Fundamental principles

Cataract surgery has the potential to transform the visual lives of patients. Modern phacoemulsification has brought reduced incision size, earlier stabilization of refraction, and more predictable astigmatic effects of surgery. In the small number of cases where surgery is associated with significant complications, it may produce a negative impact on the lives of patients, often during the later years of their lives. The ophthalmologist has to tread the line between restoring sight and risk of complications by using knowledge and skill to optimize surgical choices and outcomes. Some major challenges in cataract surgery persist including peroperative posterior capsule rupture, inadvertent loss of the crystalline lens into the vitreous, postoperative endophthalmitis, and late sight-threatening complications of retinal detachment and corneal decompensation.

Surgeons are likely to perform at the highest level when they feel relaxed in their working environment. Experience shows that surgeons working in a good team, providing complementary skills (ophthalmologists, anesthetists, nurses, optometrists, orthoptists, technicians, operating department assistants), will be able to acquire the information they need for informed decision making with patients and high quality surgery. Indeed, successful cataract surgery requires much more than the surgical act of a cataract procedure. It involves matters as far reaching as the construction of medical facilities to make care delivery streamlined, mastery of technologies both established and innovative, the building of efficient teams with workers who function in harmony, and an evolved level of interpersonal skills from members of the team. With these and other building blocks can an efficient service providing cataract treatment be established.

So the fundamental principles in cataract surgery are like those for medicine as a whole. Assessment of a patient is reliant on history and clinical examination with additional technical examination including parameters such as refraction, keratometry, corneal topography, and biometry. The patient’s visual symptoms and needs form a crucial part of this interchange. Coexisting eye disease such as diabetic eye disease, age-related macular degeneration (AMD), glaucoma, and amblyopia must be taken into account. The intraocular lens technologies now available need to be selected to give patients the best chance to achieve their visual goals. This will involve consideration of the target refractive outcome after cataract surgery with use of monofocal, toric or multifocal lens implants and possibly incisional corneal astigmatic modification where appropriate. The method of anesthesia for cataract surgery will depend on surgeon/patient preference based on the patient’s age, general health, level of anxiety, and ability of patients to cooperate. It is desirable to offer written or video information for patients about their diagnosis and treatment. The internet now offers an extensive if unfiltered information resource for patients.

Development of modern phacoemulsification

Duke-Elder1 credits Daviel (1753) with the earliest description of cataract surgery as we understand it today. Prior to this, treatment of cataract had relied on dislocation of the opaque human lens into the vitreous cavity (the technique of couching). During the 20th century advances in instrument manufacture, development of sutures, and the introduction of the operating microscope came together to produce successive decades of rapid development in cataract surgery. The use by Ridley of extracapsular cataract surgery combined with the first intraocular lens in London in the late 1940s set the trend. Whilst lens implants did not gain wide acceptance for many years, by the mid-1970s extracapsular cataract surgery combined with posterior chamber lens implantation presented a reliable and safe way of restoring vision in patients with cataract. It proved much more acceptable to patients than the alternative of aphakic spectacles worn after intracapsular cataract surgery. Anterior chamber supported lens implants lost popularity during this period and are now used only where capsular support for a posterior chamber lens has been lost.

During the period 1973–9 Kelman was working on ultrasonic fragmentation of the human lens using 3 mm corneoscleral incisions. In the early days of the technique2, there were concerns about corneal endothelial cell damage caused by phacoemulsification. Later refinements including phacoemulsification within the capsular bag and use of viscoelastics combined with improving technology have significantly reduced this concern. Early phacosurgeons also experienced problems with dense brunescent cataracts which were resistant to fragmentation with the early generation of ultrasonic handpieces.

The move towards acceptance of phacoemulsification as the preferred method of cataract surgery in the western world followed the description of the opening of the anterior lens capsule using a continuous circular tear (continuous curvilinear capsulorhexis or CCC) by Gimbel and Neuhann in 19903. This opened the path to phacoemulsification within the capsular bag (as opposed to the anterior chamber) initially using a group of strategies for removing the lens nucleus known as divide and conquer2 and later phaco chopping techniques (Nagahara’s horizontal chop, Dillman’s vertical or ‘quick’ chop, and Koch’s stop and chop). Some aspects of the extracapsular operation, such as hydrodissection of the nucleus and simultaneous irrigation and aspiration to remove lens cortex, were carried forward and updated to complete the operation.

In parallel with developments in instrumentation, machines, and surgical technique has come development of lens implant materials and design. Ridley chose polymethylmethacrylate (PMMA) as the material for his intraocular lens. The weight of early lenses that mimicked the shape of the human lens led to the design of lenses with a smaller and thinner optical component and some light supporting legs (haptics). This change allowed a substantial reduction of lens weight and largely abolished the tendency to subluxation within the eye. With PMMA lenses incision lengths for phacoemulsification remained at around 5 mm. The introduction of lenses made of pliable silicone allowed reduction of wound sizes to nearer 3 mm. Later generations of lens materials included hydrophobic and hydrophilic acrylic materials that were also pliable at body temperature allowing introduction to the eye by folding or via specially designed introducers. The reduction of wound length with these new lenses largely removed the need to suture wounds due to self-sealing wound design and reduced the unpredictability of astigmatic effects of wounds.

Accurate choice of lens implant power has become possible following developments in preoperative biometry. The early contact ultrasound ‘A’ scan axial length measurements have largely been superseded by immersion ‘A’ scan or optical biometry methods. Lens power calculation formulae have also evolved to make refractive outcomes more, if not entirely, predictable.

Goals of surgery

The primary goal of surgery is to remove the opaque human lens and, in almost all situations, replace the lost optical power with a lens implant. This should result in improved visual function for the patient. Box 8.1 lists what can be considered additional goals in cataract surgery.

Indications for surgery