|Year : 1991 | Volume
| Issue : 4 | Page : 154-158
Management of secondary pupillary membrane in aphakia (YAG discission vs parsplana membranectomy)
SK Angra, CB Rai, VK Kalra
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, New Delhi, India
S K Angra
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, New Delhi
Source of Support: None, Conflict of Interest: None
Forty aphakic eyes, with secondary pupillary membranes, underwent pars plana membranectomy and YAG laser discission randomly. Visual improvement was similar in both the groups. IOP remained low for a week in pars-plana membranectomy while it transiently increased following YAG laser discission Complications like anterior chamber reaction, corneal edema and CME were more after pars plana membranectomy than in YAG laser discission. In membranes thicker than 1.2 mm, only pars plana membranectomy is recommended.
|How to cite this article:|
Angra S K, Rai C B, Kalra V K. Management of secondary pupillary membrane in aphakia (YAG discission vs parsplana membranectomy). Indian J Ophthalmol 1991;39:154-8
|How to cite this URL:|
Angra S K, Rai C B, Kalra V K. Management of secondary pupillary membrane in aphakia (YAG discission vs parsplana membranectomy). Indian J Ophthalmol [serial online] 1991 [cited 2020 Dec 5];39:154-8. Available from: https://www.ijo.in/text.asp?1991/39/4/154/24435
| Introduction|| |
Capsular and lenticular remnants left in situ following extra-capsular cataract surgery may lead to formation of secondary pupillary membranes (after cataract) jeopardising the visual gains. Its incidence can be as high as 50%. Numerous techniques have been described in the literature to negotiate these membranes. However, the comparative evaluation studies are lacking in terms of safety and success.
We endeavoured to compare the efficacy of pars plana membranectomy and YAG laser discission with regard to visual outcome, corneal thickness, endothelial cell changes and IOP changes, in prospective randomised, age and sex matched cases.
| Material and methods|| |
40 eyes of 38 patients with secondary papillary membranes (after cataract) in aphakia of more than 3 months duration with best corrected visual acuity less than 6/12 were entered in this study. Detailed history was taken. Examinations included visual acuity measurement, refraction, Goldmann's applanation tonometry, corneal thickness by pachymeter, average central endothelial cell count by CEM-4 specular microscope and thickness of the after cataract by Ocuscan 400 contact A and B scan with DER. These eyes were randomly allocated into two groups.
The first group underwent standard pars plana membranectomy. We endeavoured to create a central 3-4 mm opening by means of vitrectomy (Ocutome) probe. Post operatively topical corticosteroid drops, systemic antibiotics and NSAID's were used.
The second group underwent discission with Neodymium YAG laser (Rodenstock, OPL-4 mode locked). The laser was set at energy level of 5 mJ per burst in all cases. The number of shots used and the energy setting were recorded in each case. The number of shots used and the energy setting were recorded in each case. The 3-4 mm opening in the membrane was achieved. Postoperatively, all cases received tablet Aspirin (1 tablet three times daily), Acetazolamide (250 mg B.D.) and topical corticosteroids (four times a day) for one week.
The corneal thickness, endothelial cell count,, iris reaction, macular status and intraocular pressure (IOP) were monitored on next day, at 1 week, 1 month and 3 months intervals.
The pupillary membrane thickness ranged from 0.53 mm to 1.36 mm (average 0.98) in the pars plana group and 0.56 mm to 1.26 mm (average 0.80 mm) in the YAG laser group [Table - 1].
Pars plana membranectomy : Time required for surgery was almost equal in all cases (35 to 45 minutes).
Satisfactory pupillary opening in the membrane was achieved in all cases. There was no closure of the opening so created during follow up [Figure - 1].
The prominent complications in the post operative period were mild to moderate uveitis in 7 eyes (35%) and fresh CME in two cases (10%) [Table - 2]. In these cases the period between two surgeries ranged from 3 months to 10 years.
YAG Laser : The number of laser spots ranged from 16 to 36 (average 23), average total energy applied was 115.5 mj (range 80 to 180 mj). Three eyes with membrane thickness of 1.20-1.26 mm required a second sitting to achieve an adequate opening. Adequate pupillary openings were established in all cases [Figure - 2].
Uveal reaction was observed in 20% of eyes. The anterior hyaloid face was broken in 50% cases with vitreous herniation in the anterior chamber in 20% cases. CME was seen in one case and the period between the previous surgery and YAG laser discission was 2 years. [Table - 2].
Visual assessment : Post membranectomy visual acuity was 6/12 or better in 35%; 6/12-6/18 in 30%; 6/24-6/36 in 25% and 6/60 or poorer in 10% eyes. Whereas after YAG laser discission visual acuity was 6/12 or better in 15%; 6/12-6/18 in 40%; 6-246/36 in 35% and 6/60 or poorer in 10% cases. One patient after pars plana membranectomy and two patients after YAG laser discission had no improvement in vision [Table - 1]. Amblyopia, high myopia, age related macular degeneration CME (fresh and old) and optic atrophy are some of the causes of non recovery of vision after the treatment.
Intraocular pressure (IOP) : Mean preoperative IOP in control (fellow eye) eyes and pars plana membranectomy were 13.05 ± 2.85 mm Hg and 12.75± 3.5 mm Hg respectively. There was significant decrease of IOP varying from 2-4 mm for a week which gradually recovered to base line [Figure - 3]
Mean pre-laser IOP was 14.90 ± 3.34 mm Hg and 13.30 ± 3.38 mm Hg in control and test eyes. While the eyes in which YAG laser discission was done, 75% eyes had increased IOP by 1 to 8 mm Hg from the pre YAG level but remained below 21 mm Hg. Mean elevation of IOP in the 1st post-YAG day was statistically significant (P). However, mean IOP on subsequent follow up was not statistically significant different from that of the pre YAU level.
Endothelial cell loss.
The pre-treatment mean endothelial cell density was 1762+_ 196 cells/mm 2 in the pars plana membranectomy group. There was an average loss of 39.50 cells (2.12%) at 1 month and 92 cells (4.94%) by 3 months after pars plana membranectomy while in the YAG laser group, there was a mean loss of 14.5 cells (0.9%) 'at one month and 20 cells (1.29%) at 3 months follow up [Figure - 5]
There was significant increase in the mean corneal thickness in the first postoperative week. However, no difference in corneal thickness was observed at 1 month and 3 months as compared to the preoperative level [Figure - 4].
Mean prelaser corneal thickness was 0.53 ± 0.04 mm and there was no statistical change in the corneal thickness at any time of follow up.
| Discussion|| |
Management of dense secondary pupillary membranes through the pars plana has been gaining popularity because this procedure avoids direct trauma to the corneal endothelium which is already compromised by previous surgery .However, recently Neodymium YAG laser has gained tremendous popularity because it is a non invasive procedure and carried fewer complication s ,
We achieved visual improvement in 95% of cases in the pars plana group and 90% in the YAG group. In both groups, posterior segment pathology like amblyopia, macular hole and optic atrophy were responsible where final visual acuity did not improve above 6/12. This substantiates the reports by other authors ,,,. There were no cases of corneal opacification or closure of the opening made in our study as have been observed by Laiesegang .
We observed a mean IOP lower than that of the preoperative IOP persisting upto 1 week after pars plana membranectomy which might be due to ciliary shock or micro leak from the sclerotomy wound. Our findings were contrary to those of Juarez et a1  who noted transient rise of IOP in the early postoperative period and could not attribute any reason for it.
After YAG laser capsulotomy there was elevation of the IOP by 1-8 mm Hg from pre-YAG IOP upto 24 hours, which might be due to the blockage of the trabecular mesh work by capsular or cortical debris. The use of prophylactic medications like oral acetazolamide, after YAG laser discission have prevented the elevation of IOP beyond 21 mm Hg. in our study. We could not find any relation between the number of laser bursts and total energy implied. This corroborates the findings of Terry et al and Liesegang ,. We could not relate the size of capsule opening to the elevation of IOP.
In our study the corneal endothelial cell loss was observed more after pars plana membranectomy than after YAG laser discission. The high percentage of cell loss after pars plana membranectomy may be due to either mechanical or chemical trauma to the already compromised corneal endothelium. These probable factors do not play any role in YAG laser discission. Enhanced age related endothelial cell loss in already compensated corneal endothelial cells due to the first surgery might be triggered by the second surgery (pars plana membranectomy) or aqueous turbulance by Yag laser bursts. In YAG laser capsulotomy Slomovic et a1  reported acute endothelial cell loss of 2.3% cells whereas in our study it was 1.29% at 3 months follow up, though the average total energy and energy per pulse used by them was lower than that of our study. Terry et al 15 and Kraff et al  reported no significant endothelial cell loss. While on the contrary Liesegang et al  has reported cell gain of 6%.
Indirect documentation of the functional status of the endothelium by measuring corneal thickness showed ;1o chances after YAG laser discission. There was increase in corneal thickness only for a week following pars plana membranectomy. This led us to suspect that the irrigating solution might be responsible for altering corneal endothelial function.
Complications like anterior chamber reaction and corneal edema were less after YAG laser capsulotomy than pars plana membranectomy. CME was more in the pars plana group (10%) than the YAG laser group (5%) which is explained by more vitreous manipulations / disturbances in pars plana membranectomy. Our findings substantiate the reported incidence of CME of 9.5%. The reported incidence of CME following Yag capsulotomy varies
from 0.04%-9.5% ,,,15.
It has been suggested that discission of the pupillary membrane should be delayed in order to reduce the incidence of CME and retinal detachment . We feel delaying the discission for several years after the primary cataract surgery does not help in preventing CME as is evident from our cases.
As regards the functional opening created in the pupillary membrane, all cases in the pars plana membranectomy group had a successful rent. 3 patients in the YAG laser group who had a thick membrane (1.20 to 1.26 mm) required a second sitting to make a successful opening. The second sitting of YAG laser discission was carried out after one week. The rupture of the vitreous face, herniation of vitreous into the A.C. and uveal reaction were common complications in such cases.
Though no definite cut off data have been evolved in the literature regarding the thickness of membrane that could be subjected to YAG laser discission our study reveals that the membrane thicker than 1.20 mm may be subjected to pars plana membranectomy and not to YAG laser discission. This is of utmost clinical significance.
We tried to compare pars plana surgical membranectomy and YAG laser discission and reached a conclusion that YAG laser discission should be preferred because it is a noninvasive out patient procedure and because of patient acceptance. Elevation of IOP should be kept in mind and prophylactic antiglaucoma drugs should be used. Pars plana membranectomy should be preferred for secondary membranes thicker than 1.20 mm and even for a thinner membrane in absence of availability of expensive YAG laser. This is also a safe method.
However, an after cataract of more than 1.20 mm needed two sittings of YAG laser capsulotomy. The disruption of the anterior hyaloid face was a common complication.
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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5]
[Table - 1], [Table - 2]