Study Of Meibomian Gland Morphology In MGD Patients And Identification Of Meibum Component By GC-MS

Part 1: The relationship between Meibomian gland loss and ocular surface function changes in MGD patientsObjective: To observe meibomian gland morphology and function in healthy individuals and MGD patients, investigate the relationship between meibomian gland loss and ocular surface changes in MGD patients, and to study the influence of long-term use of eye drops on meibomian gland morphology and function.Methods: Totally 131 outpatients and 50 healthy volunteers from the Second Affiliated Hospital of Fujian Medical University between Oct 2013 and Oct 2014 were recruited. The following information from each subject was recorded: personal information, medical history, OSDI scores, assessment of the lid margin, meibum expression scores, tear break-up time, fluorescein staining test, schirmer I test, and noncontact infrared meibography check-up. Various parameters in different types of MGD patients were analyzed, and the correlation between meibomian gland loss values and other parameters were analyzed using Spearman correlation analysis.Results: Among the 50 healthy individuals, TBUT was shorter than 5 seconds in 18% individuals, and FL were positive in 12% individuals. MGL scores were as follows:0 in 23 cases, 1 in 22 cases, 2 points in 5 cases, Structure accounting for respectively 46%, 44% and 10%, The average OSDI score is 8(IQR: 5-11.75), and average score for female(median : 11, IQR: 5.75-13) was significantly higher than for male(median: 6, IQR: 5-8.75)(P = 0.017.131). In total, 88 cases were diagnosed with MGD in the 131 outpatients(67.2%), in whom MGL score of 0 points, 1 point, 2 points, 3 points, 4 points, 5 points, and 6 points accounted for 14.50%, 24.43%, 16.03%, 14.50%, 14.50%, 9.16% and 6.87%, respectively; in particular, 49 cases were found to have simple MGD, and 39 patients were diagnosed with mixed MGD(MGD and ATD). MGL score of 1 point, 2 points, 3 points, 4 points, 5 points and 6 points accounted for MGD of 9.09%, 23.86%, 21.59%, 21.59%, 13.64% and 10.23%, respectively; the mean MGL in the lower eyelids(1.96±0.727)was significantly greater than that of the upper eyelids(1.58±0.672,P=0.008), MGL mostly in the 2-4 score; compared with mixed MGD, SIT and TBUT of simple MGD were significantlyhigher(P <0.001),However, FL was significantly lower(P <0.001), OSDI and MGL have no significant difference(P = 0.071); MGL and SIT, FL, OSDI, meibum scores showed a significant positive correlation in MGD patients(R values were0.660, 0.536, 0.620, 0.562, P <0.001), but MGL and TBUT was significantly negatively correlated(R values were-0.589, P <0.001).OSDI, FL, MGL, eyelid margin assessment, and meibum scores in those with eye drops use of less than 2 years were significantly higher than control group(t=17.014,7.813,6.447,7.213 and 4.543, respectively, p <0.001), but TBUT score was significantly lower than control group(t =-3.877, p <0.001); MGL, FL, eyelid margin scores and meibum scores in those with a medication history more than 2 years were significantly higher than those with medication history less than 2 years(t =5.159, 2.604, 2.883 and 3.597, respectively, p <0.01), but TBUT score was significantly shorter(t =-4.918, p <0.001); there was no significant difference in SIT and OSDI between the two groups(p= 0.533, p=0.442, respectively).Conclusion: Preclinical MGD can exist in partial normal population, which is characterized by meibomian gland morphology abnormalities and tear component changes. Ocular outpatient have a high incidence of MGD, and a considerable population is concurrent with ATD. MGL scores were mostly moderate. MGL was positively correlated with SIT, which may be due to a compensatory increase in tear secretion caused by MGL; the long-term use of eye drops can change the meibomian gland morphology and physiological function and affect the ocular surface.Part 2: Identification of meibum component in MGD patients by GC-MSObjective:To analyze and identify the meibum component from healthy individuals and the patients with meibomian gland dysfunction(MGD) by gas chromatography-mass spectrometer(GC-MS).Method:The meibum from twenty healthy person and nineteen MGD patients were separated and analyzed by GC-MS. The component of meibum was identified by El mass fragmentation and the standard substance in the database. The relative content of the components was calculated by the method of chromatographic peak area normalization.Result:In the 39 samples that were analyzed by GC-MS, 102 chromatography peaks were separated and 23 compounds were identified, including 3 alkanes, 4 alkenes, 2 alcohols, 1 aromatic hydrocarbon, 7 esters, 4 fatty acids, 1 amide, and 1 phenol. However, there was no corresponding physical mass library information in the remaining 79 GC peaks, no identification could be performed. The relative concentration level of palmitoleic acid, palmitic acid, stearic acid, and squalene in MGD groups was statistically significantly lower than that in healthy controls.(tpalmitoleic acid=0.977,tpalmitic acid=2.105,t Stearic acid=1.820,t Squalene=2.804,p<0.05).Conclusions: Palmitoleic acid, palmitic acid, stearic acid, and squalene level was dramatically decreased in MGD patients compared to the healthy group,suggesting that MGD is related to changes of the meibum components.