Container with safety features for cleansing medical devices

A system for measuring the electrical conductivity of disinfecting and rinsing solutions within a cleansing container includes a power supply for driving a pair of detectors and/or a meter, a conductivity probe for measuring the electrical conductance of the solutions, an oscillator, amplifier, and rectifier circuit, and indicators such as colored lights for indicating the type of solution within the container. The entire measuring system may be miniaturized and provided within the lid of the container. The system is particularly adapted to ensure that the correct steps are taken during the disinfection of contact lenses.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention generally concerns a container into which articles employed 
in medical applications are placed for sterilization and further concerns 
a container designed to ensure that proper steps are taken during a 
disinfecting regimen. More particularly, this invention deals with the use 
of the electrical conductivity of aqueous disinfecting solutions or any 
other electrolytic solutions used for removing residuals that may be 
harmful to living tissues from surfaces of the articles. 
2. Description of the Prior Art 
There are many disinfecting agents available for use in aqueous solutions. 
Some of the well-known germicidal agents are hydrogen peroxide, 
thimerosal, chlorohexidine, glutaraldehyde, alcohols, and inorganic salts. 
The concentrations of these agents range from about 0.001% to 30% or more. 
Some of these solutions may contain ionic salts to maintain a certain 
tonicity in order to be compatible with the physiological fluids. 
Normally a second solution is used in combination with the disinfecting 
solution during a disinfecting regimen. The second solution may include 
distilled water, saline or other solutions containing agents specific for 
interaction with a particular disinfectant. The purpose of the second 
solution usually is to remove, neutralize or decompose excess germicidal 
agents remaining on the articles after the disinfection step. This can be 
accomplished simply by physical removal, or by reacting the disinfecting 
agent chemically or physically such that the final products are rendered 
harmless to living tissues. The second solution is usually called a 
neutralizing agent. The concentrations of this solution usually depend on 
the concentrations of the disinfectant used. 
Germicidal agents are used to sterilize such articles and devices as 
surgical tools, contact lenses, dental appliances, catheters, syringes, 
and packaging materials. Any residual amount of the germicidal agent 
remaining after treatment may require removal depending on the affects of 
the agent upon living tissue. For example, in cases where the application 
of the article or device containing residual amounts of germicidal 
solution may cause cellular damage or, at the very least, a significant 
amount of irritation to the patient or user, the germidical agent must be 
removed. 
A specific case in point is the disinfection of soft contact lenses with 
hydrogen peroxide. This method of disinfection is a common practice for 
contact lens wearers. Hydrophilic soft contact lenses may contain up to 
80% water and therefore absorb or even concentrate hydrogen peroxide 
within the lens matrix. After the disinfecting step, residual hydrogen 
peroxide must be removed before insertion of the lenses into the eyes as 
hydrogen peroxide will adversely react with the eye tissue and this is 
usually accomplished by treating the lenses with a neutralizing solution. 
A problem associated with the such systems is that it is very easy for a 
patient to forget which solution is in the cup. Moreover, the patient may 
accidentally use the wrong sequence of solutions in the disinfection 
regimen. For example a neutralizing solution may be mistakenly used 
initially and followed by a hydrogen peroxide solution. 
Thus, there exists the need for a cleaning system for contact lenses which 
alerts the user to the presence of harmful cleaning agents and which 
informs the user when a proper cleaning sequence has been completed. 
SUMMARY OF THE INVENTION 
Accordingly, this invention has been made to overcome the problems 
described above, and therefore has an object to provide a container which 
will prevent the above-noted errors and will ensure that the patient has 
taken the correct steps in disinfecting contact lenses and has properly 
neutralized any residual hydrogen peroxide before inserting the lenses 
within the eyes. 
Another object of the invention is to provide a sterilizing container 
adaptable for use with thermal disinfection systems. 
Yet another object is to inform a patient or user if the proper solution 
such as a saline solution and/or the correct volume of such solution was 
used during disinfection. One such example would be in a situation where 
the patient normally uses salt tablets dissolved in distilled water to 
thermally disinfect lenses. If the patient forgets to add the salt tablets 
or adds too many tablets the system will provide a warning signal 
immediately after submerging the lenses in the solution to warn of an 
improper solution concentration. 
Still another object is to warn a patient or user when insufficient 
solution has been added to the container and/or to warn when the solution 
level in the container has decreased due to leakage of the container. 
A further object is to provide a visual signal indicating when the proper 
time period for both disinfection and neutralization has elapsed. 
The foregoing and other objects are achieved according to the present 
invention through the use of the electrical conductivity properties of the 
above-noted disinfecting and neutralizing solutions. A system for 
measuring electrical conductivity in the disinfecting container or case 
may include a power supply for driving detectors and/or a meter; a 
conductivity probe for measuring the electrical conductance of the 
solutions; as oscillator, amplifier, and rectifier circuit as a current 
source; a detector and/or meter circuit as an indicator of conductance; a 
case for holding the solution; and a cover for the case. 
The energy source for this system can be either a battery or power from AC 
household current. The electrodes of the conductivity probe can be 
constructed out of any electrically conductive material that is compatible 
with the solution in question. For example, if hydrogen peroxide is used 
as a disinfectant, the probe material may be of aluminum, tin or other 
metals that do not catalyze the decomposition of peroxide. The indicator 
can be either a meter with a scale and needle, a digital meter or a 
plurality of lights of different colors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The apparatus developed in accordance with the present invention will now 
be described in conjuction with the drawings wherein a device is provided 
for measuring and indicating a difference in the electrical conductivity 
of disinfecting solutions and neutralizing solutions to ensure that a 
prescribed disinfecting regimen has been properly conducted. Where 
hydrogen peroxide is used as a disinfectant and is subsequently 
neutralized with a neutralizing solution, the difference in electrical 
conductivity between the two solutions is indicated by either a meter or 
by a pair of different colored lights to indicate and identify the 
presence or absence of each solution. The ionic strength of the hydrogen 
peroxide is typically much lower than that of the neutralizing solution. 
This difference can be used advantageously to monitor the disinfecting 
process. 
More particularly, the ionic strength of the neutralizing solution is such 
that it is compatible or isotonic with human serum and tear fluid. That is 
to say, the salt concentrations of these neutralizing solutions are such 
that they are nearly equal to those present in serum or tear fluid. The 
normal ionic strength of the serum or tear fluid exhibits a tonicity of 
285-310 milliosmoles/kg, which is equivalent to about 9 milligrams of 
sodium chloride per milliliter of fluid. The present invention takes 
advantage of the salt contents of these neutralizing solutions and, if 
necessary, gives a warning to the user of any impending danger due to 
misuse of the solutions. 
A specific example according to the invention uses a container or case for 
disinfecting hydrophilic soft contact lenses with hydrogen peroxide. A 
subsequent neutralization of the hydrogen peroxide with sodium pyruvate is 
carried out. The entire process is monitored and evaluated as set forth 
below. 
The germicidal agent, hydrogen peroxide, is normally in solution at a 
concentration of 30 mg/ml and may contain trace amounts of stabilizers, 
i.e., phenacetin, sodium stannate, sodium pyrophosphate, and sodium 
nitrite. The conductance of such solution is 250 .mu.mhos/cm. The 
dissociation constant of hydrogen peroxide, 1.78.times.10.sup.-12 
@20.degree. C., is slightly greater than that of water. The only other 
sources of ions in commercial hydrogen peroxide are the stabilizers which 
are added in trace amounts. 
The neutralizing solution has the following composition: 
______________________________________ 
mg/ml 
______________________________________ 
Poloxamer 407 10.0 
Sodium Chloride 2.0 
Potassium Chloride 
1.0 
Sorbic Acid 2.0 
Sodium Borate 2.2 
Edetate Sodium 1.0 
Boric Acid 10.0 
Sodium Pyruvate 5.0 
Purified Water Q.S. 
______________________________________ 
The conductance of this neutralizing solution is 5,500 .mu.mhos/cm. 
An example of the case used for containing the above solutions is 
illustrated in FIG. 1. The electronic components to be described below 
will preferably be housed in the lid 1, for example, within housing 2. The 
solutions will be contained in the case 3. 
After completing the proper initial cleansing steps, the articles to be 
disinfected such as lenses 5 are placed in a basket 7 attached to the lid 
1 of case 3. The case 3 is then filled with hydrogen peroxide, usually 10 
cc. When the case 3 is closed with the lid 1, a switch mechanism 9 
activates a timer 21 shown in FIG. 2. The action of turning or rotating 
the lid 1 to secure it onto the case 3 causes the switch 9 to ride against 
the wide lip 11 of the case 3, thereby depressing switch 9 via a sliding 
camming action. Timing mechanism 21 is preferably housed within lid 1. Of 
course a simple snap fit or bayonet coupling rather than the threaded 
engagement between the lid 1 and the case 3 may be used, as well as any 
other well-known connection. 
Normally, disinfection takes 10 minutes. During this period a signal such 
as a steady light 13 may be displayed whenever button 15 is depressed to 
indicate the presence of peroxide. Light 13 rather than light 17 will 
illuminate because the lower electrical conductivity of the hydrogen 
peroxide solution than that of the neutralizing solution will be detected 
and used to select the illumination of one of the pair of indicators 
lights, 13 and 17. The electronic logic to be discussed below will 
identify a solution by its conductivity and cause the appropriate light 
13, 17 to illuminate or to provide power to a switch 15 which operates 
such light. The purpose of button switch 15 is to conserve energy, 
especially when disposable batteries are used for an energy source. Of 
course, button switch 15 is optional such that a constant power supply may 
be fed to lights 13 and 17. 
After the 10 minute disinfection period, or any other predetermined 
disinfection period programmed or preset into timer 21, light 13 will 
begin to blink when the button switch 15 is depressed to indicate that the 
proper time has elapsed for adequate disinfection. This provides an 
indication to the user that the next cleaning step should begin, namely 
the neutralizing step. Timer 21 includes a standard circuit for generating 
an intermittent signal whenever a predetermined period of disinfection or 
neutralization has been completed such as the 10 minute period noted 
above. This signal will cause light 13 or 17 to blink on and off. 
After the disinfection period is completed the lid 1 is unscrewed or 
removed from the case 3 so that switch 9 opens thereby causing the timer 
21 to be reset to zero in a conventional known manner. After discarding 
the hydrogen peroxide solution, the case 3, lid 1 and basket 7 are rinsed 
with neutralizing solution. After discarding this rinse solution, the case 
3 is refilled with neutralizing solution for the neutralizing step and the 
lid 1 is replaced. 
Securing the lid 1 to the case 3 causes the timer 21 to be activated again. 
This time however, because of the higher conductance of the neutralizing 
solution, light 17 will be lit when switch button 15 is depressed rather 
than light 13. Thus, light 17 indicates the presence of neutralizing 
solution. After a lapse of, for example, 10 minutes, depressing the button 
15 will cause light 17 to be displayed as a blinking light indicating an 
adequate period has elapsed. The lenses 5 are now ready to be worn by the 
user. 
The circuitry required to carry out the invention is schematically depicted 
in FIG. 2 wherein a power source is shown as battery 19 which is connected 
to timer 21 via switch 9. The plunger 10 of switch 9 is actuated as 
indicated above by contact with the lip 11 of case 3 to start the timer 
21. Removal of lid 1 will automatically reset the timer 21 to zero. The 
timer 21 may be designed to provide a steady output from battery 19 during 
an initial disinfection period, such as the 10 minute period described 
above. After this initial period the timer may be preset to provide an 
intermittent output so that either light 13 or 17 will be intermittently 
actuated to provide a blinking effect depending upon the conductivity of 
the solution within case 3. As noted above, switch 15 is optional and may 
be omitted such that a steady power output from battery 19 is available at 
all times to lights 13 and 17 and such that a logic circuit discussed 
below will determine which light will be lit. 
An oscillator 23 receives power directly from battery 19 which provides a 
steady voltage of, for example, 30 5 volts to oscillator 23 as shown. 
Oscillator 23 is designed to convert the DC power from battery 19 to AC 
power having a frequency of, for example, 5 kHz. The alternating current 
from oscillator 23 is supplied to conductivity probe 25 having spaced 
electrodes which become immersed in a solution within case 3 upon closing 
of lid 1. Alternating current is preferred to operate probe 25 to prevent 
polarization of the electrodes and electrolysis of the solution. 
Probe 25 provides a signal proportional to the conductivity of the solution 
within which it is immersed. This signal is amplified by amplifier 27 and 
fed to rectifier 29 to convert the AC signal to a DC signal suitable for 
input into meter 31 and/or conductivity detectors 33 and 35. The detectors 
may take the form of any conventional device for detecting the electrical 
signal level from amplifier 27 such as a comparator or Schmitt trigger 
device. Thus, meter 31 will offer a quantitative or qualitative reading 
over a continuous scale via a needle pointer or digital scale 
representative of the conductivity of the solution in case 3, while 
detectors 33 and 35 will provide inputs to logic circuit 37 which will 
determine whether light 13 or 17 will be illuminated. The detectors may be 
adjustable to accommodate their sensitivities to different solutions 
having different conductivities. 
Instead of relying on timer 21 to trigger a blinking signal indicating that 
sufficient time had elapsed for a particular step, it may be possible to 
establish a threshold conductivity so that, for example, signal light 13 
will remain illuminated until the disinfectant has dissipated to a preset 
concentration level if the conductivity of the neutralizing solution 
changes significantly during the neutralizing step. At this time the 
threshold conductivity will be exceeded and signal light 13 will be 
extinguished by logic circuit 37 while at the same time signal light 17 
will be illuminated to indicate that the disinfectant has been adequately 
neutralized. Light 13 may be designed as a red light to indicate a warning 
signal, while light 17 may be designed as a green light to indicate a 
safety signal. Thus, probe 25 will send a constant signal to detectors 33 
and 35 which will in turn provide logic circuit 37 with a further output 
signal corresponding to the electrical conductance of the solution. The 
signals from detectors 33 and 35 will change value at the predetermined 
threshold value so that one light will extinguish while the other 
illuminates. 
In a preferred embodiment the sensitivity of the probe 25 is adjusted or 
set in accordance with the conductivity of the hydrogen peroxide 
disinfecting solution so that the conductivity of such solution is 
sufficient to generate an adequate output from probe 25 and to maintain 
light 13 in an illuminated state during the disinfection step. If too weak 
or too strong a solution is used, the detectors 33, 35 may be arranged to 
prevent illumination of one or both lights. 
The sensitivity of probe 25 may be adjusted so that the conductivity of the 
disinfecting solution is sufficient to generate an adequate signal to 
cause light 13 to illuminate during the disinfecting step and further 
adjusted so that the conductivity of the neutralizing solution is 
sufficient to cause light 17 to illuminate during the neutralizing step. 
If the wrong type of solution is used, a warning signal may be provided by 
meter 31 indicating the presence of a conductivity outside the range of 
that representative of the correct solution. For example, the scale of 
meter 31 may be marked to indicate an acceptable range of conductivity 
within the middle of the scale. Readings on the extreme high end and low 
end of the scale would then be labeled as unacceptable, thereby warning 
the user of a potential problem such as the presence of solutions having 
inadequate or excessive strengths. 
Instead of relying on meter 31 to provide a warning signal, detectors 33 
and 35 may be set to provide a warning signal by illuminating lights 13 
and/or 17 upon detecting a conductivity outside an acceptable range. For 
example, should a disinfecting solution require salt tablets, the 
detectors can be arranged to generate a warning signal via lights 13 
and/or 17 if too few or too many tablets are added, as the resulting 
conductivity will lie outside an acceptable predetermined range programmed 
into detectors 33 and 35. Of course, a third detector and a third light 
could be provided to signal the presence of an excessive solution 
concentration. 
It is also possible to provide a warning signal to the user in the case 
where an insufficient quantity of solution is present in case 3. This is 
accomplished by disposing probe 25 within lid 1 so that its electrodes 
will extend into the solution to a point below which an insufficient 
quantity solution is considered to be present. Thus, when the level of 
solution falls below probe electrode 37 or 39, a negligible conductivity 
will be present such that an alarm signal will be generated in the same 
manner as in the case where insufficient tablets have been dissolved in 
the solution. 
An alternative design fixes the probe electrodes against or partially 
within the inner wall of the case 3 for connection with the probe and 
associated electronics upon closure of lid 1. These electrodes would be 
positioned at a preset level above the bottom of the case 3 to provide a 
signal indicating the presence of insufficient solution within case 3. 
It is of course possible to incorporate the conductivity sensing elements 
of the invention in the bottom of the case 3 without detracting from the 
objective of this invention. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.