Introduction
In cataract disease, the lens comprises thin, transparent, highly organized protein fibers converted into white opacity. When the lens osmolality changes and is hydrated, it becomes opaque, preventing the passage of light, and eventually leading to blindness. However, diabetic cataracts start with fluid accumulation and progress to blindness (Patil et al., 2014). All breeds of small animals are mostly affected bilaterally. Cataracts are often classified into morphological, etiological, and the degree of opacification (Gelatt & Wilkie, 2011). In the surgical context, a classification system that assesses the degree of cataract opacity or maturity is very useful, as this quantification of lens opacity correlates with clinical vision (Feng et al., 2022). Cataract complications include lens-induced uveitis, posterior capsular opacification, increased intraocular pressure (Shokoohimand et al., 2024), prolonged inflammation, retinal detachment, and persistent corneal edema. After lens removal, signs such as lens-induced uveitis, characterized by the slow or imperfect pupillary response to mydriatics, may progress; so, medical therapy is needed (Verloop & Read, 2023). Two common cataract surgical techniques are manual extracapsular cataract extraction (MECCE) and intraocular lens phacoemulsification (PHACO). In the MECCE surgical technique, the lens is extracted through a large corneal or limbal incision line. The PHACO technique removes lens material through a small incision with fragmentation, emulsification, and aspiration (Li et al., 2022). The MECCE technique is a primitive procedure and the most common procedure that expert ophthalmologists perform when PHACO is unavailable. Also, due to the size and density of the cataractous lens and the thick capsule, MECCE is still recommended for canine cataracts (Davidson et al., 1990; Beteg et al., 2008).
This study investigated the functional vision and postoperative complications after 27 MECCEs in 19 dogs.
Material and Methods
A retrospective study of 27 MECCEs was performed on 19 dogs with bilateral or unilateral cataracts. The sex, breed, age, and bilateral or unilateral MECCE of each animal were recorded in Table 1.
Some of the dogs were sexually intact.
Preoperative considerations
Preoperatively, the systemic health, the pupillary light reflex (PLR), and ultrasonography of the eyes with a linear 7.5-15 MHz transducer (Esaote Mylab 30 gold CV, Via di Caciolle, Firenze, Italy) were assessed and observation of both eyes for ocular disease was performed under the microscope (Topcon, OMS-300, Japan). Medical treatments (24 h before surgery) were topical prednisolone acetate 1% (one drop, Q6h, Sina Darou, Tehran, Iran), topical ciprofloxacin 3% (one drop, Q6h, Sina Darou, Tehran, Iran), systemic prednisolone (1 mg/kg, Q12h, Aburaihan pharmaceutical Co., Tehran, Iran). Also, 90 min preoperatively, a topical nonsteroidal anti-inflammatory drug (NSAID) (Diclofenac sodium 1%, one drop, Q30 min, Sina Darou, Tehran, Iran) was used. Meloxicam 2% (0.2 mg/kg, SC, Razak Laboratories, Karaj, Iran) and cefazolin (22 mg/kg, IV, Q12, AFA Chemie Pharmaceutical Company, Tehran, Iran) injections were done before surgery and once 24 hours later. Topical tropicamide 1% (three drops, Q6h, Sina Darou, Tehran, Iran) was administered 2 hours before surgery. Following premedication with Acepromazine (0.05 mg/kg, IM, Neurotranq Alfasan, Holland), Propofol 1% (4 mg/kg, IV, Braun Melsungen AG, Melsungen, Germany) as an induction dose was injected and maintained with isoflurane gas (Aerrane, Guayama, Spain) and 100% oxygen.
Surgical technique
The animals were placed in dorsal/lateral recumbency, and around the eyes were washed with a 5% povidone-iodine solution. Then the eyelids, corneal, and conjunctival surfaces were carefully flushed with lactated Ringer’s solution. Their surfaces were cleansed with a 2% povidone-iodine solution. After the placement of the drape, the palpebral fissure was kept open with a lid speculum, and fixation of the eyeball and exposure were achieved using a silk 4-0 bridle suture. A peripheral (about 160-180 degrees) corneal incision (from 9 O’clock to 3 O’clock on the superior cornea near the limbus) was performed to enter the anterior chamber (AC). First, a partial incision (90% thickness) was made with the Beaver No. 6400 microsurgical blade. The AC was filled with air, and the anterior capsule was stained by trypan blue (Amp 1 mL, Abzar Teb Pouya Co., Tehran, Iran) before the capsulorhexis to facilitate identification of the anterior lens capsule. After being penetrated by a keratome, the incision was completed by a corneal scissor. The AC was kept during the capsulotomy procedure (can-opener technique) with viscoelastic material (Visicrom 2%, Croma Pharma GmbH, Austria).
The nucleus was expressed by simultaneous compression on the superior and inferior (6 and 12 o’clock) limbal area. Cataract cortices and lens material were aspirated by a Simcoe irrigation/aspiration cannula. The corneal incision was closed with a nonabsorbable suture (Nylon, 10-0, spatula needle, Kiyohara Industrial Park, Utsunomiya, Tochigi, Japan) in a continuous pattern (Shoelace). About 90% of the thickness of the cornea was sutured to ensure the apposition of all layers of the cornea. Finally, the AC was reformed with lactated Ringer’s solution (Figure 1).
Postoperative considerations
Topical ciprofloxacin 3% (one drop, Q3h) and topical tropicamide 1% (three drops, Q8h) were administered beginning the day of surgery for one week after surgery. Topical prednisolone acetate 1% (one drop, Q3h) was administered for one month. Also, systemic ciprofloxacin (250 mg, 15 mg/kg, PO, Q12h, Tehran Darou Co., Iran) was administered for three days. The vision was evaluated by the dog’s response to a menacing gesture and its subsequent movement. For the bilateral surgery group, each eye was assessed separately. By microscope and ophthalmoscopy, an ocular examination was performed on every operated eye for 1, 2, and 4 weeks, and every 2 months until 2 years after the surgery.
Results
In this report, the average age of the studied dogs was 11.9 years. About 10.53% of dogs were less than 5 years old, 10.79% were between 5 and 10 years old, and 73.68% were between 10 and 15 years old. Also, 52.63% of cases were female, and 47.36% were male. In addition, 57.90% of animals, unilaterally, and 42.10% of animals, bilaterally, suffered from cataracts. All animals were healthy and had no history of head trauma, ocular disease, etc. In ultrasonography, in all cases, the lens was abnormally echogenic and slightly thicker than usual, and the global size was within the normal limits in all cases (Figure 2).
The PLR was checked, which was positive in all dogs. In the follow-up, there were no signs of glaucoma (acute corneal edema and redness of the eyes in any case). In most cases, the patient had good vision during postoperative examinations. Only in one case, severe retinal atrophy was seen, but the cause was unclear.
Discussion
Cataracts in dogs often develop as a result of the aging process and increase after 8 years old, but in young dogs at three years or less, they may develop (Kibar et al., 2014). Similar to our study, the average age of involvement in cataracts is reported to be over 8 years (Patil et al., 2014; Chahory et al., 2003; Guerra et al., 2018). However, Heywood (1971) showed that the appearance and timing of cataracts in beagle dogs were up to 1 year of age. He stated that the early development of cataracts can depend on the breed of the animal. Also, Guerra et al. (2018) indicated that the most common breeds in the United Kingdom with cataracts are the Labrador Retriever and Jack Russell, which could be due to the incredible popularity of these two breeds in the UK; otherwise, similar to our study, cataracts can affect most dog breeds.
The symptoms of cataracts (uveitis, blindness) are often not recognized by dog owners, and they notice when the eye lenses have become white (Fischer et al., 2018). At the stage of late maturity (mature cataract), vision is completely lost. Therefore, unlike humans, in dogs, cataracts are diagnosed at relatively late stages, resulting in hardening or liquefaction of the lens (Davidson et al., 1990). In the ultrasonography, the abnormal echogenicity of the lens was confirmed. The thickness of the lens was higher than usual, and the global size was within the normal limits in all cases. In the clinical evaluation, the lens was opacified, and surgery was needed. Cataract surgery is a selective treatment in animals to improve their quality of life. Therefore, the correct selection of the patient, especially in the early stages of the disease, is essential to maximize the successful surgical outcome (Fischer & Meyer-Lindenberg, 2014). In the past years, the MECCE technique in dogs has been a standard and popular procedure for lens extraction. This method extracted the anterior lens capsule, lens cortex, and nuclear material (Patil et al., 2014). Various studies have shown that surgery in the immature stages has a higher success rate than in the mature and hyper-mature stages. However, in the Leasure et al. (2001) study, the comparison of tonometry results in different stages of cataract formation showed a significant difference only between the groups with immature and hypermature cataracts.
Today, the PHACO technique has been introduced as a standard method for cataract surgery due to smaller incisions and a reduction of surgical time compared to the MECCE technique. The only disadvantage of this method is the high equipment and materials cost (Linebarger et al., 1999). In the cataract cases of dogs, the size, the density of the cataractous lens, and the thickness of the capsule increased. So, the approach of MECCE as a primitive and economical method that does not need special equipment has been recommended (Patil et al., 2014). In the preoperative assay, the PLR was assessed, which was positive in all dogs; the absence of the reflex could be considered positive for retinal disease. Startup (1969) stated that pupillary response to light is an essential evaluation factor.
One of the reasons for the success of cataract surgery is the use of a suitable suture. Unlike some studies that used absorbable sutures (Vicryl, 7-0 to 9-0, simple interrupted or continuous pattern) (Biros et al., 2000; Chahory et al., 2003), in the present study, a corneal incision closed with 10-0 nylon suture contained a spatula needle with a continuous pattern (shoelace) that no need to remove the stitches. Only in one case was a loose suture removed and then replaced. Patil et al. used the MECCE method after 3 months of follow-up and found a success rate of 75%. They used a 10-0 nonabsorbable monofilament suture, which is thinner than nylon 8-0, and no sutures were removed (Patil et al., 2014). Also, in the study of Bonea, which used the MECCE method, the sclera and the conjunctiva were sutured with 8-0 mono nylon in three separate stitches. However, in this study, after 30 days, posterior capsular opacification developed, and the dog had partial vision loss, but no other postoperative complication was observed (Bonea & Igna, 2022). In another study, the corneal incision was closed using simple sutures with 10-0 black nylon after successful PHACO surgery (Kang et al., 2022). In other studies, the use of nonabsorbable threads such as silk 10-0 and Prolene 8-0 in the MECCE method, it has also been reported (Patil et al., 2014; Beteg et al., 2008).
Care and evaluations after each surgery show the degree of its success. In this study, the dogs became active and comfortable in the first days after the surgery. Most dogs had sufficient vision to deal with obstacles at post-surgery examinations, which increased their self-confidence and ultimately helped improve their quality of life. Two weeks after surgery, clinical symptoms such as corneal opacity and posterior capsular fibrosis, which led to definite corneal opacity, were not observed. Suppose excessive handling and postoperative complications can be prevented. In that case, MECCE can be an alternative for owners who cannot afford lens costs and would like to resolve vision loss in their pets (Bonea & Igna, 2022).
Surgery is considered to have failed when dogs develop painful and blinding complications such as endophthalmitis, retinal detachment, or glaucoma (Bonea & Igna, 2022). Topical antibiotics, NSAIDs, and mydriatics reduce corneal edema, posterior capsular opacity, and anterior uveitis. In this study, preoperative administration of the topical NSAID and systemic NSAID was done. Chandler et al. (2007) recommended using COX-2 inhibitors to prevent posterior capsule opacification. Also, Yi et al. (2006) recommended that a single intravenous dose injection of flunixin meglumine at the time of induction of anesthesia is advantageous in preventing fibrin formation. Among the symptoms of glaucoma are acute corneal edema and redness of the eyes (Moumneh et al., 2020). In the follow-up, there were no signs of glaucoma (acute corneal edema and redness of the eyes in any case).
Despite the availability of advanced techniques, PHACO cataract surgery is not yet accessible in all centers. The MECCE procedure can be a viable alternative in cataract surgery for dogs, given the limitations of capsular thickness, hardness, and the size of cataract lenses, as well as the unavailability or unaffordability of canine lenses. Although the number of animals studied is minimal, reporting successes of the MECCE method can greatly contribute to canine cataract treatment.
Ethical Considerations
Compliance with ethical guidelines
In this study, we gave enough information to the animal owners about the type of operation, and consent was obtained from them.
Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.
Authors' contributions
Conceptualization, supervision, methodology, data collection, review and editing: All authors; Data analysis: Shiva Amanollahi; Investigation and writing: Shiva Amanollahi Ehsan Lajmiri.
Conflict of interest
The authors declared no conflict of interest.
Acknowledgments
The authors thank the staff of the Faculty of Veterinary Medicine Teaching Hospital of Ferdowsi University of Mashhad, Mashhad, Iran, for their cooperation.
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