What are the components of the lacrimal system, and what are the positions of these components in the system?
The lacrimal (tear) gland: Each eye has one lacrimal gland, which is situated in the upper outer part of the eyeball, along with auxiliary lacrimal glands Krause and Ciaccio that are under the edge of the eyelid and secrete the aqueous layer of the tear. In general, different layers of the eye are as follows:
- The innermost and thinnest layer is made of mucus and secreted by certain cells in conjunctiva.
- The middle layer is the thickest layer and is actually like a highly diluted salt solution. It is produced by the main and auxiliary lacrimal glands. This layer protects moisture of the eye and keeps out dust and foreign bodies. The disorder in secretion of this aqueous layer is the most frequent cause of dry eye that is also known as keratoconjunctivitis sicca.
- The outermost layer of tear is very thin and greasy and is secreted by meibomian glands. The major role of this layer is to prevent the evaporation of its underlying aqueous layers.
Tear spreads over the eye surface, then enters the lacrimal duct and lacrimal sac through two small puncta that are in the inner edge of the upper and lower eyelids. Finally, tear enters the nose through the nasolacrimal duct. This is why our nose runs when we cry. Therefore, as shown in the following figure, the lacrimal system consists of the main and auxiliary lacrimal glands, the lacrimal sac, and the nasolacrimal duct.
What is the nasolacrimal duct obstruction?
The blockage of the narrow nasolacrimal duct, which normally drains tear from the eye surface, is called nasolacrimal duct obstruction. It is either acquired or congenital. However, the congenital type is discussed here.
What causes the congenital nasolacrimal duct obstruction?
The congenital nasolacrimal duct obstruction is prevalent in children, as 6-10% of children are born before their tear duct is fully opened. Some references report the prevalence of obstruction in infants as 50%. The blockage is caused by a membrane remaining at the end of the nasolacrimal duct on the nose side.
What are the symptoms of congenital nasolacrimal duct obstruction?
Usually, infants with such problem show some symptoms within 2-6 weeks after birth, of which the most frequent symptom is tearing. Neonates have no reflex tear secretion (shedding tears) when crying, and in case of any tear secretion, it is more likely pathological (caused by a disease). Other symptoms of the obstruction include discharge, recurrent inflammation of conjunctiva, and inflammation or infection of lacrimal sac, and in these cases, the area under the eyes and around the nose becomes red, inflamed, and sensitive to touch. The area may be inflamed, and mucus secretion may occur in the inner side of eyes. In 1/3 of cases, both eyes are involved. The symptoms in infants usually exacerbate with dust and wind, however, there is no photophobia.
Note: The congenital glaucoma must be taken into account in infants with photophobia and tearing.
How is the congenital nasolacrimal duct obstruction diagnosed?
- A gentle pressure on the lacrimal sac will release the fluids from puncta.
- A substance like fluorescein is dropped into the eye, then the presence or lack of the obstruction is diagnosed based on the time the substance disappears or the time it appears in the oral pharyngeal cavity (that is evaluated using cobalt’s blue light). Performance of this diagnostic method in infants has its own specific difficulties. To do the test, a drop of 1% fluorescein is dropped into the conjunctiva, then it is left for 2-5 minutes. Under normal conditions, no fluorescein should remain in the eye after 5 minutes.
How is the congenital nasolacrimal duct obstruction treated?
Most of the time, the congenital nasolacrimal duct obstruction in children is resolved spontaneously, as in 95% of children, the nasolacrimal duct is opened before they become 1 year old. The interventional treatments of the obstruction include the surgical and conservative methods.
- The conservative treatment involves care of the patient, the lacrimal sac massaging, and use of topical antibiotics. To massage, one should wash his hands, put his index finger on the medial side of the eye (near the nose), and press downward. Moreover, warm compresses may be suggested in this situation. If there is an infection, a topical antibiotic ointment or drop is useful. It must be noted that the antibiotic does not treat the obstruction.
- If the nasolacrimal obstruction is not treated after some months using the above treatments, a severe infection occurs, or the infant has relapsing infections, the infant must undergo probing, which is successful in 85-95% of children under one year old. However, the success of probing decreases with children’s age.
Probing is a surgical operation lasting 10 minutes. In this operation, a thin metal probe is passed through the lacrimal duct to open the obstruction. Some physicians believe that the suitable age for probing is six months in which probing can be done in clinics without general anesthesia. However, some other physicians think that probing should be delayed up to the age of one year in order to give maximum chance to the infant for the spontaneous opening of the lacrimal duct. In this case, probing is done in the operating room under general anesthesia.
- If the probing is not successful, or it reveals a lacrimal duct stenosis, more extensive surgical procedures, such as silicone tube intubation, may be needed. In silicone tube intubation, a silicone tube is placed in the lacrimal duct for 6 months for expanding the duct. After 6 months, the tube is removed through a minor surgery.
- Balloon Dacryoplasty is a newer method of Balloon Catheter Dilation, in which a balloon is placed in the corner of the eye inside the lacrimal duct. In the beginning, the balloon is expanded with a sterile fluid for 90 seconds, then the fluid is removed, and the balloon is expanded again for 60 seconds, and finally, the fluid is removed. The success rate of this method has been reported as 80-100%.
- In some rare cases in which children continue to shed tears after the above treatments, they may undergo dacryocystorhinostmy (DCR), like adults.
This method that is the main treatment for patients with the congenital obstruction must be used in people with relapsing dacryocystitis, return of the mucoid fluid, painful enlargement of the lacrimal sac, or tearing. Although there are various methods for treatment of the obstruction, the principle technique in all of them is to open a passage from the lacrimal sac toward the nose.