Study: Four subtypes of MGD
This study looks at meibomian gland dysfunction as a cluster of four subtypes - two that deliver, and two that don’t:
Too much oil
Normal amount of oil
Too little oil
Among their conclusions, that (as one would expect) the types with oil “underdelivery” are the most likely for patients to experience symptoms, and “non-obvious” is the hardest to diagnose.
Functional and Morphological Evaluation of Meibomian Glands in the Assessment of Meibomian Gland Dysfunction Subtype and Severity. Xiao J et al, Am J Ophthalmol. 2019 Sep 14.
To classify subtypes of meibomian gland dysfunction (MGD) and evaluate dependency of dry eye signs, symptoms and parameters with MGD subtype.
Cross-sectional study STUDY POPULATION: The right eyes of 447 patients with MGD of various subtypes and 20 healthy volunteers.
Patients were classified into four subtypes of MGD based on meibum expression, meibum quality, and MG loss on meibography images (meibograde of 0 to 6). Subtypes were those with high meibum delivery (hypersecretory- and non-obvious MGD) and those with low meibum delivery (hyposecretory- and obstructive MGD). Additional clinical tests included tear film break-up time (TFBUT), ocular staining, osmolarity, Schirmer I, blink interval timing and Ocular Surface Disease Index (OSDI) questionnaire.
78 eyes had hypersecretory MGD, 49 eyes had non-obvious MGD, 66 eyes had hyposecretory MGD and 254 eyes had obstructive MGD. Increased tear film osmolarity and lower TFBUT was found in the low delivery groups; hyposecretory (P=0.006, P=0.016) and obstructive MGD (P=0.008, P=0.006) relative to high-delivery MGD (hypersecretory and non-obvious groups, respectively). Worse ocular symptoms and ocular staining were also found in low delivery MGD groups than the high delivery MGD groups (P<0.01 and P <0.006, respectively).
Patients with low-delivery MGD had worse dry eye parameters and ocular symptoms than those with high meibum delivery, indicating the pivotal role of meibum secretion in ocular surface health that should be targeted in MGD therapy. Furthermore, non-obvious MGD cannot be diagnosed using traditional dry eye tests, and requires morphologic assessment of meibography images to confirm MG loss.