Problem of Acute ocular hypotonia in modern ophthalmosurgery

If to evaluate mechanisms of linear deformation of the eye tissues on the whole in conditions of its acute hypotonia, they can be presented in the form of the following diagram: graduate reduce in the volume of fibrous capsule - enlargement of the area of the surface of the uvea to the phase of hyperemia - reduce (in emptying of intravitreous cavities) or increase (in swelling) of the surface of the vitreous - disorder of normal anatomic relations of conjugated areas of the ocular membranes in its deformation from the outside. The essence of linear deformation of ocular tissues in its extraocular and intraocular forms is shown on pictures 13 and 14.

As it is seen from picture 13, one and the same area of sclera A-B in normal condition (I) and in deformation of the membranes (II) corresponds to different in sizes areas of surfaces of the uvea and the vitreous A'-B', that depends upon radius of curvature of surface deformation membranes.

1-sclera

2- choroid

3-vitreous body

Pic. 13. Extraocular form of linear deformation of the eye membranes

On picture 14 linear deformation of ocular tissues relative to each other is presented in the following conditions: in the changes of uveal blood-stream (vascular spasm - B, vascular hyperemia-C), swelling of the vitreous (D), or retraction of its fibrillar stroma resulting from emptying of intravitreous cavities (E), retraction of fibrous capsule lack of hydraulic compression from the inside (F).



pic. 14. Types of intraocular forms of linear deformation of the eye

We can suppose that after termination of operation as ophthalmotonus is recovering and intraocular blood circulation is normalising, “motion” of membranes relative to each other again will take place. Evidently elements of linear deformation of membranes also take place in early postoperative period when resulting from development of reactive syndrome concentration of humoral factors of inflammation [89] is increased. Paresis of uveal vessels is intensified and area of surface of choroid tissue is changed.

Arising of “excess” in the surface of the choroid relative to area of conjugated parts of sclera causes a tendency to detachment of uveal tract from sclera with development of negative pressure between the membranes. “Vacuum effect” of choroidal hyperemia in combination with abundant fenestration of endothelium of its capillaries [76] may promote humor transsudation into suprachoroidal space and development of late CCD.

Similar processes accompany reactive syndrome also in the zone of contact of uveal tract with retina and vitreous. Enlargement of the volume and area of the surface of the vitreous resulting from edema also promotes linear deformation of membranes in this zone [90].

* * *

So, two main forms of deformation of ocular tissues in conditions of its acute hypotonia can be defined: volume and linear. More typical displays of volume deformation of the eye are: emptying of anterior chamber, spontaneous rapture of hyaloid membrane with prolapse of the vitreous, expulsive haemorrhages of CCD.

One of the main solving factors promoting development of volumetric changes is linear deformation of ocular membranes. It's possible to define the following pathogenetic chains:

1) linear deformation of uveal tract relative to sclera - destroy of suprachoroidal plate, vacuum effect of deformation - transsudative reaction of choroid, haemorrhages - CCD, hemorrhagic exudation into suprachoroidal space;

2) linear deformation of the surface of the vitreous relative to retina and uveal tract - posterior detachment of the vitreous - stretching and injuring of hyaloidoangioretinal commissures - sub- and intravitreous haemorrhages, macular edema, retina detachment.

CHAPTER 5. Complications of acute ocular hypotonia

Status of this problem in modern ophthalmologic literature may be defined as follows. On the one hand, there is large amount of publications dedicated to complications of intraocular surgery, and on the other hand, practically there are no works concerning purposeful study of role of ocular acute hypotonia in pathogenesis of these complications.

Whereas, analysis of pathophysiological and topographic changes arising in the eye tissues in quick decrease of ophthalmotonus shows that acute hypotonia is not just one of types of ocular conditions but presents a syndrome described by a whole complex of specific pathophysiological reactions [117-120,71-74]. If not take into consideration role of mechanical trauma varying in broad limits, practically during any intraocular operation or perforated wound, accompanied by decompression of the eyeball, one and the same pathophysiological reactions are developed typical for acute hypotonia of the eye. Hence in the present review we tried to include only complications which develop under the influence of acute hypotonia of the eye or result from it. Into this group we included also those complications the main cause of which is mechanical trauma but which could develop only in conditions of acute hypotonia.

Hemorrhagic complications

Frequency of hemorrhagic complications of intraocular operations is in the limits 2,8%-36,0% [97,101,105,127]. The main reasons of haemorrhages are mechanical injury of ocular vessels during the operation or trauma [149] and expressed breaches of intraocular hemodynamics arising in the decrease of ophthalmotonus in the ocular cavity [20].

As it is known, as microsurgery develops traumatism of intraocular operations becomes much less. However many authors pay attention to the fact that risk of hemorrhagic complications is rather high [48,89,105]. It shows important role of acute hypotonia of the eye in the pathogenesis of mentioned complications.

Bochkareova A.A. and Zabobonina A.P. [20] think that one of the reasons of haemorrhages during the operations on cataract is hypotonia, at which the vessels are overloaded with blood. The second reason causing development of vitreous haemorrhages is, in the authors' opinion, drop of ophthalmotonus in anterior chamber, deviation of the vitreous forward and its posterior detachment. As a result strains occur and ruptures of hyaloidoangioretinal commissures with injury of retinal vessels appear.

Kallachan A. [82] thinks that the reason of haemorrhages into the anterior chamber and the vitreous is in the ruptures of capillaries of operational wound, ciliary body and retinal membrane under the influence of normalising intraocular pressure.

Ivanov D.F. and co-authors [79] with the help of rheoophthalmographic investigations have found that there is real statistic link between the level of pulse volume of blood, flowing in the time unit through the vessels of internal membrane of the eye, and risk of intraocular haemorrhages during cavitary operations on the eyeball. In particular, drop of bloodstream level in the vessels of ocular membranes provides prophylaxis of intraocular haemorrhages and detachments of the uveal tracts of the eye.

Link between decompression and hypotonia of the eye is traced more distinctly in development of the most severe complication of cavitary operation- expulsive haemorrhage [27,63,114]. The fact of developing of this complication only in the case of traumatic depressurization of the eyeball points out itself to the leading role of hypotonia in its development [82,134]. So, in accordance with data of Shmeleova V.V. [149], expulsive haemorrhage in the series of cases is developed immediately after termination of cornea dissection, that is in the moment when the surgeon has not yet made any manipulations in the ocular cavity and mechanical trauma of intraocular tissues is minimal.

Pathogenesis of expulsive haemorrhage is rather clear and in accordance with opinion of most of the authors is connected with drop of extravasal pressure. As a result of this hyperemia “ex vacuo” arises with the next rupture of one of ciliary vessels [104].

Experimental work of Astahov U.S. [10] also proves it. He as it was mentioned above, has found that blood-filling in PLCA of cats in decrease of ophthalmotonus is 3 times increased.

It's necessary to notice that till the present moment the main method of struggle with expulsive haemorrhage is posterior sclerectomy and blood evacuation from suprachoroidal space [149]. This method can not be considered as effective and pathogenetically directed influence on bleeding vessel.

Many of the ophthalmologists pay attention to the fact that more often hemorrhagic complications of intraocular operations occur in the patients having initial defects of the vascular wall, the reason of which can be: diabetes mellitis, atherosclerosis, hypertonic disease, metabolism disorders and so on [20,27,106]. Also influence of emotional condition of the patient on vasculomotor reactions and frequency of haemorrhages [133] are discussed.

Prolapse of the vitreous

Vitreous prolapse is one of the most serious and spread complications of intraocular operations and especially cataract extraction. In accordance with the data of series of the authors in this operation even made at modern microsurgical level, frequency of prolapses of the vitreous reaches 6%-11% [20,128], moreover about 1/3 of the eyes 2-3 years after the operation worth nothing from the functional point of view.

There are many different factors promoting prolapse of the vitreous. So, Maximov V.U. and Shulga L.V. [111] on the basis of written enquiries of the doctors and literature data pick out 16 of such factors. However in the available literature we did not find any works containing analysis of concrete role of acute ocular hypotonia in pathogenesis of mentioned complication. Let us consider the problem from this point of view.

If to exclude mechanical injuries of the vitreous membrane connected with operational peculiarities, pathologic changes in the eye, surgeon's carelessness and so on, and to consider only the cases of so called “spontaneous” prolapse of the vitreous [149] impossible, we could not but pay attention to the differences into investigators' opinions relatively to pathogenesis of this complication.

Because prolapse of the vitreous is a consequence of deep topographic (volumetric) changes in the eye cavity analysis of which was made above, in the present section we are going to consider only the main opinions of this question.

Pisetskaya S.F. [128]), Egorov V.V. [41] think that the main reason of prolapse of the vitreous is its removal to the front after operational depressurization of the eyeball resulting from prevailing of pressure in posterior chamber of the eye. Some other authors are of the same opinion [20].

Kovalenko M.D. and Kravtsova G.M. [91] suppose that the reason of hypertension of posterior segment of the eye is accumulation of retrovitreous humor (RVH) between the vitreous and the retina resulting from opening of anterior chamber and quick coming ciliary block. As the authors think, disturbance of fluid flow through the pupil leads to its accumulation in the retrovitreous space in the form of additional chamber. The only drawback of this concept is the following: as our investigations show, in keeping of normal humor secretion in 1,5-2,0 mm3 per 1mm of perfused pressure in a minute [97] for accumulation of RVH volume, comparable for example with volume of anterior chamber, even if full ciliary block is available, 10-15 minutes will be necessary.

In the series of articles there is an opinion that the reason of prolapse of the vitreous may be increase in the volume of the uveal tract at the expense of reactive hyperemia [133,144,69]. However, absence of concrete data about dynamics of intraocular blood stream at the stages of operational intervention did not let the authors give quantitative estimation of these volumetric changes.

Posagennikov A.P. [133] has also investigated relations between level of general arterial pressure of 454 patients having cataract during the operation, and frequency of prolapse of the vitreous and has got the following results: in the patients with high AP (arterial pressure) (180/90-240/120mm of m.c.) prolapse of the vitreous was observed in 56% (!) of cases; among the patients with normal or moderately increased pressure - only in 3,4% of cases.

Many of the authors pay much attention to the pressure on the eye from the outside (that is to the factors of extraocular deformation, which were mentioned above).

Elevation of intraorbital pressure is supposed to be one of the reasons of prolapse of the vitreous within the operation. Increase of intraorbital pressure occurs when the head of the patient is excessively thrown back and blood is accumulated in orbital veins [158]. In accordance with opinions of Bochkareova A.A. and Nevednik L.M. [19] ophthalmotonus also depends on turgor and hydrophylic nature or orbital tissue cellular.

Important role, in our accordance belongs to volumetric deformation, which is characterized by thickness of the choroid, swelling of the vitreous, contraction of the sclera and also linear deformation of conjugated tissues.

So, basing on the literature data a conclusion can be made that topographic changes which develop in the eye in acute hypotonia are one of the main reasons of such widely spread complication of intraocular operation as prolapse of the vitreous. However existing points of view are mainly based on theoretical suppositions and facts of clinical observance. There is need in more deep investigations and experimental ground of existing pathogenetic theories.

Detachment of uveal tract

Similar to expulsive haemorrhages, detachment of uveal tract (DUT) occurs usually after operational or traumatic depressurization and decompression of the eyeball, this points out to close connection of this complication with acute hypotonia of the eye [47,120,147].

Wide introduction of microsurgery has led to significant shortage of clinical forms of detachment of uveal tract. At the same time utilisation of modern diagnostic equipment helped to find subclinical forms of DUT in 78%-100% of the patients several hours after cavitary operations [7,63]. As Eroshevskiy T.I. [47] thinks “… there is an impression that in the opening of the eyeball in any operation detachment of uveal tract is almost inevitable.”

Most of the authors think that hypotonia of early postoperative period plays leading role in pathogenesis of DUT [4,45].

Bochkareova A.A., Zabobonina A.V. [20] consider emptying of anterior chamber and removal irido-lenticular diaphragm to the front within operational intervention are the main factors of DUT development. In this case ciliary body is mechanically detached because of lens traction and removal of the vitreous basis to the front. However, the authors in their discussions don't take into consideration the fact, that drop of pressure in the anterior chamber can not lead to increase in the volume of the vitreous for short period of time, and when extraocular deformation or thickening of the choroid occur at the expense of hyperemia, its internal surface removes to the front together with the vitreous and the sclera.

In opinions of Makeeva G.V. and Nemenko F.P. [110] development of ciliochoroidal detachment (CCD) occurs in the result of significant difference of protein concentration into suprachoroidal fluid and into the humor of anterior chamber (7,24% and 0,02% correspondingly).

Some of the authors pay great attention to disorders of eye hemodynamic in development of DUT (CCD) [6,96]. So, Alexeev V.N. and Pisetskaya S.F. [6] have found that in the patients with CCD there is significant lowering of rheographic coefficient to 0,78. On the basis of this the authors make a conclusion of sharp aggravation of intraocular hemodynamics in arising of CCD. However, we think that the authors in their discussions do not consider peculiarities of rheoophthalmography methods and don't pay attention to the fact that even in the cases of maintenance of normal level of uveal bloodstream in CCD drop of interelectrode resistance and decrease of rheographic coefficient at the expense of shunting of electrodes with suprachoroidal fluid will be inevitable.

Volkov V.V. [155,156] explains the origin of DUT by the theory of “vacuum-syndrome” in which the leading role is given to deformation of membranes of the eyeball. DUT results from “self-spreading” of “self-smoothing” of elastic sclera and formation of negative pressure between the membranes.

The question is discussed concerning the origin of the humor into suprachoroidal space. Even in the beginning of our century Fuke [59] indicated that the reason of CCD is rupture of scleral spur and pouring of humor of anterior chamber between the membranes.

There is an opinion that the vitreous looses its humor when CCD occurs [64,155].

Balyasnikova N.V. and Zykov N.I. [16] represent the mechanism of development of CCD in the following way: under the influence of trauma (contraction) deformation of rigid sclera occurs with destruction of plates of suprachoroidal space and impairment of permeability of vascular walls of the uveal tract. Humor from the vessels begins to flow into suprachoroidal space. The other authors [4,126] also point out to the fact that ciliary body in pathological conditions can produce humor into supraciliary space.

In our opinion, important role in the pathogenesis of early and late CCD belongs to impairments caused by linear deformation of ocular tissues (p.37) though mentioned displays of acute hypotonia of the eye practically were not studied.

So, at present two different mechanisms of development of detachment of ciliary body and choroid are defined. In one case it develops because of arising communication between anterior chamber and suprachoroidal space, intensification of uvea-scleral flow off, impairment of the functioning of ciliary body and development of stable hypotonia. In the other cases the reason of DUT may be impairment of permeability of the choroid vessels and accumulation of transsudate into suprachoroidal space.

Other complications of acute ocular hypotonia

One of the main eye elements sensitive to acute hypotonia is the lens. Frequency of the lens dimness after cavitary operations, in accordance with some authors, is from 2% to 15% [2,94]. Quick cataract progressing is the main reason of failing sight after antiglaucomatous operations [29,47]. There are separate notices about the cases of spontaneous destroy of the lens after cavitary operation [150].

For a long time it was supposed that such complication of intraocular operations as cystiform macular edema is typical for operation of cataract extraction and is not connected directly with drop of ophthalmotonus within operational intervention [60,61,159]. However in 80^th years separate works began to appear in which the authors show to direct link between cystiform macular edema with acute hypotonia of the eye and possibility of arising of such complication after any depressive operation [38]. For all this macular edema is not usually seen and not always diagnosed because of choroid edema and humor accumulation into suprachoroidal space. However biomechanism of influence of ocular hypotonia on development of macular edema is not yet clear.

Influence of method of anaesthesia on peculiarities of clinics and character of complications during the operation of cataract extraction and in postoperative period

Comparative analysis of two basis methods of anaesthesia having reflections in the series of publication of last year [18,62,93] lets us make a conclusion that when operation on cataract extraction is made under endotracheal anaesthesia in comparison with local anaesthesia, natural anatomic form of the eyeball is less breached. On the whole, amplitude of hemodynamic deviations diminishes because of vessels of uveal tract become not sensitive to mechanical and physical irritants (thermocoagulation, lavage of anterior chamber) [120,149].

At the same time while choosing method of anaesthesia the surgeon should take into consideration that under ETN paresis and hyperemia of vessels are intensified and mechanisms of neuro-reflex regulation of vascular tonus are sharply slowed down. It has special meaning for the patients with elevated risk of haemorrhages (suffering from diabetes mellitus, atherosclerosis, hypertonic disease, breaches in blood coagulation and so on.)

In our opinion, the following circumstance is very clinically important: in conditions of general anaesthesia sensibility of uveal vessels to pharmacological medicines [120] phenylephine hydrochloride, Acetylcholinum) is kept that gives possibility to use them for managing of hemodynamic of the eye during operative intervention.

CHAPTER 6. Modern methods of prevention and treatment of complications connected with acute ocular hypotonia

At present in ophthalmologic practice many methods of prevention and treatment of complications of intraocular operations are applied. Most of them somehow influence upon the complex of pathophysiological and topographic changes typical for condition of acute hypotonia of the eye. Conventionally all existing methods may be divided into preoperative and postoperative.

Preoperative methods

More traditional are methods of pharmacological preparation of the patient aiming to drop IOP. With this goal, as a rule, means of dehydrational therapy are used - Diamoxum, Glycerolum, Urea, Furosemidum and other [128,149], decreasing volume of the vitreous and reducing production of intraocular humor. Practice has shown that in the cases when it is possible to obtain significant drop of IOP before the operation, probability of complications within the operational period becomes minimal. Insufficiency of pharmacological hypotensive means is the following: when they are used it is impossible to relieve ophthalmotonus lower than 15-12 mm. of m.c. and level of IOP overfall in opening of ocular cavity is kept high. Besides, mentioned medicines influence on the general condition of human organism and that limits their usage.

Some of the authors think that it is necessary to correct general arterial pressure in a proper time and create normal psycoemotional mood before the operation [39,133].

Ivanov D.F. and co-authors [79] with the aim to prevent hemorrhagic complication recommend besides medicamental preparation apply vasosection on the branches of orbital artery - temporal, superorbital, angle that helps to decrease volumetric bloodstream into intraocular vessels.

Many ophthalmosurgeons recommend using of local hypothermia of the eyeball before the operation [1,116,131] allowing obtain more favourable reaction of content of the eyeball after its opening. Mechanism of hypothermia's effect is not yet clear to the end. Lazarenko V.I. and co-authors [102] with the help of original method of rheoophthalmography have investigated influence of local hypothermia on hemodynamic of uveal tract. The authors have found that immediately after stoppage of cooling vasoconstrictive effect has place, leading to decrease of rheographic coefficient and 10-20 minutes after vasoconstrictive effect of after-action begins.

One of the most widely spread way of physical influence on the eyeball before dissection of its fibrous capsule is oculocompression. Most of the ophthalmosurgeons perform compression of the eyeball with the use of fingers [26,50,98]. The others use special oculocompressors providing accurate dosing and evenness of pressure on the eye [19,37]. Hypotensive effect of oculocompression is in strengthening of flow off of intraocular humor, dehydration of the vitreous and retraction of its fibrillar stroma [19].

However in the last years there were publications of negative effect of mechanical compression of the eye and in particular increase of risk of expulsive haemorrhages in the first minutes after its termination [63].

Series of methods are aimed to prevention of possible deformation of the eyeball after drop of ophthalmotonus. The following methods can be attributed to them: suturing of supporting (bearing) rungs [54] to fibrous capsule or usage of special rings- suckers [112], canthotomy [149], usage of blepharostats not pressing the eyeball [97] and others.

Full relaxation of extraocular musculature also provides relieve of pressure on the eyeball, that influences ophthalmosurgeons to look for new methods of anaesthesia [22,43,86]. So in the last years a tendency to more wide usage of methods of general anaesthesia in the ophthalmosurgery appeared [18]. Series of works is dedicated to study of specific of usage of general anaesthesia during intraocular operations and in particular to its influence on hydro- and hemodynamics of the eye. In accordance with data of Kovalevskiy E.I. and Ruzmetov M.S. [93], volumetric blood stream in the vessels of ciliary body in the children's eyes within surgical stage of intravenous anaesthesia is decreased at an average by 48,1% and in nitrous oxide- narcotanum-oxygen anaesthesia by 69,8%. . Decrease of intraocular hemodynamics in inducing of anaesthesia by 10%-20% from initial stage was marked by Bartnovskiy V.I. [18].

Insufficiency of well-known works is the following: investigations of blood circulation were made on pair eyes, which were not the subject of surgical intervention. Till the present moment in the literature there is a limited number of publications devoted to comparable study of influence of different methods of anaesthesia on the complex of pathophysiological reactions defined by us as syndrome of acute hypotonia of the eye [120].

Operational methods

More physiologic, in the opinion of many authors is conducting all necessary manipulations without decompression of the eye, under normal intraocular pressure [70]. At present some types of operations on glaucoma [5], cataract [95], pathology of the vitreous [107], which may be performed practically without significant drop of ophthalmotonus. With this purpose special irrigation devices are used making hydraulic backwater in the ocular cavity. The most perfect of them (“Kelman-Kavitron”, “Ocutom”) are equipped with tracing computer system, regulating balance of feeding and taking out of irrigation solution and supporting relatively constant intraocular pressure [149].

At separate stages of operation ophthalmotonus is maintained also when special instruments are used, tamponing corneal or scleral wound [51]. But known methods of maintenance of normal intraocular pressure can be used only in condition of hermetic bond of the instrument with the ocular cavity. In the cases when during the operation wide dissection of fibrous capsule is necessary, and decompression of the eye becomes inevitable, some of the authors propose to relieve ophthalmotonus in slow tempo by means of gradual letting the humor from anterior chamber out through corneal wound [151], or slow aspiration of intraocular humor by syringe [41]. Gradual decompression in accordance with the authors' opinion to some extent reduces influence of “hydraulic stroke” on the eye tissues arising in sharp drop of ophthalmotonus and in particular promotes adaptation of intraocular vessels to drop of extravasal pressure. However mechanisms of favourable influence of slow relieve of ophthalmotonus were not studied in fact, so optimal regimes of the eye decompression are not worked out.

Last years a new trend of ocular microsurgery is developed intensively - viscosurgery [14]. The aim of viscosurgery is to recovery lost humor mediums of the eye preventing rough topographic changes in the cavity of the eyeball. Because of usage of viscid high molecular solutions some increase of eye turgor is obtained. Mainly the following substitutions of intraocular humor and the vitreous are used: Gealonum [14,65, 124,157], Methylcellulose [49,109], Gelatin [75,78].

However wide usage of Gealonum and other similar substitutes is prevented by high cost of such preparations. Some authors show to impairment of flow out and increase of ophthalmotonus in early postoperative period after applying of gealonum [162].

Principally new trend in intraocular surgery (Chatminskiy U.F., 1975) is the work under the creation of special sluice with the help of which any intraocular operations could be made without depressurization of the eyeball cavity and drop of intraocular pressure [70]. However presence of some unsolved technical questions and in particular problem of reliable joint of elements of ocular system - sluice chamber prevents clinical usage of this working out.

* * *

On the whole, analysis of current publications of ophthalmosurgery and ophthalmotraumatology lets us make a conclusion that at present there is a tendency towards more purposeful and differential study of questions concerning acute hypotonia of the eye and also to the search of new methods of prophylaxis of pathologic influence of hypotonia on the intraocular tissues.

Clinical evaluation of method of controlled dosed eye decompression *

While making experimental investigations of hemodynamics of the rabbits' eyes after drop of ophthalmotonus we have found direct dependence of degree of disorders of blood circulation on regime of decompression of the eyeball. Also optimal speed of decompression was defined: 0,111-0,055 gPa per second. It lets us apply the method and device for the eye decompression in the clinic in making planned intracapsular extraction of senile cataract. With the aim to keep and reuse intraocular humor lost while using principle of communicating vessels, one more compound device for the eye decompression was constructed. The basis of this device is aspiration system [120].

Method of controlled dosed decompression (CDD) of the eye with the help of system of communicating vessels (CV) we conventionally called as CDDCV, method of decompression with the help of aspiration system we called as CDDAS.

As far as methodology and statistic results of general application of technology of Controlled Dosed Decompression of the eye just before a cavitary operation were described in the previous publications [120,71-75], in the present work we shall discuss only general characteristic of results and conclusions of usage of this obviously promising method of making intraocular operations, conducted in conditions of inevitable decompression of the eyeball.

* - the work was made on initiative and participation of Hatminskiy U.F.

So, clinical practice has shown that the most favourable reaction of ocular content (for making operation) to decompression (2-3 degree) in the patients with CDD was more often (CDDCV-79,1%; CDDAS - 70,8%) than at the opening of anterior chamber in traditional way under local anaesthesia (64,4%) and only by 7,6%-15,3% more seldom than in the patients operated under endotracheal narcosis (ETN) (86,7%). On such index as an average level of depth of anterior chamber (considering extreme degrees of deformation of anterior chamber 1 and 4) the patient whom the method of CDDCV (CV with preliminary compression = 2,73+0,08) was applied turned out to be in the most favourable position, difference with similar index of the patients of the first group (3,14+0,06) turned out to be statistically true (p<0,001).

The same conclusion can be made analysing reaction of ocular content to removal of the lens. In this case frequency of the most favourable reaction (2-4 degree) in the patients applying CDDCV, CDDAS and ETN was quite similar (70,2%; 66,7% and 73,3% correspondingly) and significantly differed from the patients operated under local anaesthesia with usual method (57,4%).

Less significant tendency to emptying the anterior chamber after drop of intraocular pressure and removal of the lens in the patients with CDD ( in comparison with the patients being operated on the usual method) had positive influence on the other peculiarities of making operations and also on the quantity of operational complications, frequency of such indices as increased bleeding of the wound and prolapse of the vitreous in the patients which were applied CDDCV turned out to be the less. In using of method of CDDAS unusually high percentage of patients with increased wound bleeding (12,5%) within operational intervention was marked.

We explain this peculiarity in the following way: accordingly to data of Remisov M.S. and co-authors [137] in the first patients to 250-300mm of humor was aspirated from anterior chamber, this evidently leads to formation of negative pressure in the cavity of anterior chamber and unfavourable influence on intraocular vessels. When we had began controlling the moment of equalising of intraocular pressure with atmospheric pressure more attentively, and had created a special microneedle for puncture of anterior chamber having a valve automatically stopping aspiration in drop of pressure in anterior chamber to the level of atmospheric, during the following operations we did not meet such complication.

While analysing postoperative period we have marked in the patients whom method of CDD was applied decrease of frequency of practically all typical complications in comparison with traditional method of cataract extraction.

Especially significantly quantity of hemorrhagic showings (from 12,8% to 3,0%), ciliochoroidal detachments arising clinically or echografically (from 12,2% to 4,2%), iridocyclitises (from 9,0% to 2,9%) decreased. As a result average vision acuteness of the patients at their discharge (patients operated with CDD) was by 0,06-0,08 higher and postoperative bed-day by 3,0 reduced.

So, as our experimental and clinical investigations have shown controlled dosed eye decompression allows obtain more favourable conditions for making intraocular operations and improving their functional results. Positive effect of CDD is connected with the following: at its usage ophthalmotonus is dropped gradually in less traumatic regime for the eye tissues. As a result uveal tract and other intraocular tissues undergo the influence of “hydraulic stroke” in significantly less degree, and within the period of gradual decompression mechanisms of tissue adaptation have time to switch on for decreased intraocular pressure.

In using of aspiration system for drop of ophthalmotonus possibility to restore chambers of the eye by its own intraocular humor.

* * *

In the process of clinical investigations we made records of intraoperational rheoophthalmography during extraction of senile cataract with the usage of method of CDD in the patients who by this or that reasons were operated under general anaesthesia. Comparison of the results with the data received earlier in examination of uveal blood flow of the patients also operated under ETN, but without appliance of CDD method showed, that an average meanings of Rq at all the operational stages on both comparable groups practically not differed from each other by more than 10%, that was within the limits of mistakes.

So, we did not find significant influence of method of controlled dosed decompression of the eye on the dynamic of changes of intraocular blood circulation during extraction of senile cataract, made under general anaesthesia. In our opinion it is very important to take into consideration this peculiarity for correct evaluation of possibilities of clinical usage of CDD method of the eye.

In conditions of deep general narcosis processes of neuro-reflector regulations of vascular tonus are slowed down and mechanisms of adaptation of intraocular vessels to drop of extravasal pressure are blocked. As a result method of CDD calculated for improving conditions for timely switching on above mentioned mechanisms in conditions of real practical applying with the usage of endotracheal narcosis evidently will be ineffective.

Some recommendations on prophylaxis of acute ocular hypotonia complications

We think that the main pathogenetic factor defining reaction of the eye content to acute hypotonia is non-conformity arising between the volume of the eyeball cavity and the volume of its content. Consequently, all the measures of influence on this reaction may be performed in two ways: 1) to exclude or make lesser deformation of the eyeball within the operation; 2) to regulate the volume of humor content of the eye.

Proceeding from these principles we tried to consolidate all known and created by us methods of influence into single pathogenetic classification:

I. Methods of diagnostic and prophylaxis of extraocular deformation of the eyeball (dropping extraocular pressure or preventing its increase):

1) Methods relieving extraorbital pressure:

a) canthotomy;

b) akinesia;

c) usage of blepharostats not pressing the eyeball;

d) usage of supporting ring of Fliring;

e) comparative tonometry and echography before and after applying devices of immobilisation of blepharons and the eye.

2) Methods relieving intraorbital pressure or preventing its increasing:

a) limiting of the volume of anaesthetics injected retrobulbarly;

b) preferable usage of general anaesthesia;

c) special control for position of persons with excessive weight and short neck on the operational table, prophylaxis of excessive thrown back of the head, bend of jugular vein and blood stagnation in the orbital veins;

d) usage of small doses of relaxants injected retrobulbarly;

e) diagnostic of retrobulbar hematoma with the usage of methods of exophthalmometry and comparative tonometry before and after retrobulbar injection in a proper time;

II. Methods of prophylaxis of intraocular deformation of the eyeball (regulating volume of humor content of the eye):

A. 1) Methods decreasing volume of intraocular humor and degree of hydration (volume) of the vitreous:

a) usage of osmotic means before the operation (Glycerolum, Urea, Diamoxum, Lasixum, Triampur compositum and others.)

b) dosed compression or massage of the eyeball with fingers before opening of anterior chamber;

c) hypothermia of the eye before the operation;

d) control and normalisation of blood pressure in a proper time;

e) usage of means increasing oncotic blood pressure (Glucose, Polyglucinum, Aminopeptidum and others.)

2) Methods reducing degree of hyperemia of vessels of the eye after its decompression:

a) intrachamber injection of vasoconstrictive medicines in doses not influencing generally on cardiac-vascular system (0,25%-1% solution of Phenylephine Hydrochloride);

b) usage of method of controlled dosed decompression of the eye (CDDCV, CDDAS, CDDCV-with preliminary compression);

c) hypothermia of the eye before the operation.

3) Methods reducing transsudative reaction of the choroid and preventing hemorrhagic complications in the phase of hyperemia of intraocular vessels:

a) well-timed exposure and treatment of diseases leading to inferiority of vascular wall or impairment of general blood pressure;

b) application of angioprotectors (in accordance with indications) within preoperative period;

c) control and in-time regulation of general blood pressure at operational table;

d) in-time psychological preparation of the patient, usage of ( in accordance with indications) means removing emotional excitation of the patient;

e) also methods described in items I-2-d); II-A-I-a,c-e); II-A-2-a-c.

III. Methods increasing volume of the eye or filling in lost volume of its liquid content (are applied when all above mentioned methods are ineffective or there is elevated IOP):

1) injection of viscous high-molecule solutions (Gealonum, Chondroitinum-sulfas, Polyvinylpyrolidone, Methylcellulose, Gelatine) into the anterior chamber;

2) posterior trepanation of sclera;

3) radial sclerotomy or fenestrated sclerectomy.

Recommendation of surgeon's tactic in case of expulsive haemorrhages arising

The most deep topographic changes into intraocular tissues and structures develop when during the operation expulsive haemorrhages occur. In especially difficult cases quick progressing of suprachoroidal haematoma leads to prolapses of the lens, the vitreous, the membranes into the wound that is practically to death of the eye as an organ.

Usually when expulsive haemorrhages occurs perforation of the sclera in posterior segment of the eyeball and drainage of suprachoroidal space [149] are performed. This method is generally accepted in ophthalmosurgery in our days. However it also has significant insufficiencies:

1) When depressurization of suprachoroidal space and evacuation of accumulated blood from it take place, low extravasal pressure is maintained artificially. This pressure causes rupture of one of the ciliary vessels and also space for effusion of new value of blood is emptied constantly. As a result drainage of suprachoroidal space on the one hand prevents development of haematoma and saves content of the eye from being squeezed out into the wound, but on the other hand vicious circle is maintained (when consequence forces the reason) and the surgeon should make drainage of suprachoroidal space on the operational table (often not successfully) for a long period of time.

2) Drainage of suprachoroidal space is not pathogenetically oriented method of preventing of expulsive haemorrhages because during it direct influence on bleeding vessel is not made. Moreover, measures taken by the surgeon in order to drainage suprachoroidal space and reduce of hypertension increasing of the eyeball at the same time deprives him of the opportunity to such influence.

As a results of our experimental and clinical investigations we have found real possibility to use series of physical and pharmacological means for more effective prevention of expulsive haemorrhages. To the mentioned means the following can be attributed: diathermo(thermo)coagulation of episcleral vessels, injection of 1% solution of phenylephine hydrochloride into posterior chamber, hydraulic decompression of the eye membranes leading to increase of tonus of intraocular vessels.

With the help of method of intraoperational rheoophthalmography we have also studied the influence of local hypothermia of the ciliary body on the vessels of uveal tract. Four patients with high-degree myopia passed through ROG records within the operation on cryopexy of the ciliary body. The investigation showed that immediately after making one cryoapplication with exposure 10 sec in projection of flat part of the ciliary body with the size 8x3mm with instrument the tip of which was preliminarily cooled into liquid nitrogen (-195,8*C), rheographic coefficient reduced at an average to 21% +/- 8,3% p<0,1 from initial level (that is more than in application of the other methods of influence) and expressed vasoconstrictive effect was kept during 8-15 minutes.

It's necessary to indicate that in clinical part of the work while making rheographic investigations within the operation of cataract extraction coagulation of episcleral vessels and intrachamber injection of Phenylephine Hydrochloride was made until ophthalmotonus was dropped. However at some operations dissection of corneosclera was accompanied by unpremeditated opening of anterior chamber and eye decompression. In these cases we had to make thermocoagulation of the vessels and intrachamber injection of Phenylephine Hydrochloride in conditions of expressed hypotonia of the eyeball.

We have paid attention to the fact that these manipulations on the background of sharp increase of rheographic coefficient connected with drop of ophthalmotonus did not cause significant (statistically true) changes of uveal blood flow. It lets us make a conclusion that effect of physical and pharmacological irritators on ciliary vessels is more expressed when perfusion pressure in them is equal or similar to physiologic. In conditions of acute hypotonia of the eye and expressed hyperemia of ciliary vessels influence of mentioned factors is not so effective yet.

Basing on above mentioned data we have worked out a complex of measures allowing to the surgeon to influence on ciliary vessels more purposefully when expulsive haemorrhages occur.

Suggested method of preventing of expulsive haemorrhages during intraocular operations is the following.

In case of arising of such complication in the moment when operational wound has been already pressurised the surgeon punctures anterior chamber with microcanule connected via elastic tube with bottle filled with normal saline solution and raised to height 400-820 mm (that is similar to 30-60mm of m.c. or 40-82 gPa) and makes (proceeding from available possibilities) cryopexia of the ciliary body, diathermo- or thermocoagulation of one or several large episcleral vessels.

Then waiting for 2-5 minutes necessary for development of full reaction of ciliary vessels to cryopexia or thermocoagulation on the background of hydraulic compression the surgeon makes linear sclerotomy in the zone of more evident accumulation of blood and drainage of suprachoroidal space.

Intraocular pressure is maintained elevated at least until the moment when fresh blood stops coming out of suprachoroidal space *.

Then by gradual displacement of the bottle of solution downwards or with the help of special electromechanical device (unfortunately there is no serial production) or step-by-step in every 60 seconds by lowering down of the bottle by 70mm (it corresponds to average speed of decompression 0,084mm of n.c./sec or 0,111gPa/sec.), intraocular pressure is relieved gradually to physiologic level.

If as far as intraocular pressure drops, bleeding starts the bottle should be quickly raised to initial level of hydraulic compression and the eye should be kept in such condition for longer period.

It's necessary to take into consideration that average diastolic pressure in orbital artery and large ciliary arteries is 55-60 mm. of m.c., average dynamic pressure : 73 mm. m.c. [136] and elevation of ophthalmotonus by more than to 60 mm. of m.c. may cause sharp impairment or even full stoppage of intraocular blood flow.

* - More favourable conditions for bleeding termination arise in dropping of perfused pressure into ciliary vessels to maximally high level (5-10mm. of m.c.). It can be reached by elevation of ophthalmotonus to 60 mm. of m.c. However not always quality of pressurising of operational wound lets us elevate IOP to such high level. That is why the surgeon chooses level of hydraulic compression 0,1 in every concrete case taking into consideration sizes of operational wound and suture reliability.

If expulsive haemorrhage passed in depressurised operational wound, the surgeon at first begins with posterior sclerotomy* and drainage of suprachoroidal space from the blood with the aim to reduce increasing hypertension of the eye and prevent prolapse of its content into the wound.

In constant evacuation of blood accumulating into suprachoroidal space operational wound is reliably sutured, then into posterior chamber microcanule is introduced with the help of which into the paraciliary space 120-150mm3 (0,12-0,15ml)1% of water solution of Phenylephine Hydrochloride or solution of Phenylephine Hydrochloride based on 40% Gelatine are instillated.

After it with the help of system for hydraulic compression ophthalmotonus is elevated to 30-60mm. of m.c. and cryopexia of the ciliary body or diathermo(thermo)coagulation of episcleral vessels is made.

When the bleeding is stopped and hydraulic compression of the eye is finished operation should be completed in general well-known way. In the first 1-2 days to prevent repeated haemorrhages 2-3 times a day subconjunctival injections of solution of Phenylephine Hydrochloride or its analogues are given under the control of general arterial pressure.

Availability of all necessary technical means prepared (cryoapplicator, thermo-, diathermocoagulator, system with balanced solution and sticked microcannula, driver of vertical linear moving of the bottle, microsyringe with solution of Phenylephine Hydrochloride and Gelatine, reliable sutures, instruments for posterior sclerotomy, possibility to control and correct general condition and hemodynamics of the patient, and so on) is very important, especially when risk of similar complication is initially high.

Proposed method was successfully used during two antiglaucomatous operations complicated with expulsive haemorrhages.

Example # 1:

Patient Popova, 62 y.o. with diagnosis “secondary non-compensated glaucoma in aphakial eye on the left” went through operation - deep sclerectomy. At the final stage of the operation during suturing of surface scleral flap, hypertension of the eye became sharply increase, anterior chamber was completely emptied, tendency to sharp prolapse of ciliary body into the wound appeared, through basal coloboma of iris excising of the vitreous began.

In the upper-outside quadrant in 5mm from limbus linear sclerotomy was made. Through scleral wound blood began to flow out and ophthalmotonus dropped a little bit. On surface scleral flap 4 additional loop sutures were made, after that into posterior chamber 0,15ml of 1% solution of Phenylephine Hydrochloride was injected.

With the help of system for hydraulic compression intraocular pressure was elevated to 350 mm.m.c. (!) and diathermocoagulation of large episcleral vessels was made in quadrant 3-12 hours in the points where vascular trunks perforate sclera.

10 minutes after ophthalmotonus was gradually relieved with speed 0,111 gPa per sec. Ophthalmotonus reached the level of 26mm m.c. (35gPa) for 6,5 minutes. Bleeding from suprachoroidal spaces was not observed.

* - If after draining of ciliary-choroidal space, relieve of IOP and wound suturing, method of hydraulic compression is supposed to be applied, we recommend to make posterior sclerotomy only by linear dissection, and better at an acute angle to sclera, because traditional V-form section does not provide reliable pressurising in suturing and promotes swelling of the uvea into the wound during compression.