Phacoemulsification cataract surgery describes the breakdown and removal of a cataract by high frequency ultrasound.
The ultrasonic waves are generated within a handpiece connected to a phacoemulsification unit. The handpiece is inserted into the cataractous lens via a small corneal incision and a circular incision within the anterior lens capsule.
During the phacoemulsification procedure, fluid irrigation and aspiration is used to maintain the shape of the globe, to keep the tip of the handpiece cool and to remove the lens fragments.
Uses
For removal of cataracts .
For removal of a subluxated lens .
For treatment of acute traumatic lens capsule rupture leading to phacoclastic uveitis .
Advantages
Phacoemulsification is a state-of-the-art technique which, in experienced hands, offers the best success rate for cataract surgery in dogs and cats.
Following removal of the cataract, the lens capsule remains in place and an artificial intra-ocular lens (IOL) can be placed within the capsule to optimize visual acuity.
Bilateral cataract surgery can be performed under the same anesthetic.
When used for treatment of lens subluxation it gives a superior postoperative outcome to lendectomy (ICLE) .
Lens capsule rupture often leads to severe and intractable complications such as uveitis and secondary glaucoma . Early phacoemulsification surgery is often successful in preventing these complications and saving vision.
Disadvantages
Phacoemulsification is a specialist surgical technique. It is essential that the surgeon has extensive microsurgical experience and has undergone detailed training in phacoemulsification techniques.
The use of an operating microscope and the correct microsurgical instrumentation and consumables are essential. Referral to a specialist ophthalmologist who is experienced in this technique is required.
Owner and patient compliance are vital. Intensive post-operative topical and systemic medications are essential for the success of this procedure, and regular post-operative re-examinations are required.
Postoperative complications may include wound breakdown, corneal ulceration , anterior uveitis, secondary glaucoma, retinal detachment .
Alternative techniques
Extracapsular cataract extraction (ECCE). This technique has been superseded by phacoemulsification.
Procedure
30-40 minutes per eye for an experienced surgeon.
Decision taking
Risk assessment
Phacoemulsification can be performed on all stages of cataract, but there is a higher risk of complications in advanced (hypermature) cataracts, and some cataracts may become inoperable due to complications such as retinal detachment, severe uveitis or secondary glaucoma.
Following a diagnosis of cataract, early referral to a veterinary ophthalmologist is advised, so that the surgical suitability can be assessed. This is especially important in the case of diabetic cataracts, which can progress rapidly to become inoperable.
Owner and patient compliance are vital. Intensive post-operative topical and systemic medications are essential for the success of this procedure, and regular post-operative re-examinations are required.
Referral to a veterinary ophthalmologist with extensive experience performing phacoemulsification cataract surgery is essential.
Anesthetist expertise
Neuromuscular blockade can be used to centralize the globe and so aid surgery. Experience of neuromuscular blockade and anesthesia is essential if using this technique.
Nursing expertise
For intra-operative assistance and post-operative medication.
Materials required Minimum equipment
Operating microscope.
Operating chair.
Phacoemulsification unit and handpiece.
Intra-ocular microsurgical kit suitable for phacoemulsification.
Artificial intra-ocular lens (IOL).
Lens inserter for foldable IOL.
Fluids, tubing and phacoemulsification consumables.
Position head with corneal surface positioned horizontally beneath operating microscope.
Aseptically prepare and drape the eye for surgery.
Place eyelid retractors.
Step 2 - Perform lateral canthotomy
Perform lateral canthotomy to increase exposure of globe if indicated.
Use perilimbal stay sutures and mosquito forceps to aid positioning of globe (if not using neuromuscular blockade).
Step 3 - Make 2 mm incision
Perform penetrating 2 mm incision with corneal stab knife (side port incision).
Step 4 - Inject viscoelastic material
Inject viscoelastic material (hydroxypropylmethylcellulose and hyaluronic acid) to maintain inflation of anterior chamber and to protect the corneal endothelium and intra-ocular structures.
Step 5 - Make 3 mm incision
Perform penetrating 3 mm incision with keratome, positioned 45°-60° from side port incision at dorsal aspect of globe.
Create a circular anterior lens capsule incision (anterior capsulorrhexis) to remove the central portion of the anterior lens capsule and allow access to the lens itself.
Hydrodissection of cataract to separate lens cortex from capsule.
Core Procedure
Step 1 - Phacoemulsification
Phacoemulsification of lens nucleus and cataractous cortex by preferred technique (eg ‘divide and conquer’, ‘phaco chop’), using the ultrasonic handpiece inserted through the perilimbal incision .
Step 2 - Irrigation/aspiration
Irrigation/aspiration to remove cortical fragments .
Capsule polishing.
Step 3 - Extend primary incision
Extend primary (dorsal) corneal incision by a few millimeters.
Place IOL into remaining lens capsule bag (through extended incision) .
Exit Step 1 - Closure
The corneal incision is closed using 8-0 or 9-0 Vicryl.
Repair lateral canthotomy wound using 4/0 or 5/0 nylon.
Regular re-examinations are recommended to check for complications. In the short-term, weekly check-ups are advisable for the first few weeks following surgery. In the long-term, regular check-ups (eg 3 monthly) are recommended, and should include intra-ocular pressure measurements.
Anti-glaucoma medications should be instigated if the intra-ocular pressure becomes elevated.
Wilkie D A, Colitz C M H (2007) Surgery of the canine lens. In: Veterinary Ophthalmologyfourth edition. Ed. K N Gelatt. Blackwell Publishing, Iowa, USA, pp 888-931.
Vetstream contributor(s)
Alison B Clode DVM DACVO , North Carolina State University, College of Veterinary Medicine, 4700 Hillsborough Street, Raleigh NC 27606, USA.
David Gould BSc (Hons) BVM&S PhD DVOphthal DipECVO MRCVS , Davies Veterinary Specialists, Manor Farm Business Park, Higham Gobion, Hitchin, Hertfordshire SG5 3HR, UK.
Referral to a specialist ophthalmologist who is experienced in this technique is required.
