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Gonioscopic changes after ICL implantation in myopic eyes:Reply
LETTERS
Reply: Drs. Trindade and Pereira are correct that their observations published in 1998 underline the results found in our study. The method used in their study gives insight into what is going on below the iris and observes much better the positioning of the haptics in the sulcus. Their work confirms our results that narrowing of the angle takes place months after surgery. They also did not observe any cases with angle closure or pigmentary glaucoma, the same as in our study, although our study has a longer postoperative follow-up. Finally, we agree that the long-term safety of ICL implantation has to be carefully evaluated, especially since most patients who receive an ICL are young.—Claudette Abela-Formanek, MD
Pars Plana Vitreous Tap in Crowded Eyes
W
e appreciate the technique of pars plana vitreous tap for phacoemulsification in crowded eyes1 because it helps to expand the anterior segment and permits comfortable phacoemulsification in these high-risk eyes. Chang suggests that a small amount of vitreous (approximately 0.2 mL) be aspirated by an automated vitrectomy handpiece without infusion through a pars plana sclerotomy. Although it is mentioned that this technique decreases the potential for vitreous traction compared with aspiration with a needle, Han et al.2 have analyzed the data of the Endophthalmitis Vitrectomy Study and shown that there is no significant difference between a mechanized vitreous biopsy and a needle tap with respect to operative complications and retinal detachment over a 9- to 12-month period. In addition, it may be difficult to exactly measure the quantity of the vitreous aspirated while using the vitrectomy handpiece, and a vitrectomy machine may not be readily available to all surgeons in our subcontinent. A simple technique for doing the vitreous tap is to take a 23- to 26-gauge needle mounted on a 1 mL tuberclin syringe. The plunger of the syringe is removed, and the needle is inserted 3.5 mm behind the limbus into the vitreous cavity. A small amount of vitreous passively flows into the syringe, without the need for suction. This is more so in cases in which the intraocular pressure (IOP) is on the high side, as in 2 of the cases described in the present study. This may be sufficient to deepen the anterior segment adequately after injection of the viscoelastic substance. Since the plunger is not used, no suction is applied and thus there is no danger of
exerting traction on the vitreous. One can also titrate the exact amount of vitreous withdrawn. In addition to facilitating surgery in crowded eyes, this technique is especially useful in eyes with phacomorphic glaucoma with a high IOP on maximal medical therapy. Besides deepening the anterior chamber, it decompresses the eye and thus reduces the IOP. This significantly facilitates cataract surgery or combined cataract and glaucoma surgery and helps prevent intraoperative complications. Thus, the technique of needle aspiration offers several advantages over a mechanized vitreous cutter: (1) It is a simple technique that can be performed without the need for a vitrectomy machine. (2) The amount of vitreous aspirated can be accurately titrated. (3) No active suction is applied, and thus there is no vitreous traction. (4) The wound is small and self-sealing. We therefore suggest passive vitreous aspiration with a needle inserted through the pars plana, combined with injection of a high-viscosity viscoelastic agent into the anterior chamber, as an alternative technique to expand the anterior chamber in high-risk eyes prior to phacoemulsification. HARINDER SETHI, MD TANUJ DADA, MD New Delhi, India
References 1. Chang DF. Pars plana vitreous tap for phacoemulsification in the crowded eye. J Cataract Refract Surg 2001; 27: 1911–1914 2. Han DP, Wisniewski SR, Kelsey SF, et al. Microbiologic yields and complication rates of vitreous needle aspiration versus mechanized vitreous biopsy in the Endophthalmitis Vitrectomy Study. Retina 1999; 19:576 –578
Reply: I would like to thank Drs. Sethi and Dada for their useful observations and suggestions. They point out that a vitrectomy machine may not be available in certain locations, and I agree that their method would be preferable to suctionneedle aspiration in this circumstance. However, I disagree that this technique is superior to using a mechanized vitrector for the vitreous tap if the latter is available. 1. If a needle is used, it must locate a pocket of liquefied vitreous for passive flow to occur. This may require that searching movements be made with the needle. The cases with miotic pupils and advanced or mature lenses that I described made the vitreous tap a “blind” procedure. The advantage of using a vitreous cutter is that the instrument need only be inserted a short distance into the eye because even formed vitreous can be removed.
J CATARACT REFRACT SURG—VOL 28, NOVEMBER 2002
1897
Reply: Drs. Trindade and Pereira are correct that their observations published in 1998 underline the results found in our study. The method used in their study gives insight into what is going on below the iris and observes much better the positioning of the haptics in the sulcus. Their work confirms our results that narrowing of the angle takes place months after surgery. They also did not observe any cases with angle closure or pigmentary glaucoma, the same as in our study, although our study has a longer postoperative follow-up. Finally, we agree that the long-term safety of ICL implantation has to be carefully evaluated, especially since most patients who receive an ICL are young.—Claudette Abela-Formanek, MD
Pars Plana Vitreous Tap in Crowded Eyes
W
e appreciate the technique of pars plana vitreous tap for phacoemulsification in crowded eyes1 because it helps to expand the anterior segment and permits comfortable phacoemulsification in these high-risk eyes. Chang suggests that a small amount of vitreous (approximately 0.2 mL) be aspirated by an automated vitrectomy handpiece without infusion through a pars plana sclerotomy. Although it is mentioned that this technique decreases the potential for vitreous traction compared with aspiration with a needle, Han et al.2 have analyzed the data of the Endophthalmitis Vitrectomy Study and shown that there is no significant difference between a mechanized vitreous biopsy and a needle tap with respect to operative complications and retinal detachment over a 9- to 12-month period. In addition, it may be difficult to exactly measure the quantity of the vitreous aspirated while using the vitrectomy handpiece, and a vitrectomy machine may not be readily available to all surgeons in our subcontinent. A simple technique for doing the vitreous tap is to take a 23- to 26-gauge needle mounted on a 1 mL tuberclin syringe. The plunger of the syringe is removed, and the needle is inserted 3.5 mm behind the limbus into the vitreous cavity. A small amount of vitreous passively flows into the syringe, without the need for suction. This is more so in cases in which the intraocular pressure (IOP) is on the high side, as in 2 of the cases described in the present study. This may be sufficient to deepen the anterior segment adequately after injection of the viscoelastic substance. Since the plunger is not used, no suction is applied and thus there is no danger of
exerting traction on the vitreous. One can also titrate the exact amount of vitreous withdrawn. In addition to facilitating surgery in crowded eyes, this technique is especially useful in eyes with phacomorphic glaucoma with a high IOP on maximal medical therapy. Besides deepening the anterior chamber, it decompresses the eye and thus reduces the IOP. This significantly facilitates cataract surgery or combined cataract and glaucoma surgery and helps prevent intraoperative complications. Thus, the technique of needle aspiration offers several advantages over a mechanized vitreous cutter: (1) It is a simple technique that can be performed without the need for a vitrectomy machine. (2) The amount of vitreous aspirated can be accurately titrated. (3) No active suction is applied, and thus there is no vitreous traction. (4) The wound is small and self-sealing. We therefore suggest passive vitreous aspiration with a needle inserted through the pars plana, combined with injection of a high-viscosity viscoelastic agent into the anterior chamber, as an alternative technique to expand the anterior chamber in high-risk eyes prior to phacoemulsification. HARINDER SETHI, MD TANUJ DADA, MD New Delhi, India
References 1. Chang DF. Pars plana vitreous tap for phacoemulsification in the crowded eye. J Cataract Refract Surg 2001; 27: 1911–1914 2. Han DP, Wisniewski SR, Kelsey SF, et al. Microbiologic yields and complication rates of vitreous needle aspiration versus mechanized vitreous biopsy in the Endophthalmitis Vitrectomy Study. Retina 1999; 19:576 –578
Reply: I would like to thank Drs. Sethi and Dada for their useful observations and suggestions. They point out that a vitrectomy machine may not be available in certain locations, and I agree that their method would be preferable to suctionneedle aspiration in this circumstance. However, I disagree that this technique is superior to using a mechanized vitrector for the vitreous tap if the latter is available. 1. If a needle is used, it must locate a pocket of liquefied vitreous for passive flow to occur. This may require that searching movements be made with the needle. The cases with miotic pupils and advanced or mature lenses that I described made the vitreous tap a “blind” procedure. The advantage of using a vitreous cutter is that the instrument need only be inserted a short distance into the eye because even formed vitreous can be removed.
J CATARACT REFRACT SURG—VOL 28, NOVEMBER 2002
1897