Veterinary Ophthalmology (2015) 18, 3, 221–228
DOI:10.1111/vop.12143
Effects of pulsed fluid lens capsule washing following phacoemulsification on lens epithelial cells and posterior capsule opacification formation ex vivo Elizabeth A. Lutz,* Anne J. Gemensky-Metzler,* David A. Wilkie* and Heather L. Chandler*,† *Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA; and †College of Optometry, The Ohio State University, Columbus, OH, USA
Address communications to: H. L. Chandler Tel.: 614-247-0005 Fax: 614-688-4474 e-mail: [email protected]
Presented in part at the 41st Annual Conference of the American College of Veterinary Ophthalmologists; San Diego, CA, USA, October 2010.
Abstract Background The aim of the study was to evaluate ex vivo the effects of using a custom tip to direct a pulsed stream of fluid to remove residual lens epithelial cells (LECs) and reduce posterior capsule opacification (PCO) formation following phacoemulsification. Methods Twenty-four canine cadaver eyes were assigned to one of three treatment groups. Six eyes (Control Group) had standard phacoemulsification only, nine eyes (Group 1) had standard phacoemulsification followed by capsular washing using intermediate settings (power = 40%, pulses per second [PPS] = 50, 30 s washing per capsule hemisphere), and nine eyes (Group 2) had standard phacoemulsification followed by aggressive capsular washing (power = 60%, PPS = 50, 60 s washing per capsule hemisphere). Results Control lens capsules had diffuse LECs remaining following standard phacoemulsification and complete ex vivo PCO formation (confluent LECs on the posterior capsule) within 4 2 days (range 2–8 days). Group 1 lens capsules had focal, equatorial LEC clusters remaining following treatment, and complete PCO formation within 9 2 days (range 5–11 days). Group 2 lens capsules had little to no LECs observed following treatment; 5 of 9 capsules had complete PCO formation within 13 2 days (range 9–14 days), and 4 of 9 capsules had no PCO formation by 24 days post-treatment. Conclusions Pulsed fluid lens capsule washing is capable of removing LECs and delaying PCO formation in canine eyes following phacoemulsification ex vivo. Use of more aggressive capsular washing settings resulted in more effective LEC removal and subsequent delay of ex vivo PCO. Key Words: canine, capsule washing, cataract surgery, ex vivo, lens epithelial cells, posterior capsule opacification
INTRODUCTION
Cataracts are the most common cause of visual impairment in dogs and humans, and of treatable blindness worldwide.1–3 Phacoemulsification with intraocular lens (IOL) implantation is the standard of care for restoration of vision.3 Cataract surgery is the most frequently performed ophthalmic surgery,2,4 and the most common long-term post-operative complication following phacoemulsification is posterior capsule opacification (PCO).1–3,5–8 Anterior and equatorial lens epithelial cells (LECs) that remain in the lens capsule following irrigation © 2014 American College of Veterinary Ophthalmologists
and aspiration undergo epithelial to mesenchymal transition (EMT), proliferation, and posterior migration along all interior surfaces of the capsule and IOL to form PCO.1–3,6,7,9–11 PCO and capsule wrinkling can obstruct the visual axis by causing secondary image distortion, light scatter, traction-induced IOL decentration, and visual impairment.1,3–6,10,11 The development of PCO is multifactorial in nature and is influenced by surgical technique, IOL biocompatibility and design, patient age, stage of cataract, and systemic and local host factors including species.1,2,10,11 Clinical studies have reported a variable incidence of PCO in adult humans
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that approaches 60%;2,5,9,12 however, in canine and pediatric human patients, the incidence of PCO formation closely approaches 100% by one-year post-operatively.1,2,13 Because meticulous surgical technique and advanced IOL design with maximal posterior capsule contact have historically been unable to completely prevent or even delay PCO formation in some patients, several mechanical and pharmaceutical methods to prevent PCO through the elimination of residual LEC following phacoemulsification have been attempted with variable short-term efficacy, and none with permanent success.1,4,7,9 As a result, innovative alternative methods by which to remove residual LEC from the capsule at the time of surgery are critical. The AquaLase liquefaction handpiece is a component of the Alconâ Infiniti Vision System phacoemulsification unit (Alcon Laboratories, Fort Worth, TX) that employs a fluidbased erosion technology for cataract removal (as opposed to conventional ultrasound phacoemulsification). This handpiece also has the potential to remove residual LECs with mechanical washing following phacoemulsification. The custom tip is constructed from plastic and stainless steel. Electrodes within the handpiece generate small pulses of warmed balanced salt solution (BSS) that exit the lumen through a flared, rounded-bevel polymer tip. BSS pulses are delivered via the AquaLase handpiece at a maximal rate of 50 pulses per second. Adjustable parameters include fluid pulse rate and pulse magnitude. This capsule washing technology has been proposed to pose a decreased risk of posterior capsule rupture, when compared with conventional phacoemulsification needles due to its smooth polymer tip, and decreased risk of thermal incisional and intraocular tissue damage from nonthermal, fluid-based technology.14–25 The purpose of this study was to prospectively evaluate the ability of using a custom tip to direct a pulsed stream of fluid to remove residual LEC at the time of routine cataract surgery and prevent subsequent PCO formation in an ex vivo canine model. MATERIALS AND METHODS
Tissues Twenty-four normal canine cadaver eyes were obtained from dogs between the ages of 3–6 years of age, deemed to be in good general health, that were humanely euthanized for reasons unrelated to this study. This research was approved by The Ohio State University Institutional Animal Care and Use Committee and followed the ARVO Resolution on the Use of Animals in Research. Eyes were collected immediately following euthanasia, rinsed in 2% betadine solution and stored in 1X phosphate-buffered saline solution (PBS, pH 7.2) at 4 °C until phacoemulsification was performed the following day (within 12 h of enucleation). Mock cataract surgery Mock cataract surgery was performed in canine cadaver eyes using a modified version of a previously established
ex vivo PCO model.6 Surgical procedures were performed at The Ohio State University, Veterinary Medical Center by three surgeons (EAL, DAW, and AGM) using the Infiniti Vision System phacoemulsification unit (Alcon). To perform surgery, each eye was secured on a styrofoam block using pins placed through bulbar conjunctival tissues. Briefly, a scalpel blade was used to incise and remove each cornea 1 mm anterior to the limbus to aid in intraocular visualization. A small corneal rim was left intact in the dorsal limbal cornea, through which two 3.2-mm limbal incisions were made 60° apart to accommodate the phacoemulsification and AquaLase handpieces in a manner that would most closely approximate in vivo physical handpiece constraints. An anterior continuous curvilinear capsulorhexis was performed, and eyes were randomly assigned to one of three treatment groups. Standard ultrasonic lens phacoemulsification, cortical irrigation and aspiration, and capsule polishing were performed for all eyes in all treatment groups, using a phacoemulsification surgical technique that has previously been described (OZiL ultrasonic phacoemulsification handpiece, Alcon, Fort Worth, TX; Microscope; Zeiss S5, Carl Zeiss Microscopy, LLC, Thornwood, NY).26 Amount of time spent and fluid used for capsule polishing were standardized between all treatment groups using an irrigation and aspiration handpiece (irrigating/aspirating handpiece 17 gauge 0.5 mm 45°, Bausch & Lomb Storz, Rochester, NY). Following routine phacoemulsification and capsule polishing, each eye was treated according to a previously designated course of capsule washing. Six eyes (Control Group) received no capsule washing, nine eyes (Group 1) received capsule washing using intermediate settings (vacuum limit 40 mmHg, 50 pulses per second [PPS], 30 s of washing per 180-degree capsule hemisphere), and nine eyes (Group 2) received capsule washing using more aggressive settings (vacuum limit 60 mmHg, 50 PPS, 60 s of washing per 180-degree capsule hemisphere). Capsule washing was performed with the capsule washing tip positioned 1–3 mm away from the interior surface of the lens capsule, and the handpiece tip was directed equatorially and anteriorly within the capsule during treatment. Small pulses of warm BSS (Alcon) were delivered through the capsule washing tip, which was directed in a horizontal sweeping motion within the capsule. Fluid temperature was maintained by the Infiniti Vision System unit at 57 °C. Fluid temperature and PPS described here have previously been deemed safe for intraocular use in humans.26 Each limbal incision site was used to treat one capsule hemisphere. Following capsule washing, Vannas scissors were used to gently excise the lens capsule from its zonular and vitreal attachments.
Lens capsule culture Excised capsules were placed in individual sterile petri dishes (with the capsulotomy facing up), and 5 mL of DMEM (Dulbecco’s minimum essential medium, Gibco,
© 2014 American College of Veterinary Ophthalmologists, Veterinary Ophthalmology, 18, 221–228
lens capsule washing on pco formation 223
Carlsbad, NY) containing 1% antibiotic and antimycotic (Invitrogen Corporation, Grand Island, NY) was used to inflate and bathe each capsule. Culture medium redistended the lens capsule, providing separation between the anterior and posterior capsules. Capsules were placed in a 37 °C, 5% CO2 incubator, treated with fresh culture media daily, and were monitored using inverted light microscopy once every 24 h for 24 days following treatment. To evaluate the effect of capsule washing on the number of residual LECs 24 h following surgery, a categorical value was assigned to reflect the relative amount of residual LEC that remained within each capsule: 0 = no LEC observed, 1 = few focal aggregates of LEC (
DOI:10.1111/vop.12143
Effects of pulsed fluid lens capsule washing following phacoemulsification on lens epithelial cells and posterior capsule opacification formation ex vivo Elizabeth A. Lutz,* Anne J. Gemensky-Metzler,* David A. Wilkie* and Heather L. Chandler*,† *Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH, USA; and †College of Optometry, The Ohio State University, Columbus, OH, USA
Address communications to: H. L. Chandler Tel.: 614-247-0005 Fax: 614-688-4474 e-mail: [email protected]
Presented in part at the 41st Annual Conference of the American College of Veterinary Ophthalmologists; San Diego, CA, USA, October 2010.
Abstract Background The aim of the study was to evaluate ex vivo the effects of using a custom tip to direct a pulsed stream of fluid to remove residual lens epithelial cells (LECs) and reduce posterior capsule opacification (PCO) formation following phacoemulsification. Methods Twenty-four canine cadaver eyes were assigned to one of three treatment groups. Six eyes (Control Group) had standard phacoemulsification only, nine eyes (Group 1) had standard phacoemulsification followed by capsular washing using intermediate settings (power = 40%, pulses per second [PPS] = 50, 30 s washing per capsule hemisphere), and nine eyes (Group 2) had standard phacoemulsification followed by aggressive capsular washing (power = 60%, PPS = 50, 60 s washing per capsule hemisphere). Results Control lens capsules had diffuse LECs remaining following standard phacoemulsification and complete ex vivo PCO formation (confluent LECs on the posterior capsule) within 4 2 days (range 2–8 days). Group 1 lens capsules had focal, equatorial LEC clusters remaining following treatment, and complete PCO formation within 9 2 days (range 5–11 days). Group 2 lens capsules had little to no LECs observed following treatment; 5 of 9 capsules had complete PCO formation within 13 2 days (range 9–14 days), and 4 of 9 capsules had no PCO formation by 24 days post-treatment. Conclusions Pulsed fluid lens capsule washing is capable of removing LECs and delaying PCO formation in canine eyes following phacoemulsification ex vivo. Use of more aggressive capsular washing settings resulted in more effective LEC removal and subsequent delay of ex vivo PCO. Key Words: canine, capsule washing, cataract surgery, ex vivo, lens epithelial cells, posterior capsule opacification
INTRODUCTION
Cataracts are the most common cause of visual impairment in dogs and humans, and of treatable blindness worldwide.1–3 Phacoemulsification with intraocular lens (IOL) implantation is the standard of care for restoration of vision.3 Cataract surgery is the most frequently performed ophthalmic surgery,2,4 and the most common long-term post-operative complication following phacoemulsification is posterior capsule opacification (PCO).1–3,5–8 Anterior and equatorial lens epithelial cells (LECs) that remain in the lens capsule following irrigation © 2014 American College of Veterinary Ophthalmologists
and aspiration undergo epithelial to mesenchymal transition (EMT), proliferation, and posterior migration along all interior surfaces of the capsule and IOL to form PCO.1–3,6,7,9–11 PCO and capsule wrinkling can obstruct the visual axis by causing secondary image distortion, light scatter, traction-induced IOL decentration, and visual impairment.1,3–6,10,11 The development of PCO is multifactorial in nature and is influenced by surgical technique, IOL biocompatibility and design, patient age, stage of cataract, and systemic and local host factors including species.1,2,10,11 Clinical studies have reported a variable incidence of PCO in adult humans
222 lutz
ET AL.
that approaches 60%;2,5,9,12 however, in canine and pediatric human patients, the incidence of PCO formation closely approaches 100% by one-year post-operatively.1,2,13 Because meticulous surgical technique and advanced IOL design with maximal posterior capsule contact have historically been unable to completely prevent or even delay PCO formation in some patients, several mechanical and pharmaceutical methods to prevent PCO through the elimination of residual LEC following phacoemulsification have been attempted with variable short-term efficacy, and none with permanent success.1,4,7,9 As a result, innovative alternative methods by which to remove residual LEC from the capsule at the time of surgery are critical. The AquaLase liquefaction handpiece is a component of the Alconâ Infiniti Vision System phacoemulsification unit (Alcon Laboratories, Fort Worth, TX) that employs a fluidbased erosion technology for cataract removal (as opposed to conventional ultrasound phacoemulsification). This handpiece also has the potential to remove residual LECs with mechanical washing following phacoemulsification. The custom tip is constructed from plastic and stainless steel. Electrodes within the handpiece generate small pulses of warmed balanced salt solution (BSS) that exit the lumen through a flared, rounded-bevel polymer tip. BSS pulses are delivered via the AquaLase handpiece at a maximal rate of 50 pulses per second. Adjustable parameters include fluid pulse rate and pulse magnitude. This capsule washing technology has been proposed to pose a decreased risk of posterior capsule rupture, when compared with conventional phacoemulsification needles due to its smooth polymer tip, and decreased risk of thermal incisional and intraocular tissue damage from nonthermal, fluid-based technology.14–25 The purpose of this study was to prospectively evaluate the ability of using a custom tip to direct a pulsed stream of fluid to remove residual LEC at the time of routine cataract surgery and prevent subsequent PCO formation in an ex vivo canine model. MATERIALS AND METHODS
Tissues Twenty-four normal canine cadaver eyes were obtained from dogs between the ages of 3–6 years of age, deemed to be in good general health, that were humanely euthanized for reasons unrelated to this study. This research was approved by The Ohio State University Institutional Animal Care and Use Committee and followed the ARVO Resolution on the Use of Animals in Research. Eyes were collected immediately following euthanasia, rinsed in 2% betadine solution and stored in 1X phosphate-buffered saline solution (PBS, pH 7.2) at 4 °C until phacoemulsification was performed the following day (within 12 h of enucleation). Mock cataract surgery Mock cataract surgery was performed in canine cadaver eyes using a modified version of a previously established
ex vivo PCO model.6 Surgical procedures were performed at The Ohio State University, Veterinary Medical Center by three surgeons (EAL, DAW, and AGM) using the Infiniti Vision System phacoemulsification unit (Alcon). To perform surgery, each eye was secured on a styrofoam block using pins placed through bulbar conjunctival tissues. Briefly, a scalpel blade was used to incise and remove each cornea 1 mm anterior to the limbus to aid in intraocular visualization. A small corneal rim was left intact in the dorsal limbal cornea, through which two 3.2-mm limbal incisions were made 60° apart to accommodate the phacoemulsification and AquaLase handpieces in a manner that would most closely approximate in vivo physical handpiece constraints. An anterior continuous curvilinear capsulorhexis was performed, and eyes were randomly assigned to one of three treatment groups. Standard ultrasonic lens phacoemulsification, cortical irrigation and aspiration, and capsule polishing were performed for all eyes in all treatment groups, using a phacoemulsification surgical technique that has previously been described (OZiL ultrasonic phacoemulsification handpiece, Alcon, Fort Worth, TX; Microscope; Zeiss S5, Carl Zeiss Microscopy, LLC, Thornwood, NY).26 Amount of time spent and fluid used for capsule polishing were standardized between all treatment groups using an irrigation and aspiration handpiece (irrigating/aspirating handpiece 17 gauge 0.5 mm 45°, Bausch & Lomb Storz, Rochester, NY). Following routine phacoemulsification and capsule polishing, each eye was treated according to a previously designated course of capsule washing. Six eyes (Control Group) received no capsule washing, nine eyes (Group 1) received capsule washing using intermediate settings (vacuum limit 40 mmHg, 50 pulses per second [PPS], 30 s of washing per 180-degree capsule hemisphere), and nine eyes (Group 2) received capsule washing using more aggressive settings (vacuum limit 60 mmHg, 50 PPS, 60 s of washing per 180-degree capsule hemisphere). Capsule washing was performed with the capsule washing tip positioned 1–3 mm away from the interior surface of the lens capsule, and the handpiece tip was directed equatorially and anteriorly within the capsule during treatment. Small pulses of warm BSS (Alcon) were delivered through the capsule washing tip, which was directed in a horizontal sweeping motion within the capsule. Fluid temperature was maintained by the Infiniti Vision System unit at 57 °C. Fluid temperature and PPS described here have previously been deemed safe for intraocular use in humans.26 Each limbal incision site was used to treat one capsule hemisphere. Following capsule washing, Vannas scissors were used to gently excise the lens capsule from its zonular and vitreal attachments.
Lens capsule culture Excised capsules were placed in individual sterile petri dishes (with the capsulotomy facing up), and 5 mL of DMEM (Dulbecco’s minimum essential medium, Gibco,
© 2014 American College of Veterinary Ophthalmologists, Veterinary Ophthalmology, 18, 221–228
lens capsule washing on pco formation 223
Carlsbad, NY) containing 1% antibiotic and antimycotic (Invitrogen Corporation, Grand Island, NY) was used to inflate and bathe each capsule. Culture medium redistended the lens capsule, providing separation between the anterior and posterior capsules. Capsules were placed in a 37 °C, 5% CO2 incubator, treated with fresh culture media daily, and were monitored using inverted light microscopy once every 24 h for 24 days following treatment. To evaluate the effect of capsule washing on the number of residual LECs 24 h following surgery, a categorical value was assigned to reflect the relative amount of residual LEC that remained within each capsule: 0 = no LEC observed, 1 = few focal aggregates of LEC (
