Animals and ophthalmic examination
The study was carried out on 60 (90 eyes) client-owned dogs with lens-related ocular emergencies. These dogs were admitted to the Ophthalmology Service at the Department of Small Animal Surgery, Faculty of Veterinary Medicine, Cairo University from November 2018 to September 2020. The study protocol was approved by the Scientific Committee of the Small Animal Surgery at Cairo University prior to investigation. No ethical approval was required, as this study investigated a series of client-owned clinical cases admitted to our clinic without involvement of experimental subjects. Informed consent was obtained from the owners of all enrolled dogs prior to performing the diagnostic and treatment procedures. Data collected from the clients included signalment, history of trauma, duration of clinical signs, and history of previous medications. Before inclusion, all dogs underwent a complete ophthalmic examination including the slit-lamp examination (SL 14 handheld slit lamp, Kowa, Tokyo, Japan), fluorescein staining (Bio-Glo® Fluorescein sodium Strips 1 mg, HUB pharmaceuticals, LLC., USA), indirect ophthalmoscopy (Riester, Germany), and measurement of intraocular pressure (IOP) using Tonopen tonometer (Tonopen XL®, Reichert Technologies, NY, USA). Topical anesthetic solution (Bexonate hydrochloride; Benox® 0.4% ophthalmic solution, EIPICO Co., Egypt) was instilled two minutes before IOP measurement. The vision status was evaluated via a menace response, pupillary light reflex, and the history of proper vision prior to the acute onset of the disease in patients with anterior luxation and existing pressure spike. The enrolled dogs were considered eligible if they were diagnosed with lens subluxation or luxation (anterior or posterior), lens-induced uveitis (LIU), lens capsule disruption, or secondary lens-induced glaucoma. Dogs with immature cataracts without evidence of related ocular abnormalities and those with incurable or infected endophthalmitis were excluded from the study. The clinical findings associated with all enrolled cases were evaluated and recorded.
Ultrasonographic examination and laboratory tests
The ultrasonographic examination was performed on 15 eyes with concurrent corneal edema using an ocular B-mode scan and a 7.5-10 MHz micro convex probe (EDAN DUS 60 PRO, digital ultrasound, Shenzhen, P.R. China). Serum triglycerides and cholesterol levels were evaluated in 3 dogs with lipid flare.
Treatment protocols
Lens subluxation/luxation with or without secondary glaucoma
Lens luxation and subluxation were diagnosed in 45 eyes (25 with anterior lens luxation, 15 with subluxation, and 5 with posterior lens luxation) and treatment protocols involved medicinal management and surgical intervention.
Medicinal management
Medical treatment was applied to the 15 eyes diagnosed with lens subluxation with (11 eyes) and without (4 eyes) secondary glaucoma, and to the 5 eyes with posterior lens luxation and associated glaucoma. The 11eyes with lens subluxation and secondary glaucoma and 5 eyes with posterior lens luxation and secondary glaucoma were treated with prostaglandin analog latanoprost (Xalatan®; Pfizer) twice daily [14,18] and pilocarpine 2% (Isoptocarpine®, Alcon, Egypt). The 4 eyes with lens subluxation and no evidence of secondary glaucoma have received only miotic agents to keep the lens stable behind the corresponding pupil; pilocarpine 2% (Isoptocarpine®, Alcon, Egypt). All treated dogs were re-evaluated at weekly intervals for 3 successive weeks.
Surgical intervention
Eyes with anterior lens luxation were treated by routine intracapsular extraction of the lens through a dorsal corneal incision [16]. Associated emergency treatment to lower the elevated IOP was performed for 19 out of 25 eyes using systemic dexamethasone sodium phosphate (0.1 mg/kg b.w. i.v., Dexamethasone® 8mg/2ml, Amriya pharmaceuticals, Egypt). Topical application of tobramycin/dexamethasone combination (Tobradex®, Alcon, Egypt), timolol maleate 0.5% (timolol®, EIPICO, Egypt) and tropicamide1% (mydriacyl®, Alcon, Egypt) was performed every 8–12 hours for 14 days until the time of surgery. Dogs were routinely pre-medicated with atropine sulphate (Atropine sulphate®; ADWIA, Egypt) and xylazine hydrochloride 2% (Xylaject®; ADWIA, Egypt) in a dose of 0.04 mg/kg b.w. s.c. and 1 mg/kg b.w. i.v., respectively. General anesthesia was achieved with ketamine hydrochloride 5% (Keiran®, EIMC pharmaceuticals Co., Egypt) in a dose of 15 mg/kg b.w. i.v. A 0.5 ml of sterile, non-pyrogenic, high molecular weight, non-inflammatory highly purified viscoelastic preparation containing sodium hyaluronate (PROVISC®, 0.55 ml sodium hyaluronate1%, Alcon, Egypt) was injected to fill the anterior chamber. The anterior chamber was then entered through a 45° angled slit made by a corneal knife. Angled incisions, varying between 150° and 170°, were made using left- and right-handed corneal scissors, and the lens was grasped and removed using a lens loop. The anterior chamber was then irrigated using sterile saline (sodium chloride 0.9%®, Union pharma, Egypt) and the corneal incision was closed using 8-0 polyglactin (coated vicryl®; Ethicon, USA) in a simple interrupted pattern. All surgical procedures were done under a binocular surgical microscope (12.5x, 66 VISION TECH CO., LTD. China). A systemic course of a 3rd generation cephalosporin (ceftriaxone®, Sandoz, Egypt) was injected for 7 successive days at a dose of 25 mg/kg b.w. i.m. The owners were advised to instill tobramycin/dexamethasone combination (Tobrdex®, Alcon, Egypt) for 7 days.
Lens induced uveitis (LIU) without glaucoma
Lens-induced anterior uveitis was diagnosed in 25 eyes and the treatment protocol included bulbar subconjunctival injection of 0.4 ml of dexamethasone sodium phosphate (Dexamethasone® 8 mg/2ml, Amriya pharmaceuticals, Egypt) at 3 days interval for 9 days (4 injections). The treatment also included topical administration of tropicamide1% (mydriacyl®, Alcon, Egypt) and tobramycin/dexamethasone combination (Tobradex®, Alcon, Egypt) 4-6 times a day for 3 weeks.
Uveitic glaucoma
Uveitic glaucoma was diagnosed in 15 eyes and treatment protocol included 4 systemic injections of dexamethasone sodium phosphate (0.1 mg/kg b.w. i.v.) at 3 days intervals. Instillations of the eye with tobramycin/dexamethasone combination (Tobradex®; Alcon, Egypt), timolol maleate 0.5% (timolol®; EIPICO, Egypt) and tropicamide1% (mydriacyl®, Alcon, Egypt) were also performed 4 times a day for 2 weeks.
Lens capsule rupture
Five eyes with traumatic scleral rupture were diagnosed in this study. These cases were associated with anterior capsule rupture and anterior luxation of the lens. All eyes were presented with acute injury and anterior lens luxation. The treatment included intracapsular lens extraction and closure of the scleral defects with 8-0 polyglactin (coated vicryl®; Ethicon, USA) in a simple interrupted pattern.