While Maltese on the whole are considered to be a breed with a relatively low incidence of eye problems, there are diseases that may arise during a dog's lifetime. Some eye diseases are inherited or congenital and some are caused by the dog's environment (trauma, viral or bacterial infections).Listed here are a few of the diseases that can affect Maltese but by ​no means are considered prevalent within the breed

Distichiasis and Ectopic Cilia: This is the inward growth of extra eyelashes which can cause scarring and ulceration of the cornea. Depending on where the extra lash originates from will determine if it is distichia or ectopic cilia. The dog may present with itchy, red, watery eyes. Surgery to correct this is usually either electrolysis or cryosurgery. Distichia is considered an inherited disease.

Entropian: This is where either the upper or lower eyelid folds in on itself and causes the eyelashes to rub on the cornea.This is similar to distichiasis or aberrantcilia in that it also causes the scarring and ulceration of the eye and if left untreated, blindness. This is a very painful condition but it is treatable. Entropian is oftentimes congenital but the mode of inheritance is unclear. This can usually be corrected by a simple surgical procedure.

Ectropian: Ectropian is the opposite of entropion where the lid margin is everted (folded out) and the conjunctiva is exposed to environmental irritants. This is common in some breeds (i.e. Bloodhound) but not generally seen in Maltese. Scarring of the skin close to the eyelid or facial nerve paralysis can cause ectropion in any breed.

Imperforation or Atresia of the Nasolacrimal Puncta & Duct: This occurs when the puncta (or hole) that connects to the nasolacrimal duct or tear duct is absent, immature or narrowed to a degree where the normal flow of tears is obstructed and flows over the margin of the lower eyelid (epiphora) and onto the face. The face remains wet where the tears flow and can be a breeding ground for bacteria or yeast. Surgery to dilate or open the puncta and duct may be beneficial initially but is not always successful long term. This condition is congenital and is seen in Maltese.

Cataracts: This is where the lens of the eye becomes cloudy or opaque thereby causing a decrease in the dog's visual acuity. There are several different types of cataracts.

• Congenital Cataracts: the puppy is born with them and it is usually bilateral (involving both eyes). Even if the puppy is born with congenital cataracts it doesn't necessarily mean it is inherited. Infections or toxins during gestation may cause this type of cataract in the unborn puppy. There are certain types of cataracts, primary congenital cataracts, which are considered heritable. Dogs with this type of cataract should never be used for breeding.
• Developmental or Early Onset Cataracts: These types of cataracts develop early on in life. They can be inherited or caused by diabetes, trauma, toxins or infections.
• Senile or Late Onset Cataracts: This occurs in animals over 6 years of age. This type of cataract occurs much less frequently in animals than humans. Most geriatric dogs develop nuclear sclerosis which is a hardening of the lens causing it to have a grayish appearance. This is not a cataract and usually will not affect the dog's vision.

Surgery by a veterinary ophthalmologist to remove the cataracts will give the dog back some of his vision.

Glaucoma: This eye disease is characterized by an increase in intraocular (inside the eye) pressure resulting from a build-up of fluid (aqueous humor) in the eye that doesn't drain properly.If left untreated, the increased pressure will cause permanent damage to the retina and optic disc which ultimately causes blindness. This disease is very painful for the dog and may be manifested by behavioral changes, the pupil may become fixed, dilated or sluggish and the globe (eyeball) may become enlarged causing a bulging eye appearance.

There are two classifications of glaucoma:

• Primary: is an inherited condition not caused by trauma or other ocular diseases and it will eventually affect both eyes. It is a developmental defect in the drainage structure of the eye.
• Secondary: is caused when other eye diseases such as intraocular tumors, lens subluxation or luxation (partial or complete dislocation), inflammation inside the eye (uveitis) or even trauma that causes an increase in intraocular pressure.

Early detection of glaucoma can often be treated with medications for the eye. In some cases the disease is resistant to medications and surgery may be indicated. When the dog's vision or comfort cannot be maintained with medication or surgery, the eye may have to be removed (enucleation). Glaucoma can occur in Maltese but it is not listed as one of the breeds commonly affected with this disease.

Progressive Retinal Atrophy (PRA):PRA is a group of inherited diseases that cause degeneration of the retina resulting in permanent blindness. Initially the dog may have night blindness which progresses into loss of vision in a brightly lit environment. The pupils may be dilated and have a slow response to light. Secondary cataracts may also occur with this disease. Diagnosis is made by Electroretinography (ERG).

There are different types of PRA:

• Early onset: this occurs as young as 6 weeks of age in some breeds and the puppies will usually be blind by 6 to 8 months old.
• Late onset: this occurs in dogs usually older than one year of age and the dog will become blind within 1 to 2 years of onset.

In most breeds studied with PRA, the disease is inherited as an autosomal recessive trait, i.e. the dog must have a gene from each parent for the disease to manifest itself. Dogs with PRA should never be bred and instead be spayed or neutered. There is no treatment for PRA and the condition is considered irreversible but painless. While PRA can occur in Maltese, they are not one of the breeds commonly listed with this disease.

Cherry Eye: This is a condition where the gland of the nictitating membrane (or third eyelid) prolapses (or bulges outward). It is unknown why the gland will prolapse but is theorized that it is caused by a hereditary weakness in the connective tissue that holds the gland into place. Veterinary ophthalmologists used to surgically remove the gland but it was found that the dog would be at an increased risk of keratoconjunctivitis sicca (dry eye) since the gland is responsible for about 30% of the tear production of the eye. A newer method of surgery sutures the gland back into place preserving the tear production capability of the eye.

Keratoconjunctivitis Sicca: Also known as Keratitis Sicca or dry eye is a condition where the eye does not produce enough tears or the tears produced may be abnormal in composition and evaporate too quickly. It usually affects both eyes and the eyes may be red, irritated, itchy and sensitive to light.Abrasions may occur when the dog rubs the itchy eyes. This can then develop into an ulceration that may eventually scar and cause blindness. The ophthalmologist can diagnose this condition by performing a Schirmer test. This is a test where a piece of filter paper is placed on the edge of the lower lid and it measures the amount of tear production in the eye. Treatment consists of eye drops or artificial tears that help to keep the eye bathed in moisture thereby reducing the irritation and the dog's tendency to rub the eye. A thicker lubricant is used before bedtime to keep the eye moist for a longer period of time. It's generally not used during the day because it can cause the vision to be blurry.

Again, just to reiterate, Maltese are not prone to inherited eye diseases.  Your Maltese should have sparkling dark eyes until well into old age.