Punctal cannula

Details Punctal cannula Punctal cannula

2000-05-08

2002-08-06

Huson, Gregory L. (Department: 3751)

Surgery

Means for introducing or removing material from body for...

Material introduced into and removed from body through...

C604S264000, C604S278000, C604S290000, C604S294000, C604S513000, C604S514000

Reexamination Certificate

active

06428502

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally pertains to cannulas. More particularly, but not by way of limitation, the present invention pertains to cannulas for the removal of punctal plugs that are often used to treat dry eye syndrome, and to cannulas for the removal of obstructions from the lacrimal canaliculi.
DESCRIPTION OF THE RELATED ART
FIG. 1
illustrates the lacrimal duct system of a mammalian eye
10
. The system includes a lower punctum
12
connected to a lower lacrimal canaliculus
14
, and an upper punctum
16
connected to an upper lacrimal canaliculus
18
. Canaliculi
14
and
18
are connected to a lacrimal sac
20
and a nasolacrimal duct
22
. A lacrimal gland
24
is connected to eye
10
via a lacrimal duct
26
. In general, tears are produced by lacrimal gland
24
and are provided to eye
10
via lacrimal duct
26
, and tears are drained from eye
10
via punctum
12
and canaliculus
14
, punctum
16
and canaliculus
18
, and nasolacrimal duct
22
.
By way of background, tears produced by lacrimal gland
24
are actually a complex composition in the form of a tear film. This tear film includes three basic layers: an outer lipid layer, an inner mucin layer, and an aqueous layer between the lipid and mucin layers. Each of the layers has a particular function. The lipid layer prevents evaporation of the tears from the surface of eye
10
. The aqueous layer provides oxygen to the cornea and contains additional chemical components that are important to a healthy eye
10
. The mucin layer provides for interaction between the lipid layer and the aqueous layer and prevents tears from “beading up” on the cornea.
Approximately 7.5 million cases of moderate or severe dry eye syndrome occur in the United States each year. An additional five million people are unable to wear contact lenses because of insufficient amounts of tear fluid. A “dry eye” is one that experiences insufficient lubrication of the cornea as a result a disturbance in the normal tear film. The condition encompasses a wide variety of disease states ranging from mild, intermittent burning and/or scratchiness with foreign body sensation, to a severe lack of aqueous layer secretion accompanied by corneal and conjunctival disease (keratoconjunctivitis sicca (KCS)). Dry eye can have a variety of specific causes and contributing factors, including arid environments, environmental airborne pollutants, certain systemic medications, auto-immune disorders, drug toxicity, hormone deficiency or changes, and even contact lens wear. However, the majority of cases of dry eye syndrome are related to two basic causes. First, lacrimal duct
26
from lacrimal gland
24
may become clogged or may malfunction so that an insufficient amount of tears reach eye
10
. In response to this cause, artificial tear products such as TEARS NATURALE® and BION® TEARS, sold by Alcon® Laboratories, Inc. of Fort Worth, Tex., were developed. Second, although lacrimal gland
24
and lacrimal duct
26
may deliver a sufficient amount of tears to eye
10
, tears may be drained away from eye
10
too quickly, creating a dry eye situation. In response to this cause, various methods and apparatus for sealing puncta
12
and
16
have been developed.
Initially, puncta
12
and
16
were sealed by stitching or by electrical or laser cauterization. Although such procedures can provide acceptable results, they are not reversible without reconstructive surgery. As it is sometimes difficult to determine whether dry eye is caused by too great of drainage or too little tear production, such procedures may expose the patient to unnecessary trauma. In addition, such procedures may result in epiphera, a condition where tears continually form on eye
10
, build up, and run down the face of the patient.
Pre-formed collagen plugs for insertion into puncta
12
and
16
or the canaliculi
14
and
18
were developed to provide a reversible sealing procedure. Collagen plugs are water-soluble and, when inserted into the puncta, typically dissolve within seven to fourteen days. Collagen plugs are thus effective as a test procedure to determine if it is desirable to more permanently seal the puncta.
Pre-formed water-insoluble plugs for insertion into puncta
12
and
16
or canaliculi
14
and
18
are described in a variety of United States Patents. For example, U.S. Pat. No. 3,949,750 to Freeman describes such a plug having a head portion that extends outside of the punctum and a barb portion that extends into the punctum and/or canaliculus. Such plugs can be seen in the corner of eye
10
, are sometimes uncomfortable, and are easily dislodged. In addition, such plugs are somewhat difficult to insert, and occasionally their size and shape causes tissue damage during insertion. If such plugs protrude too far from the puncta, they can cause irritation to the sclera. Furthermore, the tissue of the punctum can be damaged due to prolonged dilation caused by such plugs. U.S. Pat. No. 5,283,063 to Freeman describes a similar plug made from a hydrogel material having a hydrating port located in its barb portion that allows canalicular fluid to enter the barb and hydrate the plug to an expanded, relatively flexible state. U.S. Pat. Nos. 5,723,005 and 5,171,270 to Herrick describe water-insoluble punctal plugs that have collapsible flared sections for improved sealing and anchoring within the canaliculus. Some of these plugs also have a retaining portion that extends outside the punctum to further anchor the plug and prevent migration down the canaliculus. U.S. Pat. Nos. 3,949,750; 5,283,063; 5,723,005; and 5,171,270 are each incorporated herein by reference.
In addition, U.S. Pat. No. 5,469,867 to Schmitt describes a method of occluding the lacrimal canaliculi and other mammalian channels or ducts by injecting a heated, flowable polymer or polymer composite of a specified composition through puncta
12
and
16
into canaliculi
14
and
18
, respectively. The specified polymer and polymer composite are non-immunogenic, biocompatible materials that are solid and/or non-flowable at body temperature or lower and flowable when heated slightly above body temperature. The polymer and polymer composite are capable of quickly changing from a flowable state to a non-flowable state by moving through only a few centigrade degrees of temperature. After injection, the polymer or polymer composite cools and solidifies to form a plug that conforms exactly to the geometry of the canaliculi. U.S. Pat. No. 5,469,867 is incorporated herein by reference, and the plugs for occluding the canaliculus or other mammalian channels disclosed therein will be referred to in this document as “cast-in place thermoplastic plugs”.
As mentioned above, it is highly desirable that a punctal plug be removable without the necessity of surgery. Various conventional techniques have been utilized to remove the above-described water insoluble plugs. For example, such plugs that have a portion extending outside the punctum are typically removed using forceps or a similar instrument.
As another example, certain cannulas have been used to “flush” water-insoluble plugs not having a portion extending outside the punctum down nasolacrimal duct
22
. More specifically, it is known to use a cannula having an outer diameter equal to or slightly greater than the diameter of punctum
12
to seal the punctum and then inject saline into the punctum. The seal is created by dilating the punctum with the cannula and the sphincter action of the punctal muscle tightening around the cannula. Saline is then injected into canaliculus
14
so as to create enough water pressure to flush the plug down nasolacrimal duct
22
. An example of a conventional cannula that has been utilized to perform this technique is the E4404 lacrimal cannula sold by STORZ Ophthalmics of St. Louis, Mo., which has a 23 gauge outer diameter, 10 mm long tip.
It is also known to use a cannula having a smaller outer diameter distal tip (e.g. 26-27 gauge) that tapers into a larger outer diameter proximal portion (e.g. 23 gauge or greater) to

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