Topical review of the relationship between contact lens wear and meibomian gland dysfunction

Contact lens (CL) wearers often suffer from ocular discomfort, which leads to cessation of CL wear. About 30% to 50% of CL wearers complain of dry eye (DE) symptoms. Meibomian gland dysfunction (MGD) is considered the most common cause of evaporative DE. Numerous studies have investigated whether CL wear might affect the meibomian glands. This manuscript reviews studies examining the relationship between CL use and MGD. A PubMed database search was conducted for studies published between 1980-2021 with one or a combination of search terms related to “meibomian gland”, “meibomian gland dysfunction”, “contact lens”, and/or “dry eye”. Of the 115 papers reviewed, 22 articles were identified that examined the association between CL and MGD. Fifteen showed that CL wear affects the morphology and function of meibomian glands (MGs), while seven reported no significant impact of CL wear on MGs. This review provides an overview of these studies, emphasizing the diagnostic tests of MGD and conclusions. The review highlights the need for longitudinal prospective large cohort studies with control non- CL wearers to clarify the ambiguous relationship between MGD and CL wear, with special attention to varying CL material and wear times in order to identify the long-term impact of CLs on MG. (AU)

Mice lacking the epidermal retinol dehydrogenases SDR16C5 and SDR16C6 display accelerated hair growth and enlarged meibomian glands.

Retinol dehydrogenases catalyze the rate-limiting step in the biosynthesis of retinoic acid, a bioactive lipid molecule that regulates the expression of hundreds of genes by binding to nuclear transcription factors, the retinoic acid receptors. Several enzymes exhibit retinol dehydrogenase activities in vitro; however, their physiological relevance for retinoic acid biosynthesis in vivo remains unclear. Here, we present evidence that two murine epidermal retinol dehydrogenases, short-chain dehydrogenase/reductase family 16C member 5 (SDR16C5) and SDR16C6, contribute to retinoic acid biosynthesis in living cells and are also essential for the oxidation of retinol to retinaldehyde in vivo Mice with targeted knockout of the more catalytically active SDR16C6 enzyme have no obvious phenotype, possibly due to functional redundancy, because Sdr16c5 and Sdr16c6 exhibit an overlapping expression pattern during later developmental stages and in adulthood. Mice that lack both enzymes are viable and fertile but display accelerated hair growth after shaving and also enlarged meibomian glands, consistent with a nearly 80% reduction in the retinol dehydrogenase activities of skin membrane fractions from the Sdr16c5/Sdr16c6 double-knockout mice. The up-regulation of hair-follicle stem cell genes is consistent with reduced retinoic acid signaling in the skin of the double-knockout mice. These results indicate that the retinol dehydrogenase activities of murine SDR16C5 and SDR16C6 enzymes are not critical for survival but are responsible for most of the retinol dehydrogenase activity in skin, essential for the regulation of the hair-follicle cycle, and required for the maintenance of both sebaceous and meibomian glands.

Meibomian Gland Morphology: The Influence of Structural Variations on Gland Function and Ocular Surface Parameters.

PURPOSE: To objectively and quantitatively characterize meibomian gland morphology and to investigate the influence of morphological variations on gland function and ocular surface and tear film parameters. METHODS: One hundred fifty subjects were enrolled. The examinations included tear osmolarity, tear meniscus height, bulbar conjunctival hyperemia, noninvasive tear film breakup time, lid margin thickness, foam secretion, meibomian gland expressibility, count of functioning glands, corneal and conjunctival staining, fluorescein breakup time, lid wiper epitheliopathy, and Schirmer test. Patient symptoms were assessed using the Ocular Surface Disease Index questionnaire. Images from noncontact meibography were analyzed using an automated method that objectively estimates dropout area, number of glands, gland length and width, and gland irregularity. RESULTS: Gland irregularity highly correlated with dropout area (r = -0.4, P < 0.001) and showed significant partial correlations with fluorescein breakup time (r = 0.162, P = 0.049) and the Ocular Surface Disease Index questionnaire (r = -0.250, P = 0.002) Subjects with dropout area <32% were divided into 2 groups: high and low irregularity. Gland expressibility was statistically significantly different between the 2 groups (U = 319.5, P = 0.006). In the high irregularity group, gland irregularity correlated with the Schirmer test (r = 0.530, P = 0.001) and corneal fluorescein staining (r = -0.377, P = 0.021). CONCLUSIONS: Automated morphological analysis of meibomian gland structure provides additional quantitative and objective information regarding gland morphology. The link between dropout area and gland function is not clear. Assessment of gland irregularity might better predict gland function and its effects on ocular surface and tear film parameters.

The significance of meibomian gland changes in asymptomatic children.

PURPOSE: To evaluate meibomian gland morphology and function in children without ocular discomfort. METHOD: A total of 266 eyes of 266 children without signs or symptoms of ocular surface dysfunction were enrolled. Morphology of meibomian glands (MG) and non-invasive break-up time (BUT) was assessed by noncontact meibography. Based on lipid layer thickness (LLT) of the tear film measurements, 66 children were chosen to be assessed by meibomian glands yielding liquid secretion (MGYLS). RESULTS: Based on the presence of physiologic conjunctival follicles (PCF), participants were divided into normal or PCF groups. The distortion and deficiency of MG function was significantly higher in PCF group (P = 0.002, 0.007, respectively). Five different gland duct shapes (vertical, tortuous, overriding, hooked, U-shaped) were observed. MG deficiency was positively correlated with age (R = 0.362, P < 0.001). Distortion and the number of MG showed no correlation with age (P > 0.05). However, distortion and deficiency of MG were negatively correlated with LLT (P < 0.001, P < 0.01). CONCLUSION: Children with PCF had significantly more MG distortion and deficiency which was associated with LLT. These results prompt future studies to determine if changes in MG morphology are congenital or acquired.

New insights into the morphology and function of meibomian glands.

Meibomian glands secrete meibum, which gives rise to the lipid layer of the tear film and thereby prevents excessive evaporation of tear fluid. Meibomian gland dysfunction (MGD) is a major causative condition of evaporative dry eye, which is more common than the aqueous-deficient type of dry eye. Noninvasive meibography relies on infrared light and an infrared-sensitive camera to reveal the morphology of meibomian glands in both the upper and lower eyelids, whereas tear interferometry allows both qualitative and quantitative evaluation of the lipid layer of the tear film. These two techniques not only provide valuable clinical information related to dry eye but also allow clinical evaluation of MGD. Tear interferometry also has the potential to distinguish the condition of the tear film between normal individuals and dry eye patients. Furthermore, combined evaluation of the noninvasive breakup time of the tear film and the interferometric fringe pattern as determined by tear interferometry allows classification of the subtype of dry eye disease.

Meibomian Gland Physiology in Pre- and Postmenopausal Women.

Purpose: The purpose of this study was to assess the change of meibomian gland physiology during the menstrual cycle and compare its physiology among pre- and postmenopausal women and men. Methods: This study involved 18 healthy subjects: 6 premenopausal women with a regular 28- to 30-day menstrual cycle, 6 postmenopausal women, and 6 men who were age-matched to the premenopausal women. All subjects measured basal body temperature every day at home and were seen once weekly for 5 weeks, and the menstrual state of the premenopausal subjects was masked until after the investigation. At each visit, the meibomian gland orifice (MGO) diameter, lid margin meibum level as meibometry value, meibomian gland morphology, and fluorescein breakup time (F-BUT) of tear film were evaluated, and serum samples were obtained for analysis of sex steroid hormones. Results: The meibomian gland physiology showed cyclic change during the menstrual cycle. The MGO diameter and meibometry value of the meibomian glands decreased in the latter half of the luteal phase until menstruation, correlating well with a shortening of F-BUT. The MGO diameter and meibometry value were significantly higher in postmenopausal women and men than in premenopausal women; however, F-BUT was significantly longer in men than in pre-/postmenopausal women. Conclusions: The findings of this study show that meibomian glands exhibit a cyclic change in premenopausal women, as well as sex- and age-related physiologic differences.

[The effect of long-term contact lens wear on the morphology of meibomian glands].

OBJECTIVE: To evaluate the effect of long-term contact lens (CL) wear on the morphology of meibomian glands (MGs) using meiboscore and digital analysis. METHODS: Retrospective study. Sixty right eyes of sixty patients were involved in this study, and the data were analyzed retrospectively. According to the duration of CL wear, all patients were divided into three groups, nonwear group (n=21), short-term group (duration of CL wear ≤3 years, n=19) and long-term group (duration of CL wear>3 years, n=20). Digital images of MGs obtained by meibography were analyzed using Image J software, providing the area percentage of MGs loss. The meiboscores were also examined, and the data were analyzed using one-way ANOVA and Kruskal-Wallis test. RESULTS: Ten out of 21 nonwearers were scored 0 point, and 11 were scored 1 point in the upper lid meiboscores, while 7 were scored 0 point, 9 were scored 1 point, and 5 were scored 2 points in the total meiboscores. Seven out of 19 short-term wearers were scored 0 point, 10 were scored 1 point, and 2 were scored 2 points in the upper lid meiboscores, while 5 were scored 0 point, 6 were scored 1 point, 6 were scored 2 points, and 2 were scored 3 points in the total meiboscores. Four out of 20 long-term wearers were scored 0 point, 7 were scored 1 point, and 9 were scored 2 points in the upper lid meiboscores, while 3 were scored 0 point, 4 were scored 1 point, 4 were scored 2 points, 4 were scored 3 points, 4 were scored 4 points, and 1 was scored 5 points in the total meiboscores. The meiboscores of the upper eyelid and total meiboscores among the three groups were significantly different (Hc=9.967, P=0.007; Hc=9.725, P=0.008). The meiboscores of the upper eyelid and total meiboscores were significantly higher in the long-term group compared to the nonwear group (Z=102.500, P=0.003, Z=100.500, P=0.003) and the short-term group (Z=120.500, P=0.050, Z=117.500, P=0.041). No significant difference was found between the short-term group and the nonwear group. The median of the MGs loss area percentage in the upper eyelid of the nonwear, short-term and long-term groups was 9.2%, 13.3% and 16.7%, respectively. The median of the total MGs loss area percentage in the nonwear, short-term and long-term groups were 6.6%, 8.8% and 13.0%, respectively. The above medians were significantly different among the three groups (Hc=6.390, P=0.041; Hc=7.019, P=0.030). They were significantly larger in the long-term wearers than the nonwearers (Z=120.500, P=0.019, Z=120.500, P=0.009). No significant difference was found between the short-term group and the nonwear group, or between the short-term group and the long-term group. No significant differences in the meiboscores or MGs loss area percentage in the lower eyelid were noticed among the three groups. The area under the curve of total area percentage of MGs loss in receiver operating characteristic analysis was 0.981 (P<0.001). CONCLUSIONS: Long-term (more than 3 years) CL wear can cause MGs loss. Digital analysis is helpful in the morphologic evaluation of MGs. (Chin J Ophthalmol, 2016, 52: 604-609).

Sondaje intraductal de las glándulas de Meibomio para el tratamiento de blefaritis posterior severa / Intraductal meibomian gland probing for the treatment of blepharitis

OBJETIVO: Describir los resultados del sondaje intraductal de las glándulas de Meibomio como tratamiento de la blefaritis posterior severa. MÉTODOS: Estudio prospectivo, longitudinal, de pacientes con signos y síntomas de blefaritis posterior severa, los cuales fueron tratados con sondaje intraductal de las glándulas de Meibomio. Se incluyó a 16 pacientes, 62,5% femeninos y 32,5% masculinos, con diagnóstico de blefaritis posterior severa y se realizó el tratamiento en uno de los ojos. Se valoró el tiempo de rotura de la película lagrimal y, en una escala subjetiva del 0-10, mejoría subjetiva de la agudeza visual, molestia subjetiva al parpadeo y fotofobia, antes del procedimiento, a la semana y 6 meses después. RESULTADOS: El 100% de los pacientes mostró mejoría estadísticamente significativa en las 4 variables estudiadas a la semana y a los 6 meses. No se presentó ninguna complicación. DISCUSIÓN: La disfunción de las glándulas de Meibomio constituye una causa frecuente de consulta en oftalmología. Este estudio tuvo como objetivo describir los resultados obtenidos al realizar un sondaje intraductal, que mostró ser seguro y eficaz en el 100% de la muestra a los 6 meses. CONCLUSIONES: Podemos concluir en este estudio que el sondaje intraductal de las glándulas de Meibomio se trata de un procedimiento eficaz y prometedor para los que muestras resistencia al tratamiento conservador

OBJECTIVE: To describe the results of the meibomian gland probing as a treatment of severe posterior blepharitis. METHODS: Prospective, longitudinal study of patients with signs and symptoms of severe posterior blepharitis, who were treated with meibomian gland probing in Centro Oftalmológico Interlomas (CENOFI). A total of 16 patients were included, 62.5% female and 32.5% male, diagnosed with severe posterior blepharitis. Treatment was performed in one eye. The time of rupture of the tear film was evaluated, using a subjective scale of 0-10 photophobia, the improvement in pain and visual acuity was measured before the procedure, and at one week and 6 months after. RESULTS: All the patients showed a statistically significant improvement in all 4 variables al 6 months. There were no complications. DISCUSSION: The dysfunction of the meibomian glands is a common reason for ophthalmology consulting. The study describes the results obtained by performing an intraductal survey, which was shown to be safe and effective in 100% of the sample. CONCLUSIONS: It can be concluded from this study that meibomian gland probing is an effective and promising treatment for blepharitis resistant to conservative treatment

[Meibomian gland morphology study progression].

The meibomian gland (MG) in the eyelids, which is the largest sebaceous gland throughout the body, synthesize and secrete lipids to form the superficial tear film layer. It plays a key role in maintaining the ocular surface health. Abnormalities in meibomian gland morphology lead to meibomian gland dysfunction, which is the main cause of evaporative dry eye. Study on meibomian gland morphology will contribute significantly to the diagnosis and treatment of meibomian gland dysfunction. This review is just focusing on the current studies about techniques to visualize the morphology of the MG and changes of meibomian gland morphology related to diseases.

Three-dimensional volumetric human meibomian gland investigation using polarization-sensitive optical coherence tomography.

In this study, polarization-sensitive optical coherence tomography (PS-OCT) capable of providing polarization contrasts such as phase retardation and degree of polarization uniformity (DOPU) was used for visualizing human meibomian glands (MGs) and investigating morphological characteristics of them. Especially, with the help of the DOPU contrast, MGs were exclusively extracted from the volumetric OCT image. In vivo PS-OCT measurements were performed on the upper eyelids of different age groups. From these measurements, different age-dependent aspects of the MG structure were also observed. Based on these observations, it can be inferred that the PS-OCT system has the potential for clinical diagnosis and investigation of MG-related dry eye diseases like MG dysfunction (MGD) and acinar atrophy.

The aging Meibomian gland: an in vivo confocal study.

PURPOSE: To evaluate age-related Meibomian gland (MG) changes by in vivo laser scanning confocal microscopy (LSCM). METHODS: Asymptomatic healthy subjects (n=100, age range 20-83 years) with an Ocular Surface Disease Index score of less than 13 were consecutively enrolled. Two additional groups, one composed of subjects under 40 years of age (n=12) and one composed of subjects over 65 years (n=12), were included without inclusion or exclusion criteria. All subjects underwent a full ocular surface evaluation, and one eye of each subject was examined by LSCM to quantify the lower lid MG acinar unit diameters and densities, orifice diameters, secretion reflectivity, interstices inhomogeneity, and acinar wall inhomogeneity. RESULTS: In the asymptomatic population, MG density and diameter decreased with age (P<0.001 and P<0.01, respectively), and secretion reflectivity and inhomogeneity of acinar walls increased (P<0.001). For the under 40-year-old subjects and the over 65-year-old subjects included without any inclusion or exclusion criteria, acinar unit density decreased with age, and secretion reflectivity, and wall inhomogeneity increased (P<0.01). There was no significant difference between the mean acinar diameters of these two groups. CONCLUSIONS: In vivo LSCM imaging of age-related MG changes showed the histologic features underlying the clinically observed MG dropout. Asymptomatic older subjects mainly showed signs of atrophic, nonobstructive, age-related MG dysfunction. Comparing volunteers with and without ocular surface symptoms, LSCM can provide important information regarding the boundary between physiologic and pathologic MG aging.

Anatomy of secretory glands in the eyelid and conjunctiva: a photographic review.

The eyelid and conjunctiva are main targets in ophthalmic plastic surgery. Although dry eyes are known to occasionally occur after ophthalmic plastic surgery, little attention has been paid to the secretory glands in the eyelid and conjunctiva. The secretary glands in the eyelid and conjunctiva contain the main lacrimal gland, accessory lacrimal glands of Wolfring and Krause, goblet cells, ciliary glands of Moll and Zeis, and the meibomian gland of the tarsal plate. Understanding the details of these glands is helpful in preventing and managing secretion reduction after oculoplastic procedures.

Characterization of the mucocutaneous junction of the human eyelid margin and meibomian glands with different biomarkers.

PURPOSE: To investigate the morphology of the human eyelid margin and the presence of different cytokeratins, mucins and stem cell markers within the skin epithelium, mucocutaneous junction (MCJ) and palpebral conjunctiva. METHODS: Eyelids of body donors were investigated histologically and ultrastructurally as well as by immunohistochemical methods using antibodies to cytokeratins 1, 4, 7, 8, 10, 13, 14, 15, and 19; mucins MUC1, MUC4, and MUC5AC and potential stem cell markers K15, BCRP/ABCG2, integrin ß1, and N-cadherin. RESULTS: The expression pattern of cytokeratins, mucins and stem cell markers varied across the different epithelia of the human eyelid. Within the MCJ, CK7, 15 and 19 were absent, whereas the epithelium reacted positive to antibodies to CK1, 4, 8, 10, 13 and 14. Reactivity was also observed for MUC1 and MUC4, but not for MUC5AC. No reactivity was determined for K15, BCRP/ABCG2 and integrin ß1 in the area of the MCJ epithelium but a strong reactivity was present for N-cadherin. CONCLUSIONS: The present immunohistochemical findings lead to a better characterization of the MCJ. Additionally, the knowledge of distribution of biomarkers like cytokeratins, mucins and stem cells can be useful in the investigation of MCJ disturbances which occur in several disorders of the meibomian glands and the lid epithelium in the course of dry eye syndrome and especially meibomian gland dysfunction.

Investigations on the conjunctival goblet cells and the characteristics of the glands associated with the eye in chinchillas (Chinchilla Laniger).

OBJECTIVE: To investigate the density and distribution of conjunctival goblet cells (GC) and study the anatomy and microscopic characteristics of glands associated with the eye in chinchillas (Chinchilla Laniger). PROCEDURE: 12 chinchillas were included in the study. Conjunctiva (divided into four regions), eyelids, and glands were embedded in paraffin wax, sectioned, stained, and analyzed. RESULTS: Highest GC densities were found in the palpebral region of the nasal and temporal conjunctiva of both eyelids (GC index: 25.1-18.2%), and lowest densities, in the bulbar and marginal region of the nasal and temporal conjunctiva of both eyelids (GC index: 1.5-0.0%). Meibomian glands extend along the entire length of both eyelids, and the whole glandular complex broadens toward the temporal canthus. This is macroscopically visible through the conjunctiva. The openings of the Meibomian glands are macroscopically not discernible. The light pink, smooth, and crescent-shaped lacrimal gland lies next to the aforementioned broadened part of the Meibomian glands in the temporal canthus. The whitish, 0.9-cm-long, smooth Harderian gland is firmly attached to the posterior part of the globe and extends nasally from the optic nerve to the equator. Furthermore, chinchillas possess two lacrimal puncta, situated on the inner conjunctival surface of both eyelids near the medial canthus. A pigmented lacrimal canaliculus originates from each punctum. The vestigial nictitating membrane is supported by a hyaline cartilage and is pigmented at its free margin. CONCLUSIONS: Chinchillas possess a Harderian gland, a lacrimal gland, and Meibomian glands. The GC density in the nasal and temporal palpebral conjunctiva is higher than in guinea pigs.

A solute gradient in the tear meniscus. I. A hypothesis to explain Marx's line.

Marx's line is a line of mucosal staining behind the mucocutaneous junction. It can be demonstrated throughout life in all normal lids by staining with lissamine green and related dyes. Of all the body orifices, only the mucosae of the eye and mouth are directly exposed to the atmosphere. In this paper, we suggest that for the eye, this exposure leads to the formation of Marx's line. The tear meniscus thins progressively toward its apex, where it is pinned at the mucocutaneous junction of the lid. It also thins toward the black line, which segregates the meniscus from the tear film after the blink. We predict that, because of the geometry of the tear meniscus, evaporation generates a solute gradient across the meniscus profile in the anteroposterior plane, which peaks at the meniscus apices at the end of the interblink. One outcome would be to amplify the level of tear molarity at these sites so that they reach hyperosmolar proportions. Preliminary mathematical modeling suggests that dilution of this effect by advection and diffusion of solute away from the meniscus apex at the mucocutaneous junction will be restricted by spatial constraints, the presence of tear and surface mucins at this site, and limited fluid flow. We conclude that evaporative water loss from the tear meniscus may result in a physiological zone of hyperosmolar and related stresses to the occlusal conjunctiva, directly behind the mucocutaneous junction. We hypothesize that this stimulates a high epithelial cell turnover at this site, incomplete epithelial maturation, and a failure to express key molecules such as MUC 16 and galectin-3, which, with the tight junctions between surface epithelial cells, are necessary to seal the ocular surface and prevent penetration of dyes and other molecules into the epithelium. This is proposed as the basis for Marx's line. In Part II of this paper (also published in this issue of The Ocular Surface), we address additional pathophysiological consequences of this mechanism, affecting lid margins.

Investigations on the conjunctival goblet cells and on the characteristics of glands associated with the eye in the guinea pig.

OBJECTIVE: To investigate the distribution and density of conjunctival goblet cells (GC) and to study the anatomy and microscopic characteristics of glands associated with the eye in the guinea pig. PROCEDURES: Twenty-five guinea pigs were used. Meibomian gland openings were counted using biomicroscopy. Conjunctiva, eyelids and glands were embedded in glycol methacrylate and paraffin. Sections were stained with hematoxylin and eosin (H&E), periodic acid Schiff's reaction (PAS) and Alcian blue (AB). RESULTS: Highest GC densities were found in the bulbar and palpebral region of the nasal conjunctiva (GC index: 13.7-16.4%). Lowest GC densities (GC index: 0.0-1.0%) were found in 3/4 limbal regions (nasal and temporal upper eyelid, temporal lower eyelid). Guinea pigs have 27.1±3.0 (mean±SD) meibomian gland openings in the upper lid and 25.7±2.3 in the lower lid. Difference between upper and lower lid was significant (P=0.037). Two subconjunctival sebaceous glands occur temporal to each eye. The Harderian gland is very large. In the lacrimal gland three different cell types were distinguished both according to the cell structure and histochemical staining. CONCLUSIONS: Goblet cell densities are lower in guinea pigs than in dogs and horses. Positive staining with PAS and AB could be an indication that mucins are produced in the lacrimal gland. If so, they may contribute to the mucin layer of the tear film. Both the extraordinarily large Harderian gland and the subconjunctival sebaceous glands produce lipids and may contribute to the lipid layer of the tear film.

Volumetric reconstruction of the mouse meibomian gland using high-resolution nonlinear optical imaging.

Recent studies suggest that mouse meibomian glands (MG) undergo age-related atrophy that mimics changes seen in age-related human MG dysfunction (MGD). To better understand the structural/functional changes that occur during aging, this study developed an imaging approach to generate quantifiable volumetric reconstructions of the mouse MG and measure total gland, cell, and lipid volume. Mouse eyelids were fixed in 4% paraformaldehyde, embedded in LR White resin and serially sectioned. Sections were then scanned using a 20× objective and a series of tiled images (1.35 × 1.35 × 0.5 mm) with a pixel size of 0.44 microm lateral and 2 microm axial were collected using a Zeiss 510 Meta LSM and a femtosecond laser to simultaneously detect second harmonic generated (SHG) and two-photon excited fluorescence (TPEF) signals from the tissue sections. The SHG signal from collagen was used to outline and generate an MG mask to create surface renderings of the total gland and extract relevant MG TPEF signals that were later separated into the cellular and lipid compartments. Using this technique, three-dimensional reconstructions of the mouse MG were obtained and the total, cell, and lipid volume of the MG measured. Volumetric reconstructions of mouse MG showed loss of acini in old mice that were not detected by routine histology. Furthermore, older mouse MG had reduced total gland volume that is primarily associated with loss of the lipid volume. These findings suggest that mice MG undergo "dropout" of acini, similar to that which occurs in human age-related MGD.

Tarsal elastic fiber distribution: an anatomic study.

PURPOSE: To analyze the distribution of tarsal elastic fibers, with special emphasis on the meibomian duct area. METHODS: Nine postmortem orbits (5 right, 4 left) of 7 Asian cadavers (mean age at death: 82 years, age range: 73-94 years), fixed in 10% buffered formalin, were used. Full-thickness sagittal sections of the upper eyelid specimens were dehydrated and embedded in paraffin and cut in 7-µm-thick sagittal sections. Sliced sections were stained with elastica van Gieson. RESULTS: Elastic fibers were demonstrated in all tarsal plates. They were mostly distributed around the meibomian ducts and much less around the acini or in the tarsal stroma. These elastic fibers were also seen in the area of the muscle of Riolan. The outer part of the meibomian acini was less surrounded by elastic fibers. CONCLUSIONS: Tarsal elastic fibers are distributed mainly around the meibomian ducts, and much less around the acini or in the tarsal stroma. The fibers were also shown to extend to the area of the muscle of Riolan. These anatomical findings may help clarify the mechanisms involved in meibomian secretion.

Nonobvious obstructive meibomian gland dysfunction.

This review presents the rationale and supporting data for a recent paradigm shift in our understanding of meibomian gland dysfunction (MGD). The historical understanding of MGD has been that of an infectious hypersecretory disorder with obvious signs of inflammation, hypersecretion, and purulent excreta. The current understanding of MGD now includes the polar concept of a less obvious or nonobvious type of hyposecretory obstructive MGD, where inflammation and other signs of pathology may be absent unless special examination techniques are employed. A new term, nonobvious obstructive MGD (NOMGD), is used to describe what may be the most common form of obstructive MGD. Obstructive MGD is an area of growing importance because obstructive MGD is now recognized to be the most common cause of evaporative dry eye, and because NOMGD seems to be the precursor to obvious obstructive MGD, it is also an important area to understand. The prevalence of NOMGD seems to be very high but currently significantly underdiagnosed. This review presents the relevant anatomy and physiology, concepts of obstructive MGD, the usual absence of inflammation in obstructive MGD, nomenclature and classification of obstructive and NOMGD, clinical diagnosis of NOMGD emphasizing the necessity for diagnostic expression, the use of a new instrument for diagnostic expression providing a standardized method of assessing meibomian gland functionality, the complementary roles of the aqueous and lipid layers, and the specific treatment of NOMGD, emphasizing that the success of treatment of all forms of obstructive MGD is dependent on the relief of the obstruction.