Meibomian Gland Morphology…
research in practice
Meibomian Gland Morphology…
… and how it affects meibomian gland dysfunction and dry eye.
Mile Brujic, O.D., Crystal Brimer, O.D.
A number of studies have documented the contribution of compromised meibomian gland (MG) function to dry eye disease (DED). Additionally, recent research links MG dropout with symptoms of dry eye, specifically elevated ocular surface disease index (OSDI) scores.
A recent study evaluated Schirmer and meibomian gland dysfunction (MGD) scores in 299 subjects to determine the prevalence of evaporative dry eye (EDE), aqueous-deficient dry eye (ADDE) and combination dry eye.1
In the study, if patients had Schirmer values <7mm and MGD grades ≤5, they were classified as ADDE. Those with Schirmer values ≤7mm and MGD grades >5 were classified as EDE. And those with Schirmer scores of <7mm and MGD >5 demonstrated a mixed mechanism etiology. The Schirmer test was conducted more than five minutes, without anesthesia.
The researchers determined that pure EDE is three-to-six times more prevalent than pure ADDE, depending on the Schirmer cutoff values used.
Also, MGD was present in 86% of the patients diagnosed with DED. Patients with mixed mechanism dry eye exhibited greater severity of DED, possibly because it represents late progression of the disease. It has been documented that when ADDE progresses in severity, it can induce a secondary EDE due to the tear film instability and corneal impairment caused by the aqueous deficiency.2 Sixty-five patients could not be classified as EDE or ADDE, despite having clinical signs of DED, possibly because they were in an early stage of the disease process.
Another recent study looked at the value of examining the MG morphology as a predictor for dry eye.3 The study used infrared photography to evaluate MG dropout, thickness and angle measurements in the upper and lower lids of 20 participants, ages 39 to 55. All subjects were healthy, non-contact lens wearers who passed strict exclusion criteria, ensuring their eyes were not affected by allergy, infection, surgery or medications. Examiners obtained a lipid layer analysis, a tear break-up time (TBUT) and an OSDI score to quantify the level of comfort for each patient. Two masked observers each had access only to the results of the tests conducted.
They looked at three MG characteristics: the area of MG dropout, the width of the most prominent MG and the angle of the most bent MG. Overall, the lower lids demonstrated thicker MGs and more MG dropout, but less bent angles when compared with the upper lids. The greatest indicator of DED was MG loss in the upper and lower lids, as it was strongly correlated to lipid layer analysis, TBUT and OSDI scores. With as little as 16.9% MG loss in the upper lid and 28.7% MG loss in the lower lid, the researchers were able to predict DED. Overall, the thickness and angle measurements had little effect on the tear film and patient symptoms in comparison with the incidence of MG dropout of both the upper and lower lids.
What this means for patient care
Utilizing a better means of determining the underlying disease process responsible for a patient’s dry eye symptoms means we, as optometrists, can more quickly arrive at a diagnosis and incorporate therapeutic options that are better targeted to treat the root of the problem, be it EDE or ADDE, and thereby achieve more effective symptom resolution. For the patient, this means a reduction in costs attributed to generalized, less effective treatments.
Real world application
A number of tests we utilize in eye care help us identify dry eye and monitor treatment success but are not definitive in determining the underlying cause(s) of the DED. Osmolarity testing is one example.1 Another is reduced TBUT, which represents an instability of the tear film, as opposed to a differentiation between ADDE and EDE.4 Corneal and conjunctival staining are also evident in both ADDE and EDE but do not aid in distinguishing the underlying etiology.1 In the firstmentioned study, the combination of Schirmer values and meibomian scores were successfully used to diagnose patients as ADDE, EDE or combined dry eye.
Utilizing the anterior segment camera for infrared photography has not been widely adapted in clinical settings but can be helpful to image the MG and assess for significant angling, thickness and most importantly, dropout. Some topographers are equipped with infrared imaging that will allow MG imaging. However, in the absence of infrared imaging technology, you can evert the patient’s upper and lower lid over your transilluminator tip to get a gross view of the MGs. This will give you a reasonable appreciation for significant MG dropout and irregular angling of the MGs.
Identifying MG deficiencies helps you better target your dry eye therapy. Recently, oil-in-water emulsion drops were proven effective in enhancing tear film stability, decreasing tear osmolarity and improving corneal staining scores in EDE patients.5 These improvements are likely a reflection of the beneficial augmentation to the integrity of the lipid layer, reducing the evaporative effects and enhancing the stability of the tear film. This data is especially useful, considering the majority of our dry eye patients are affected by MGD.
Another study showed the evaporative rate of tears decreases after digital meibomian expression in both healthy individuals and those who have keratoconjunctivitis sicca and MGD.6 A new automated device (Lipiflow, Tearscience) supplies heat to the inner lid while delivering a pulsating pressure to the outer lid, thereby creating MG expression. One study showed that a single 12-minute treatment of the device provided patients with sustained clinical improvement and symptomatic relief of MGD for nine months.7
DED is complex and multifactorial. As our knowledge of its etiology increases and our diagnostic technologies improve, our therapeutic approaches can become more targeted. Incorporating a multistep approach to diagnosing the patient’s underlying dry eye and incorporating treatments specific to that etiology can significantly enhance our success in providing dry eye treatment that provides relief, patient loyalty and referrals for care. OM
1. Lemp, MA, Crews La, Bron AJ, et al. Distribution of aqueous-deficient and evaporative dry eye in a clinic-based patient cohort: a retrospective study. Cornea 2012 May;31 (5):472-78.
2. Bron AJ, Yokoi N, Gafney E, Tiffany JM. Predicted phenotypes of dry eye: proposed consequences of its natural history. Ocul Surf. 2009 Apr;7(2): 78–92.
3. Pult H, Riede-Pult BH, Nichols JJ. Relation between upper and lower lids’ meibomian gland morphology, tear film, and dry eye. Optom Vis Sci. 2012 Mar;89 (3):E310-5.
4. Cedarstaff TH, Tomlinson A. Human tear volume, quality and evaporation: a comparison of Schirmer, tear break-up time and resistance hygrometry techniques. Ophthalmic Physiol Opt. 1983;3(3):239–45.
5. McCann, LC, Tomlinson A, Pearce EI, Papa V. Effectiveness of artificial tears in the management of evaporative dry eye. Cornea. 2012 Jan;31(1):1-5.
6. Arciniega, JC, Wojtowicz JC, Mohamed EM, McCulley JP. Changes in the evaporation rate of tear film after digital expression of meibomian glands in patients with and without dry eye. Cornea. 2011 Aug;30(8):843-47.
7. Greiner, JV. A single LipiFlow Thermal Pulsation System treatment improves meibomian gland function and reduces dry eye symptoms for 9 months. Curr Eye Res. 2012 Apr;37(4):272-8.
|DR. BRUJIC IS A PARTNER OF PREMIER VISION GROUP, A FOUR-LOCATION OPTOMETRIC PRACTICE IN NORTHWEST OHIO. HE HAS A SPECIAL INTEREST IN GLAUCOMA, CONTACT LENSES AND OCULAR DISEASE MANAGEMENT OF THE ANTERIOR SEGMENT. E-MAIL HIM AT BRUJIC@PRODIGY.NET.|
DR. BRIMER OWNS CRYSTAL VISION SERVICES, AN OPHTHALMIC EQUIPMENT AND PRACTICE MANAGEMENT CONSULTING COMPANY. SHE PRACTICES IN WILMINGTON, NC AND HAS A SPECIAL INTEREST IN CONTACT LENSES AND DRY EYE MANAGEMENT. E-MAIL HER AT DR BRIMER@ CRYSTALVISIONSERVICES.COM, OR SEND COMMENTS TO OPTOMETRICMANAGEMENT@GMAIL.COM.
Optometric Management, Volume: 47 , Issue: June 2012, page(s): 76 77