|Year : 1989 | Volume
| Issue : 2 | Page : 62-63
Lowering of intra ocular pressure-various methods
S Tony Fernandez, Noel Moniz
CBM Ophthalmic Institute, Little Flower Hosptial, Angamally - 683 572, India
S Tony Fernandez
CBM Ophthalmic Institute, Little Flower Hosptial, Angamally - 683 572
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Fernandez S T, Moniz N. Lowering of intra ocular pressure-various methods. Indian J Ophthalmol 1989;37:62-3
| Introduction|| |
The thought of operating on a hard eye is not pleasant to any ophthalmic surgeon, especially to an anterior segment surgeon who does not like to loose vitreous. All the hypotonic methods whether it be manual mechanical or by drugs were designed to prevent and minimise the loss of vitreous. Inspite of the best hypotony a surgeon is not able to totally eliminate vitreous loss though he is able to reduce it. Numerous, simple and sophisticated methods are available to produce hypotony, but these may not be accessible to every ophthalmic surgeon. With this in mind, we decided to review the various methods available for hypotony and how to recognize hypotony on the table.
VARIOUS METHODS FOR PRODUCING OCULAR HYPOTONY: These can be divided as
DIGITAL PRESSURE: Digital pressure is exerted against the closed eye lids with the fingers after keeping a pad. Pressure can also be exerted with the heel of the hand. When exerted with the fingers this is done by alternate pressure of the fingers of either hand, or the heels of the hand. The pressure should be released every 30 seconds for five seconds to ensure against a vascular occlusion. Generally digital pressure has to be applied for 5 minutes before tension is checked. If tension has not come down to the required amount - massaging cane be repeated. Normally a tension less than 10 mm Hg is aimed at.
- Pressure Bandage
- Super Pinkie
- Paediatric B.P.Cuff
- Honan's Baloon and
- Balanced Weight
After giving the retrobulbar and facial anaesthesia, an eye pad is folded in half and kept ever the closer lids followed by another eye pad over it. If the bandage is tied with the right tension one should just be able to push the index forger under it. The bandage should be kept for about 5-7 minutes. Tension is then checked.
This is a rubber ball to which is attached a 15" elastic band which is tied round the head. The ball exerts a pressure of approximately 30 mm Hg on the eye ball. The time for attaining hypotony varies from 10 to 20 minutes depending on the age of the patient.
PAEDIATRIC B.P. CUFF
A modified paediatric B.P. Cuff to which are attached two self adhesive Velcro straps can be used for this purpose. The inflatable part of the cuff is placed over the closed lids and inflated to approximately 30 mmHg on the sphygnomanometer Hyptotony is achieved in 20-30 minutes.
HONAN'S INTRA OCULAR PRESSURE REDUCER
This consists of a rubber bellows connected to a rubber bulb and a manometer similar to a sphygnomanometer. It has got a Velcro strap which splits into two as it goes behind, for a good fit on the occiput. The dial of the gauge is colour coded for easy reading. There is a pressure release valve set to 60 mmHg in case of accidental high pressure either due to human or instrumental error. Hypotony is achieved in 10 to 15 minutes at 30 mmHg.
PRECAUTIONS WITH THE ABOVE DEVICES
- The rubber band or the encircling band along should not press on the eye and cause the 30 mmHg pressure on the eye.
- The patient should not move his head in any way which may cause the loosening of the band and thus decrease the pressure on the eye.
- The eyelids should always be closed to prevent damage to the corneal epithelium.
This is a weight made of ordinary steel / stainless steel and weighing 550 grams. This weight was introduced to us by Prof.F. Muller, West Germany.
The weight is placed over a folded eye pad placed over the closed eye lids. Effective hypotony with the IOP less than 10 mmHg is obtained in 3 to 4 minutes. If further hypotony is needed the weight should be removed for about 30 seconds and can be placed again for a further 3 minutes.
Caution is to be taken that the lids are closed to prevent damage to the corneal epithelium. This device should not be used in aphakes, pseudophakes before needing and in patients who have undergone a keratoplasty or fistulising procedure for glaucoma. The advantage of this method is the simplicity of use.
- I.V. Mannitol
- I.V. Diamox
- Glycerine by mouth
- Oral Diamox
300 cc of 20% I.V.Mannitol should be given for a period of 20 to 30 minutes, 45 minutes prior to surgery. The action of IV Manitol will start in 30 minutes and the peak action lasts up to a maximum of 3 hours. The dose is 2 gms/kg. weight. The patient should not be allowed to drink water after IV Mannitol as its hyperosmotics effect decreases. If the tension is found to be high after using a mechanical device for hypotony or after the eye ball is opened 40 to 50 cc of mannitol can be given IV on the table over a period of 2 minutes. One should wait for a few minutes for the Mannitol to act before resuming the operation. This method of administration is called "Mannitol Push"
Contrary to IV Mannitol, IV Diamox 500 mg gives instantaneous hypotony. We have used this drugs when the tension was high on the table and found it to be excellent. However it is difficult to get in India.
MECHANISM OF HYPOTONY
The mechanical devices used for creating the hypotony do so by dehydrating the vitreous and also by orbital decompression, where as IV Mannitol and IV Diamox induce hypotony purely by vitreous dehydration.
REDUCTION OF EXTERNAL PRESSURE ON THE VITREOUS
The main aim of hypotony is avoid to vitreous loss and to have a smooth surgery. Even the best of hypotony is of no use, if the associated factors are not looked into:
- Poor retrobulbar and facial block will increase the intra ocular pressure by movement, and orbital spasm, resulting in vitreous loss.
- Mechanical pressure which cause pressure on the eye ball by a small palpebral aperture must be taken care off.
- Speculum pressure on the eye ball should be avoided.
- Collapse of the sclera which is usually an unrecognized cause for vitreous loss especially in young patients is to be avoided.
INTRA OPERATIVE SIGNS OF GOOD HYPOTONY
The Cornea becomes concave after the section if the tension is low, an air bubble spontaneously enters the anterior chamber, and there is no forward bulge of the lens iris diaphragm.
WHEN THE INTRA OCULAR PRESSURE IS HIGH
The Lens iris diaphragm bulges forward as soon as the section is made, cornea does not fall back or air does not enter the anterior chamber, iris pushes out through the section and horizontal tenssion folds are seen on the cornea.
At times inspite of a perfect hypotony pre-operatively and a low Schiotz reading, one finds that the lens iris diaphragm bulges forward on making the section. This is possibly due to a concealed retrobulbar haemorrhage, and IV Diamox or Mannitol should be given with an ampule of calmpose. When the tension is controlled, the operation can be proceeded with.
| Conclusion|| |
The various methods of producing hypotony and the various ways of recognizing the hypotony or raised pressure have been discussed. All the methods whether it be digital pressure or a mechanical device are effective in producing reading on the Schiotz scale of less than 10 mmHg. Some of the devices are cumbersome to apply and others need a long duration of application. After a comparison of the commonly available devices we have came to a conclusion that the balanced weight is the best.
[Figure - 1], [Figure - 2], [Figure - 3]