A METHOD OF DETERMINING THE PATENCY OF THE NASOLACRIMAL APPARATUS*

W. P. C A L L A H A N , M.D., I

W . D. S Toronto,

The manifestation of chronic tearing is encountered not uncommonly in the practice of ophthalmology. The diagnosis and treat-ment of this condition has been controver-sial for many years. One of the difficulties in this respect has been the problem of lo-calizing the obstruction in the nasolacrimal passages. In the past no test was available for this purpose which was technically fea-sible, clinically useful and which, used by different investigators, produced comparable results.

MODEL EXPERIMENTS

A brass model of the lacrimal sac and na-solacrimal duct was fashioned by lathing and filing, appropriate measurements being taken from Duke-Elder 's Textbook of Ophthalmology.* For the sake of simplicity, only important bends and valves were incor-porated in the brass mold (fig. 1 ) . The mold was warmed and impressed on a plate of Perspex. The plastic melted under the warm brass and right- and left-sided plastic nega-tives were thus prepared. The two sides were glued together with Rasin-bond liquid, a type of glue designed for Perspex plastic. The lower end of this model was considered to represent the counterpart of the plica na-solacrimalis. The upper pole of the en-glassed chamber was entered by two 27-gauge Luer needles. These needles have an inside diameter of approximately 0.25 mm which is within the range of normal canalicular diameters. For technical conven-ience this lumen of the canaliculus was left

* From the Department of Ophthalmology and the Department of Medicine, Laboratory of Car-diovascular Physiology, Faculty of Medicine, Uni-versity of Toronto, and the Department of Engi-neering, St. Michael's Hospital.

t Duke-Elder, S. : Textbook of Ophthalmology. London, Kimpton, 1933, v. 1.

' . G . FORBATH, M . D . , AND

. BESSER

Canada

unchanged to the point of junction with the sinus of Maier (fig. 1-B).

When the "nasal end" of this model was left open, the condition was considered to represent a state of "normal, free flow." "Complete obstruction" of the nasal end was accomplished by plugging the nasal end of the "duct" with a brass screw. "Partial obstruction" was produced by stuffing the outflow with C-media filter fiber. This material, in contrast to ordinary cotton, is nonwettable. I t s porous consistency allows fluid to flow through it but it still presents an impediment to free flow. Obstruction of the "lacrimal puncta" was produced by plugging the 27-gauge needles. The same procedure was used to provide a model of the condition referred to as "canalicular block" (fig. 2 ) .

One of the needles serving as a canaliculus was connected to a thick-walled polyethylene tube with a three-way stop-cock on its distal end ( fig. 3 ) . The stop-cock was connected to a syringe and to a strain gauge,* gauge con-trol,* and recording unit.* The system was filled with saline from the syringe, following which different pressures were applied to the system by manual pressure on the piston of the syringe. The pressure curve, its rise and decline, was recorded by a Visicorder on photographic (ultraviolet-type) paper.5

I t was assumed that the falling velocity of the pressure, measured as the geometrical appearance of the curve, would depend upon the patency of the openings in the model na-solacrimal apparatus (fig. 4 ) .

* Statham type, physiological pressure transducer (P 23-De)

t Honeywell Ltd. Model 902641 Φ Honeywell. Visicorder, Model 1108 § Kodak, Linagraph direct print paper, improved.

476 W. P. CALLAHAN, P. G. F O R B A T H AND W. D. S. BESSER

a ( j ! 4 * m m ( T W € 0 e A L 0 )

PUNCTA iACf t fMAUS

, VALVC OF KftAUSE

PLKA LACR(MAUS(VAtVC OF HAySNC«;

Fig. 1 (Callahan, Forbath and Besser). Preparation of the model nasolacrimal apparatus. (A) Mea-surements of the nasolacrimal passages. (B) Manufacturing of the model. (1 and 2) Brass positive. (3) Perspex negative, right and left side. (4) "Punctum and canaliculus," represented by a 27-gauge Luer needle.

Fig. 2 (Callahan, Forbath and Besser). Types of obstructions in the model nasolacrimal appara-tus. In each figure the arrow points to the site of "pathology." (A and B) Upper and lower puncta and canaliculus. (C) Lacrimal sac. ( D ) Naso-lacrimal duct. ( 1 ) Canaliculi open. Nasolacrimal duct, free flow. (2) Canaliculi open. Nasolacrimal duct, partial obstruction. (3) Canaliculi open. Naso-lacrimal duct, complete obstruction. (4) Lower canaliculus blocked; nasolacrimal duct: partial ob-struction.

GROUP A. CANALICULI OPEN

1. A pressure of 100 mm H g was applied on the lacrimal sac following which the pressure in the sac rose quickly. The "dia-stolic dip" or falling· velocity of the pressure-varied with the patency of the nasolacrimal opening:

a. Under conditions of free flow a rapid fall of pressure was obtained (fig. 4-A1) .

b. With partial obstruction the pressure rose normally but the "diastolic" slope was sluggish (fig. 4-A2) .

c. With a state of complete obstruction the pressure rose quickly and then showed a very slow fall (fig. 4-A3) .

2. A pressure of 200 mm H g was applied in the same way. The pressure rise was sud-den and the downward slopes of pressure were depicted as follows :

a. In the case of free flow, the fall was sudden except for an "anacrotic" notch at the level of 100 mm H g (fig. 4-B1) .

b. In the case of partial obstruction after the initial sudden rise a fairly rapid pres-sure drop was observed to the level of 100 mm Hg, from which level a sluggish fall of pressure was seen (fig. 4-B2) .

c. In the case of complete obstruction, after the sudden initial rise there was a fair-ly quick fall of pressure to the level of 100

PATENCY OF NASOLACRIMAL APPARATUS 477

-4 A

Fig. 3 (Callahan, Forbath and Besser). The measurement of flow curves in the model nasolacrimal apparatus. (A) Model with cana-liculi open, nasolacrimal duct par-tially obstructed. (B) Three way stop-cock; (r) syringe used to pro-duce positive pressure; (Δ) thick-walled vinyl connecting tubing. (E) Statham strain gauge.

RECORDING GALVANOMETER.

TO

STRAIN SAUGE

t PRESSURE.

mm Hg, following which there was hardly any pressure change (fig. 4 -B3) .

GROUP B. CANALICULI BLOCKED

1. When a pressure of 100 mm H g was applied on the model, the result was almost the same as that depicted in Figure 4-A1 and A2. In contrast to the results in Figure 4-A3, there was no fall of pressure in the model of canalicular block.

2. A pressure of 200 mm H g was ap-plied.

a. In the case of free flow the pressure fell rapidly without the phenomenon of the "anacrotic" notch (fig. 4-C1) .

b. In the case of partial obstruction the sluggish velocity of pressure fall began at the top of the curve and continued in the same sluggish manner down to zero pres-sure (fig. 4-C2) .

c. In the case of complete obstruction the level of pressure was maintained at 200 mm H g (fig. 4-C3) .

The results of our studies with the model are summarized in Table 1.

DISCUSSION

The plastic model tear duct described here-in is not an identical replica of the human nasolacrimal apparatus but we consider that it is sufficiently similar to permit valid studies of hydrodynamic flow. As far as the nasolacrimal sac and duct are concerned we believe that the similarity between the model and the natural state is close, not only hy-drodynamically but also anatomically. It is recognized that in any cavity the pressure is practically the same at any point, irrespec-tive of the shape of the cavity. The shape of

478 W. P. CALLAHAN, P. G. F O R B A T H A N D W. D. S. BESSER

Fig. 4 (Callahan, Forbath and Besser). Flow curves in the lacrimal sac. (A, B and C) Model ex-periments. (A) Canaliculi open. (1) Free flow. (2) Partial obstruction. (3) Complete obstruction. (B) Canaliculi open. (1) Free flow. Arrow points to the anacrotic notch at 100 mm Hg. (2) Partial obstruction. Note the change in pressure fall at 100 mm Hg. (3) Complete obstruction. (C) Canalic-

the cavity is important, however, in that it influences the flow of any substance within the cavity, and the flow, in turn, influences the pressure. On the other hand the model described constitutes a poor imitation of the lacrimal puncta and canaliculi, not only be-cause it required the designing of a sim-plified replica of a very minute channel sys-tem but also because it was not possible to produce a good model of the intricate valve apparatus in that system. For these reasons we feel that while the results of our model experiments are clinically applicable the findings of the studies on the nasolacrimal duct are more valid than are those on the puncta and canaliculi. With these reserva-tions it is considered that the data obtained in this investigation are applicable in clinical practice.

The results of our studies on the model suggest that a pressure level of 100 mm H g is the borderline below which outflow from the tear sac occurs only toward the nasolac-rimal sac and that pressures over 100 mm H g will open up the canaliculi and result in retrograde flow. This hypothesis is based on the following observations :

a. There is an "anacrotic notch" in the pressure curve at the level of 100 mm Hg, and there is free flow at the lower end of the system if the pressure is over 150 mm Hg. This notch is similar to the anacrotic notch in arterial pressure curves indicative of aortic-valve closure. The notch observed in the pressure curves obtained with our

uli blocked. (1) F>ee flow. Note the absence of the anacrotic notch. (2) Partial obstruction; grad-ual fall of pressure. (3) Complete obstruction. ( D ) Case 2. (1) Left eye, normal curve. (2 and 3) Right eye. Note in (3) change of pressure-fall velocity at 100 mm Hg level (similar to B2), partial obstruction of the right nasolacrimal duct. Diagnosis: partial obstruction of the right nasolac-rimal duct. ( E ) disc 1.(1 and 2) Right eye. (3 and 4) Left eye : Y points to the normal anacrotic notch (similar to B-1) ; X points to the absence of the anacrotic notch (similar to C-1). Diagnosis: right canalicular obstruction.

PATENCY OF NASOLACRIMAL APPARATUS 479

TABLE 1

T Y P E S OF LACRIMAL FLOW CURVES

Canaliculi

Open

Blocked

Nasolacrimal Duct

Open

Partial obstruction

Complete obstruction

Open

Partial obstruction

Complete obstruction

Pressure (mm Hg)

100

200

100

200

100

200

100

200

100

200

100

200

Curve

Sudden decline

Sudden decline with anacrotic notch at 100 mm Hg

Sluggish decline

Sudden fall to 100, then sluggish decline

Maintains high level, drops slowly

Fast drop to 100, then maintains level—slow drop

Sudden decline

Sudden decline without anacrotic notch

Sluggish decline

Sluggish decline from top of curve

Maintains high level without drop

Same

tear-duct model disappeared when the cana-liculi were blocked.

b. When partial obstruction was present pressures over 100 mm Hg were not associ-ated with a sluggish descent in the pressure curve because at pressures above this limit the canaliculi opened and retrograde flow occurred in the duct system.

On the basis of these experiments it is concluded that no pressures in excess of 100 mm Hg should be employed in studies of the patency of the nasolacrimal duct. In in-vestigations of the patency of the canaliculi, the upper and lower canaliculi must be probed separately. Pressure over 100 mm Hg should be applied and the range of 100-200 mm Hg or over will then reflect the patency of puncta and canaliculi. If a pres-sure of 100 mm Hg is applied, the fluid flows away through the lacrimal canal, but if a pressure over 100 mm Hg is applied, the fluid flows away through both the lacrimal canal and the canaliculi. As a result there is a different pressure curve from 200-100 to that from 100 to zero. Because these two parts of the curve can be identified it is pos-

sible to decide whether the obstruction is in the canaliculus, or in the canal.

CLINICAL STUDIES

Two types of operations are used in the treatment of excessive tearing : ( 1 ) by-pass-ing the obstructed nasolacrimal duct by creating a direct communication between the lacrimal sac and nasal cavity; and (2) wid-ening of narrowed puncta or canaliculi.

In the past no satisfactory procedure was available whereby the site of obstruction to the flow of tears could be localized with pre-cision. Many ophthalmologists were of the opinion that, if the tear ducts are sufficiently patent to transmit fluid injected into them, there is no indication for dacrocystorhinos-tomy. On account of this difficulty in local-izing obstructions in the lacrimal duct sys-tem the treatment of epiphora is still a con-troversial subject. The following examples are cited to illustrate the value of our tech-nique of flow curve recording in cases in which the usual methods of clinical testing were inadequate.

480 W. P. CALLAHAN, P. G. F O R B A T H AND W. D. S. BESSER

C A S E R E P O R T S

CASE 1

A 12-year-old boy (fig. 4-E) had repeated at-tacks of conjunctivitis for the past three to four years. For 16 months before admission lie noticed that tears ran from the right eye over his face. For the past six months this had become particu-larly bothersome during the winter.

On physical examination he showed some swell-ing of the eyelids particularly on the right side. There was also suggestive narrowing of the punc-ta, on the right side. The right lower canahculus was distended with a probe and a canimla was then introduced into the right tear sac. It was felt that the nasolacrimal duct could easily be washed through. His symptoms did not improve however and the patient was subsequently investigated by the flow method.

Investigation of the left eye showed a normal rise followed by a sudden fall of pressure. An ana-erotic notch was present in the flow curve when a pressure of 200 mm Hg was applied (fig 4-E3 and

The right lower canahculus was difficult to probe. When the needle finally entered the lacrimal sac and a pressure of 100 mm H g was applied a fall in pressure of normal velocity was observed. When a pressure of 200 mm Hg was applied it was noted that no saline appeared at the upper punctum and there was no anacrotic notch in the flow curve (fig. 4-E1 and E2) . An attempt was made to probe the upper canahculus but this was impossible. A di-agnosis of occlusion and stenosis of the puncta and canaliculi of the right eye was made.

A three-snip incision of the right lower punctum (unroofing of the canahculus) was carried out, following which the patient reported marked im-provement of his symptoms.

CASE 2

A 48-year-old woman (fig. 4-D) gave a history of repeated conjunctivitis and upper respiratory in-fections (sinusitis) for the past five years. In the previous two years she had noted that tears ran from the right eye over her face. Examination re-vealed normal puncta and no visible ophthalmologic pathology. Both tear ducts could be injected through manually. Her symptoms eventually wor-sened and a flow study was carried out.

The flow curves were normal for the left eye (fig. 4-D1). When a pressure of 100 mm Hg was applied to the right eye the velocity of the pressure curve was sluggish (fig. 4-D2). When a pressure of 200 mm Hg was applied, saline appeared at the upper punctum and the flow curve showed a fall of pressure to a level of 100 mm Hg, following which it again showed a sluggish decline (fig. 4-D3). The diagnosis was incomplete obstruction of the right nasolacrimal duct with normal canaliculi.

Fifteen cases of epiphora have been studied. The test showed that 13 had partial

nasolacrimal obstruction and two cases had canalicular obstruction. Ten of the 13 cases of partial nasolacrimal obstruction were clinically improved by dacryocystorhi-nostomy.

DISCUSSION

Although the number of cases investigat-ed to date is small, it is our opinion that the measurement of pressure-fall velocity by means of an electromanometer is of value in localizing the anatomic site of obstruction in the nasolacrimal apparatus. It might be possible to replace the electromanometer by a manometer employing a fluid system (for example, a water manometer) but the sen-sitivity of the measuring apparatus would limit the information obtained. We do not consider, for instance, that a water manom-eter could record the anacrotic notch in the flow curve and it therefore could not provide accurate information as to the state of canlicular patency.

The cost of an electromanometer and re-cording apparatus is quite high but many hospitals now have such devices in their car-diovascular or pulmonary function laborato-ries. This apparatus can be used for nasolac-rimal flow pressure studies without any modification.

It would be premature to advocate that pressure fall velocity recording should now be adopted by all departments of ophthalmo-lgy. Nevertheless, this procedure was found to be feasible and capable of provid-ing information of value in cases in which the diagnosis could not be established by other techniques.

I t is emphasized again that manual wash-ing-through of the nasolacrimal duct is not an adequate test of its patency. If only par-tial obstruction is present the results of this procedure may be normal. It is in cases of this nature in particular that the technique of flow recording is most valuable.

S U M M A R Y

By means of a plastic (Perspex) model

of the nasolacrimal apparatus it was possi-

PATENCY OF NASOLACRIMAL APPARATUS 481

ble to reproduce facsimiles of complete ob-struction of the puncta and canaliculi, and of complete and incomplete obstruction of the nasolacrimal duct.

An experimental method was designed to obtain flow curves in the model by means of electromanometric recording. The model ex-periment indicated that the velocity of the fall of the pressure in the lacrimal sac was of value in establishing the site and type of obstruction in the nasolacrimal duct system. Characteristic flow curves were obtained for the types and sites of obstruction produced.

The curves obtained in the model experi-ments were compared with those of patients with epiphora. By this means it was possible

In previous studies, it has been shown that, when segments of the cornea are separated, either by one or two impermeable discs, the cornea remains in a physiologically normal state.1 These findings were of particular sig-nificance in view of the recent concept that either the endothelial or epithelial barrier plays a major role in controlling the hydra-tion of this tissue. Recently, the view has been put forward that, as a result of active move-ment of water across the endothelium, this membrane serves as the principal regulator of corneal hydration.2 Evidence that the epithe-lium is also involved has also been advanced

* From the Ophthalmological Research Unit, the Wilmer Institute, The John Hopkins University School of Medicine. This investigation was sup-ported by Fight for Sight grant-in-aid G-2S4 of the National Council to Combat Blindness, and by Public Health Service research grant NB-048S4 from the National Institute of Neurological Dis-eases and Blindness.

to localize the site of nasolacrimal obstruc-tion and to plan a proper bypass operation which was followed by disappearance of the excessive tearing.

It is considered that this method of re-cording the velocity of pressure fall consti-tutes a valuable procedure in cases in which other diagnostic methods have failed to lo-calize the anatomic site of lacrimal obstruc-tion.

30 Bond Street (2).

ACKNOWLEDGMENTS

We wish to acknowledge the valuable assistance of Mr. Arthur Smialowski of the Department of Medical Photography, St. Michael's Hospital. Case 1 was of a patient of Dr. Michael Shea, Toronto, Canada.

by Langham.3 Thus, the finding that the cor-nea can remain deturgesced in the presence of interlamellar discs suggests that fluid must move over relatively long distances if it is to be removed by either one or the other limiting membranes. In order to observe this in greater detail, a study has been made of the rate of deturgescence, following temperature rever-sal, on either side of the disc after stromal swelling induced by cold. This investigation has been further broadened to observe the effects on corneal swelling when the aqueous humor is replaced by air.

METHODS

Male albino rabbits weighing five to seven pounds were anesthetized with parenteral sodium pentothal. In the manner previously described1 an 8- or 10-mm polypropylene disc was inserted into a surgically made stromal cleft, thus dividing the cornea into

WATER MOVEMENT IN RABBIT CORNEAS CONTAINING A PLASTIC INTERLAMELLAR DISC*

REFRIGERATION OF EYES WITH AIR IN THE ANTERIOR CHAMBER

PRIOR TO K E R A T O P L A S T Y

IRVIN P. POLLACK, M.D.

Baltimore, Maryland