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Influence of Elevated Intraocular Pressure on the Posterior Chamber–Anterior Hyaloid Membrane Barrier During Cataract Operations

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Influence of Elevated Intraocular Pressure on the Posterior Chamber–Anterior Hyaloid Membrane Barrier During Cataract Operations LABORATORY SCIENCES Influence of Elevated Intraocular Pressure on the Posterior Chamber–Anterior Hyaloid Membrane Barrier During Cataract Operations Shiro Kawasaki, MD; Yoshitaka Tasaka, MD; Takashi Suzuki, MD; Xiaodong Zheng, MD, PhD; Atsushi Shiraishi, MD; Toshihiko Uno, MD; Yuichi Ohashi, MD Objective: To investigate the influence of elevated in- (Spearman rank correlation; r=0.703, PϽ.001). In ex- traocular pressure on the posterior chamber–anterior hya- periment 2, mean peak intraocular pressure was signifi- loid membrane (PC-AHM) barrier during cataract op- cantly greater in the ruptured capsule–type eyes than in erations in ex vivo porcine eyes. the AC-, zonule of Zinn–, AHM (PϽ.001), or AHM- tear– (P=.02) type eyes, as well as in the AHM- and AHM- Methods: A pressure transducer was connected to por- tear–type eyes compared with the AC and zonule of Zinn cine eye anterior chambers (ACs). In experiment 1, ACs type eyes (PϽ.001). Intraocular pressure was signifi- were perfused for 20 seconds with balanced salt solu- cantly higher in eyes infused with ophthalmic viscosur- tion containing 1.0-µm fluorescein beads (10 eyes per gical devices with a higher molecular weight or sodium bottle height: 45, 85, 145, and 285 cm). In experiment hyaluronate concentration (PϽ.05). 2, 5 ophthalmic viscosurgical devices with different mo- lecular weights and sodium hyaluronate concentrations Conclusions: Stress on the PC-AHM barrier increases were infused into the ACs (20 eyes per ophthalmic vis- as intraocular pressure increases. Ophthalmic viscosur- cosurgical device). After continuous curvilinear capsu- gical devices with a higher molecular weight or sodium lorrhexis, hydrodissection was performed. After both ex- hyaluronate concentration might induce increased IOP periments, PC-AHM barrier staining was evaluated during cataract operations. through the Miyake-Apple view. Clinical Relevance: To maintain normal PC-AHM bar- Results: Types of fluorescein staining patterns were clas- rier function, excessive intraocular pressure should be sified as AC, zonule of Zinn, AHM, AHM tear, and rup- avoided during cataract operations. tured capsule. In experiment 1, plateau intraocular pres- sure and staining type were positively correlated Arch Ophthalmol. 2011;129(6):751-757 HE SPACE BETWEEN THE Hydrodissection is necessary to sepa- posterior capsule of the rate the lens nucleus and capsule.3-5 How- lens and the anterior ever, in humans, this procedure has been hyaloid membrane (AHM) reported to cause posterior capsule rup- is thought to act as a ture,6 lens nucleus dislocation,7 and de- Tmechanical barrier separating the physi- tachment of the AHM.8 Rapid fluctua- ological and functional anterior portion tions in the IOP or elevated perfusion of the eye from the posterior portion of pressure during hydrodissection might the eye. This barrier is referred to herein cause AHM detachment or tears.1 as the posterior chamber–anterior hyaloid The magnitude of increased IOP dur- Author Affiliations: membrane (PC-AHM) barrier. During ing hydrodissection is strongly influ- Departments of Ophthalmology normal phacoemulsification and aspira- enced by the characteristics of the oph- (Drs Kawasaki, Tasaka, Suzuki, tion operations, the function of the thalmic viscosurgical device (OVD) filling Zheng, Uno, and Ohashi), PC-AHM barrier is well maintained and the anterior chamber (AC). For example, Ophthalmology and intraocular perfusion fluid does not flow when a viscoadaptive OVD is used, the IOP Regenerative Medicine into the vitreous cavity.1 However, in has been reported9 to increase to 170.9 (Dr Shiraishi), Cell Growth and recent years, significant increases in mm Hg in a porcine eye model. Tumor Regulation intraocular pressure (IOP) have been To our knowledge, there have been no (Dr Shiraishi), and Infectious 2 Diseases (Dr Ohashi), Ehime reported during phacoemulsification, studies on the effect of OVDs of different University Graduate School of especially during hydrodissection, molecular weights (MWs) on the PC- Medicine, Shitsukawa, nucleus fragmentation, irrigation and AHM barrier in porcine eyes. The pur- Toon-City, Ehime, Japan. aspiration, and intraocular lens insertion. pose of this experiment was to evaluate the ARCH OPHTHALMOL / VOL 129 (NO. 6), JUNE 2011 WWW.ARCHOPHTHALMOL.COM 751 ©2011 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/28/2021 effect of 2 factors on the integrity of the PC-AHM bar- inserted under the anterior capsule at the 6-o’clock position, rier in isolated porcine eyes: perfusion pressure and in- contralateral to the corneal incision, and a mixture of fluores- creases in IOP during hydrodissection in ACs filled with cein bead solution and balanced salt solution was rapidly in- OVDs. fused at a rate of 3.0 mL per 10 seconds. Hydrodissection was performed by a surgeon (S.K.) who had no knowledge of which OVD had been used. The experiment was conducted on 20 eyes METHODS with each OVD and, immediately after the hydrodissection, the eyes were enucleated and examined as in experiment 1. Porcine eyes were selected as previously reported1 and exam- ined with a slitlamp microscope. Eyes with corneal trauma or STATISTICAL ANALYSES other obvious abnormalities were not used. Spearman rank correlation tests were used to determine whether EXPERIMENT 1 a significant correlation existed between IOP and the staining type, a measure of AHM impairment. The Jonckheere trend test The effects of the pressure exerted on the PC-AHM barrier by was used to investigate these trends in more detail. Analysis of intraocular perfusion were investigated. To monitor the IOP, variance (ANOVA) was used for comparisons between mul- tiple groups; when a significant difference was found by ANOVA a 16-gauge needle attached to a pressure sensor (DI-151RS; Ͻ DATAQ Instruments, Inc, Akron, Ohio) was introduced into (P .05), the Tukey-Kramer multiple comparison test was per- the AC at the 9-o’clock position of the cornea 1.5 mm inside formed. Data are given as mean (SD) unless otherwise indi- the limbus. A closed-eye condition was maintained, and there cated. was no leakage of the infusion fluid from the 16-gauge needle or pressure sensor. RESULTS A 27-gauge needle was attached to a bottle containing per- fusion fluid consisting of balanced salt solution (BSS Plus; Al- con Laboratories, Fort Worth, Texas) and 1.0-µm fluorescein EXPERIMENT 1: EFFECT OF PERFUSION bead solution (Fluoresbrite Carboxylate YG 1.0-µm Micro- PRESSURE ON THE PC-AHM BARRIER spheres; Polysciences Inc, Warrington, Pennsylvania) at a ra- tio of 100:3.0 mL. The 27-gauge needle was introduced into Classification of Staining Patterns the AC at the 12-o’clock position of the cornea. Each eye was Observed via Miyake-Apple View perfused for 20 seconds, using bottle heights of 45, 85, 145, and 285 cm. Ten eyes were tested at each height. The fluorescein bead staining patterns of the zonule of At the end of the perfusion, when the 27-gauge needle was Zinn, ciliary body, AHM, and vitreous cavity observed removed, IOP returned to a normal level after 4 to 5 seconds via the Miyake-Apple view were classified into 4 types: in most eyes, with continuous leakage from the wound. Any the AC, zonule of Zinn (Zinn), AHM, and AHM tear IOP that remained relatively high was allowed to return to a normal level before the 16-gauge needle was removed. As a re- (AHT). The AC type was designated as a staining pat- sult, the AC did not collapse. tern in which fluorescein beads remained in the AC After the procedure, the eyes were cut horizontally at the (Figure 1A). When the fluorescein beads reached the equatorial region using a razor blade; the fluorescein staining zonule of Zinn, such eyes were classified as the Zinn type of the zonule of Zinn, ciliary body, AHM, and vitreous cavity (Figure 1B). Eyes in which the fluorescein beads were was then examined by ophthalmic surgical microscope via the situated in the space between the zonule of Zinn and the Miyake-Apple view10,11 and videotaped (camera: DXC-C33; Sony AHM were classified as the AHM type (Figure 1C); eyes Corp, Tokyo, Japan; lens: ML-0310VF; Moritex Corp, Tokyo). in which beads reached the vitreous cavity through tear formation in the AHM were classified as the AHT type EXPERIMENT 2 (Figure 1D). Formation of an AHM tear was visually con- firmed at the time of dissection.1 The influence of the pressure exerted on the PC-AHM barrier Eyes were also examined by scanning electron mi- during hydrodissection was investigated. A 2.8-mm corneal in- croscopy. In the AC-type eyes, a small number of fluo- cision was made at the 12-o’clock position in the porcine eyes, rescein beads were found in the zonule of Zinn (Figure 1E) and 0.4 mL of a viscoelastic substance was infused into the AC. and almost no beads were found in the ciliary body Four types of OVDs with different MWs and concentrations of sodium hyaluronate were tested: a very low-viscosity disper- (Figure 1I). In Zinn-type eyes, a large number of fluo- sive OVD (OVD-A: MW, 600 000 to approximately 1 200 000 rescein beads were found in the zonule of Zinn Da; 10 mg/mL), a medium-viscosity dispersive OVD (OVD-B: (Figure 1F), but almost no beads were seen in the cili- MW, 1 530 000-2 130 000 Da; 10 mg/mL), a viscous cohesive ary body (Figure 1J). In AHM-type eyes, many fluores- OVD (OVD-C: MW, 1 900 000-3 900 000 Da; 10 mg/mL), and cein beads were found in both the zonule of Zinn a viscoadaptive OVD (OVD-D: MW, approximately 4 000 000 (Figure 1G) and the ciliary body (Figure 1K). In AHT- Da; 23 mg/mL). In addition, 1 medium-viscosity dispersive OVD type eyes, the zonule of Zinn was partially damaged near (OVD-E) containing 30 mg/mL of hyaluronate and 40 mg/mL the AHM tear (Figure 1H).
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