MGD is a common cause of dry eye and lid tenderness. Blockage of the meibomian glands can now be treated directly under local anesthesia using fine disposable probes.
Although dry eye is a complex, multifactorial disease, meibomian gland dysfunction (MGD) may be its single most common cause.1 MGD results primarily from the physical obstruction of the meibomian gland duct and orifice, leading to the secretion of too little meibum or meibum that lacks sufficient qualitative properties to be effective in its primary function: stabilizing the tear film.2
Instability of the tear film, increased evaporation, and the resulting hyperosmolality of the tear film can follow from the lack of tear lipids, with further consequences including increased bacterial growth on the lid margin, evaporative dry eye symptoms, and ocular surface inflammation.
The causes of meibomian gland obstruction are interrelated. Meibomian glands are sebaceous, and androgens control the lipid production of sebaceous glands throughout the body. With aging and the fall-off of sex-steroid hormone levels, particularly testosterone, meibum viscosity increases, while its production and secretion falls off; not surprisingly, post-menopausal women comprise a large fraction of MGD patients.3,4
Meibomian glands are ontologically related to hair follicles—they have been described as “hair follicles without the shaft”—and retain a cellular commitment to keratinization.5 Normally, keratinization is inhibited by testosterone, but with low androgen levels keratinization of the meibomian duct epithelium can occur. Obstructive keratinization can take place at the orifice itself, or gritty keratinized cellular debris can mix with the thickened meibum and plug the orifice. Once the gland is occluded, unsecreted meibum collects, causing elevated intraductal pressure, enlargement of the central glandular duct, and swollen and tender lids.4
The processes of hyperkeratinization can occur without inflammation, but inflammation may also play a role in MGD.4 Direct observation of the meibomian gland by in vivo confocal microscopy found intra- and periglandular inflammation that was reduced by corticosteroid therapy (which also improved dry eye signs and symptoms).6-8 Increased intraductal pressure can result in inflammation that may be a cause of the diffuse and periductal fibrosis often seen on autopsy of meibomian glands of postmenopausal women.4 It is possible that circumferential fibrosis around the gland and orifice may impede meibum secretion.9,10
Common current treatment regimens for MGD include lid heating, massage, compression, lid cleaning, and physical expression of the glands. Heating decreases the viscosity of meibum, possibly melting some plugs and allowing freer flow. Heating might also increase meibum production. Lid scrubbing aims at opening blocked ductal orifices and keeping them open.
Warm compresses followed by lid massage may help mobilize the meibum. Physical expression of blocked glands has the goal of removing the obstruction and emptying the gland. This may require little effort, but often more than a little force is necessary and pain can be a limiting factor for treatment.11
A new approach to treating obstructive MGD involves opening the meibomian glandular orifice and duct directly.12 This technique, intraductal meibomian gland probing, can also be coupled with delivery of steroid, antibiotics, and/or other medication into the newly-patent ducts. The feasibility and success of this approach has required the recent commercial development of disposable fine stainless steel probes (Rhein Medical) for opening the meibomian gland orifices and clearing blockages deep within the glandular duct, and microcannulae for drug delivery (Figure 1).
The process of intraductal meibomian gland probing is straightforward. A bandage contact lens is first applied. Then, about 15 minutes after the administration of 8% lidocaine and 25% jojoba topical anesthetic ointment, the lid margins are visualized under slit-lamp illumination. One hand is used to evert the lid margin, while the other hand inserts the thin (76-micron) shaft of the steel probe through the blocked glandular orifice and distal duct (Figure 2).
Each gland probing takes no more than a few seconds to accomplish. In nearly half the glands a single “pop” is felt or heard as the probe is inserted.13 This may be associated with the release of a collar of periglandular fibrotic obstruction. A gritty sensation is felt in about one-third of glands, likely due to multiple sequential “pops.”13,14 The probing procedure usually takes less than 15 minutes. Typically two lids are done at a time, but all lids can be done if patients find it more convenient and have someone to drive them home.
The probes come in different lengths, from 1 to 6 mm. The 1- or 2-mm length is used first, as these are stiffer and can get through fibrosis or keratinization at the lid margin and distal duct. However, glands can have deep blockages even though meibum is expressible from more superficial acini. In these glands, attempts to express meibum may cause further inflammation. For these cases, the longer probes may be used to fully clear the gland, especially when there is persistent tenderness deep in the lid.
The treatment can be learned quickly, and adverse sequelae are rare. If a shaft bends in use, it should be disposed of before breakage can occur.
Patients with complaints of lid margin thickness or tenderness from obstructed glands can gain particular benefit from this treatment. For these patients the main goal is to release increased intraductal pressure from within the gland. To prevent damage to the glands, expression should not be done until ducts have been probed and are patent throughout their length. If one pushes too hard to express blocked glands, physical damage to the gland can lead to more inflammation, scarring, and atrophy or to chalazion.
For patients with dry eye, the goal is to provide sufficient meibum outflow; and for them probing increases functionality. A working threshold for the effectiveness of a lid as a unit is five functioning glands per lid (as determined by expressibilty of meibum). Patients with fewer active glands per lid benefit from intraductal probing. Clinically, it appears that opening the obstructed gland upregulates meibum production and release, resulting in the stimulation or regeneration of “dormant” glands.
This can happen very quickly: in one study the average number of glands with expressible meibum jumped in a week from 2.47 per lid before probing to 8.0 afterward.13 An implication of this observation is that patients with subclinical disease may benefit from probing as well.
Newly-developed microcannulas allow the intraductal administration of steroids, which quickly reduces the amount of lid swelling and pain and improves the overall clinical effectiveness over probing alone.15
In the first series of 25 patients treated with intraductal meibomian gland probing, symptom relief was immediate in nearly all (96%; 24/25) patients, and by 4 weeks was seen in all.12,14 Patient responses to treatment were not solicited; nonetheless 40% of patients reported better lubrication. At a mean follow-up of 31.2 months, 62% (13/21) patients did not require retreatment. The time of retreatment for the eight patients (38%) requiring it averaged 18.7 months.13,16
The beneficial effects of probing depend in most cases upon continued effective management of the underlying MGD. In the worst case, without any effective treatment for the underlying condition, retreatment may be needed in as little as 2 months. But the normal duration of treatment is in the range of 12 to 18 months or longer.
MGD develops as a result of adverse conditions, and once open, the glands need protection from both local and systemic causes. Once the gland is open, expression and warm compresses become more effective. Therapies including antibiotics (such as doxycycline) and omega-3 fatty acid nutritional supplementation can improve the quality of meibum; and comorbid conditions—such as allergy, aqueous tear deficiency, and anterior blepharitis—that have adverse effects on the meibomian gland also need appropriate treatment. Intraductal probing improves the effectiveness of the standard treatments, and these treatments in turn prolong the effects of the probing.
THE BOTTOM LINE
Fine disposable steel probes have been developed that allow opening of plugged and obstructed meibomian gland orifices and ducts. Probing can provide rapid relief of lid swelling, tenderness, and inflammation from obstructive MGD. There is evidence that intraductal probing also improves the functionality of blocked meibomian glands, increasing the availability of meibum and decreasing the symptoms of MGD and dry eye.
Steven L. Maskin, MD, FACS, practices at the Dry Eye and Cornea Treatment Center, Tampa, FL. He is the creator of the Maskin Meibomian Gland Intraductal Probe (Rhein Medical). He has patents pending on the method of intraductal probing, diagnostic and treatment apparatus, and jojoba treatment solutions for MGD. Freelance writer Zaid Smith, PhD, assisted in the preparation of this article.
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