Year : 1983 | Volume
: 31 | Issue : 7 | Page : 986--989
Intra-ocular lens implants-an experimental study
AK Sood, Sandeep Mithal, Devendra Sharma
Department of Ophthalmollgy LLRM Medical College, Meerut, India
A K Sood
Department of Ophthalmology, L.L.R.M. Medical College, Meerut
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Sood A K, Mithal S, Sharma D. Intra-ocular lens implants-an experimental study.Indian J Ophthalmol 1983;31:986-989
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Sood A K, Mithal S, Sharma D. Intra-ocular lens implants-an experimental study. Indian J Ophthalmol [serial online] 1983 [cited 2021 Jun 14 ];31:986-989
Available from: https://www.ijo.in/text.asp?1983/31/7/986/29724
Extraction of the cataractous lens is one of the most successful and gratifying operation in the history of mankind. But the management of the resulting aphakia has been a problem till the advent of Intra ocular Lens Implantation, by which most of the problems of aphakia could be counteracted. Though the method has already attained wide popularity and acceptance throughout the world, let not many histopathological studies have been taken up or are available in the literature which is bound to go a long way in evaluating different postoperative complications.
MATERIAL AND METHODS
A study was undertaken on albino rabbits to review postoperative complications in the light of histopathological changes produced by intraocular implants. Study was carried out on a total number of 20 rabbits (40 eyes) in the Department of Ophthalmology, LLRM Medical College, Meerut. Cataract was induced in both the eyes by injecting 0.3 ml of 8% Magnesium Chloride in the lens. An extra capsular lens extraction was done in both the eyes, followed by a Dannheim non-perforating elastic anterior chamber angleimplant (with two loops), as a primary procedure in the right eye. In the left eye no implant was given and it served as a control.
After implantation, eyes were followed-up every day for one week, every third day for two weeks, weekly for 6 weeks and monthly for 4 months (a total follow-up of 6 months). After this the animals were sacrificed for histopathological examination of the control as well as the study eye.
I. Ist Post-Operative Day
Study Group-All the cases showed mild lid oedema. Mild to moderate degree of iritis with conjunctival and circum-corneal ciliary congestion was seen in 12 eyes (60%) and mild corneal oedema was observed in 10 eyes (50%).
Control Group-All the cases showed mild lid oedema. Mild to moderate iritis with conjunctival and circumcorneal ciliary congestion was seen in 11 eyes (55%) and none of the cases showed corneal oedema.
II. At The End of Ist Week
Study Group-9 eyes (45%) showed evidence of iritis, whereas mild to moderate degree of corneal oedema persisted in 8 eyes (40%). Only 1 eye (5%) showed dislocation of lens.
Control Group-Six eyes (30%) evidences of iritis whereas none of the cases showed corneal oedema.
III. At the End of One Month
Study Group-In 6 eyes (30%) evidences of iritis were still there whereas mild to moderate corneal oedema persisted in 4 eyes (20%). One more lens was dislocated on the 8th day of operation (total 10%).
Control Group-None of the eyes showed an evidence of iritis or corneal oedema after 15 days itself.
IV. At the End of 3rd Month
In study group only 2 eyes (10%) had evidence of iritis whereas corneal oedema persisted in 4 eyes (20%).
V. At the End of 6th Month
In study group none of the cases showed any evidence of iritis whereas corneal oedema persisted in all the 4 cases (20%), two out of which had dislocation.
After 6 months of follow-up animals were sacrificed and their eyes were subjected to histopathological examination after fixing with formaline.
HISTOLOGY-AFTER 6 MONTHS
Study group: At the end of 6th month a histopathological study was carried out in the 4 eyes (20%) clinically showing corneal oedema, which was confirmed by the increase in the thickness and separation of Descemets memberane from the rest of the layers. Iris stroma revealed mild vascular dilatation and mononuclear cell infiltration which is clearly appreciable.
Peripheral anterior synaechiae were also seen in 3 eyes (15%). Marked fibrosis was seen at the angle of anterior chamber at the site of loop insertion in all the cases. Besides that 3 eyes show presence of fibrous tissue in the form of band aggregated again near the angle.
Control group: Except for few macrophages and fibrosis nothing severe was evident. Fibrosis was less marked in these cases as compared to the eyes of study group.
The reports of intra-ocular lens implantation in the animals are only few and results in one study cannot be compared well with other because of two main variables namely the lens model and the experimental animal used.
In our study carried out on albino rabbits, extra-capsular extraction was carried out because anterior hyaloid membrane being adherent to the back of the lens had lead to loss of vitreous invariably when intracapsular extraction was attempted. Anterior chamber-lens were chosen rather than iris clip lens which were not suitable because of the thin iris structure in the study animal and further more irido capsular lens were not available at the time of study in the country and the import was not possible because of the cost factor.
There is no doubt that the pseudophakos surgery is more traumatising to the corneal endothelium than routine lens extraction surgery. Corneal endothelial cell loss after pseudophakos surgery have varied from 2040% as compared to 12-15% cell loss in routine lens extraction as estimated by the clinical specular bio-microscopy. Corneal oedema indirectly indicated the extent of corneal endothelial decompensation and can be considered to be a good parameter of endothelial cell loss as a result of pseudophakos surgery. In our study 50% cases had corneal oedema on 2nd post-operative day. In almost half of these cases it resolved between a fortnight and a month. Similar observations were reported by Eifrig and Dough man.' In cases with complications such as severe iritis and dislocation of lens the incidence of corneal oedema was 20% which persisted even after one month.
In control group corneal oedema was present in none of the cases. Presence of corneal oedema in study group is explanable by comparatively more handling of the cornea during the procedure of lens implantation than routine cataract surgery.
The fact that almost all the eyes except for those with some complications, attained complete resolution of the corneal oedema is in agreement with the view expressed by Bounne and Kaufman 2sub that the loss of corneal endothelial cells at surgery generally does not effect the corneal functions for more than 3 months. But on the other hand, cornea being completely normal is not a guarantee that even after years it will maintain its clarity. Besides, a cornea with decreased endothelial cell density is more susceptible to further insult like glaucoma, inflammation and artificial lens degradation-products as compared to one with a normal endothelial cell density. This is simply because there are less viable endothelial cells to be lost in the former category.
There is no significant difference in the incidence of iritis in the control and in the study group (study group 60%, control group 55%). Left-out lens matter in the anterior chamber is one of the most important precipitating factor in both the groups. But on further follow-up it was noticed that iritis took one week to a fortnight to resolve in the control group, whereas in the study group it took from 3 weeks to more than a month to resolve.
In the study group although there was no clinical evidence of iritis at the time of sacrificing the animal, but on histop athological examination all the eyes showed evidence of low grade iritis in the form of mononuclear cell infiltration and vascular dilatation in iris stroma as compared to none in the control group. This difference may be due to constant rubbing of implant over the iris and excessive manipulation of the iris or it may require still greater time to resolve histologically, which is a difficult thing to comment upon and needs still longer follow-ups.
Incidence of dislocation which is the most dreadful complication of intra-ocular lens implantation was only 10% in our study. The maximum incidence was present in early post-operative days, as out of two dislocated lenses the first occurred on 2nd day and second on the 8th day. No further dislocation was observed after this. There are two factors responsible for dislocation. Firstly, the animal regained their normal activity as soon as the anaesthesia was over and showed exaggerated activity in the cage in form of rubbing their anterior limbs over their eyes leading to dislocation. Secondly in the first few days after lens implantation following extracapsularlens extraction, the lens position and centering depends entirely on the pupillary constriction around the pseudophakos. The lenticulo-iris adhesion take about 5-6 days to form but the animal was ambulatory on the Ist day itself, thus leading to dislocation.
The incidence of complications after intraocular lens implantation in the experimental animal are minimal, but still better results can be expected in human-beings because of many factors. Most important of which is the care in the post-operative period, stabilization of head and bed rest. Microscopic study also showed that there is minimal tissue reaction to the material placed inside the eye ball. Hence the surgical results are bound to be better in the human subjects as compared to the animal experimental studies.
|1||Eifrig and Doughman, 1977, Ophth. Surg. 81: 149 2. Bounne and Kaufman,1977, Amer. J. Ophthalmol., 81: 4|