Lacrimal Pump Mechanism

The lacrimal pump mechanism is a sophisticated system orchestrated by the orbicularis muscle, responsible for regulating tear flow and drainage. Comprising preal and pretarsal portions, this mechanism ensures efficient tear distribution and prevents excessive tearing.

Table of Contents

Key Components of the Lacrimal Pump:

Pre-Blink Stage:
- The orbicularis muscle is relaxed.
- Tears easily enter the canaliculi, residing in close proximity to the puncta.
Blink Stage:
- Orbicularis oculi muscle contracts, closing puncta and canaliculi.
- Preal orbicularis contracts, creating negative pressure in the lacrimal sac.
- Tears are drawn into the lacrimal sac.
Post-Blink Stage:
- Lacrimal sac collapses, allowing tears to flow down the nasolacrimal duct.

In our previous post we understood lacrimal syringing which basically deals with the daignosis of the nasolacrimalapparatus obstructions. Toady we shall discuss two important tests namely the FDDT and jones dye test 1 and 2 . Before we understand them its important to understand three important causes of epiphora:- hyperlacrimation, lacrimal pump failure, and partial obstruction.

HYPERLACRIMATION

Hyperlacrimation refers to excessive tearing beyond the normal range, often leading to epiphora or watery eyes.

Lacrimal pump is normal so tears will reach the lacrimal sac normally
Pathway is patent so syringing is also positive
Probing also is normal ( no obstruction ).

LACRIMAL PUMP FAILURE

Epiphora due to failure of lacrimal pump mechanism
So tears will NOT reach the lacrimal sac normally
Pathway is patent so syringing is also positive
Probing also is normal ( no obstruction )

PARTIAL OBSTRUCTION IN APPARATUS

Epiphora due to failure of complete drainage
Some fluid reaches the throat but most overflows
LACRIMAL pump NORMAL so tears reach the sac normally
Pathway is partially patent so syringing will be normal with some regurgitation based on the force with which syringing is done .

Fluorescein Dye Disappearance Test (FDDT)

The FDDT involves the application of 2% fluorescein dye into the conjunctival sac of both eyes. This water-soluble dye is commonly used in ophthalmic examinations due to its fluorescent properties, allowing for easy visualization and tracking.

Procedure:

Application of Fluorescein Dye: A small amount (usually one drop) of 2% fluorescein dye is instilled into the conjunctival sac of each eye.
Observation Period:
- Patients are instructed to blink normally.
- The ophthalmologist observes the eyes for fluorescein staining over a specific period, typically 5 minutes.
Interpretation of Results:
- Normal eyes exhibit almost complete disappearance of the dye within the observation period.

Significance of the Fluorescein Dye Disappearance Test:

Assessment of Tear Drainage:
- The FDDT primarily evaluates the efficiency of tear drainage.
- Prolonged retention of fluorescein dye beyond the normal timeframe suggests inadequate tear drainage.
Identification of Lacrimal System Issues:
- Abnormal FDDT results indicate potential problems within the lacrimal apparatus.
- Lack of dye disappearance may result from a lack of tone in the lacrimal sac, lacrimal pump failure, or obstructive issues.
Less Invasive Alternative:
- Compared to more invasive procedures like syringing, the FDDT is a less intrusive yet effective method for evaluating tear drainage.
Applicability in Special Cases:
- FDDT is particularly useful in uncooperative patients or pediatric populations where more invasive tests may be challenging.

JONES DYE TEST

Procedure:

Jones Dye Test 1 (Primary Test):
- One drop of a fluorescent dye, often fluorescein, is instilled into the conjunctival sac of each eye.
- A cotton bud soaked in anesthetic solution is then placed in the inferior meatus of the nose.
- After a waiting period (usually 5 minutes), the ophthalmologist observes for the presence of the dye on the cotton bud.

Interpretation:

Positive Jones Test 1: If the dye is present on the cotton bud, it indicates a patent lacrimal system and suggests normal tear drainage.
Negative Jones Test 1: Absence of dye on the cotton bud may signify issues such as lacrimal pump failure or obstruction.

Jones Dye Test 2 (Secondary Test):
- Conducted if Jones Test 1 is negative.
- Involves syringing, a procedure where a saline solution is gently flushed through the lacrimal drainage system.