Year : 1979 | Volume
: 27 | Issue : 4 | Page : 187--189
Anterior synechia in corneal surgery
Civil Hospital, Ahmedabad, India
Professor of Ophthalmology, Institute of Ophthalmology, Civil Hosp., Ahmedabad
|How to cite this article:|
Kalevar V. Anterior synechia in corneal surgery.Indian J Ophthalmol 1979;27:187-189
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Kalevar V. Anterior synechia in corneal surgery. Indian J Ophthalmol [serial online] 1979 [cited 2021 Jan 24 ];27:187-189
Available from: https://www.ijo.in/text.asp?1979/27/4/187/32622
Corneal pathology in tropics is more often associated with iris involvement. This has to be dealt with either before or at the time of grafting. A critical assessment of a case for the time and type of synechiotomy to be performed is an important factor for the ultimate goal of attaining a round pupil.
A corneal scar with iris involvement was always considered an unfavourable recipient, Elsching and Castroviejo. Most of the leucomata, we have to deal are complicated with varying grades of iris involvement. About 16 years ago when we analysed our first 100 cases, we too considered corneal opacities with iris involvement amongst unfavourable indications. The observations and increasing experience however made us realise that it is the extent and degree of iris involvement and its amenability to pre-operative or operative separation which is significant rather than its mere presence.
Materials and Methods
A critical slit-lamp examination is a must in any corneal case and so it is in a case with iris adhesion.
Quite a bit can be known about the synechiae if seen carefully. The points to be specifically noted are:
(a) Is the pupillary margin involved in synechia?
(b) How wide or broad is the synechia?
(c) How much is the iris lifted forwards?
(d) Is the iris healthy or atrophic?
(e) Are there any obvious blood vessels from the iris to the scar?
(f) Is there associated pigmentation of the posterior surface adjoining or away from the synechia site?
(g) Is there even the sliiihtest change in the curvature of the cornea at the site of synechia?
The surgical experience over the years has shown us that it was more often possible than hitherto believed to release the synechia maintaining an adequate iris diaphragm and a round pupil. Based on these observations, we classified anterior synechia in the following three grades.
(A) Contact synechia
This type of iris involvement is most insignificant because it is only a very loosely attached contact between the anterior surface of iris and the endothelial surface of cornea. It can easily be separated pre-operatively in a closed synechiotomy procedure or can be left to be tackled at the time of grafting without any adverse consequences. Such a separation always maintains a round pupil which has great advantages at the time of grafting and even post operatively, when an intact iris diaphragm is a boon.
(B) Iris adhesion
This iris involvement in the cornea is firm. Attempts to separate pre-operatively by close synechiotomy may be often successful. If not, a careful direction and separation at grafting is always possible without loss of iris tissue. When it is done meticulously it is often possible to maintain a round pupil. Close synechiotomy for iris adhesion needs skill and a balanced judgement to know when to stop further attempts to avoid a bleeding iridodialysis. If close synechiotomy has to be abandoned for fear of this complication, a dissection and separation of synechia at the time of grafting should be planned with better magnification perferably under the microscope. This way there remains a better change of retaining a round pupil.
A corneal scar with iris adhesion where pupil has been maintained round by pre-operative or operative synechiotomy, should be considered on par with simple opacity without iris involvement and therefore a favourable recipient, other factors apart.
The advantages of round pupil are:
(1) It responds to miotics preoperatively. This is important in penetrating grafts. If a pre-operative synechiotomy is not successful and the adhesion is separated carefully at the time of operation to maintain a round pupil, a strong miotic like carbachol can be used directly on the iris to contract the pupil instantaneouly unless of course the iris is markedly atonic. In those cases of lamellar where recipient preforation occurs, a small round pupil is again a distinct advantage from the point of view of restoration of anterior chamber.
(2) During full thickness surgery an intact iris diaphragm helps in prevention and management of forward movement of the lens which can prove disastrous.
(3) Anterior chamber restoration at the end of operation is facilitated if iris diaphragm is intact.
(C) Iris incarceration
This grade of iris involvement in a corneal scar is not only an important factor in the consideration of suitability or otherwise of a recipient but it also has to be considered in the assessment of the final outcome of surgery. It is practically impossible to separate such incarceration in a closed synechiotomy and therefore it must be attended to at the time of grafting. Even when the separation is done skillfully, meticulously and with adequate magnification, it often results in an enlarged papillary coloboma or an iridectomy coloboma separate from the pupillary aperture. If such iris coloboma with or without inclusion of pupil, is very irregular, some kind of regularity in the pupillary shape can be obtained by suturing the iris with 10.0 perlon suture wherever this is feasible.
The most important complication on the table in a case with large coloboma is the difficulty during suturing when the atonic iris keeps coming between the donor and recipient edges of cornea and can be caught in a suture if adequate care is not taken to avoid it. Reformation of anterior chamber at the end of operation in these cases may pose a problem of enormous magnitude because not only that the air does riot remain in the anterior chamber but tends to slip behind the iris making the matter worse. Extensive anterior synechia to the graft-host junction post-operatively is an expected hazard in these cases. These complications lead to secondary rise of intra-ocular tension which may jeoparadise anatomical intergrity of the eye and is not, certainiy the transparency of the graft.
In more sever degrees, when a greater part of iris diaphragm is involved in this third grade loss of iris tissue in disengagement is too much resulting in a ragged pupillary opening with only a peripheral portion of iris tissue in place. Leaving such ragged rim serves no purpose and may actually be greatly harmful for the graft because this narrow peripheral part of iris can not be kept separated from the graft margin. The extensive peripheral adhesion which invariably exists in these cases, causes blockage of the angle and the presumed secondary rise of intra ocular tension. It is therefore better to remove the narrow rim of iris from its attachment to the ciliary body. In such circumstances of course the lens, even if transparent has to be removed, otherwise the lens invariably moves forwards and can cause damage either by rise of intra ocular tension or by remaining in contact with the endothelial surface of the graft. Except when there is a degenerated membranous cataract, it is better to remove the lens extra-capsular so as to retain the posterior capsule which will support the hyaloid face and prevent its coming in contact with the endothelium of the graft. Such a surgery, depending on the size of the graft has been described by us as Total or Sub-total Penetating Keratoplasty.
Anterior synechia to graft margin
One more type of anterior synechia that a corneal surgeon has to deal with, is post-operative anterior synechia which is a fairly common post-operative complication in full thickness grafting. This can be blamed on:
(a) Anterior synechiae are common in large sized grafts because iris is nearer the graft-host junction and .an easily be pinched by a raw posterior gap. This is particulary prone to occur if the sutures are placed superficially and tightened firmly. Both these factors go towards causing an increased posterior marginal gap which is an open invitation to the iris.
(b) Post-operative anterior synechia is of course expected in those cases where reformation of anterior chamber with air injection has not been possible. whatever the reasons.
(c) The original pathology with gross iris involvement resulting in irregular coloboma of the iris not properly managed. The remaining iris being more or less atonic is expected to be more prone to synechia. The details have been described above.
Adequate number of corneo-corneal sutures to seal off the anterior chamber which is fully restored at the end of a full thickness graft is the important factor which stands against formation of anterior synechia to the graft union. Prevention of post-operative synechia is therefore dependent mainly on restoration of anterior chamber at the end of operation and its maintenance post-operatively.
In earlier years when small grafts were practised, a wide dilatation of pupil used to be routine to keep the iris away from graft-host junction. But this is an era of large grafts. Smaller grafts ate not possible in extensive scarring and in cases of advanced keratoconus. However some times a mushroom graft with a small penetrating part and a larger lamellar wing can solve problems of having to do a big 9 or 10 mm graft.
I would like to add a word about closed anterior synechiotomy, necessary both for pre-operative and postoperative anterior synechia.
A knife point puncture, limbal or extra limbal should be made diametrically opposite the synechia preferably where anterior chamber depth is reasonably good. A synechiotomy knife spatula should be introduced and swept across the synechia. Care must be taken that the point of the knife is always visible. The plane of the knife must be maintained parallel to the iris plain. This is to avoid injury to the anterior surface of the lens or endothelium of the cornea (particularly important in post-operative synechiotomy after full thickness graft). It is important to observe the stretch on the iris in adjoining sector so that the same can be relieved before irido-dialysis occurs.
The post-operative synechiotomy also should be done through limbal or extra-limbal puncture and not through inter-stitch gap unless ofcourse the graft size is big and limbus to limbus. In a smaller graft, entry through inter-stitch gap will cause difficulty in maintenance of plane of the knife-spatula and is also likely to cause injury to the anterior lens and endothelium of the graft. Injection of sterile air or saline through the knife point puncture to ensure complete separation of iris from the posterior corneal surface is a must. Presence of air bubble in anterior chamber helps discover any irregulatity in its depth.
It is important to judge the time of surgical intervention in case of post-operative anterior synechia. It is indicated immediately and urgently if:
(a) there is progressive oedema in the graft from the site of synechia.
(b) there is increasing vascularisation in the same sector of the graft.
If transparency of the graft is not jeoparadised and if vessels are not invading the graft, synechiotomy can be delayed and planned to be done under favourable circumstances a few weeks later in a quiet eye.
Anterior synechiotomy can be a very simple surgery and can be accomplished within a minute but it is also a tricky surgery. One can get into a chain of complications on the table and afterwards. I have seen an American surgeon struggling for an hour to separate a post-operative synechia and that too with diffidence. We are more objective and optimistic. But we have become so after years of painful as well as pleasant surprises. I therefore suggest that be prepared for these surprises. More often than not, there will be pleasing results provided the guidelines are based on discreet judgement associated with delicate fingers and patience.
|1||Castroviejo, R., 19,6, Amer. J. Ophthal., 29, 108. |
|2||Dhanda, R.P., Kalevar, V., 1963, Amer. J. Ophthal., 55, 1217.|
|3||Elsching, A., 1930, Keratoplasty, Arch. Ophthal., (Chicago) 4, 165.|