Topical azithromycin therapy for meibomian gland dysfunction: clinical response and lipid alterations

Abstract

Purpose: Meibomian gland dysfunction (MGD) is a common clinical problem that is often associated with evaporative dry eye disease. Alterations of the lipids of the meibomian glands have been identified in several studies of MGD. This prospective, observational, open-label clinical trial documents the improvement in both clinical signs and symptoms of disease and spectroscopic behavior of the meibomian gland lipids after therapy with topical azithromycin ophthalmic solution.

Methods: Subjects with symptomatic MGD were recruited. Signs of MGD were evaluated with a slit lamp. Symptoms of MGD were measured by the response of subjects to a questionnaire. Meibum lipid, lipid-lipid interaction strength, and conformation and phase transition parameters were measured using Fourier transform infrared spectroscopy.

Results: In subjects with clinical evidence of MGD, changes in ordering of the lipids and resultant alteration of phase transition temperature were identified. Topical therapy with azithromycin relieved signs and symptoms and restored the lipid properties of the meibomian gland secretion toward normal.

Conclusions: Improvement in phase transition temperature of the meibomian gland lipid with the determined percent trans rotomer composition of the lipid strongly suggests that the ordering of the lipid molecules is altered in the disease state (MGD) and that azithromycin can improve that abnormal condition toward normal in a manner that correlates with clinical response to therapy.

Figures

Figure 1

Subjects with MGD reported global improvement in symptoms in response to 4 weeks of topical azithromycin therapy. Symptoms were assessed from a questionnaire. Subjects with MGD prior to treatment (filled bars). Subjects after 4 weeks of treatment (open bars). *FBS= foreign body sensation

Figure 2

Signs of MGD were restored in patients with MGD in response to 4 weeks of topical azithromycin therapy. (filled bars): Subjects with MGD prior to treatment. (open bars): Subjects after 4 weeks of treatment.

Figure 3

Tear breakup time increased significantly after 4 weeks of topical azithromycin treatment (open bars) compared to patients with MGD prior to treatment (filled bars).

Figure 4

ML phase transition temperature was statistically significantly reduced in subjects treated with topical azithromycin therapy for 4 weeks but the phase transition temperature did increase greater than one month after therapy was stopped (open bars). Comparison of data from a larger study previously shows the increase in the phase transition temperature of ML from subjects with MGD compared to ML from subjects without MGD (closed bars).

Figure 5

ML hydrocarbon order at 33.4°C was statistically significantly different in MGD subjects after 4 weeks of topical azithromycin therapy but regressed during two months after therapy was stopped (open bars). Comparison of data from a larger study shows the increase in hydrocarbon order of ML from subjects with MGD compared to ML from subjects without MGD (normal) (closed bars). More order indicates stiffer lipids with stronger lipid-lipid interactions.

Figure 6

The ML lipid-lipid interaction enthalpy at 33.4°C statistically significantly decreased on azithromycin therapy but returned to elevated levels two months after azithromycin was stopped (open bars). Comparison of data from a previous study shows the increase in lipid-lipid interaction enthalpy of ML from subjects with MGD compared to ML from subjects without MGD [normal] (closed bars). ML lipid-lipid interaction enthalpy was calculated from the enthalpy of the phase transition and the percentage of trans rotomers at 33.4°C.

Figure 7

MALDI-TOF spectra of ML and azithromycin. A) Azithromycin sensitivity study. The relative intensity of the azithromycin bands beginning at 749 Da increased with increasing amounts of azithromycin. Azithromycin could be detected as low as 11 ng. The matrix was DBH. B) Expanded 749 Da region of azithromycin spectra with different matrixes: a) DBH Cs matrix. b) DBH Ag matrix c) DBH matrix. d) Calculated isotopic distribution for azithromycin. C) Expanded spectra with different matrixes: a) DBH matrix; b) DBH Cs matrix; d) DBH Ag matrix. c) Calculated isotopic distribution for azithromycin-Cs adduct. e) Calculated isotopic distribution for azithromycin-Ag adduct. D) ML spectra. a) typical averaged spectra of ML with DBH/Cs matrix from subjects without MGD. b) typical averaged spectra of ML with DBH/Cs matrix from subjects with MGD. c) Calculated isotopic distribution for azithromycin d) Calculated isotopic distribution for azithromycin-Ag adduct e) Calculated isotopic distribution for azithromycin-Cs adduct f) typical averaged spectra of ML with DBH/Ag matrix from subjects without MGD. g) typical averaged spectra of ML with DBH/Ag matrix from subjects with MGD. When comparing spectrum a with b and spectrum f with g, no differences were found in regions where azithromycin would be expected (spectra c, d, e). We conclude from this observation that azithromycin concentration is below the detection limit of 1 ρmole per mg of ML or absent in ML from subjects treated with azithromycin.