Retrospective Study of Long-Term Outcome of Phacoemulsification in 22 Feline Eyes with Presumed Congenital/Juvenile Cataracts (2007–2020)
ABSTRACT
The objective of this study was to determine the complication risk and prevalence after phacoemulsification in cats with presumed congenital/inherited cataracts. Twelve client-owned cats were included in the study. This retrospective study spanned 13 yr and involved 22 eyes. The median age at the time of surgery was 15 mo (range: 4.5–168 mo of age). Recorded complications were 3 eyes developed postoperative ocular hypertension, 1 eye developed glaucoma, 7 eyes developed feline herpes virus-1 signs, and 7 eyes developed postoperative uveitis >2 wk after surgery. No eyes had developed intraocular sarcomas at the time of their last exam. All eyes remained visual at last follow-up (range: 0.5–121 mo). Success was defined as a comfortable and visual eye without intraocular neoplasia, glaucoma, a partial or complete retinal detachment, or uveitis that occurred >2 wk after surgery or persisted longer than 2 wk. Twenty-one out of 22 eyes had a successful outcome. In this study, cats with presumed congenital/juvenile cataracts who underwent phacoemulsification had an excellent outcome.
Introduction
Cataracts in cats are most often secondary to chronic uveitis.1–5 Trauma, metabolic disorders such as hypocalcemia, dietary deficiencies, drug or toxin effects, and radiation are also known to cause secondary cataracts in cats.1,2,6–13 Hereditary cataracts are most likely inherited through an autosomal recessive mode and have been documented in Bengal cats in France and Russian blue cats in Sweden.1,4,14 Documented congenital cataracts include posterior nuclear Y-suture involvement in Birman kittens, triangular cortical cataracts in Himalayan kittens, and posterior cortical cataracts in other breeds.1,4,14–18 Congenital cataracts are also associated with Chédiak-Higashi syndrome in cats involving the posterior nucleus, sutures, cortex, and capsule.19 Senile cataracts are thought to be uncommon in cats; however, in one study, all cats by the age of 16 yr had some degree of lens opacity.2
The overall prevalence of cataracts in cats is generally thought to be lower than in dogs, but a recent study determined the prevalence of cataracts in a large study population of cats to be 13%, compared to approximately 15% in dogs.20 Cataract surgery, however, remains much less common in cats than dogs, despite some practitioners’ belief that success rates in cats appear to be better than in dogs.1 According to Glaze (2007), the feline uvea responds less intensively to surgical trauma than in canines and postoperative inflammation can be controlled more easily.19 The reason for fewer surgical cases in cats than in dogs is undocumented, but the authors postulate it may be because of a higher prevalence of incipient or immature cataracts in cats that are slowly progressive compared to dogs. Owners and surgeons may not choose to pursue surgery in these patients because of their vision still being present. Additionally, secondary cataracts are more common in cats than in dogs, which may carry a higher chance of being inoperable and/or carry higher risks of postoperative complications.1 Secondary cataracts may be inoperable because of intractable uveitis or secondary complications such as glaucoma, lens luxations, and retinal detachments.1 Another reason is the high rate of diabetic cataracts in dogs, which are not present in cats because of the low activity of aldose reductase in lenses of older cats.1,21,22 As such, reports on feline cataracts and cataract surgery are limited because of the low incidence of operated cataracts in feline populations compared to canine populations.
Secondary complications due to the presence of chronic cataracts include phacolytic uveitis, glaucoma, retinal detachment, and lens luxation.1,19,20,23 In dogs, the rate of complications without surgery varies between 20 and 75%, and complication rates after phacoemulsification range from 10 to 26%, depending on the study.24–35 However, there have been limited reports in cats.5,20,32 One study followed three cats for at least 16 mo following cataract surgery, with one cat developing secondary glaucoma.20 A recent study of 71 cats with various etiologies of cataracts were followed after phacoemulsification for an average of 198 days.5 The most common short-term complications were uveitis (34.1%) and corneal ulceration (26.8%).5 Long-term, the most common complications reported were posterior capsular opacification (36.1%) and synechia/dyscoria (34.0%).5 The authors postulate that presumed congenital/juvenile cataracts in cats have a better success rate for lifelong vision than those that develop from underlying pathology, but there is no published data focusing on this population. The purpose of this study was to determine the potential success of phacoemulsification in felines with presumed inherited cataracts and the prevalence of both short- and long-term complications after surgery.
Materials and Methods
Sample Selection
Records from 2007 to 2020 were reviewed. Cats with cataracts secondary to chronic uveitis, trauma, or other causes were excluded. Clinical support for the presumed congenital/juvenile etiology included no flare or cell in the aqueous humor, no synechia, no keratic precipitates, no rubeosis irides, and no changes to iris coloration to support previous infectious or inflammatory uveitis at the time of initial presentation. Other supporting evidence included a bilateral nature (even if asymmetric), progression over time, and a lack of other ocular or systemic cataract-inducing disorders at the time of presentation or historically.
All cats underwent a full ophthalmic examination on initial presentation by one of three board-certified veterinary ophthalmologists, including slit-lamp biomicroscopya, indirect binocular ophthalmoscopyb,c,d, and intraocular pressure (IOP) evaluation using applanation tonometrye. Eyes were dilated following the administration of topical tropicamidef before indirect ophthalmoscopy. Cataracts were categorized by location within the lens and the stage of maturity as described by Glaze and Gelatt (2007).1
Before to surgery, ocular ultrasoundg was performed to evaluate for a retinal detachment and other posterior segment disease, and both photopic and 5 min dark adaptation scotopic electroretinogramsh were conducted. Serum chemistries and complete blood counts were performed before anesthesia. Animals over the age of 7 yr were offered geriatric screening, which included thoracic radiographs and an abdominal ultrasound by a board-certified veterinary radiologist, and was performed based on client preference.
Preoperative Treatment
Preoperative medications were started 24 hr before surgery and included a topical nonsteroidal anti-inflammatory (NSAID) q 6 hri,j, a topical steroid q 6 hrk, and a topical antibiotic q 6 hrl,m. All patients were given a single dose of topical atropinen upon hospital admission the day of the surgery.
Surgical Procedure
All patients were anesthetized under the guidance of a board-certified veterinary anesthesiologist. Sedation included butorphanolo (0.2 mg/kg IV) and midazolamp (0.1 mg/kg IV). Propofolq (6.0 mg/kg IV to effect) was used for induction. Cefazolinr (22.0 mg/kg IV) was given after induction. Isofluranes was used for maintenance anesthesia, and patients were maintained on IV fluids intraoperatively. The periocular area was clipped of hair and aseptically prepared and draped, and it and the globe were flushed with 1:50 dilute betadine solution and balanced salt solution. After mechanical ventilation was achieved, a neuromuscular block was performed using cisatracuriumt (0.1 mg/kg IV). A barraquer wire eyelid speculum was placed, and diluted 1:10,000 epinephrineu was instilled in the conjunctival cul-de-sac. A beaver blade was used to make an approximately 4 mm partial-thickness corneal incision, followed by a full-thickness stab incision through the cornea into the anterior chamber using a 3.2 mm keratome. Epinephrine (1:10,000 dilution) was injected into the anterior chamber for vasoconstriction and further mydriasis. The anterior chamber was inflated with one of two types of cohesive viscoelastic substancesv,w. Vannas scissors were used to make an anterior lens capsulotomy to begin an anterior capsulorhexis. Utrata forceps were used to complete a continuous-tear curvilinear anterior lens opening, approximately 4–6 mm in diameter. A phacofragmentation and aspiration handpiece tipx was inserted through the corneal and anterior lens openings, and the lens was fragmented and aspirated. The remaining lens cortex was removed by irrigation and aspiration, followed by polishing of the anterior and posterior lens capsules. The lens capsule and anterior chamber were re-inflated with viscoelastic material, and insertion of a 53-diopter intraocular lens (IOL) into the remaining capsular bag was attempted. The type of IOL was based on availability at the time of surgeryy,z. The viscoelastic material was removed from the anterior chamber by irrigation and aspiration, and the cornea was closed in a double continuous pattern using 9-0 polyglactin 910 braided sutureaa. This procedure was repeated on the contralateral eye for all cats who received bilateral surgery. Neuromuscular blockage was reversed with neostigmine methylsulfateab (0.05 mg/kg IV). After recovering from anesthesia, cats were discharged to the care of their owners the same day of surgery. If no owner concerns were noted after discharge, the first recheck examination was scheduled for 2 wk after surgery. If client concerns were noted, cats were examined at various time points before the scheduled 2 wk examination.
Postsurgical Treatment
Treatment after surgery varied slightly depending on the patient’s needs but included 2 wk of wearing an e-collar, oral amoxicillin/clavulanic acidac,ad approximately 13.0 mg/kg per os (PO) q 12 hr for 2 wk, and topical medications q 6 hr for the first 2 wk, including an antibiotic (ofloxacin or neopolygram), corticosteroid (1% prednisolone acetate), NSAID (diclofenac or flurbiprofen), and lubricantae. The topical NSAID and steroid were tapered over the following 6 mo, depending on patient needs and response to therapy, to a recommended once daily administration. Some owners discontinued medications without direction. Other less common postoperative medications included an oral NSAIDaf (1 tablet PO q 24 hr for 3 days) and a topical anti-glaucoma medicationagq 8 hr if postoperative hypertension (POH) was exhibited.
Analysis
The complete ophthalmic examination findings were reviewed for each postsurgical evaluation. Postoperative success was defined as a comfortable and visual eye without intraocular neoplasia, glaucoma, a partial or complete retinal detachment, or uveitis that developed more than 2 wk after surgery or persisted for longer than 2 wk. Complications were recorded as an increase in IOP over 25 mm Hg within the first 4 hr after surgery (POH), as well as persistent uveitis, or glaucoma, retinal detachment, and feline herpesvirus-1 (FHV-1) symptoms (persistent conjunctivitis, keratitis, and/or corneal ulceration) at any time postoperatively.
Results
Twenty-two eyes of 12 cats met the criteria for inclusion in the study. Sexes included 7 castrated males, 4 spayed females, and 1 intact male. Patients included domestic shorthair (7/12), long hair (2/12), and medium hair (1/12) cats, one Siberian cat, and one ragdoll cat.
Cataract stages at presentation were late immature (6/22), mature (9/22), and hypermature (7/22) (Table 1). Comorbidities included cerebellar hypoplasia in one cat, and retinal dysplasia discovered after phacoemulsificiation in another. One patient presented at age 11 mo with bilateral, lower eyelid entropion presumed to be due to chronic conjunctivitis, in addition to bilateral, mature cataracts. Conjunctivitis workup was positive for calicivirus, FHV-1, mycoplasma, and Bartonella hensela exposure, and the patient was treated perioperatively with azithromycin at 10.0 mg/kg PO q 24 hr for 21 days. This patient’s cataracts were not considered secondary to any of these infectious diseases, because there were no signs of previous or active uveitis at presentation.
Cataract stage in one eye of two cats progressed between presentation and the time of surgery. Surgery was done an average of 40 days after initial diagnosis, ranging from 1 day to 6 mo. The median age at the time of surgery was 15 mo, ranging from 4.5 to 168.0 mo. Presurgical electroretinograms and ocular ultrasounds did not show any abnormalities that resulted in the cancellation of the surgery. During surgery, two eyes of two different cats were found to have equatorial lens capsule ruptures, which were not observed on preoperative ocular ultrasound. One of the eyes with a lens capsule rupture did not have an IOL placed. All other eyes had successful IOL insertions. No other intraoperative complications were reported in any cats. The cat with bilateral entropion underwent bilateral, permanent lateral canthotomies combined with a bilateral modified Hotz-Celsus procedure at the same time as the cataract surgery.
Median follow-up was 19 mo, with examinations ranging from 2 wk to 125 mo. A single cat with bilateral, mature cataracts was lost to follow-up 2 wk after the operation. The cat had surgery performed at an age of 5 mo and died 9 yr later from intestinal neoplasia. The owners were contacted for the purpose of this study, and they stated that the cat was hunting flies in the house shortly before his death.
Total postsurgical complications in this study included nine eyes of five cats that experienced POH, uveitis, glaucoma, or presumed FHV-1 flare-up(s). No patients experienced a retinal detachment or posttraumatic sarcoma after the operation.
Only two eyes of two cats developed multiple postsurgical complications other than those associated with multiple episodes of presumed FHV-1 flare-ups. One eye of cat 10 developed uveitis 2 wk after the surgery and glaucoma 7 mo after the surgery. One eye of cat 1 developed uveitis 63 mo after the surgery and then an FHV-1 flare-up 121 mo after the surgery.
Three eyes of two cats experienced POH within 4 hr after surgery. One of the three eyes that experienced POH later developed glaucoma.
Seven eyes of four cats exhibited uveitis at the time of the 2 wk recheck examination or afterward. The median onset was 2 wk after the operation (range: 0.5–63 mo). One cat developed a lipid flare 2 days after the operation due to daily high-fat meals, including duck pâté and coconut oil. Once the diet was corrected, the lipid flare resolved. No cases of uveitis persisted more than 2 wk.
One cat developed glaucoma in the left eye 7 mo after surgery, with an IOP recording of 32 mm Hg (normal values: 10–20 mm Hg).1 This cat also exhibited POH in the left eye, and a posterior capsular tear of the right eye that was discovered in surgery. The cat was initially treated with dorzolamide-timolol but switched to latanoprost PO q 12 hr after IOP continued to rise despite therapy. After changing topical therapy, IOP remained controlled. This cat remained sighted at the time of the last follow-up (13 mo after surgery).
Seven eyes of five cats developed symptoms of presumed FHV-1 flare-up (conjunctivitis, keratitis, and/or corneal ulceration) after the operation. No respiratory signs were noted. The median time to development of FHV-1 signs was 3 mo after the operation with a range of 2 wk to 121 mo. Four eyes of two cats developed conjunctivitis with a median postoperative onset of 5 mo (range: 4–17 mo). One cat developed bilateral keratitis 2.5 mo after surgery. Three eyes of two cats developed dendritic corneal ulcers. The median onset was 2 mo after surgery, with a range of 2 to 121 mo. All patients with these signs responded to topical 0.2% cidofovir twice daily.
As stated previously, success was defined as a comfortable and visual eye without intraocular neoplasia, glaucoma, a partial or complete retinal detachment, or uveitis that developed 2 wk after surgery and/or persisted more than 2 wk. Data were available for eight cats 12 mo after surgery, five cats after 24 mo, and four cats after 36 mo. Four cats were followed for at least 60 mo. One eye of one cat developed glaucoma 7 mo after surgery and therefore did not meet the criteria for a successful outcome after this time point. Twenty-one eyes met the criteria for a successful outcome at their last examination. All eyes of all cats remained visual in this study at their last examination. No cats developed intraocular neoplasia after surgery.
Discussion
This is the first retrospective study of outcomes of cataract surgery in cats solely with presumed congenital/juvenile etiology using the same surgical protocol and similar pre- and postoperative care, including long-term follow-up. One study recently conducted in the United Kingdom by Fenollosa-Romero et al. evaluated the surgical success of feline cataract surgery on cataracts of all etiologies completed at five different locations with different surgical and perioperative care methods.5 The visual success rate was 92.6% at 1 yr in the Fenollosa-Romero study, whereas in this study all cats remained visual at 1 yr.5 This study, in addition to the current study, supports the possibility that phacoemulsification in cats has a high chance of success. However, more research is needed to confirm these results and to monitor for complications that may occur long-term.
During the entirety of the study, complications defined here as persistent uveitis, glaucoma, retinal detachment, intra-ocular neoplasia, and FHV-1 symptoms occurred in 11 eyes of seven cats, which is consistent with the incidence of complications in the Fenollosa-Romero study (41.6%), excluding their data of posterior capsular opacification and synechiae/dyscoria. The majority of complications that occurred in the present study were due to FHV-1 symptoms. The FHV-1 symptoms may or may not have been due to the surgery and aftercare.
In dogs, performing surgery on advanced stages of cataracts rather than at earlier stages carries a poorer prognosis.1,24,26,27,30 This has not been established in cats but may not be as important for prognosis. As mentioned previously, this may be because the feline uvea responds less to surgical trauma, and inflammation is more easily controlled in cats with topical therapy.1,19 The authors of the Fenollosa-Romero study stated that no conclusion could be drawn from their data pertaining to visual outcome at 1 yr after surgery and cataract stage before phacoemulsification, because the occurrence of blindness after surgery was too low.5 This information is important for patient prognosis, however, and more studies in this area are needed to determine if a relationship between cataract stage at the time of surgery and a successful outcome exists.
Patients studied here experienced a similar incidence of postoperative uveitis (five eyes of three cats) compared to the patients from the Fenollosa-Romero et al. study.5 As any intraocular surgery causes uveitis, this was not unexpected. All cats in this study with uveitis that occurred more than 2 wk after surgery underwent a complete blood count, blood serum chemistry, Toxoplasma gondii testing, and Bartonella henselae testing. All results were unremarkable or negative. In all cases, the uveitis was quickly responsive to adjustments in topical therapy. The cat followed for the longest time after surgery began experiencing uveitis over 9 yr after surgery after developing jejunal carcinoma and a paraneoplastic-associated anemia. In no cases did uveitis persist more than 2 wk.
Three eyes of two cats experienced POH within 4 hr after surgery. One cat was 5 yr of age, and the second was 14 yr of age. It is possible that the chronicity of cataracts before presentation and/or numerous other factors, such as the duration of phacoemulsification time, type of viscoelastic, irrigation/aspiration time, and others may have played a role, but these factors were not evaluated. One eye of one cat that experienced POH went on to develop glaucoma. The patient was found to have an equatorial lens capsule rupture at the time of surgery followed by an episode of postoperative uveitis, all of which could have contributed to the development of glaucoma 7 mo after surgery. As stated in the results, the IOP in this eye remained well-controlled on topical therapy, and the eye was visual and comfortable at the time of the last follow-up (13 mo after surgery). Even though, historically, latanoprost is thought to be less effective in cats than carbonic-anhydrase inhibitors as reported in one study in which it failed to lower IOP in normal cats, its use in cats needs to be further explored as evidenced by this study and a recent study conducted by McDonald et al.36,37
Retinal detachment is a well-documented postoperative complication of canine cataract surgery and occurs in 1.2% of cats with all types of cataract etiology in the Fenollosa-Romero study.1,5,24–27,30,34,35 No patients in this study developed retinal detachment.
Only cats with presumed primary inherited cataracts were included in this study, which may have resulted in the low incidence of all aforementioned complications. However, due to the small study population and the exclusion of cats with secondary cataracts, further research is needed. Chronic uveitis, although leading to cataract formation, also incites the development of a preiridal fibrovascular membrane, changes the composition of the vitreous, and potentiates the formation of hyalitis and vitreal membranes, all of which increases the risk for glaucoma and retinal detachment.1
Seven eyes of four cats developed symptoms of an FHV-1 flare-up after surgery, including conjunctivitis, corneal ulcers with redundant epithelium or dendritic appearance, and/or keratitis. It was suspected that most FHV-1 carriers would exhibit a flare-up shortly after surgery, because surgery, wearing an e-collar, perioperative eye drops, and the experience of traveling to a veterinary hospital can all be considered stressful events for cats; however, only one cat developed a flare immediately after surgery at the 2 wk recheck examination. All other cats who experienced an FHV-1 flare-up were at least 2 mo after phacoemulsification. Two cats had recurring presumed FHV-1 flare-ups. Each episode resolved within 2 wk with treatment.
Some veterinary ophthalmologists are hesitant to perform cataract surgery in cats because of the concern for postoperative intraocular sarcoma development, but the risk and role that intraocular surgery plays in the development of intraocular sarcomas of cats is unknown. Ocular sarcomas of felines are locally invasive neoplasms that are often associated with a history of ocular trauma.38–41 They have the potential to metastasize and usually result in the enucleation of the affected eye.38–41 None of the cats included in this study developed intraocular sarcomas. In the Fenollosa-Romero study, one eye of one cat developed an intraocular sarcoma approximately 20 mo after phacoemulsification. However, the cataract etiology was previous trauma, which is a known risk factor for sarcoma development.1,5,38–41 The Comparative Ocular Pathology Laboratory of Wisconsin database contains over 20 cases of intraocular sarcomas of cats after ocular surgery, but the entire history of the cats was not reported (R. Dubielzig, personal communication, March 2020). Future study in this area is needed before a relationship between phacoemulsification and the development of intraocular sarcomas in felines can be deduced.
Limitations of this study are those pertaining to a retrospective study, including a small number of cases, the lack of a control group, the loss to follow-up of one patient, and the nonspecificity of records. Records did not include all the same information for each patient, for example, including the average phacoemulsification power and absolute phacoemulsification time. Future studies could continue to follow current cases and add more cases to the study prospectively with phacoemulsification conducted under the previously discussed protocol. Future studies may also include a control group of cats whose owners decline cataract surgery but who would receive regular ophthalmic examinations to establish a baseline of the prevalence of ocular complications naturally over time, as has been done in canine studies.24–27 Further study is also needed regarding ideal patient selection for feline cataract surgery and surgical success, because this is increasingly known to be important in canines.28,29,32,42–44
Conclusion
The study of feline cataracts and cataract surgery is vital for the future treatment and success in our feline populations after diagnosis of a cataract. Success in the present study was defined as an eye that is visual and comfortable without persistent inflammation, partial or complete retinal detachment, intraocular neoplasm, or glaucoma. All eyes remained visual and comfortable at the last follow-up examination, ranging from 0.5 to 121 mo after surgery. One eye developed glaucoma; however, pressures were well-controlled at the last follow-up examination (13 mo after surgery), and the patient remained sighted. Twenty-one eyes of 11 cats met the criteria for success at their last follow-up examination. The results of this study suggest that cats undergoing cataract surgery with presumed inherited and congenital cataracts may have an excellent long-term success rate with few postoperative complications. None
The authors of this paper would like to thank Dr. Joe Hauptman of Michigan State University for his expertise in the statistical data.
Contributor Notes
