N.M.G. Vieira; J.J.T. Ranzani; C.V.S. Brandão; M.G. Sereno; G.T. Angélico; C. Donatti; A.C.L Rodrigues; D.N. Cremonini; J.L.V. Chiurchiu
The present work refers a case report of a howler monkey attended at the ophthalmology service of the UNESP Veterinary hospital, campus Botucatu, with total blindness. It was detected mature cataract in the right eye and hypermature in the left eye. The surgery for extraction of the cataract was performed by the phacoemulsification technique in both eyes. The surgery was a success with total recovery of eyesight.
Introduction
The crystalline, or lens, is a elliptic structure, biconvex, transparent, without blood vessels, anchored equatorially to the ciliary body by zonular fibers, keeping it suspense posterior to the iris and anterior to the vitreous, It is composed by an external capsule of basal membrane, anterior epitheliums, differentiated fibers and amorphous substance. It can be divided in regions called cortex (external region, near the capsule) and nucleus (central region). Because of is avascular condition, the lens nutrition is made by the aqueous and vitreous humor (Slatter, 1990). The lens functions consists in transmission and refraction of the light, due to its transparency and curvature, and the retina image focusing obtained by its accommodation capacity (Slatter, 1990, Gelatt, 1991).
Cataract can be defined by an unspecific affection that results in the clouding of the capsule or crystalline fibers, due to alterations in the lamellar architecture of its structures (Barnett, 1985; Johnson e Miller, 1990; Gelatt, 1991; Glover e Constantinescu, 1997; Shiels & Hejtmancik, 2007). The refraction index variation is caused by changes in the cells structures of the lens, in the proteins, or both. The cataract is normally associated with the rupture of the lens microarchitecture, formation of vacuoles, causing significant optical density flotation resulting in light dispersion, as well as an increase in the concentration of high weight protein clusters, about 0,1 nm or bigger (Shiels & Hejtmancik, 2007).
Currently the phacoemulsification is the chosen technique for cataract removal and consists in the fragmentation of the crystalline using ultrasound (emulsification), with concomitant aspiration of the emulsified material threw a small incision. These procedures must be performed according to a sequence of interrelated events: Incision, injection of viscoelastic, capsulorhexis, hydrodissection, hydrodelineation, phacoemulsification, and closure (Davidson et al., 1991, Nasisse et al., 1991, Bistner, 1992, Williams et al., 1996, Glover e Constanti-Nescu, 1997). In Humans the success rate using these technique can reach 95%, showing better results than other techniques (Whitley et al., 1993b, Jaffe et al., 1997).
Case Report
It was attended at the veterinary hospital of Botucatu a primate, of the species Alouatta caraya, common name Simian, female, originated from the Zoo "Quinzinho de Barros" of Sorocaba city, presenting total blindness. After ophthalmological exam, it could be seen that the direct and consensual pupil reflexes were present; Schirmera test on the right eye was 3 mm/min and on the left eye 10 mm/min; intraocular pressure (IOP), measured by the applanation tonometerb, on the right eye was 11 mmHg and on the left eye 15mmHg, and the presence of lens opacity on both eyes. The diagnostic was mature cataract on the right eye and hypermature cataract on the left eye. The surgery was performed by bimanual phacoemulsification in both eyes, in the same surgical procedure, initiated by two incisions at the cornea at approximately 1 mm of the limbus. The main incision was made in the shape of a tunnel using a 3.2 mm angled blade. A second auxiliary incision was made with an n. 15 blade. After the incisions, it was injected adrenaline in the anterior chamber to promote mydriasis on the left eye only. It was injected trypan blue on the anterior chamber for better visualization during capsulorhexis, and then viscoelastic substancec filling the entire anterior chamber. It was performed the circular capsulorhexis continuous with the aid of a Utrata forceps and capsulorhexis cystotome, followed by hydrosection, rotation and phacoemulsification of the lens core with the phacoemulsification probe.d The fracture technique used was phaco-chop and the phacoemulsification parameters were set in 60% of ultrasonic power in both eyes, 40 cc/min on the right eye and 30 cc/min on the left, 12 pulses/sec on both eyes, with a vacuum of 400 mmHg on the right eye and 251 mmHg on the left eye. The aspiration of the cortical waste was performed with an irrigation/aspiration pen from the device. On the right eye, the posterior capsule of the lens ruptured, being necessary the vitrectomy. The intraocular lens was not attached. Finally, it was performed the aspiration of the viscoelastic substance, injection of an air bubble on the anterior chamber, and hydration of the surgical borders. A simple suture using 10-0 mononylon was made on the main incision. The ultrasound time represented the quantity, showed in minutes, of the phacoemulsification device, and it was of 0.2 minutes on the right eye and 0.8 minutes on the left eye.
Soon after the surgery, with the animal still anesthetized, it was performed the specular microscopye, type A ultrasoundf and keratometryg exams. In the specular microscopy the endothelial cell count was 20 in all readings: with an average of 1725 cells/mm2 in six measures on the right eye and 1729 cells/mm2 in two measures on the left eye. On the type A ultrasound, the average using six measures of the axial length of the ocular bulb was 18,40 mm on the right eye and 18,07 mm on the left eye. On the keratotomy the average in four measures was 0,6875 mm on the right eye and 1,0625 mm on the left eye. Two months after the surgery, a new ophthalmologic exam was made, where the direct and consensual pupil reflexes were absent in both eyes, the IOP on the right eye was 14 mmHg and on the left eye 11mmHg; opacity of the cornea close to the limbus on the incision site, and posterior synechia in both eyes; opacity on the anterior capsule remaining from the capsulorhexis and opacity of the posterior capsule on the left eye. The animal showed good eyesight, checked by positive threat test, obstacle diverting and location of foods on the cage.
Endnotes
a. Schirmer test--Ophtalmos--Brazil
b. Tonopen XL, Mentor, Netherlands
c. Viscoat 2%
d. Universal II--Alcon--USA
e. SP 2000P, Topcon Europe, Netherlands
f. Echo Scan US-800, Nidek--Japan
g. K-500 auto keratometer, Nidek--Japan
Conclusion
The phacoemulsification technique was effective for the cataract treatment in the species above referred. Even with the complications trans and post-op (vitreous protrusion, posterior synechia, capsular opacity) the surgical procedure was considered satisfactory, due to the return of most activities lost during the evolution of the disease.
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