Meibomian gland inflammation in dogs

Overview

Eyelid glands and the tear film

Meibomian glands lie within both upper and lower lids. Ducts open at the margin, allowing secretions to spread across the surface. Imaging in 12 dogs found an average 30.50 upper and 29.42 lower lid glands. Mean gland length was 2.60 mm. Glands lie within the thin connective tissue tarsal plate, so margin inspection does not show the entire gland. Conjunctiva lines the inner lid, through which a deep chalazion can be visible. Gland oil forms the outermost tear layer. This slows evaporation. It also helps lids slide during blinking.

Inflammation and dysfunction

Dysfunction can thicken secretions or reduce their quantity. Structural changes do not always mean inflammation. A 15-year-old Miniature Dachshund had damaged ducts in a dropout area without tissue inflammatory cell accumulation.

One gland abscess produces a local lesion. Several inflamed glands can cause broader margin swelling.

Causes

Blockage, inflammatory reactions and bacteria

A chalazion can develop when a duct blocks and secretions accumulate. Rupture can release oil into surrounding tissue. Oil outside the gland can trigger a local foreign-body reaction. A persistent reaction can form an inflammatory cell nodule, or granuloma. Macrophages, cells helping remove material from tissue, can gather around the oil.

Bacterial infection can instead form a gland abscess called an internal hordeolum, or stye.

Staphylococci and streptococci are among the bacteria most commonly isolated from adult bacterial blepharitis. Secondary infection can also introduce bacteria into an existing chalazion. Streptococci occurred in inflamed gland discharge from one two-year-old crossbreed.

Tumours can block ducts

A gland tumour can obstruct oil drainage and cause a chalazion. Chalazia also occur without tumours. They can contain pale, thick, cheese-like secretion.

A Brazilian ocular tissue study identified 25 gland adenomas, 33 epitheliomas and 15 adenocarcinomas. Nine of the 15 adenocarcinomas had associated chalazia. Histology can show an inflammatory nodule beside a tumour, with cells gathered around oil.

Risk factors

Chalazia particularly affect older dogs. Adenomas and epitheliomas are common margin tumours in middle-aged and older dogs. One gland study compared nine dogs with sebaceous adenitis against nine breed- and age-matched healthy controls. Affected dogs had more structural gland changes. Their lipid layer was also thinner. Schirmer tear production did not differ significantly from controls.

Gland dropout affected 64% of 14 examined dry-eye Shih Tzu eyes. Among 28 same-breed control eyes, 17.8% had dropout. Gland shortening affected 64% of dry-eye eyes. Controls had shortening in 46%.

Typical symptoms

A chalazion may be clearest on the inner lid despite only a small external bulge.

• A yellowish or pale inner-lid lump.
• Margin redness and swelling.
• Tenderness with a bacterial abscess.
• Mucoid discharge in the corner.
• Squinting or rubbing around the eye.
• Increased tearing.

Small chalazia can be painless. Several lids can be affected together, as in a seven-year-old Shih Tzu with lumps on both upper and lower lids. Pus can drain spontaneously onto the margin. Inner conjunctiva over a chalazion can become red and raised. Several adjacent abscesses may occur at gland openings. Persistent bacterial inflammation can ulcerate margin skin. It can also leave scarring.

Complications and consequences

Corneal irritation and evaporation

A weak lipid layer can accelerate evaporation despite normal aqueous production. An unstable film can leave the cornea dull. Chronic disturbance can encourage superficial corneal vessels. Extensive pigmentation can impair vision. A gland tumour can rub enough to ulcerate the cornea. Prolonged obstruction can atrophy a gland. Histology in a 14-year-old Cairn Terrier found chronic inflammation in an upper-lid dropout area. Little normal gland structure remained around the duct. The dog also had glaucoma.

Diagnosis at the vet

Margin, lump and cornea

The vet examines both lids and eye surfaces. Lid eversion reveals internal lumps and redness. Slit-lamp examination assesses openings for blockage. Extra lashes can emerge through gland openings and are checked too. Lashes matching surrounding hair may need magnification. Dysfunctional secretions can be cloudy and thick rather than clear oil. Pus culture can identify bacteria. Cytology looks for cocci and inflammatory cells. Fine-needle sampling can guide further investigation or treatment of unusual or persistent lumps. Biopsy identifies suspected tumour lesions. Fluorescein checks for corneal ulcers.

Tear function and imaging

Schirmer testing assesses production. Tear break-up time measures the interval to the first dry spot after blinking. The seven-year-old Shih Tzu's film broke up at around six seconds in both eyes. Schirmer results were 18 mm per minute right and 17 left. At least 20 seconds has been reported as normal break-up time, though brachycephalic dogs can have shorter times.

Reflected light patterns assess the lipid layer. Infrared imaging shows shortening, thickening or partial loss. The lid is everted so its inner surface can be illuminated. Healthy glands usually look pale. Dropout appears dark.

A 59-dog study found mean margin thickness of 1.18 mm with dysfunction. Controls averaged 1.00 mm. At least 1.20 mm was a possible sign of dropout exceeding one-third of the area. Thickening can therefore warrant more detailed imaging.

Treatment

Abscesses and chalazia

For bacterial gland infection, the vet can select antibiotics using culture and susceptibility results. An abscess can be opened at the clinic to allow drainage. Chalazion contents can be removed through an incision on the conjunctival side. A tumour blocking the duct may be removed simultaneously. Surgery aims to preserve margin shape so the closed lid protects the surface. Removing small tumours can preserve more tissue than removing larger ones.

Local freezing may suit some small margin tumours. One study found recurrence in 10 of 38 masses after local excision and freezing, or 26.3%. Recurrence was detected after an average six months. No histology was performed, so exact tissue types were unknown.

Vet-directed warm compresses can relieve symptoms. Warming may help thick secretions leave gland openings. Corticosteroid eye medication is unsuitable with corneal ulcers.

Tear support and follow-up

Lipid-containing ointment can reduce evaporation when secretion cannot maintain the film. A dog with sebaceous adenitis improved over three weeks. Imaging still showed obstructed ducts despite improvement. Prognosis after chalazion treatment is generally good. Local inflammation in a 10-year-old crossbreed resolved after surgical drainage.

Prevention

Renewed blockage can cause recurrence. Trim long hair contacting the surface to stop rubbing. Removing a damaging extra lash can prevent repeated corneal friction. A collar protects against scratching during recovery. Incomplete closure may require prescribed lubricating ointment to protect exposed cornea. Gentle handling practice in puppyhood helps later drop application.

Important for dog owners

Watch whether a margin lump touches the eye or causes tearing as it grows. Leave drainage to the vet because opening may be needed through the inner lid. Wash hands before and after medication. Keep the bottle tip away from surface and lids to prevent contamination. Sterile eye wash can remove discharge before prescribed medicine. Report worsening redness after application. Mention other eye products before starting new treatment.

Frequently asked questions

Is a chalazion the same as a stye?

A chalazion develops when a duct blocks and secretion remains in the gland. An internal stye is an acute Meibomian abscess. Styes can be clearly painful, whereas chalazia are often firm and painless.

Could a small pale lump be a tumour?

An inner-lid pale lump can be a blocked gland chalazion. The same lid may still have a duct-blocking tumour. Histology helps establish tumour involvement and required treatment. The tumour may lie on the margin while the inflammatory lump lies deeper.

Can I squeeze the lump?

Drainage belongs to the vet, who may open it through the inner lid. A recommended warm compress may ease symptoms before further care. Pain or cloudiness needs prompt examination.

Can eyes be dry despite discharge?

An inadequate lipid layer can make tears break up too quickly. Mucoid discharge can still collect in the corner. The vet can measure break-up time separately because tear quantity and stability assess different things.

Can chalazia recur?

New lumps can form on the same or another lid after treatment. The vet assesses nearby duct-blocking tumours. Growth causing surface rubbing may warrant removal.