Managing Postoperative Pupillary Membranes

Managing Postoperative Pupillary Membranes

LETTERS inconsistent vision , the expense of multiple fittings , and significant comp lication risks of their own . The recent improvements in PKP ha...

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LETTERS

inconsistent vision , the expense of multiple fittings , and significant comp lication risks of their own . The recent improvements in PKP have improved the risk/benefit ratio of the procedure to a point where it should be considered as a primary alternative for the experienced refractive surgeon when approaching a patient with early to moderate keratoconus . In my opinion , only experienced corneal surgeons should be performing PKP. As Drs. Sugar and McLeod suggested, this does raise public health issues if inexperienced , untrained general ophthalmologists are allowed to perform PKP. The results demonstrated in this paper also prove the point that in the hands of an experienced, meticulous corneal surgeon, excellent results are obtainable. In this age of health maintenance organ izations (HMOs) and general distrust of professionalism, it is particularly appropriate to note the excellent results that can be obtained with an experienced corneal transplant surgeon . Many HMOs have no cornea specialist. In my opinion, this is a disservice to their patients, posing a public health hazard .-Kurt A. Buzard, MD

Repair of Wound Dehiscence

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n their paper, I Buzard and Fundingsland provide documentation of a generous volume of keratoconus patients. However, 1 was surprised that 31 % of patients required wound dehiscence repair. While the use of the vacuum trephine, particularly in keratoconus patients, is known to cause undercutting of the host peripheral tissue with resultant thin peripheral support and possible leak or dehiscence, the trephine technique was not identified. Also, the fact that peripheral host tissue required trimming with scissors implied that a vacuum trephine technique was not used. Since one third of corneal transplant patients in any diagnostic category should not routinely require resuturing or other treatment for dehiscence, please provide clarification. SAMUEL M. SALAMON, MD, FRCSC

Cleveland, Ohio, USA Reference 1. Buzard KA, Fundingsland BR. Corneal transplant for keratoconus: results in early and late disease. J Cataract Refract Surg

1997; 23:398-406

Reply: The issue of repair of wound dehiscence during the "sutures in " phase of the postoperative course after corneal transplant is not a repair of frank dehiscence (in 972

fact, I have not had a corneal transplant wound that leaked in any of the cases) but is an alternative to the sequential removal of sutures to control astigmatism in the "sutures in" period described by Binder, Waring, and others. As an aside, I am very aware of the issue of undercutting of the host opening and do not use a Hessberg trephine for this reason . I have described both the technique and indications for application of this technique to reduce postoperative astigmatism and to stabilize spherical equivalent. The average 43.00 diopter (D) keratometery readings postkeratoplasty combined with the excellent uncorrected visual acuities support the application of additional sutures and repair of the "microdehiscence." This is in distinction to early removal of sutures in which the keratometry readings often average 46.00 to 48.00 D. These patients are often left significantly myopic and the simple act of removing sutures at the conclusion of wound healing often results in an unstable corneal transplant wound with steepening of the graft. There are those who feel that the type of suture pattern, specifics of intraoperative technique (such as through and through suturing), and sutures in postoperative management have little effect on the ultimate refractive outcome of the graft, but this paper clearly demonstrates otherwise. Considered individually, each small innovation may be difficult to gauge in terms of the overall improvement in corneal transplantation , but added together corneal transplantation has undergone a revolution that has not been generally recognized in the ophthalmic community. Repair of the wound dehiscence, replacing the unwise sequential early removal of sutures, is one such innovation.-Kurt A. Buzard, MD

Managing Postoperative Pupillary Membranes

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e read with interest the article on the application of the neodymium:YAG (Nd:YAG) laser in the management of postoperative pupillary fibrin membrane by Virdi and coauthors. I Laser discission of anterior chamber fibrin membranes that are unresponsive to medical therapy carries some obvious advantages. It is a relatively noninvasive procedure that can be done under local anesthesia on an outpatient basis. Although this technique appears to be effective and safe, it does carry some potential risks and disadvantages. 2 The laser treatment may damage the implanted intraocular lens (IOL) and carries the risk of irritating the iris with further inflammatory consequences. There is a possibility of intraocular pressure rise and deleteri-

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LETTERS

ous effects on the corneal endothelium. Additionally, the laser equipment is expensive to own and maintain and thus may not be readily available in all settings, especially in developing countries. We recently saw a middle-aged Chinese woman with uveitic cataract in whom we had performed an extracapsular cataract extraction (ECCE) with capsular IOL implantation. On the first postoperative day, she was found to have a pupillary fibrin membrane developing, which turned out to be unresponsive to frequent topical and subconjunctival steroid treatment. On postoperative day 7, we planned to treat the patient with anterior chamber recombinant tissue plasminogen activator (tPA) injection. Twenty-five micrograms of tPA in 0.1 mL solution was prepared in a 1.0 mL syringe with a 30 gauge needle attached. The procedure was performed under topical anesthesia with standard aseptic techniques at the slitlamp. A lid speculum was used for better exposure. Before we injected the tPA, the fibrin membrane was mechanically disrupted and separated from the pupillary margin with the needle passed through a peripheral corneal site in the anterior chamber. The fibrin membrane, after being separated from the IOL and the pupillary margin, rapidly contracted and shrank into something like a tiny cotton ball measuring about 0.5 mm in diameter. Since the fibrin membrane had now been totally separated from the IOL and pupillary margin and sank into the inferior part of the anterior chamber, tPA injection was withheld. The contracted fibrin material was observed to disappear completely over the subsequent 36 hours. In another diabetic woman who had had cataract extraction and IOL implantation also complicated by a pupillary fibrin membrane, a similar mechanical discission of the fibrin membrane with a 30 gauge needle was performed on postoperative day 8. The contracted fibrin material dissolved within 36 hours. The successful use of tPA to treat postvitrectomy fibrin formation has been well documented. 3 Application of tPA in the treatment of postcataract fibrin membrane was, to our knowledge, first reported by Moon et al. in 1992. 4They performed this maneuver in 52 eyes and reported complete fibrinolysis in 90% of eyes and partial fibrinolysis in the remaining 10%. They claimed that 47% of the fibrin membranes were lysed within 30 minutes, while the remainder were lysed within 1 hour. Complications included pain

(4 eyes), anterior chamber hemorrhage (4 eyes), and

anterior chamber turbidity (3 eyes). Both Nd:YAG laser discission and tPA injection are effective in treating postoperative pupillary membranes.1.3,4 However, they have some potential side effects and problems. Also, Nd:YAG lasers may not be readily available, and tPA is very expensive. Both patients mentioned had complete resolution of the pupillary fibrin membrane without laser surgery or tPA injection. We propose that simple mechanical discission of postoperative pupillary fibrin membrane be considered when there is a persistent membrane despite good inflammation control. In such a situation, the mechanical discission is best done around postoperative day 7 to 10, when the contractile component of the fibrin membrane is prominent. DENNIS S.c. LAM, FRCS, FRCOPHTH CLEMENT c.Y. THAM, BM, BCH ALFRED T.S. LEUNG, FRCS DOROTHY S.P. FAN, MBCHB

Shatin, Hong Kong References 1. Virdi M, Beirouty ZAY, Saba SN. Neodymium:YAG laser discission of postoperative pupillary membrane: peripheral photodisruption. J Cataract Refract Surg 1997; 23:166-168 2. Liebmann JM, Ritch R. Laser iridotomy. Ophthalmic Surg Lasers 1996; 27:209-222 3. Jaffe GJ, Abrams Gw, Williams GA, Han DP. Tissue plasminogen activator for postvitrectomy fibrin formation. Ophthalmology 1990; 97:184-189 4. Moon J, Chung S, Myong Y, et aI. Treatment of postcataract fibrinous membranes with tissue plasminogen activator. Ophthalmology 1992; 99: 1256-1259

Experience with PRK for Hyperopia

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he article by Dausch et al. 1 on photorefractive keratectomy (PRK) for hyperopia was a positive contribution to the subject. I have carried out the same form of treatment at The Eye Academy in 45 eyes with a follow-up of 12 months and have had basically similar results. I would like, however, to make the following comments. We have found definite differences in response of the low hyperopes (up to +3.50) and the higher hyperopes (up to +6.50). In our experience, at 6 months all behaved in the same fashion. However, at 1 year the low hyperopes were stable with no significant

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