(1990) 4, 226-229

The Superior Peripheral : Prevention of Block due to Silicone Oil

A.-J. ELLIOTT, A. S. BACON, J. D. SCOTT Cambridge

Summary Superior peripheral iridectomy has been performed in 40 patients who have under­ gone silicone oil surgery for and who are aphakic. Only two developed raised due to pupil block by liquid silicone and in each case the seemed to be closed by proliferative membrane rather than the silicone meniscus. This ty pe of iridectomy is particularly suitable in patients requiring intracapsular extraction after previous and silicone oil surgery.

Silicone oil injection is a valuable technique in often necessary. When this is carried out treating difficult retinal detachments because through a standard cataract incision it is of its ability to demonstrate and separate pre­ simpler to do superior iridectomies rather retinal membranes and to provide a perman­ than an inferior iridectomy which requires the ent tamponade for retinal breaks. \-3 However, use of a suction cutter. However, it is believed under certain circumstances it may also tam­ that a superior iridectomy would be ineffec­ ponade the pupil causing pupil block; con­ tive.5 This belief is based on the idea that, as tinued production of aqueous then pushes silicone is less dense than aqueous, it would silicone through the pupil against the surface tend to move upwards to occlude a superiorly tensile forces which act to keep the silicone placed iridectomy. We report a series of bubble behind it. Drainage of anterior cham­ patients treated with superior peripheral ber aqueous continues until the chamber is iridectomy. filled with silicone when the intraocular pres­ sure rises. Silicone oil mediated pupil block Patients and methods causing intra-ocular hypertension was first Records of all patients who had undergone a described by Ando who with other authors vitrectomy and silicone oil procedure in described the 6 o'clock position peripheral iri­ Addenbrookes hospital followed by intracap­ dectomy in aphakic to prevent this com­ sular with retention of the plication.4-6 In addition, continued presence silicone, the second procedure having been of silicone oil in the anterior chamber having carried out between July 1986 and December entered by this mechanism may lead to 1988, were examined particularly to identify characteristic keratopathy. 7-9 the occurrence of pupil block with or without opacities frequently develop in eyes raised intraocular pressure, silicone oil in the which undergo vitrectomy and silicone oil anterior chamber or silicone oil keratopathy. injection. Incidences of 49% to 100% have The technique of cataract extraction was as been reported9,10 and cataract extraction is follows. Under general anaesthesia a superior

Correspondence to: Andrew J. Elliott FRCS FCOphth MRCP, Senior Registrar, Department of , Clinic 3, Addenbrookes Hospital, Hills Road, Cambridge. THE SUPERIOR PERIPHERAL IRIDECTOMY 227

Table I Indications for sIlicone oil was unclear. In one patient the cataract extraction preceded the vitrectomy-silicone Number of oil procedure. Follow up ranged from one to Diagnosis atients p 30 months (median nine months). In no case was there significant loss of sili­ Proliferative vitreoretinopathy 21 Proliferative diabetic retinopathy 10 cone oil. Giant tear 7* Two patients developed an acute increase in Trauma 1 intra-ocular pressure (36 mmHg and Retinal angiomatosis with 45 mmHg) and had anterior chambers com­ proliferative vitreoretinopathy pletely filled with silicone oil, this complica­ * includes two patients with Stickler's syndrome tion occurred at six weeks and eight months after cataract surgery respectively. In each corneal incision was usually followed by two case there were two superior iridectomies peripheral iridectomies made at 11 o'clock which appeared to be occluded by prolife­ and 1 o'clock using de Wecker's scissors. Very rative membrane. Creation of superior and small apertures were avoided. Chymotrypsin inferior iridotomies with the YAG was injected through the iridectomies and allowed the anterior chamber to refill with after two minutes the lens could usually be aqueous and the pressure to fall in each case. expressed and only rarely was a cryoprobe or No patient had silicone oil keratopathy. other instrumentation necessary. Loss of sili­ The results are summarised in Table II. cone oil, if it occurred was recorded. Anterior Discussion vitreous remnants or membranes were One serious drawback to the use of liquid sili­ removed so that in every case the silicone bub­ cone in aphakic eyes is that it can cause pupil ble had access to the pupillary aperture. If sili­ block and be forced into the anterior chamber cone entered the anterior chamber after resulting in an early post-operative rise in extraction it was not removed or replaced in intraocular pressure by open angle trabecular the knowledge that silicone surface tension blockage, or a characteristic keratopathy in would allow it to return behind the pupil very the long term if constant endothelial contact is soon after surgery. maintained.9•10 Results The inferior iridectomy described by Ando Forty patients, 23 males and 17 females, aged and Zivojnovic has resulted in a reduction in between 19 and 86 years (mean 49) had catar­ frequency of these complications.s They act extraction with silicone oil preservation found that keratopathy was almost universal during the study period. 2000 cs silicone oil in aphakic patients with silicone oil operated had been used throughout. The indieations on before this technique (11 of 16 eyes), com­ for silicone oil are listed in Table I. pared to only six of 62 eyes with an inferior iri­ Thirty-eight patients had had double dectomy. It is not stated whether any patients superior peripheral iridectomies as described with an inferior iridectomy developed acute above. One patient had a single superior iri­ due to pupil block by silicone, but dectomy and the case record of one patient four had silicone oil in the anterior chamber in

Table II Complications due to pupil block by silicone oil (no. of patients)

Silicone oil in anterior chamber with acute rise Interval between of intraocular pressure Silicone keratopathy operations (median)

Intracapsular cataract extraction after vitrectomy and silicone oil 18 months procedure (39 patients) 2 o (range 1 to 144) Vitrectomy and silicone oil procedure after cataract extraction (1 patient) o o 2 months 228 A. J. ELLIOTI ET AL. contact with at the end ior and superior peripheral iridectomies has of the observation period and another patient been reported, however it can be estimated with oil in the anterior chamber had YAG from the likely rate that such a laser to re-open the iridectomy so that the oil trial would need to enter at least 200 patients could move back into the posterior segment. in each group to have a 50% chance of show­ This supports the desirability of an iridec­ ing a significant difference were one to exist, tomy. However they speculate that silicone even assuming a doubling of the complication oil, being less dense than water, would tampo­ rate to be the least difference between the nade a superior peripheral iridectomy. Laga­ techniques which is clinically important.1 3" nowski and Leaver also conclude from their The use of a superior peripheral iridectomy retrospective series of 44 patients that a allows the cataract extraction to be performed patent inferior peripheral iridectomy is effec­ in the standard intracapsular manner and tive in reducing the anterior segment compli­ does not require the use of a suction cutter. 11 cations of silicone oil in the aphakic eye. Superior iridectomies are also cosmetically Our results show that using a superior per­ more acceptable. Nevertheless, we have not ipheral iridectomy results in a very low inci­ ruled out the need for an inferior peripheral dence of pupil block and that silicone does not iridectomy in cases where lensectomy is com­ readily occlude a superior iridectomy. More­ bined with vitrectomy and silicone oil over, the two patients who developed pupil injection. block demonstrated proliferation over the iri­ In conclusion, superior peripheral iridec­ dectomy rather than tamponade by silicone. tomy is associated with a low incidence of One possible explanation is that silicone oil pupil block when cataract extraction with does not easily enter recesses. This physical preservation of silicone oil is performed as a characteristic has been demonstrated in rab­ second procedure. bit and cat silicone tolerance experiments References where silicone could not be made to enter the I Cibis PA, Becker B, Okun E, Canaan S: The use of iridocorneal angle when injected directly into liquid silicone in retinal detachment surgery. Arch 12 Ophthalmol1962, 68: 590-99. the anterior chamber. It is improbable that a 2 Scott JD: A rationale for the use of liquid silicone. silicone bubble would conform to the recess of Trans Ophthalmol Soc UK19 77, 97: 235- 7. the ciliary sulcus in the manner suggested5 and 3 Aaberg TM: Management of anterior and posterior there is more likely to be a meniscus of aque­ proliferative vitreoretinopathy. XLV Edward ous between the bubble and the recess. Jackson Memorial Lecture. Am J Ophthalmol 1988, 106: 519-32. Also, after cataract extraction performed 4 Ando F: Intraocular hypertension resulting from as a second operation, as in all but one patient pupillary block by silicone oil. Am J Ophthalmol in our series and unlike the Rotterdam/ 1985,99: 87-8. Nagoya patients5 who were aphakic at the 5 Beekhuis WH, Ando F, Zivojnovic R, Mertens DAE, Peperkamp E: Basal iridectomy at 6 time of silicone injection, the relative silicone o'clock in the aphakic eye treated with silicone fill is reduced, not because silicone is lost oil. Prevention of keratopathy and secondary during the extraction, which is rare, but glaucoma. Br J Ophthalmol198 7, 71: 19 7-200. because the volume of the lens is now occu­ 6 Zborowsky-Gutman L, Treister G, Naveh N, Chen V, Blumenthal M: Acute glaucoma following vit­ pied by aqueous. This may reduce the like­ rectomy and silicone oil injection. Br J Ophthal­ lihood of pupil block if the silicone does not mol 198 7,71: 903--6. completely contact the pupillary aperture, 7 Sternberg P Jm, Hatchell DL, Foulks GN, Landers and so a comparison with the Rotterdam/ MB III: The effect of silicone oil on the . Arch O hthalmol1985, 90-4. Nagoya series is not strictly valid. Eight p 103: B Beekhuis WH, van Rij G, Zivojnovic R: Silicone oil patients in Laganowski and Leaver's series keratopathy: indications for keratopathy. Br J had lens extraction and an inferior peripheral Ophthalmol1985, 69: 24 7-53. iridectomy subsequent to silicone oil and 9 Leaver PK, Grey RHB, Garner A: Silicone oil injec­ would be more comparable, but complica­ tion in the treatment of massive preretinal retrac­ tion II. Late complications in 93 eyes. Br J tions were not reported separately for this Ophthalmol19 79, 63: 361- 7. 11 group. to Federman JL and Schubert HD: Complications No prospective comparison between infer- associated with the use of silicone oil in150 eyes THE SUPERIOR PERIPHERAL IRIDECTOMY 229

12 after retinavitreous surgery. Ophthalmology Armaly MF: Ocular tolerance to silicones. Arch 1988, 95: 870--6. Ophthalmol1962, 68: 390-5. II Laganowski He and Leaver PK: Silicone oil in the 13 Miller DK and Homan SM: Graphical aid for deter­ aphakic eye: the influenceof a six o'clock periph­ mining power of clinical trials involving two eral iridectomy. Eye1989, 3: 338-48. groups. Br Med J1988, 297: 672--6.