JPS582694B2 - applanation tonometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION It is well known that intraocular pressure measurement is essential for early diagnosis of glaucoma.

The instrument that measures intraocular pressure is called a tonometer, and there are various types of tonometers, among which the applanation tonometer is the most commonly used type.

An applanation tonometer is an applanation tonometer that applanates the cornea of the subject's eye with the plane of a prism, and gradually increases the pressure until the diameter of the flattened part of the cornea reaches the standard size. It is designed to read the pressure being applied.

Conventional tonometers use two springs: a main spring for pressurization and a compensation spring for the main spring. Some compensate for pressure changes and provide a nearly linear relationship to the commanded movement depending on the adjustment of the main spring.

The object of the present invention is to improve this applanation tonometer, to enable sufficiently accurate intraocular pressure measurement with one spring, and to simplify the structure and facilitate manufacture.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

1 and 2, an adjustment mechanism mounting board 2 is fixed to the case 1, and a scale dial 3 having a scale readable from the outside of the case 1 is mounted to the adjustment mechanism mounting board 2. A connecting gear 4 is fixed to the axis of the scale dial 3.

This connecting gear 4 meshes with an adjustment dial 5 that can be operated from the outside of the case 1.

The adjustment dial 5 also meshes with a pinion 6' of a winding shaft 6 provided on the base plate 2, and the inner end of a pressure spiral spring 7 is fixed to this winding shaft 6.

The outer end of the spiral spring 7 is fixed to a locking member 8, and this locking member 8 is screwed into a threaded portion of a zero adjustment shaft 9 that is rotatably attached and operable from the outside of the case 1. The zero adjustment shaft moves forward and backward as the zero adjustment shaft rotates.
(see figure).

On the other hand, there is a shaft 10 on the extended axis of the winding shaft 6, and an applanation arm 11 is attached to this shaft 10 via a base member 15.

The applanation arm 11 has a prism holder 12 at its tip to which an applanation prism 13 can be attached, and a balance weight 14 at its rear end for maintaining balance around the shaft 10.

An arm 15' projecting from the base member 15 of the shaft 10 is fixed to a substantially middle spring portion of the spiral spring 7.

The case 1 is also provided with a lamp 16 for illuminating the applanation plane of the applanation prism 13 and a magnifying glass 17 for observing the applanation plane through the applanation prism 13.

In the above mechanism, the spring characteristics from the inner end of the spiral spring 7 to the arm 15' of the base member 15 are adjusted (changed in length), and the rotation angle of the adjustment dial 5 and the arm of the base member 15 are adjusted. The pressurizing torque of is kept in a proportional relationship.

This pressurizing torque acts as an applanation force via the applanation arm 11.

A tension of about 10% of the maximum torque applied to the spiral spring 7 is always applied between the arm and the outer end of the base member 15, contributing to the stability of the rest at the zero position.

That is, the posture error of the tonometer is absorbed.

This armor also contributes to compensation for changes in applanation pressure due to changes in the position of the applanation prism during intraocular pressure measurement.

In other words, if the position of the applanation prism 13 that applanates the cornea deviates from the reference position, an error will occur in the applanation pressure by that amount, but it works in the opposite direction to compensate for this error.

This is because the characteristics are the same since one spiral spring is used.

First, the examiner holds an applanation tonometer and applies an applanation prism to the subject's cornea.

When the adjustment dial 5 is turned in the direction of the arrow, the winding shaft 6 rotates, the spiral spring 7 is wound, and the acting force is transmitted through the arm of the base member 15 located approximately in the middle of the spiral spring 7. Applanation prism 13 applanates the cornea.

The flattening pressure at that time is displayed on a scale dial 3 rotating via a connecting gear 4.

The applanation pressure is further increased, and it is confirmed through the loupe 17 that the diameter of the flattened portion of the cornea has reached the standard size.

The display on the scale dial 3 at that time is the intraocular pressure of the subject.

Intraocular pressure can be measured using the above procedure, but it is necessary to perform zero adjustment before measurement.

This involves turning the zero adjustment shaft 9 from the outside of the case 1 to adjust balance errors (for example, changes in weight due to applanation prism replacement) at the zero scale position.

As is clear from the above description, according to the present invention, since one spiral spring is used, the adjustment mechanism and the applanation prism balancing member are separated, resulting in a simple structure and easy assembly.

Further, since the inner and outer ends of the spiral spring are stopped from rotating and one herk of pressure is used between them, there is little error in posture due to the weight of the spiral spring.

Further, since the applanation prism is kept stationary at the zero position with tension always applied between the inner end and the outer end, stability is good.

In addition, since the pressure torque is extracted from approximately the middle of the spiral spring, the inner and outer spring characteristics are constant, and when pressure is applied, the position of the applanation prism is within the movable range.
Even if there is a slight change, the applanation pressure on the cornea remains unchanged.

Furthermore, the zero point resting position of the applanation prism can be easily adjusted.

[Brief explanation of the drawing]

FIG. 1 is a plan view of one embodiment of the present invention, FIG. 2 is a side view,
FIG. 3 shows the lines AA in FIG. 1. 'This is a sectional view showing the zero adjustment mechanism. 1... Case, 2... Adjustment mechanism mounting board, 3...
Scale dial, 4... Connecting gear, 5... Adjustment dial, 6... Winding shaft, 7... Spiral spring, 8... Locking member, 9... Zero adjustment shaft, 10... - Shaft, 11... Applanation arm, 12... Prism holder, 13... Applanation prism l1, 14... Balance weight, 15... Base shaft member, 16... - Lamp, 17...・Loupe.

Claims (1)

[Claims] 1 In an applanation tonometer that applies applanation pressure to the cornea of the eye to be examined to produce a flat area of a reference size, one spiral spring is arranged, and the winding axis of the spiral spring is adjusted by an adjustment mechanism and a pressure display. of the spiral spring. 1. An applanation tonometer, characterized in that the outer end is connected to a zero point adjustment mechanism for regulating the static position of the flattening prism, and the applanation pressure is taken out from approximately the midpoint of the spiral spring.