The Dedicated Ophthalmology Referral Practice

Phacoemulsification

Phacoemulsification is the preferred technique. It literally translates from the Greek phaco - the crystalline lens, and emulsion - solids in liquid. The phaco unit harnesses the ultrasound given off from two crystals set close together in a handpiece, changing the power into a mechanical vibration of a titanium needle.

The needle vibrates at 40,000 times a minute, approximately 800 times a second! It shatters the solid material which mixes with the irrigation fluids fed down an outer plastic coaxial sleeve.

The resulting emulsion is sucked up the middle of the needle. This means that a solid, almost round, canine lens (11 x 11 x 8mm) can be removed through a 3.5mm corneal incision.

It is this ability to use small incision surgery plus the positive irrigating fluid pressure within the globe during the operation that gives us such an improvement over previously used methods.

The "skills suitcase" required by veterinary intraocular phaco surgeons is similar to our medical colleagues. Techniques to master include: anterior chamber entry; two-handed working; use of viscoelastic materials; continuous curvilinear capsulorrhexis, hydro-dissection; grooving and cracking; phacoemulsification; irrigation aspiration; capsular polishing; lens implantation; posterior capsulorrhexis; anterior vitrection and corneal closure.

It is important to understand that we no longer need to wait for a cataract "to become ripe" as used to be said for Granny's cataracts. With these new techniques it is much better to refer a case early, ideally when it is still possible to make an assessment of the peripheral retina.

The incidence of lens-induced anterior uveitis and even post-operative retinal detachment (see next page) increases if cases are hypermature before surgery is carried out.

An exciting development has been our ability to use the phaco small incision techniques on some subluxating or even dislocated clear lenses. The difficult part is to fix the lens during phacoemulsification of the lens substance, but once the capsular bag has been emptied it is delivered through the same small incision.

This leaves a much more normal looking eye, having used a 3.5mm incision compared to 14mm or more for the traditional intracapsular lendectomy. Other work has shown that astigmatism (corneal distortion) is minimal using the small incision approach compared to traditional methods.

An intraocular lens (iol) prepared for implantation.

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Intraocular lens implants may be used. Typically they would have a 7mm optic with a 15mm overall haptic length. A power of 36 to 40 dioptres is required to achieve emmetropia.

Debate continues about the absolute need of IOLs in the canine. There is no doubt that implanted dogs become visually rehabilitated more quickly in the first few days. There is also evidence that a correctly placed IOL with a good back push helps to minimise the development of posterior capsular secondary opacities. However, by three months after surgery it is difficult, if not impossible, to tell implanted from aphakics when running them through an obstacle course.

Post-operative
Retinal Detachment/...

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The phacoemulsification (phaco) handpiece has a central titanium needle and a co-axial irrigation sleeve. The needle vibrates 40,000 times per minute. Emulsified lens substance is aspirated up the centre of the handpiece.

1. Technology and Microsurgery

2. Phacoemulsification

3. Post-operative retinal detachment

4. Prognosis

This is a crystalline cataract usually associated with ageing. Both sets of suture lines can be seen.

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This lens shows a central brown opacity. It contains haemosiderin. It is associated with a patent hyaloid artery entering the lens at the posterior pole and presents an extra challenge to surgery. Vitrection and bipolar cautery will be carried out after a normal phacoemulsification of the lens substance.

Click the image to see a high resolution version.

The two-handed phaco technique, using 1mm and 3.5mm clear corneal incisions, provides best control of the lens. The picture is taken from the "surgeon's viewpoint", that is sitting at the 12 o'clock position with the upper eyelid closest.

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In comparison to the small incision phaco surgery (pictured above), traditional extracapsular delivery involves a major (14mm or more) side opening of the globe.

This is the latest type of iol which is made of hydrophylic acrylic plastic. It is soft and pliable enough to be injected through a 3mm needle. This means that we use the same 3.2mm incision as for the phaco needle.

Click to see a high resolution version.