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Modified technique for anterior chamber decompression for high intraocular pressure following phacoemulsification
LETTERS
the results of the FDA trial demonstrate that only a small fraction of patients truly benefits from this approach.dTheo Seiler, MD, PhD, Tobias Koller, MD, Michael Mrochen, PhD Financial Interest Statement: Drs. Seiler and Mrochen are paid consultants to WaveLight. Dr. Koller has no financial interest in any product or technology mentioned. REFERENCES 1. Somani S, Tuan KA, Chernyak D. Corneal asphericity and retinal image quality: a case study and simulations. J Refract Surg 2004; 20:S581–S585 2. Manns F, Ho H, Parel J-M, Culbertson W. Ablation profiles for wavefrontguided correction of myopia and primary spherical aberration. J Cataract Refract Surg 2002; 28:766–774 3. Kezirian GM. Q-factor customized ablations. J Cataract Refract Surg 2006; 32:1979–1980
Modified technique for anterior chamber decompression for high intraocular pressure following phacoemulsification In their article demonstrating early postoperative hypotony following anterior chamber decompression as a risk factor for intraocular contamination, Chawdhary and Anand1 describe a decompression technique in which gentle pressure is applied just posterior to the cataract wound using the tip of a sterile minim. They clearly demonstrate anterior chamber contamination with the appearance of fluorescein flare or frank influx of fluorescein into the anterior chamber during the transient period of hypotony. While we agree that hypotony may result in anterior chamber contamination, this can be avoided using a slightly different technique. Since 2000, we have been routinely performing anterior chamber decompression for the same circumstances and have had no cases of hypotony or endophthalmitis. Under topical anesthesia, we use a 27-gauge needle attached to a 1.0 cc syringe to gently press on the central portion of the posterior lip of the temporally located main corneal wound. This is in contrast to pressing on the sclera just posterior to the main corneal wound using a sterile swab, as described by Chawdhary and Anand. Using our technique, we are able to control the release of small quantums of aqueous, resulting in a decrease in intraocular pressure (IOP) of 5 to 10 mm Hg per instance. We repeat the procedure as necessary until the desired IOP is attained. The type of instrument and location of decompression affect the amount of fluid released. Pressing on the sclera just posterior to the wound using a sterile minim requires more pressure to effectively induce transient wound gape to decompress the anterior chamber. Hence, there is a tendency to apply more pressure than is necessary, resulting in more aqueous egress and hypotony. Pressing on the posterior lip of the wound using an instrument with a tip that has a small surface area touching the corneal wound results in a more controlled decompression. KRISTINE E. BACSAL, MD SOON-PHAIK CHEE, FRCS Singapore
REFERENCE 1. Chawdhary S, Anand A. Early post-phacoemulsification hypotony as a risk factor for intraocular contamination: in vivo model. J Cataract Refract Surg 2006; 32:609–613
Reply: We thank Bacsal and Chee for their interest in our article.1 Several techniques can be used to induce anterior chamber decompression. It can be done through the side-port or the main corneal incision, depending on the incision site and the convenience of the slitlamp. Similarly, a sharp or a blunt instrument can be used to apply pressure to the posterior lip of the incision. Any sterile instrument that is not uncomfortable for the patient and readily available in a ward or clinic setting can be used. We use the tip of sterile minims to apply gentle pressure just posterior to the entry wound to induce decompression because patients are less apprehensive with a minim approaching the eye since they have experienced this many times during instillation of eyedrops. In our experience, increased patient apprehension with the use of a sharp instrument, such as the 27-gauge needle used by Bacsal and Chee, may reduce cooperation and increase the risk for ocular injury. A lacrimal cannula with a blunt end may be a safer option for surgeons intending to use a thinner instrument. The authors quote us using a ‘‘sterile swab’’ on sclera to induce decompression. However, we have never tried this technique and it was not mentioned in the article. Bacsal and Chee’s claim of controlled decompression by releasing small quantums of aqueous, resulting in a 5 to 10 mm Hg drop in IOP, has several shortcomings. The variations in individual corneal incisions, precompression IOP, and patient cooperation may make it difficult to consistently apply controlled pressure and achieve a 5 to 10 mm Hg drop in IOP. Anterior chamber decompression remains an uncontrolled procedure because of these variables. The authors repeat the procedure as necessary until the desired IOP is achieved and had no cases of hypotony following decompression. However, they have not clarified their desired endpoint IOP. Our aim during decompression is to induce deliberate hypotony rather than normal IOP. This is because of an anticipated rapid rise in post-decompression IOP with loss of hypotensive action in this procedure. Hildebrand et al.2 found that a mean precompression IOP of 47.1 mm Hg immediately dropped to a mean IOP of 4.7 mm Hg following the decompression procedure and then steadily rose to a mean IOP of 38.5 mm Hg within an hour of decompression. The results in our study were consistent with these findings. Therefore, even if Bacsal and Chee consistently achieved the controlled egress of aqueous, they would have to repeat the procedure several times to induce deliberate hypotony to preserve the effects of anterior chamber decompression for a meaningful period. In our article, we mentioned that irrespective of the mechanism for hypotony in the early postoperative period, the corneal wound in a hypotonic eye may become incompetent, with the risk for intraocular contamination due to the effect of suction from blinking/eyelid squeezing on a deformable globe. In this scenario, a more controlled release of small quantums of aqueous, necessitating several repetitions, would be at no less risk for intraocular contamination than an aqueous release by our method. However, if the authors’ endpoint for decompression is a normal IOP, the hypotensive effects of the procedure will be so transient that it will lose its clinical value. Bacsal and Chee have not experienced any cases of endophthalmitis with their modified technique. In our case series, no eye with intraocular contamination developed endophthalmitis. As
J CATARACT REFRACT SURG - VOL 32, DECEMBER 2006
1983
the results of the FDA trial demonstrate that only a small fraction of patients truly benefits from this approach.dTheo Seiler, MD, PhD, Tobias Koller, MD, Michael Mrochen, PhD Financial Interest Statement: Drs. Seiler and Mrochen are paid consultants to WaveLight. Dr. Koller has no financial interest in any product or technology mentioned. REFERENCES 1. Somani S, Tuan KA, Chernyak D. Corneal asphericity and retinal image quality: a case study and simulations. J Refract Surg 2004; 20:S581–S585 2. Manns F, Ho H, Parel J-M, Culbertson W. Ablation profiles for wavefrontguided correction of myopia and primary spherical aberration. J Cataract Refract Surg 2002; 28:766–774 3. Kezirian GM. Q-factor customized ablations. J Cataract Refract Surg 2006; 32:1979–1980
Modified technique for anterior chamber decompression for high intraocular pressure following phacoemulsification In their article demonstrating early postoperative hypotony following anterior chamber decompression as a risk factor for intraocular contamination, Chawdhary and Anand1 describe a decompression technique in which gentle pressure is applied just posterior to the cataract wound using the tip of a sterile minim. They clearly demonstrate anterior chamber contamination with the appearance of fluorescein flare or frank influx of fluorescein into the anterior chamber during the transient period of hypotony. While we agree that hypotony may result in anterior chamber contamination, this can be avoided using a slightly different technique. Since 2000, we have been routinely performing anterior chamber decompression for the same circumstances and have had no cases of hypotony or endophthalmitis. Under topical anesthesia, we use a 27-gauge needle attached to a 1.0 cc syringe to gently press on the central portion of the posterior lip of the temporally located main corneal wound. This is in contrast to pressing on the sclera just posterior to the main corneal wound using a sterile swab, as described by Chawdhary and Anand. Using our technique, we are able to control the release of small quantums of aqueous, resulting in a decrease in intraocular pressure (IOP) of 5 to 10 mm Hg per instance. We repeat the procedure as necessary until the desired IOP is attained. The type of instrument and location of decompression affect the amount of fluid released. Pressing on the sclera just posterior to the wound using a sterile minim requires more pressure to effectively induce transient wound gape to decompress the anterior chamber. Hence, there is a tendency to apply more pressure than is necessary, resulting in more aqueous egress and hypotony. Pressing on the posterior lip of the wound using an instrument with a tip that has a small surface area touching the corneal wound results in a more controlled decompression. KRISTINE E. BACSAL, MD SOON-PHAIK CHEE, FRCS Singapore
REFERENCE 1. Chawdhary S, Anand A. Early post-phacoemulsification hypotony as a risk factor for intraocular contamination: in vivo model. J Cataract Refract Surg 2006; 32:609–613
Reply: We thank Bacsal and Chee for their interest in our article.1 Several techniques can be used to induce anterior chamber decompression. It can be done through the side-port or the main corneal incision, depending on the incision site and the convenience of the slitlamp. Similarly, a sharp or a blunt instrument can be used to apply pressure to the posterior lip of the incision. Any sterile instrument that is not uncomfortable for the patient and readily available in a ward or clinic setting can be used. We use the tip of sterile minims to apply gentle pressure just posterior to the entry wound to induce decompression because patients are less apprehensive with a minim approaching the eye since they have experienced this many times during instillation of eyedrops. In our experience, increased patient apprehension with the use of a sharp instrument, such as the 27-gauge needle used by Bacsal and Chee, may reduce cooperation and increase the risk for ocular injury. A lacrimal cannula with a blunt end may be a safer option for surgeons intending to use a thinner instrument. The authors quote us using a ‘‘sterile swab’’ on sclera to induce decompression. However, we have never tried this technique and it was not mentioned in the article. Bacsal and Chee’s claim of controlled decompression by releasing small quantums of aqueous, resulting in a 5 to 10 mm Hg drop in IOP, has several shortcomings. The variations in individual corneal incisions, precompression IOP, and patient cooperation may make it difficult to consistently apply controlled pressure and achieve a 5 to 10 mm Hg drop in IOP. Anterior chamber decompression remains an uncontrolled procedure because of these variables. The authors repeat the procedure as necessary until the desired IOP is achieved and had no cases of hypotony following decompression. However, they have not clarified their desired endpoint IOP. Our aim during decompression is to induce deliberate hypotony rather than normal IOP. This is because of an anticipated rapid rise in post-decompression IOP with loss of hypotensive action in this procedure. Hildebrand et al.2 found that a mean precompression IOP of 47.1 mm Hg immediately dropped to a mean IOP of 4.7 mm Hg following the decompression procedure and then steadily rose to a mean IOP of 38.5 mm Hg within an hour of decompression. The results in our study were consistent with these findings. Therefore, even if Bacsal and Chee consistently achieved the controlled egress of aqueous, they would have to repeat the procedure several times to induce deliberate hypotony to preserve the effects of anterior chamber decompression for a meaningful period. In our article, we mentioned that irrespective of the mechanism for hypotony in the early postoperative period, the corneal wound in a hypotonic eye may become incompetent, with the risk for intraocular contamination due to the effect of suction from blinking/eyelid squeezing on a deformable globe. In this scenario, a more controlled release of small quantums of aqueous, necessitating several repetitions, would be at no less risk for intraocular contamination than an aqueous release by our method. However, if the authors’ endpoint for decompression is a normal IOP, the hypotensive effects of the procedure will be so transient that it will lose its clinical value. Bacsal and Chee have not experienced any cases of endophthalmitis with their modified technique. In our case series, no eye with intraocular contamination developed endophthalmitis. As
J CATARACT REFRACT SURG - VOL 32, DECEMBER 2006
1983