Canalicular obstruction is a condition in which the canaliculus (the upper or lower canaliculus; vertical part about 2 mm + horizontal part about 8 mm = about 10 mm in total) or the common canaliculus (from the junction of the upper and lower canaliculi to the entrance of the lacrimal sac) is blocked. Main causes include inflammatory scarring and postoperative adhesions.
With obstruction of only one upper or lower canaliculus, tearing is often not seen. In contrast, with common canalicular obstruction or bilateral canalicular obstruction, drainage of tears into the nasolacrimal duct is impaired, causing marked tearing (epiphora). Prognosis varies greatly depending on the extent of the blocked area and the degree of scarring.
Anatomically, the upper and lower canaliculi each run from the inner end of the eyelid toward the nose, bypass the Horner muscle, join in the common canaliculus, and then open into the lacrimal sac. Understanding this route is directly linked to diagnosis and treatment strategy.
It has been reported to occur secondarily after EKC (epidemic keratoconjunctivitis)1), and a multicenter study showed that about 60% of anticancer drug-related lacrimal drainage obstruction involved punctal and canalicular damage2).
The site of obstruction is different. In canalicular obstruction, resistance is felt when the probe is inserted 10 mm or less. In nasolacrimal duct obstruction, the probe can reach the lacrimal sac. The treatment also differs: canalicular obstruction is treated with endoscopic recanalization of the lacrimal passage plus tube insertion, or CDCR. For nasolacrimal duct obstruction, DCR (dacryocystorhinostomy) is standard. The prognosis for canalicular obstruction is generally worse than for nasolacrimal duct obstruction.
The main symptoms are as follows.
The Yabe-Suzuki classification1) is used to grade the severity of canalicular obstruction.
| Grade | Bougie insertion length | Communication between the upper and lower canaliculi | Clinical significance |
|---|---|---|---|
| Grade 1 | ≥11 mm | Present | Equivalent to common canalicular obstruction. Endoscopic recanalization is relatively easy to indicate |
| Grade 2 | ≥7–8 mm | None | Obstruction is proximal to Grade 1. It becomes harder to pass through. |
| Grade 3 | <7–8 mm | None | Obstruction is more proximal. Many cases are difficult to pass through. |
Grades 2 and 3 are much more difficult to treat than Grade 1, and in some cases it may be necessary to move on to a skin incision approach or CDCR.
Inflammatory scarring
Stevens-Johnson syndrome (SJS): Often causes severe scar-related obstruction.
Ocular cicatricial pemphigoid: persistent epithelial damage from chronic inflammation
After chronic conjunctivitis / EKC: post-inflammatory fibrosis blocks the canaliculi
Postoperative
After eyelid surgery: scarring at the inner canthus compresses and blocks the canaliculi
After lacrimal drainage surgery: adhesions may develop after surgery on the punctum and canaliculi
Medication-induced
S-1 (tegafur preparation, TS-1®): the active metabolite 5-FU directly damages the lacrimal mucosa. Can become severe
Long-term use of glaucoma eye drops: chronic irritation from preservatives (BAK) and similar agents is involved
After trauma or infection
Traumatic obstruction: incomplete healing and scar formation after a canalicular tear
After canaliculitis (Actinomyces infection): luminal blockage caused by concretion formation and chronic inflammation
Lacrimal duct obstruction caused by S-1 (a combination drug of tegafur, gimeracil, and oteracil potassium) often becomes severe. Among anticancer drug–related lacrimal duct obstructions, punctal and canalicular damage accounts for about 60%2), and the longer the time since tearing begins, the more refractory it becomes. It is important to note that the obstruction may continue to progress even after the drug is stopped.
Because lacrimal duct obstruction caused by S-1 can easily become severe, it is recommended to see an ophthalmologist early when tearing starts and to consider tube intubation. While the anticancer drug is still being used, removing the tube can make re-obstruction more likely, so it is preferable to keep the tube in place as long as treatment continues. Coordination between the treating physician (medical oncology) and ophthalmology is important.
Detailed prevalence data for canalicular obstruction are limited, but associations with the following diseases and situations have been reported.
In lacrimal system disorders after SJS, canalicular obstruction is likely to occur, and severe cicatricial obstruction is often difficult to treat. Acquired lacrimal obstruction after EKC (epidemic keratoconjunctivitis) has been reported relatively often in East Asia1).
Multicenter studies have reported lacrimal system disorders in patients using S-12). In addition, lacrimal sac biopsy during DCR (dacryocystorhinostomy) for lacrimal obstruction reportedly found granuloma formation/reactive lymphoid hyperplasia in 5.9% and tumors in 1.4% (69% of which were malignant)3). This makes it important to rule out neoplastic lesions in the differential diagnosis of tearing and lacrimal obstruction.
Confirm whether irrigation passes through each upper and lower punctum. The irrigation test is the first step in estimating the site of obstruction, but its agreement with actual dacryoendoscopic findings is said to be about 70%1). Reflux and a sense of resistance during irrigation are clues for diagnosis.
Keeping in mind the length of the canaliculus (about 10 mm), estimate the extent of obstruction from how far the bougie can be inserted. In cases of total canalicular obstruction, inserting a metal bougie produces a membranous sense of resistance just before the lacrimal sac. Metal bougies can easily create a false passage, so they must be handled with particular care.
Lacrimal endoscopy, covered by insurance in 20181), allows direct observation of the obstruction site and is extremely useful for diagnosis. It can also assess the degree of fibrosis at the blocked site and signs of inflammation in the mucosa. It can classify not only whether the blockage is in the common canaliculus or the nasolacrimal duct, but also the detailed location within the nasolacrimal duct1).
The specifications of the scope used are as follows.
Dacryocystography is useful for confirming the site of obstruction and the condition of the lacrimal sac, but it can sometimes be difficult to judge whether the contrast agent has reached the blocked site1). CT/MRI is recommended in combination to rule out lesions outside the lacrimal drainage system and to confirm bony obstruction1, 4).
| Disease | Bougie findings | Irrigation findings | Characteristic findings |
|---|---|---|---|
| Canalicular obstruction | Resistance at 10 mm or less | Reflux | Grade determined by the Yabe-Suzuki classification |
| Punctal obstruction | Cannot be inserted into the punctum | Cannot be performed | Findings of punctal papilla confirmation and closure |
| nasolacrimal duct obstruction | Can reach the lacrimal sac | Reflux | Reflux with swelling or pressure over the lacrimal sac area |
| Canaliculitis | Resistance in the canaliculus | Purulent reflux | Concretions and Actinomyces infection |
Treatment for canalicular obstruction is selected stepwise according to the Grade in the Yabe-Suzuki classification and the condition of the obstruction.
Grade 1 (common canaliculus obstruction)
Endoscopic recanalization using DEP / SEP is the first choice
Insert a silicone tube and remove it 2 to 10 months later. The Kaplan-Meier survival rate at an average of 878.3 days after surgery was 94%
Grades 2 and 3 (more proximal obstruction)
Try DEP/SEP. If perforation is difficult, move to metal bougie dilation or the skin incision method
The longer the obstruction distance, the more difficult it becomes. If eyelid edema occurs, stop the surgery
Neither the upper nor lower canaliculus can be opened
CDCR (conjunctivodacryocystorhinostomy) is indicated
Choose the Jones tube method (87% of patients felt it was effective) or the conjunctival pedicle flap method (success rate 75%)
Anesthesia
Perform anesthesia within the lacrimal passage using 4% lidocaine hydrochloride solution. If the effect is insufficient, add an infratrochlear nerve block with 2% lidocaine (a branch of the first division of the trigeminal nerve) and intraorbital infiltration anesthesia1).
Procedure
After sufficiently dilating the canaliculus with a punctal dilator, insert a nunchaku-type silicone tube or a catheter-type tube. When inserting it, advance the tip little by little while carefully checking the feel of the obstructed site, and do not force it in. The narrowed lacrimal passage may also be enlarged beforehand with a bougie. Metal bougies are prone to creating a false passage and must be handled with particular care.
The inserted tube is usually left in place for 1 to 2 months and then removed (in Grade 1, it may be left for as long as 2 to 10 months1)). If the tube remains in place for 9 months or longer, complications of cheese wiring (pressure cutting at the punctum) have been reported1), so long-term placement requires caution.
Using endoscopic lacrimal duct recanalization makes it possible to safely penetrate the blockage under direct vision1).
Treatment results for Grade 1: The mean postoperative Kaplan-Meier survival rate at 878.3 days is 94%1), suggesting a favorable prognosis. The reported re-occlusion rate in canalicular obstruction is about 0 to 18.2%1).
If perforation can be achieved with DEP/SEP, tube insertion is performed in the same way. If the obstruction is long, the endoscopic view shows a continuous white wall-like image. Strong pushing should not be attempted; instead, leave the sheath in place and use a thin bougie to probe for a dimple or pit as a starting point for perforation.
If the endoscopic image takes on a yellowish color, it means orbital fat beneath the mucosa is visible, and there is a risk of eyelid edema. If eyelid edema occurs, stop the surgery. If only one side can be opened, place a unilateral lacrimal tube.
In cases using anticancer drugs, removing the tube tends to cause re-obstruction, so it is preferable to keep the tube in place while the drug is still being used2).
For common canalicular obstruction that cannot be traversed from the punctum, a skin-incision approach is used.
CDCR is indicated for cases in which both the upper and lower canaliculi cannot be opened.
Jones tube method
The Jones tube is a glass tube that completely bypasses the canaliculi and drains tears from the conjunctival sac into the nasal cavity. One report found that 87% of patients felt the treatment was effective5). It must be left in place for life, and if it shifts position or becomes dirty, it may need to be repositioned or replaced. In Japan, Jones tube is not approved, so its use is restricted (as of 2023)1). Use of the Jones tube in Japan was first reported in 1969 by Nakagawa et al.5).
A Jones tube is a glass tube that completely bypasses the canaliculi and drains tears from the conjunctival sac into the nasal cavity. It is used in cases where both the upper and lower canaliculi cannot be opened (CDCR candidates). One report found that 87% of patients felt the treatment was effective. It must be left in place for life, and may need repositioning or replacement if it shifts or becomes dirty. Its use is restricted in Japan because it is not approved there (as of 2023).
Conjunctival pedicle flap method
A success rate of 75% has been reported5). This method temporarily places a silicone sponge used in retinal detachment surgery, but the procedure is complicated and may cause limited outward eye movement.
Endonasal CDCR
An endonasal method using a conjunctival pedicle flap has also been reported5). As with the external approach, there is a risk of limited outward eye movement.
This is a recently reported procedure that uses the lacrimal sac and nasolacrimal duct as an alternative to blocked canaliculi, directly anastomosing the lacrimal sac to the conjunctival sac6). In all 11 cases followed for 1 year after surgery, tearing symptoms improved and no complications were reported6). It is expected to be an alternative to CDCR, but long-term results are still needed.
| Treatment | Indications | Success rate | Notes |
|---|---|---|---|
| DEP/SEP+ tube (Grade 1) | Common canalicular obstruction | 94% (mean 878 days) | Indwelling period: 2–10 months1) |
| Skin incision approach | Common canalicular obstruction that cannot be traversed from the punctum | No data | Procedure under direct microscopic visualization |
| CDCR (Jones tube) | Neither the upper nor lower canaliculus can be opened | 87%5) | Requires lifelong placement. Not approved domestically |
| CDCR (pedicled conjunctival flap) | Same as above | 75%5) | Risk of limited abduction |
| Conjunctivodacryocystorhinostomy | Same as above | 100% (11 cases)6) | More long-term outcome data are still needed |
The reported re-obstruction rate for canalicular obstruction is about 0–18.2%. In Grade 1, the Kaplan-Meier survival rate is good at 94% (mean follow-up 878.3 days), but re-obstruction can still occur even after opening. The risk is higher if the underlying disease (such as SJS) remains active or if the obstructed segment is long. A report also found a 64% survival rate at 3,000 days after surgery, so follow-up with the long-term recurrence risk in mind is necessary.
The canaliculus lumen is lined with nonkeratinized stratified squamous epithelium, which functions in the passage and protection of tear fluid components. The canaliculus consists of a vertical segment (about 2 mm) and a horizontal segment (about 8 mm), with a total length of about 10 mm. The upper and lower canaliculi join the common canaliculus (about 2–5 mm long) via Horner’s muscle (the posterior limb of the medial canthal tendon) and open into the lacrimal sac.
When inflammation or trauma affects the canaliculus, obstruction develops through the following process.
If the scar is extensive or the inflammation is severe, surgical reconstruction becomes difficult.
Tegafur (the main component of S-1) is metabolized in the body to 5-FU (fluorouracil). 5-FU is secreted into the tear fluid and directly damages the epithelial cells of the lacrimal drainage mucosa, causing canalicular obstruction. The risk increases with the dose and duration of treatment, and a key feature is that obstruction may continue to progress even after epiphora symptoms appear.
The common canaliculus is located at a position that can be approached from the skin side at the level of the medial canthal tendon. This anatomical relationship is the theoretical basis for puncture procedures using a skin incision approach. When the obstructed segment is long or the scarring is severe, surgical reconstruction is extremely difficult, and bypass procedures such as CDCR or dacryocystorhinostomy with lacrimal sac transposition become options.
Lacrimal sac transposition is a surgical technique reported in recent years6), and it is expected to be an alternative to CDCR. At 1 year after surgery, improvement in tearing was seen in all 11 cases, and no complications were reported. As long-term results accumulate, comparison with CDCR will be an important future issue.
Lacrimal endoscopy has been continually improved, from the early 2002 model (6,000 pixels) to the 2012 model (10,000 pixels) and the 2020 model (improved to a depth of focus of 1.5–7 mm), making it possible to observe the site of obstruction in greater detail. With the spread of SGI and G-SGI, the risk of submucosal misinsertion has been reduced1), and standardization of the procedure is expected in the future.
In addition, establishing a method to determine the best time to remove the tube based on lacrimal endoscopy findings is thought to lead to better postoperative outcomes1).
A report has shown a 3,000-day survival rate of 64% after tube removal6). This suggests the need for long-term follow-up, and regular postoperative observation with lacrimal irrigation testing is important.
