraction in TED patients can cause obstructive MGD
- Studies have found increased structural loss of the MGs only in the upper eyelid
Meaning: Dry eye management should always include a complete MG assessment to establish the role of MGD in TED patients.
Why are upper eyelid MGs necessary for comprehensive MGD evaluations?
While abnormal morphological features are more frequently observed in the upper eyelid, a high prevalence of gland dropout has been reported in the lower eyelid of patients.
Although upper eyelid assessment may be more difficult due to eversion difficulty and chair-time, innovative technologies can facilitate adequate eyelid exposure for accurate image capture, interpretation, and diagnosis.
Expert opinion?
One analysis of age-wise prevalence data revealed no clear difference in the morphological features of the MGs in normal individuals with increasing age.
- Further: In addition to severely short glands, various other MG morphological characteristics may also be present in normal individuals.
Meaning: Interpreting these findings necessitates consideration of other clinical signs and symptoms, and the combination of MG loss in both eyelids showed the best predictability for dry eye.
Limitations?
These included:
- The diagnostic criteria for MGD were not uniform across studies, and the use of different meibography equipment resulted in images that were difficult to compare, leading to issues with reproducibility
- Without a clear understanding of the histological and morphological changes observed in MG dropouts, some conclusions remain open to interpretation
Take home.
Morphological changes in the MG must be interpreted along with other clinical indicators for comprehensive assessment, and thorough evaluation of both upper and lower eyelids is necessary when assessing the relevance of MG function to ocular surface health.