Wednesday, February 16, 2011

Facoemulsificação em um Poodle seguida de implante de LIO Acrivet 30V

Cataract Surgery with Phaco followed by lens implant in a Dog.

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Cataract Surgery using a one-handed Phacoemulsification technique followed by implantation of a foldable acrylic intraocular lens in dogs: results and postoperative complications in 180 cases.

João Alfredo Kleiner
VETWEB Veterinary Ophthalmology
Curitiba - Pr   -   Brazil

Cataract is defined as any opacity localized into the lens nuclear region or its capsule and it is one of the most common eye diseases on the routine of a small animal ophthalmology practice and a potentially blinding and inflammatory cause. With the advent of the phacoemulsification with foldable intraocular lenses implant the results obtained in the surgery became much better. This article intends to describe the results and complications of the one-handed technique phacoemulsification followed by implantation of a foldable acrylic intraocular lens in a 180 eyes of different dog’s breeds.
Key words:  cataract, phacoemulsification, intraocular lenses, dogs.


The lens is an avascular, transparent and biconvex structure situated behind the iris, in front of the vitreous body and supported at the equator by the lens zonules or suspensory ligaments 1. The changes in tension of these zonules alter the optical power of the lens and focus objects situated at different distances from the eye. Besides being avascular, the lens does not have nerve supply and it is composed of 1/3 proteins, 2/3 water and other components (lipids, aminoacids, electrolytes and carbohydrates) that comprise 1%. This high protein concentration is responsible for high refractive power of the lens which along with the accommodation constitutes its main function 2. The human eye has a total refractive power of 60 diopters and the lens contributes 13 to 16 diopters. In the dogs the contribution of the lens is 40 diopters and the remaining refraction is provided by the cornea 3.
The canine lens volume is approximately 0.5 ml and it 7 mm in thickness at the anteroposterior axis and is 10 mm in diameter. The lens is surrounded by a basement membrane structure called the lens capsule that has elastic properties and is PAS – positive. The reported thickness of the canine capsule at its equator is 8 – 12  μm, 50 – 70 μm anteriorly and only 2 – 4 μm posteriorly 4.
The loss of lens transparency is common in all pathologies that affect this structure and cataract is among the most frequent of intraocular lesions and the major cause of blindness in the dog 5. Cataract is defined as any loss of transparency of the lens and/or its capsule, leading to visual deficits, astigmatism and commonly blindness.
Generally behavior changes associated with cataracts are not noted until we have 40 to 50% of lens opacity and usually bilateral. When the opacities are localized in the visual axis, the behavior changes are much more evident. The menace response remains present till the lens is totally opaque.
The opacities may vary in size, shape, region, etiology age of development and progression. The basic mechanism of cataract formation is due to protein disarrangement and among the mainly causes one can point out heritage, diabetes, intraocular inflammation, traumas, retinal diseases (progressive retinal atrophy), radiation and toxic substances 6.
Cataract is more prevalent in dogs than in cats and among the predisposed breeds are Poodle Toy, Cocker Spaniel, Schnauzer, Pekinese and Dachshunds 7, 8. Phacogenic uveitis, glaucoma and phthisis bulbi are among the major complications of untreated cataracts 9, 10. The only treatment for cataract is its surgical removal and the recommended procedure nowadays is phacoemulsification.
The modern phacoemulsification surgery was developed by Charles Kelman in 1967 and it was a big evolution in the treatment of cataract. In 1949, Dr. Harold Ridley invented the first intraocular lenses (IOLS), based in the studies of airplanes pilots that sustained eye injuries during the World War II caused by the explosion of the cockpits that were made of acrylic. He found out that this material had a high refractive power and was inert in the intraocular media. Those first lenses were heavy and were associated with a lot of complications. Ten years went by and Cornelius Birkhorst upgraded the Ridley’s model and the technique for its implantation 11.
Nowadays the intraocular lenses have an advanced design and technology and can be implanted through a very small incision (foldable) and one can find different types specially made for dogs, cats and horses.
The present article tends to show and describe the results obtained with cataract surgery using the one-hand phacoemulsification technique followed by acrylic foldable intraocular lens implant in dogs.

            The medical records were evaluated of 136 dogs without any other eye or systemic diseases that had uni or bilateral cataract in different stages of development treated surgically utilizing the one-hand phacoemulsification technique followed by an acrylic  foldable IOL implantation at São Bernardo Small Animal Hospital in Curitiba, Parana – Brazil from years 2005 to 2009.
            All patients included in this study had normal electroretinograms using the bpm-200 retinographer.
            The dogs were fasted for 12 hours anesthesia and pupil dilation was achieved with tropicamide every 15 minutes, 1% atropine sulfate every 20 minutes and sodium diclofenac every 25 minutes for 4 hours prior to surgery Gatifloxacin drops were administered every 10 minutes, starting one hour before the procedure. General anesthesia was induced with ketamine (10 mg / Kg) and diazepam (0,5 mg / Kg) and maintained with isofluorane. Central positioning of the globe was achieved using a regional four point block ( 3, 6, 9 and 12 o’clock) with lidocaine 2% and bupivacaine 0.5% mixed in the same syringe at the ratio of 1 : 4 (for example 0.5 ml of lidocaine with 2 ml of bupivacaine). The amount injected varied between the breeds and the anatomic characteristic of the globe. When operating in a large breed dog with very deep orbit, the administration of some fluid (sodium chloride 0.9%) into the retrobulbar space using a 22 gauge needle, entering behind the lateral aspect of the zygomatic arch was done in order to push the globe forward for exposure . Using these steps there is no need to perform a lateral cantotomy and it lessen the surgical time. The solution that is used into the retrobulbar space is rapidly absorbed a couple hours after the procedure. Three minutes before the main incision, a drop of povidone iodine 5% is used in the conjunctival sac and it is rinsed thoroughly before the incision is made.
            There is no need for using the blepharostat with the one handed technique and the eyes can be kept open utilizing a couple vertical mattress sutures on the upper and lower palpebral region. The incision size for most phacoemulsifiers used in veterinary medicine is 3.2 mm and should be always tried to be done in a three plane fashion and with a disposable scalpel blade. Before entering the cornea, a small incision line is made in the epithelium, that way the incision is more precise and easily to be made self sealant.
            To facilitate the capsulorhexis, mainly in older animals where the anterior lens capsule is thicker, the use of tripan blue is recommended. The volume for a good staining is 0,2 ml and one should wait 3 to 5 minutes before the next step. Viscoelastic is then injected from the distal end toward the incision in order to wash away all the tripan blue and to achieve a good mechanic mydriasis. The first step for a good, round and symmetric capsulorhexis is to puncture the anterior capsule, with an insulin needle, and prolong the incision clock wise and counter clock with a vannas scissors.
            The next and very important step is the hydrodissection that is done with a 27 gauge needle inserted just below the anterior capsule in order to separate the lens from its capsule and make possible for manipulating the cataract during the nucleus fragmentation. It’s very important to wash up some of the viscoelastic from the anterior chamber before the infusing more liquid otherwise the incidence of posterior capsule rupture will increase. The other important thing is to make the hydrodissection with very low pressure and very delicate in order to avoid traumatic posterior capsule rupture due to lentoides that could be very adhered to the lens capsule.
Nucleus fracture can be done with different ways and the easiest one is the “divide and conquer” technique. A 30 0 flared phaco tip is preferred because it has a bigger opening than other tips making the nucleus fragmentation much faster. When the two major sulcus are done, the pre-chopper of Akahoshi is utilized to crack the nucleus in four parts. Care should be taken during the manipulation of the last fragment to avoid surge. One advice is to push the posterior capsule back with viscoelastic solution before starting the emulsification on this last piece.
It’s very important to polish the posterior capsule in order to decrease the opacification that can appear later after the procedure. The edge of the anterior lens capsule should be very well polished to minimize the cellular replication and shrinkage.
There are different types of intraocular lenses IOLS specially made for dogs of different sizes and they should be used every time it’s possible in order to provide emetropia, diminish the posterior capsule opacification and to counter balanced the high vitreous pressure.
The IOLS should be folded and implanted using the manufactures cartridge and injectors in order to diminish fractures of the haptics and the optical zone. Before setting the IOL into the cartridge sulcus, a good amount of viscoelastic should be used to form a protecting surface.
After the IOL is implanted into the capsular sac, a good time should be spend aspirating the remaining viscoelastic material in order to decrease the incidence and severity of postoperative ocular hypertension.
When the incision is not well sealed 2 or 3 stitches using a 9-0 nylon material are recommended and 0,3 ml of betamethasone dipropionate subconjuntivaly is done in order to control the postoperative uveitis.
Artificial tears TID for 30 days, atropine sulfate 0,5 % BID for 12 days, prednisolone acetate 1% TID for 25 days, ketorolac trometamol BID for 25 days and gatifloxacin TID for 15 days are the drugs utilized during the postoperative period. No systemic drugs were utilized.
The posterior capsular opacity was graded on a scale of 1 to 3 (1= discrete opacity around the lens edge with clear visual axis and perfect visual fundus; 2= more evident opacity around the lens edge and in the visual axis decreasing the transparency and fundus not completely visual; 3= severe opacities all over the posterior lens capsule impairing the fundus visualization causing visual disturbances).
            The parameters analyzed were signalment (breed, age and gender), stage of cataract development, corneal edema, fibrin formation, capsular opacification, dyscorias, synechiaes, IOL fractures, glaucoma, Hyphema and retinal detachment.

            The most prevalent breed was the Toy Poodle as reported in the table 1.
Toy Poodle
Cocker spaniel
Lhasa apso
Mixed breed
Bichon frise
Yorkshire terrier
Cane corso
Dogo argentino
Scoth terrier
Fila brasileiro
Golden retriever
Basset hound
French bulldogs
Fox terrier
136 patients
180 eyes
Table 1: Breed prevalence for cataract surgery.   

            Fibrin formation was more frequent in mature and hypermature cataracts due to longer surgical time and more ultrasound power used to break the lens material. All cases resolved in 2 or 3 weeks after the surgery.
            Corneal edema at the incision site was considered normal in all cases causing no visual impairing and were much less evident in those cases where nonabsorbabel suture (8-0 nylon) was used.
            The major long time postoperative complication (table 2) observed utilizing the one-hand technique phacoemulsification followed by acrylic lens implant was the posterior capsular opacification that was notably more frequent in dogs that had harder and more matured cataracts. In the majority of the patients those opacities did not preclude a fundic examination.   
Postoperative complications
Number of eyes
Capsular Opacification grade 1
Capsular Opacification grade 2
Capsular Opacification grade 3
Focal corneal edema
IOL fracture
Retinal detachment
Table 2: Major complications observed after phacoemulsification.

            Considering the regaining of vision, the success rate of the surgery was very high. Out of 180 eyes operated utilizing the one-handed phacoemulsification technique followed by an acrylic foldable IOL implantation, only  9 eyes were sightless.

Figure 1: Two mattress sutures utilized to hold the superior and inferior eyelids open.
Figure 2: Two years after lens implant. Visual axis clear. Grade II capsular opacification.

Figure 3: Cane Corso one year after the surgery with Erlichiosis. Capsular opacity grade III.

Figure 4: Focal corneal opacity in a Cocker Spaniel 7 months after surgery.

Figure 5: Glaucoma one year after surgery without lens implant.

Figure 6: IOL optic zone fracture.

Figure 7: Schnauzer 3 years after phaco and lens implant. Capsular opacification grade I.

            The advantage of not having the blepharostat holding the eyes open is that there is no pressure in the globe and there is less leakage from the incision and the anterior chamber is maintained.
            The posterior lens capsule opacities where more frequent in harder cataracts because the capsule polishing was much more difficult to perform in those cases. Sometimes no matter how hard the posterior capsule is polished, there were some lens material adhered to it and these will form lentoids (fibrous pseudometaplasia) and originate denser opacities. Some cases the lens capsules can form wrinkles and adhesions between the anterior and posterior capsules originating denser opacities (figure 1). Some studies showed that it could be prevented with an intra-ocular lens implantation that forms a space between the capsules preventing adhesions and proliferation of epithelial cells on the posterior capsule 12.
            Previous researches demonstrate that the polymethylmethacrylate  (PMMA) lens have a greater incidence of posterior capsular opacification than the acrylic ones and it might be due to the greater contact of the acrylic polymer to the lens capsule originating a physic barrier for the cells to migrate 13.
            No matter how good the polishing of the posterior capsule is done we always going to have some degree of opacity but fortunately most of the opacities occur around the lens optic edge and do not interfere with central vision.
            The three cases that had grade 3 capsular opacification greatly impairing the vision acuity were patients with systemic diseases (Ehrlichiosis, leptospirosis and decompensated diabetes mellitus) and those pathologies probably were the reason of this complication cause they were related with the presence of chronic uveitis(figure 2).
            Focal corneal opacities were normal because of the healing process but sometimes when absorbable suture material was used and the stitches not removed a hard-healing corneal ulcer would appear at the incision site and could take a long time to resolve (figure 3). So it is advised always to remove the sutures after 2 or 3 weeks.
            Dyscorias and posterior synechiaes were more common in hard cataracts where more ultrasound power was used causing more damage to the iris surface but no important visual disturbance was noted.           
            Hyphema cases were related to self trauma in the same week after the procedure in two cases because the dogs were left alone at home and bang their heads against the furniture.
            The incidence of long time glaucoma (more than one year time frame after the procedure) was very low compared with the cases where an acrylic foldable IOL was not implanted 14. Two cases were Cocker Spaniels and one Toy Poodle. Possibly the IOL decrease the incidence of long time glaucoma because somehow they can counteract the high vitreous pressure that dogs have doing so they prevent the vitreous to obliterate the drainage angle, but further studies need to be done to confirm this hypothesis (figure 4).        
            IOL fractures occur more frequently at the haptic zone due to incorrect folding and accommodation of those into the cartridge but did not interfered with its centralization and vision so no need for removing then (figure 5). When the plate shape IOLS where used no fractures where reported considering the more robust design they have.
            Considering the complications related to the stage of cataract development the higher incidence was observed in mature and hypermature ones, probably due to longer surgical procedures and more severe uveitis 15.
            The success rate of the phacoemulsification followed by an acrylic foldable intraocular lens implant is very high and only a few complications were observed and the sooner the surgery is done (when the cataract is not too hard) the better are the results and outcome for the recovering of the vision (figure 6).


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