GB2108391A

GB2108391A - Speculum for medical instruments

Info

Publication number: GB2108391A
Application number: GB08132808A
Authority: GB
Inventors: Barden A Conroe
Original assignee: Welch Allyn Inc
Current assignee: Welch Allyn Inc
Priority date: 1981-10-29
Filing date: 1981-10-30
Publication date: 1983-05-18
Also published as: JPS5889229A; DE3143610A1; AU7695881A

Abstract

A light conducting plastics speculum for a medical instrument such as a sigmoidoscope, seen in section at 11 has two coatings 19 and 21 on its interior surface. The coating 19 and a similar coating 20 on the outer surface have a lower index of refraction than the material of the speculum 11 so as to produce internal reflections and reduce light loss and the coating 21 is of an anti-glare material for reducing external reflections to a minimum. <IMAGE>

Description

SPECIFICATION Speculum for medical instruments This invention relates generally to medical diagnostic instruments of the class employed for the examination of body cavities, and is particularly concerned with light conducting specula for use with such instruments.

US patent no: 3,417,746 discloses an endoscope having a disposable light conducting speculum of a type to which the present invention relates. This speculum is made of a clear transparent plastics material having good light transmitting properties.

The annular proximal end of the speculum receives light from a permanent or non-disposable light source head, and this light is transmitted by the speculum wall to its distal end where the light is emitted and illuminates the area being examined.

The exterior surface of the speculum is normally coated with a plastics material having a refractive index that is lower than that of the speculum material to reduce light loss through the speculum wall.

The interior surface of the speculum described just above is glossy and this results in reflections from the area being viewed that may be objectionable to the physician and may also interfere with image contrast.

According to the present invention, the interior of such a speculum has a first coating of a material having an index of refraction that is lower than that of the speculum material and a second coating on top of the first, of a material having a flattener as a filler. The first coating is of the conventional material for reducing internal reflection and the second coating which over-lies the first functions as an anti-glare coating which effectively minimises light reflection. The second coating needs to be non-toxic and also to be resistant to sterilisation and germicidal solutions. If the speculum is made of a material which produces internal reflections, only the second coating is required.

An example of an instrument speculum in accordance with the invention, will now be described with reference to the accompanying drawings, in which:~ Figure 1 is a perspective view of a speculum for a disposable sigmoidoscope; Figure 2 is an enlarged transverse section through the speculum taken on line 2-2 of Figure 1; and Figure 3 is a fragmentary longitudinal section through the proximal end of the speculum.

A speculum for a body-cavity-entering instrument is shown generally at 10. As illustrated, the speculum 10 is a disposable, light transmitting speculum for a sigmoidoscope such as that disclosed in the US patent no: 3,417,746 mentioned previously. The invention is not limited to specula for sig moidoscopes as it can be advantageously utilised in the specula of various other instruments.

The speculum 10 includes a tubular, slightly tapered body member 11 of a clear transparent plastics material such as an acrylic. Also forming a part of the speculum are a liner member 12 and a shield 14 at the proximal end 16 and a tip member 15 at the distal end. The linear member, shield and tip member serve substantially the same functions as the corresponding members in the US patent referred to above. Light from a permanent light source head (not shown) enters the polished annular proximal end 16, Figure 3, of the body member 11 and is transmitted by the member to its distal, light emitting end 17, Figure 1.

The interior and exterior surfaces of the speculum body member 11 are completely coated with a material having a lower index of refraction than that of the body member, the interior and exterior coatings being shown in an exaggerated manner at 19 and 20 in Figure 2. These coatings cause the light entering the speculum body member 11 to be internally reflected whereby there is very little loss between the proximal and distal ends of the body.

Coatings of fluorocarbon materials and fluoro-silicones, for example, have proved satisfactory for this purpose.

In addition the interior surface of the speculum body member is provided with a second coating 21 that covers the first interior coating 19. The second coating 21 substantially eliminates light reflections back into the eyes of the examining physician. This anti-glare coating can be a flat paint, varnish or lacquer material having a filler that is a flattener or anti-gloss compound. A white coloured formulation marketed by General Paint and Chemical Co. of Chicago, Illinois, United States of America and known as P-l has been found to be a very good anti-glare coating.

With the interior and exteriorcoatings 19, 20 and 21 on the speculum body member 11, the light transmission is excellent so that the area being viewed is well illuminated and, at the same time, objectionable reflections from the illuminated area are reduced to an effective minimum, as is interference with image contrast. The coatings employed are, of course, non-toxic and also are resistant to sterilisation and germicidal solutions.

It should also be noted that polymers such as polystyrene that do not require a lower refractive index material for their light transmitting performance can have only a single anti-glare coating applied to them.

Claims

1. A light transmitting speculum of plastics material for a medical instrument, the interior of the speculum having a first coating of a material having an index of refraction that is lower than that of the speculum material and a second coating on top of the first, of a material having a flattener as a filler.

2. A speculum for a medical instrument and formed of light transmitting plastics material, the speculum having a first coating on its interior and exterior surfaces that has a lower index of refraction than that of the plastics material of the speculum, and a second coating in the interior of the speculum overlying the coating of lower index of refraction, the second coating being of a material that effectively minimises light reflection.

3. A speculum according to claim 1 or claim 2 wherein the first coating is a fluorocarbon.

4. A speculum according to any one of the preceding claims wherein the second coating is a flat paint, varnish or lacquer.

5. A speculum according to any one of the preceding claims wherein the second coating material is resistant to sterilisation and germicidal solutions.

6. A medical instrument speculum formed of a light transmitting plastics material, the optical characteristics of which are such as to produce internal reflections, the interior of the speculum having a single coating of a material that effectively minimises light reflection, the coating being resistant to sterilisation and germicidal solutions.

7. A speculum according to claim 6 wherein the coating includes a flattener as a filler.