Exp Eye Res. (1976) 22, 193-194
LETTERTOTHEEDITORS
An Inexpensive Blowgun Device for Anterior
Chamber Paracentesis
A new anterior chamber paracentesis device for lab use is described using the blow gun principle. It has the advantage of being very inexpensive and easy to build in any lab. That device is able to send a needle t,owards the cornea, exerting a pressure of 6.4 kg/cm3.
In 1960, Sears reported that the rise in intraocular pressure, miosis and iris vessel lea.kage induced during manual cannulation of the rabbit’s anterior chamber, could be avoided by the rapid introduction of the needle using a specifically constructed spring gun device. Since that time, others have attempted (Kinoshita et al., 1973; Kazdan et al., 1965; Lorenzetti and Sancilio, 1967) to develop cannula guns by modifying available spring devices. As most of them require a machinest and are expensive. we describe a paracentesis device using the blow gun principle. This device, as will be shown,.uses inexpensive materials, may be built by any lab technician, and is as effective as more complicated paracentesis instruments. Since paracentesis in the laboratory is done to perform either manometry, perfusion, or aqueous sampling, the needle must be attached to the appropriate tubing, and the system ready to perfuse before insertion of the needle int.0 the anterior chamber. In this case, a 25.gauge needle is attached to a three-way stopcock. Appropriate tubing is led from one of the stopcock terminals to a perfusate (Fig. 1). This stopcock is inserted onto the front end of a tuberculin syringe barrel. The rear flange of the barrel is cut away and the barrel packed with gauze. Thus the lleerlle-stopcock-syringe barrel combination becomes t,he missile. The gun is a piece of glass tubing, 12 mm in diameter, and 300 mm long. A piece of soft) tubing may be tiMed to the rear end of the glass tube, so that the experimenter may sit erect as he blows the gun. The syringe barrel is then placed in t,he front) end of the gun, so that the stopcock ant1 neetlle are suspended outside the gun. The needle tip is placed 5 cm from the cornea. with the needle parallel to the plane of the iris. Four lines were painted, 90” apart, in ortlel to :rinl the needle. The gun was then fired with R swift blow. The procedure takes some practice so we sta.rted eanulating cow eyes as shown in Fig. 1. Then we cannulated 10 rabbit eyes. d major problem is to aim the needle parallel to the iris in the rabbit eye which haa a shallow anterior chamber. The simple maneuver of grabbing the conjunctiva with a forceps and elevating the eye proved helpful in solving this problem. rsing this maneuver the iris was nicked in only one of the 10 eyes. The procedure brought up the question of how much force was being used to introduce the needle into the eye. In order to determine the maximal force developed by this system, the missile was aligned against the footplate of an ophthalmodynamometer. and fired 10 times. The means of 10 forceful 1~10~~:s of t,he device yielded a mean reading of 95 mmHg 1vit.h a st,andard deviation of 5 mmHg, which converts to a force of 128 g. Since the cross-sectional area of a 25-gauge needle is approximately 0.05 cm, the pressure applied to the cornea at the moment of impact becomes 6.4 kgicm3. 193
LETTERTOTHEEDITORS
An Inexpensive Blowgun Device for Anterior
Chamber Paracentesis
A new anterior chamber paracentesis device for lab use is described using the blow gun principle. It has the advantage of being very inexpensive and easy to build in any lab. That device is able to send a needle t,owards the cornea, exerting a pressure of 6.4 kg/cm3.
In 1960, Sears reported that the rise in intraocular pressure, miosis and iris vessel lea.kage induced during manual cannulation of the rabbit’s anterior chamber, could be avoided by the rapid introduction of the needle using a specifically constructed spring gun device. Since that time, others have attempted (Kinoshita et al., 1973; Kazdan et al., 1965; Lorenzetti and Sancilio, 1967) to develop cannula guns by modifying available spring devices. As most of them require a machinest and are expensive. we describe a paracentesis device using the blow gun principle. This device, as will be shown,.uses inexpensive materials, may be built by any lab technician, and is as effective as more complicated paracentesis instruments. Since paracentesis in the laboratory is done to perform either manometry, perfusion, or aqueous sampling, the needle must be attached to the appropriate tubing, and the system ready to perfuse before insertion of the needle int.0 the anterior chamber. In this case, a 25.gauge needle is attached to a three-way stopcock. Appropriate tubing is led from one of the stopcock terminals to a perfusate (Fig. 1). This stopcock is inserted onto the front end of a tuberculin syringe barrel. The rear flange of the barrel is cut away and the barrel packed with gauze. Thus the lleerlle-stopcock-syringe barrel combination becomes t,he missile. The gun is a piece of glass tubing, 12 mm in diameter, and 300 mm long. A piece of soft) tubing may be tiMed to the rear end of the glass tube, so that the experimenter may sit erect as he blows the gun. The syringe barrel is then placed in t,he front) end of the gun, so that the stopcock ant1 neetlle are suspended outside the gun. The needle tip is placed 5 cm from the cornea. with the needle parallel to the plane of the iris. Four lines were painted, 90” apart, in ortlel to :rinl the needle. The gun was then fired with R swift blow. The procedure takes some practice so we sta.rted eanulating cow eyes as shown in Fig. 1. Then we cannulated 10 rabbit eyes. d major problem is to aim the needle parallel to the iris in the rabbit eye which haa a shallow anterior chamber. The simple maneuver of grabbing the conjunctiva with a forceps and elevating the eye proved helpful in solving this problem. rsing this maneuver the iris was nicked in only one of the 10 eyes. The procedure brought up the question of how much force was being used to introduce the needle into the eye. In order to determine the maximal force developed by this system, the missile was aligned against the footplate of an ophthalmodynamometer. and fired 10 times. The means of 10 forceful 1~10~~:s of t,he device yielded a mean reading of 95 mmHg 1vit.h a st,andard deviation of 5 mmHg, which converts to a force of 128 g. Since the cross-sectional area of a 25-gauge needle is approximately 0.05 cm, the pressure applied to the cornea at the moment of impact becomes 6.4 kgicm3. 193
