Download PDF - Oftalmo.com

ORIGINAL ARTICLE
ARCH SOC ESP OFTALMOL 2008; 83: 589-594
ANATOMICAL REPERCUSSION ON THE ZONULAR
APPARATUS AFTER A CAPSULAR TENSION RING
INSERTION IN SWINE EYES
ESTUDIO EXPERIMENTAL SOBRE LA REPERCUSIÓN
ANATÓMICA DE LA ZÓNULA DE ZINN TRAS LA INTRODUCCIÓN
DE UN ANILLO ENDOCAPSULAR EN OJOS DE CERDO
COLOMÉ-CAMPOS J1, ORTEGA-USOBIAGA J2, SHAHIN M1, FORCADELL M3, PINO A3,
FORTEZA T3, BAUBÍ C3
ABSTRACT
RESUMEN
Purpose: To carry out an experimental and descriptive study that exhibits the anatomical repercussions
on the zonular apparatus after a capsular tension
ring (CTR) is inserted.
Methods: CTRs were inserted in five swine eyes
(four with forceps, one with an injector). Two additional eyes were left untouched for control purposes. The integrity of the suspensory ligament was
examined by scanning electron microscopy.
Results: We did not observe alterations in the integrity of the zonular apparatus. The suspensory ligaments adopted a new fold configuration.
Conclusions: CTR insertion is a safe therapeutic
tool to maintain the integrity of the lens zonules in
elastic, large diameter capsular bags (Arch Soc Esp
Oftalmol 2008; 83: 589-594).
Objetivos: Valorar experimentalmente la integridad morfológica de los ligamentos suspensorios de
la zónula de Zinn (LSZZ) tras la introducción de un
anillo de distensión capsular (ADC) mediante un
estudio descriptivo.
Métodos: Se utilizaron siete ojos de cerdo a los
cuales se realizó una extracción extracapsular de
cristalino transparente. A cuatro se introdujo un
ADC con pinzas y al quinto con inyector. Los otros
dos se utilizaron como control. Se examinó la integridad anatómica y la nueva configuración de los
LSZZ con un microscopio electrónico de barrido.
Resultados: No se observaron alteraciones en la
integridad de los LSZZ. Los LSZZ adoptan tras la
introducción de un ADC una nueva trayectoria de
repliegue consecuencia de la nueva disposición del
saco capsular.
Conclusiones: En un modelo experimental con
ojos de cerdo no se encontraron lesiones en los
LSZZ por lo que parece que, en cápsulas elásticas y
Key words: Capsular tension ring, lens zonules,
clear lens extraction, zonular dialysis.
Received: 26/9/07. Accepted: 25/9/08.
1 Ph.D. in Medicine. Ophthalmology Service. Verge de la Cinta Hospital of Tortosa. Tortosa. Spain
2 Ph.D. in Medicine. Baviera Clinic. Bilbao. Spain.
3 Graduate in Medicine. . Ophthalmology Service. Verge de la Cinta Hospital of Tortosa. Tortosa. Spain
Correspondence:
Jordi Colomé Campos
C/. Joan Miró, 3, esc. B 3.º 2.ª
43500 Tortosa
Spain
E-mail: [email protected]
COLOMÉ-CAMPOS J, et al.
de gran diámetro, la inserción de un ADC no produce roturas en los LSZZ.
Palabras clave: Anillos de distensión capsular,
zónula de Zinn, extracción extracapsular de cristalino transparente, diálisis zonular.
INTRODUCTION
The presence of defects in the integrity of the
Zinn Zonule (SLZZ) suspensory ligaments is a circumstance that makes surgical intervention of the
cataract by means of phacoemulsification difficult
even in the hands of experienced surgeons.
Different maneuvers are known to rectify this
surgical problem, from the realization of classical
and practically obsolete intracapsular or extracapsular surgery, to the introduction or placing of the
intraocular lens in distinct locations of the capsule
sac (CS) such as the anterior chamber or the ciliary
sulcus. A nearly standard surgical resource is the
introduction of a capsular tension ring (CTR) in the
interior of the CS.
The effectiveness that the CTR generates is well
known since the beginning of its use in 1991(1)
when we find ourselves against a weakness or dialysis of the SLZZ to conserve the anatomical integrity of the CS thanks to the forces of centrifugal traction that the CTR generates in the absence of the
lens. In this way, it is normal to place the CTR in circumstances such as pseudo exfoliation syndrome,
myopia magna, aniridia, uveitis and pigmentary
retinosis, as well as cases of maximum expressions
of weakness such as the zonular dialysis that we find
in badly formed syndromes such as the Marfan,
Ehlers-Danlos or Weill- Marchesani or even the
post-traumatic or iatrogenic etiology (2) (3). There
are extreme cases where these CTR require a suction
support that makes it necessary to suture it in the
walls of the ocular globe (4). The introduction technique of the CTR is manual, even with the help of
forceps or perhaps an injector. However, when we
proceed to place it there is a degree of aggression in
the integrity of all the CS and its stabilization ligaments, even more at the area of initial introduction,
which is where the maximum tangential traction (5)
is generated. The aim of our study is to understand
under electronic microscope and by means of a
descriptive study the extent of aggression that the
use of these rings cause. If so, then perhaps it is
590
worth considering that the use of CTR may, in some
circumstances, generate possible risks that modify
the practice of surgical intervention.
SUBJECTS, MATERIAL AND
METHODS
Seven pig eyes of eight months from the municipal slaughterhouse were used. After sacrificing the
animals, they were enucleated for 30 minutes. Afterwards they were placed in a recipient with saline
phosphate 0.1 M tampon and conserved at 4ºC. At
12 hours of the enucleation and after the excision of
the corneal-scleral cask and the iris a 5mm diameter
capsulorrhexis was performed with the help of a
cystotome and Utrata forceps proceeding from the
extracapsular extraction of transparent lens after
hydro-expression maneuvers. The cortex was aspirated with a Simcoe type cannula. Directly afterwards a series of CTR of PMMA, selected randomly, were introduced into each eye. The first four
rings were introduced with a McPherson type forceps and the fifth with the help of an injector. For the
first eye we used a CTR Corneal ® model ATC110
of 11mm of diameter, for the second a CTR Oculaid
® model PC275 of 12 mm, for the third eye a CTR
Morcher ® type 14 of 12 mm, for the fourth eye a
CTR Ophtec ® of 13 mm and for the fifth eye we
introduced an CTR AMO Injector Ring ® of 11 mm
(table I). As control we used two eyes, one which
had only had a extracapsular extraction of transparent lens realized but without the introduction of ring,
and the other where the lens had been conserved. To
stop we proceeded to resect the posterior wall of the
ocular globe with the aim of obtaining an anterior
and posterior perspective of the SLZZ.
The ocular globes were introduced into a fixing
substance of glutaraldehyde at 6% according to the
Karnovsky technique (6) and were conserved at a
minimum of 4ºC for 2 hours prior to processing.
The samples were washed with phosphate tampon and fixed with tetraosimio oxide to proceed
ARCH SOC ESP OFTALMOL 2008; 83: 589-594
Endocapsular rings and Zinn zonule
Table I. Capsular distention rings utilized
in the study
Capsular distention rings
Material
Diameter
Corneal® ATC 110
Oculaid® PC275
Morcher® 14
Ophtec®
AMO® Injector Ring
PMMA
PMMA
PMMA
PMMA
PMMA
11 mm
12 mm
12 mm
13 mm
11 mm
with dehydration by means of a series of alcohols of
growing concentrations and finished in a solution of
aniloacetate. After obtaining the critical point with
CO2 the samples were recovered with gold by the
«sputtering» procedure. The distance of work used
was 39 mm and the scanning electron microscope
used was a JSM-6400 property of the Universidad
Rovira y Virgili.
The SLZZ were selected from the quadrants of
the four main meridians of each eye in steps of 130
micrometers and their integrity observed, measured
in number of fibrillar fractures, and density, counting the number of fibers within the 130 micrometers. The configuration of the trajectory of the
SLZZ was also studied to determine whether it
maintained its normal straight line, and the insertion at the level of the capsular sac, registering the
number of disinsertions. The study was made from
an anterior perspective comparing it with the control eyes and the images enlarged to10X, 75X,
150X, 200X, 250X, 300X, 400X, 600X, 1000X and
2500X were registered.
Fig. 1: Scanning electron microscope image (x600)
where the integrity of the suspensory ligaments is shown
at its CS insertion (arrow) after the introduction of an
CTR with injector.
Fig. 2: Scanning electron microscope image (x150) showing the imprint generated by CS (*) on adapting to the
small orifices in the present CTR (arrow).
RESULTS
No alterations in the SLZZ integrity were detected in any of the eyes studied, since in none of the
evaluated quadrants, either for those that introduced
a CTR, with an injector (fig. 1) or not (figs. 2, 3 y
5), or for the control eyes (fig. 4) were any fractures
or disinsertions observed. The density was kept stable with average figures of 43 fibers per every 130
micrometers, very similar to that of the control eyes
that was 46 fibers.
However, alterations in the configuration or trajectory of the SLZZ were found when compared
with the control eyes, as the presence of a capsular
sac in absence of the lens but with the introduction
of an CTR caused changes in the architecture of the
tridimesional network of the SLZZ, in such a way
Fig. 3: Scanning electron microscope image (x75) showing the relief of the edges of the capsulorrhexis (arrow)
and of the Zinn zone (*).
ARCH SOC ESP OFTALMOL 2008; 83: 589-594
591
COLOMÉ-CAMPOS J, et al.
Fig. 4: Scanning electron microscope image (x100) showing the ciliar muscle (*) and the density of the fibers for
one of the studied quadrants in the control eye.
that these lost the normal straight line configuration
presenting a new trajectory and arrangement in the
shape of posterior angulation and fold (fig. 6).
DISCUSSION
The study of the present work has been carried
out on young pig eyes. It is assumed that the integrity of all the suspensory system of the lens as well as
the elasticity of the CS was completely conserved
(7). On extrapolation the design of the work on
humans it should be considered that the CTR is normally used on eyes that supposedly exhibit weakened zonules, where the resistance to traction in the
course of the cataract operation is much less than
under normal circumstances, as has been observed
in ocular postmortem tinctions (8). For example it
has been demonstrated that in pseudoexfoliative
syndromes the resistance of the SLZZ to traction is
four times less, and in some patients the fibers are
even found broken or deteriorated before the surgical act (9).
The CS of pig eyes are estimated to be a diameter superior to that of humans (10), but despite this,
in our study, on treating young eyes we have
observed a CS with an average diameter of 12.1 mm
(fig. 7), slightly greater than CS of the human eye
that is of 10.3 to 10.8 mm of diameter when it is
empty (11, 12). We have used CTR designed for use
in humans and of an average size of 11 mm. We
could imagine that the introduction of an ADC in a
SC of greater size requires less friction- resistance
than the introduction in a SC of lesser size.
592
Fig. 5: Scanning electron microscope image (x100) showing the ciliar muscle (*) and the density of fibers in its
insertion to the CS for one of the quadrants studied in an
eye with CTR. Anatomical changes were not observed
with respect to the control eye.
The introduction maneuver of an ADC is relatively easy in normal conditions. However in some complex cases or if the entrance is made in an excessively traumatic manner, or even if the design of the CTR
is not the most adequate, it could generate severe
traction on the fornix of the CS that could even perforate it (2). It has been described that the use of CTR
with the help of injectors could avoid or minimize the
traction forces on the SLZZ and the CS. It is with this
aim that we have used one of the eyes for observing
the microscopic response after its introduction.
The SLZZ exhibits an enormous distending
capacity and an important firmness in capsular and
ciliar insertions (13). It has been described that the
fibers could increase in length four times their orig-
Fig. 6: Scanning electron microscope image (x300) showing the back of the equator of the lens CS (*) after the
introduction of a CTR and the new configuration of the
posterior fold that the suspensory ligaments adopt (arrow).
ARCH SOC ESP OFTALMOL 2008; 83: 589-594
Endocapsular rings and Zinn zonule
Fig. 7: Diameter of the lens of one of the pig eyes used.
inal size (14, 15) without evidence of breaks, fissures or disinsertions. However with the passing of
time the SLZZ become finer and decrease in number which causes an important interpersonal variability of traction resistance (16), circumstances to
consider when performing maneuvers that could
alter the previously debilitated anatomical integrity.
We have found alterations in the trajectory of the
SLZZ compared with control eyes, and we assume
that they are due to the fact that the CTR generate
centrifugal forces on the equator of the CS that provokes certain distension on the SLZZ. It will also
have to be contemplated that with the extraction of
the lens the biconvexity of the CS remains reduced,
a factor to consider for interpreting the new disposition of the SLZZ and its possible repercussion in
the mechanism of accommodation.
REFERENCES
1. Hara T, Hara T, Yamada Y. «Equator ring» for maintenance of the completely circular contour of the capsular
bag equator after cataract removal. Ophthalmic Surg
1991; 22: 358-359.
2. Menapace R, Findl O, Georgopoulos M, Rainer G, Vass
C, Schmetterer K. The capsular tension ring: designs,
applications, and techniques. J Cataract Refract Surg
2000; 26: 898-912.
3. Pitrová S. A distance ring for stabilization of the lens capsule (a multicenter clinical study). Cesk Slov Oftalmol
1998; 54: 299-304.
4. Tokuda Y. In the bag IOL suture fixation represents a new
approach to zonular dehiscence. Ocular Surgery News
1997; 8: 9.
5. Colomé Campos J, Pérez Moreda F, Belmonte Martínez J.
Estudio experimental de la acción de los anillos endocapsulares en relación a la extensión de la diálisis zonular.
Microcirugia Ocular 1999; 7: 33-38.
6. Karnovsky MJ. A formaldehyde-glutaraldehyde fixative of
high osmolality for use in electron microscopy. J Cell Biol
1965; 27: 137-138.
7. Krag S, Olsen T, Andreassen TT. Biomechanical characteristics of the human anterior lens capsule in relation to
age. Invest Ophthalmol Visc Sci 1997; 38: 357-363.
8. Wilson DJ, Jaeger MJ, Green WR. Effects of extracapsular cataract extraction on the lens zonules. Ophthalmology 1987; 94: 467-470.
9. Guzek JP, Holm M, Cotter J, Cameron JA, Rademaker
WJ, Wissinger DH, et al. Risk factors for intraoperative
complications in 1000 extracapsular cataract cases. Ophthalmology 1987; 94: 461-466.
10. Lee DH, Lee HY, Lee KH, Chung KH, Joo CK. Effect of a
capsular tension ring on the shape of the capsular bag and
opening and the intraocular lens. J Cataract Refract Surg
2001; 27: 452-456.
11. Galand A, Bonhomme L, Collée M. Direct measurement of
the capsular bag. J Am Intraocul Implant Soc 1984; 10:
475-476.
12. Richburg FA, Sun HS. Size of the crushed cataractous
capsule bag. J Am Intraocul Implant Soc 1983; 9: 333335.
13. Streeten BW, Licari PA. The zonules and the elastic microfibrillar system in the ciliary body. Invest Ophthalmol Vis
Sci 1983; 24: 667-681.
14. Raviola G. The fine structure of the ciliary zonule and
ciliary epithelium. With special regard to the organization
an insertion of the zonular fibrils. Invest Ophthalmol
1971; 10: 851-869.
15. Canals M, Potau JM, Costa J. Estructura y propiedades
elásticas de la zónula cristaliniana. Arch Soc Esp Oftalmol 1999; 74: 131-136.
16. Buschmann W, Linnert D, Hofmann W, Gross A. The tensile strength of human zonule and its alteration with age.
Albrecht Von Graefes Arch Klin Exp Ophthalmol 1978;
206: 183-190.
ARCH SOC ESP OFTALMOL 2008; 83: 589-594
593