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	<em>Each generation of cataract surgery continues to become incrementally better than the previous one as surgeons continue to innovate, according to&nbsp;<strong>Dr Max Treacy</strong>&nbsp;and&nbsp;<strong>Mr Paul O&rsquo;Brien</strong>.</em></p>
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	<strong>What is a cataract?</strong><br />
	A cataract is a cloudiness of the crystalline lens of the eye that usually occurs over the age of 65 years but can occasionally develop before that age. There are different types of cataract and the commonest is called a &lsquo;nuclear cataract&rsquo; because it is due to hardening of the nucleus of the lens, which turns a yellow-brown colour.</p>
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	The cataract may eventually become white and opaque and render the patient blind. The formation of a cataract can also be caused by a metabolic imbalance and a higher incidence of this disease occurs, for example, in diabetics.</p>
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	Furthermore, injury to the eye, including retinal detachment surgery, can cause a cataract, as can certain drugs such as steroids. When older people develop cataracts they may notice that they can read without their glasses and actually think their eyes are improving for a period, before noticing that their distance vision has deteriorated. This is often referred to as &lsquo;second sight of the elderly&rsquo; and occurs because of a myopic shift due to lens swelling in the earliest stages of cataract formation.</p>
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	<strong>Treatment</strong><br />
	The only treatment for cataracts is surgery. Twenty years ago it was necessary to wait until the cataract &lsquo;ripened&rsquo; before surgery was performed.</p>
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	Modern surgical methods allow removal of a cataract at a much earlier stage nowadays due to the high chance of excellent unaided visual acuity post-operatively.</p>
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	This is especially important if the patient is a driver and can no longer meet the minimum driving standard. Patients may also experience symptoms of severe glare whilst driving at night, despite retaining good visual acuity, as measured on a Snellen chart. This is most commonly noted in patients with posterior subcapsular cataracts. In fact, if a driver is unable to drive in dim light they may need cataract surgery, despite acuity of 6/6.</p>
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	<strong>Cataract surgery in Ireland</strong><br />
	Cataract surgery is one of the most commonly performed operations in Ireland and elsewhere in the developed world. It consistently ranks as one of the procedures which has the most positive impact on patient quality of life and enjoys high rates of patient satisfaction. In this country in 2011 there were 9,500 cataract operations performed in public hospitals and 80 per cent of these patients were over 65 years of age. These numbers were probably mirrored in the private hospitals.</p>
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	The vast majority of cases are performed as day cases under local anaesthetic.</p>
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	<strong>Shunned by Colleagues</strong><br />
	The original operation for removing cataracts rendered the patient aphakic, or without a lens in the eye. This meant that the patient had to wear very strong spectacle lenses (+12 dioptres) which were ungainly (looked like milk bottles) and distorted the vision of those wearing them.</p>
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	Harold Ridley was a Moorfields ophthalmologist who conceived of and implanted the first intra-ocular lens to replace the natural lens removed from the eye during cataract surgery. Ridley treated many eye casualties during World War II and noticed that splinters from the Perspex cockpit canopies on aircrafts remained inert in the anterior chamber of the eye, causing no reaction, while glass splinters caused internal inflammation.</p>
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	This observation gave him the idea of inserting a plastic intraocular lens to replace the natural lens. An intraocular lens is optically far superior to glasses and eliminates the distorted postoperative visual image.</p>
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	In 1949 Harold Ridley performed the first implant of an intra-ocular lens manufactured by the Rayner Company from perspex.&nbsp; Like many innovators, Ridley was shunned and castigated by his colleagues for years before the use of intraocular lenses became commonplace. Harold Ridley was eventually knighted by the British Monarch in the year 2000 at the age of 94 years and only one year before his death, which is interesting, as the introduction of the intraocular lens must have been one of the greatest medical advancements of the 20th Century.</p>
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	<strong>Refinement of the procedure</strong><br />
	Intraocular lenses have been used in Ireland since the 1970s and the original cataract operation was an intra-capsular cataract extraction (ICCE), whereby the crystalline lens (including its capsule) was removed. This was a successful operation in most cases but had a significant post-operative complication rate of retinal detachment.</p>
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	This was caused by the forward drag of the vitreous on the retina while it herniated through the pupil into the anterior chamber. This complication was reduced dramatically with the introduction of the extra-capsular cataract extraction (ECCE) operation, where the posterior capsule of the lens was preserved, thereby holding the vitreous in position and preventing forward movement.</p>
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	Initially, intra-ocular lenses were positioned in the anterior chamber and with the introduction of the ECCE operation, it was possible to place the intra-ocular lens behind the pupil in the posterior chamber, thereby permitting improved postoperative visual outcomes and less complications.</p>
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	IOLs placed in the anterior chamber were often associated with a late complication of corneal decompensation, which in turn necessitated a corneal transplant. By placing the IOL behind the iris in the capular bag, the incidence of corneal decompensation reduced significantly.</p>
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	The most recent operating technique which most surgeons use is called phacoemulsification. This operation involves opening the anterior capsule in a circular fashion (anterior capsulorhexis) and introducing an ultrasonic probe into the crystalline lens, which breaks up the lens into tiny pieces which are then removed through the probe until all the lens material has been removed. This operation is gentle and preserves the posterior capsule.</p>
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	Charles D Kelman, who died in 2004, was an Ophthalmologist at the Manhattan Eye, Ear and Throat Hospital in New York who invented phacoemulsification. Kelman invented this technique having been inspired by his dentist&rsquo;s ultrasonic cleaning instruments. Unlike Harold Ridley, he was much appreciated in his own country and received the National Medal of Technology from President George H Bush in 1992.</p>
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	Another major advancement in the technique of cataract surgery is the ever-shrinking wound size. Initially, the operation was conducted through an eight millimetre wound, then six millimetres, and then it became possible to fold the intraocular lens, which allowed it to be inserted through a 3.2 millimetre wound.</p>
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	Some surgeons now perform sutureless &lsquo;micro-incision&rsquo; cataract surgery through a wound of only two millimetres. The advantage of tiny incisions is that there is less corneal astigmatism induced by the procedure; astigmatism occurs when the optically important cornea is distorted.</p>
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	Modern lenses are made from soft plastics, which are foldable and are injected through the small incision. The vast majority of cataract surgery utilises standard spherical lenses but not all patients have perfectly spherical eyes. Many people have a certain degree of natural astigmatism where the eye is shaped more like a rugby ball than a football.</p>
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	When spherical intraocular lenses are used for these people, they still require glasses to see clearly postoperatively. Recently, premium toric lenses have become available for astigmatic patients who want the best possible uncorrected visual acuity and these lenses are inserted into the eye at a specific orientation to allow that patient to see clearly without glasses. These lenses cost around &euro;400 and are not covered under any health insurance plan.</p>
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	Similarly, they are not provided in public hospitals unless patients opt to pay for them personally.</p>
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	The natural ability of the eye to focus the crystalline lens for reading is gradually lost through ageing and this is known as presbyopia. When an artificial lens is inserted into the eye the ability to focus is entirely lost, therefore the patient requires reading glasses for close work. There are modern multifocal intraocular lenses that are akin to a pair of varifocal glasses, which allow patients to see in the distance and near.</p>
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	Currently, these lenses tend to cause some glare and distortion; patients who are fastidious or are perfectionists tend not to like these lenses, as they feel that the distance vision may be slightly compromised and their night-driving ability can be affected by glare and halos.</p>
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	This is why up to seven per cent of multifocal lenses need to be explanted due to patient dissatisfaction. However, the majority of people who are deemed suitable for multifocal lenses are delighted with the outcome and can function independently of glasses for up to 90 per cent of daily tasks. Multifocal IOLs are not covered by health insurance plans and cost around &euro;650 per eye.</p>
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	<strong>Day-case procedure</strong><br />
	It is not long ago that cataract patients would routinely spend a week in hospital. However, nowadays, more than 95 per cent of cataract surgery is conducted as a day-case procedure and rarely is general anaesthesia required. Either topical or sub-tenon&rsquo;s anaesthesia is utilised to anaesthetise the eye.</p>
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	Sub-tenon&rsquo;s&nbsp; local anaesthetic involves a curved, blunt cannula being passed behind the eye in the space between the sclera and sub-tenon&rsquo;s capsule and a local anaesthetic drug being injected. This technique has the benefit of paralysing the eye muscles in addition to numbing the eye.</p>
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	Topical anaesthetic is where a drop of proxymetacaine is used to numb the cornea and lidocaine is infused into the anterior chamber to numb the iris. Topical anaesthesia is faster than sub-tenon&rsquo;s and requires less recovery time but has the disadvantage of allowing the patient move the eye during the operation.</p>
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	<strong>Complications</strong><br />
	Cataract surgery has become very streamlined over the years but nonetheless is still a major intraocular operation that takes many years for a surgeon to master. Most Irish consultants would have performed in excess of 1,000 cataract operations prior to the completion of higher surgical training.</p>
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	The most feared complication is bacterial endophthalmitis; the rate of endophthalmitis is said to be approximately one in 1,000 and this rate has dramatically reduced in recent years with the introduction of prophylactic intraocular antibiotic given at the end of surgery.</p>
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	Retinal detachment is another major complication of cataract surgery and the risk of detachment is much higher in patients with preoperative myopia greater than 6 dioptres. The rate of retinal detachment is also higher when the all-important posterior capsule is ruptured during surgery.</p>
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	The most important factor affecting the rate of capsule rupture is surgeon seniority. Postoperative inflammation may also occur, causing cystoid macular oedema. The incidence of this is reduced by the routine prescription of topical steroid drops in the first postoperative month.</p>
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	<strong>Future directions</strong><br />
	There is much talk amongst ophthalmologists about the introduction of femtosecond laser-assisted cataract surgery. Femtosecond lasers have been used in ophthalmology since the early 2000s in the area of corneal refractive surgery and in particular for LASIK (laser in-situ keratomileusis).</p>
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	In cataract surgery, the laser is used to make the corneal incision wounds, fashion the capsulorhexis and break up the lens nucleus. These steps of cataract surgery tend to be the most difficult for trainees to learn so femtosecond laser-assisted cataract surgery may help achieve even more consistent results in the future, particularly for inexperienced surgeons.</p>
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	Furthermore, corneal laser refractive surgery can be used as an adjunct to cataract surgery to give the patient the best possible postoperative uncorrected visual acuity. However these laser platforms can cost up to &euro;1 million so are unlikely to be seen in our public hospitals any time soon.</p>
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	In fact, using a femtosecond laser may not be financially feasible as it adds &euro;300-400 to the cost of each cataract procedure. There is also a worry that the laser part of the procedure will be carried out away from theatre by junior surgeons, whilst senior surgeons finish off the operation in the main theatre. This would leave junior surgeons less opportunity to learn to operate.</p>
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	In conclusion, cataract surgery has become much less traumatic for the patient and the rates of complication have reduced dramatically since the 1970s, when we first started implanting plastic lenses. Nonetheless, it is still a major decision for the patient and surgeon to undertake cataract surgery and it should only be considered when the cataract is significantly interfering with the patient&rsquo;s quality of life.</p>
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	We now have methods and materials which allow surgeons to accurately predict postoperative outcomes and leave patients without the need for distance glasses and in some select cases without the need for reading glasses either. Each generation of cataract surgery continues to be incrementally better than the previous as surgeons continue to innovate.</p>
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	<li style="list-style-type: square; margin: 0px 0px 0px 20px; padding: 0px;">
		<em><strong>Dr Max Treacy</strong>&nbsp;SHO, Royal Victoria Eye &amp; Ear Hospital, Dublin and&nbsp;<strong>Mr Paul O&rsquo;Brien</strong>, Consultant Ophthalmic Surgeon, RVEEH and Blackrock Clinic, Dublin, and Chair of the Irish College of Ophthalmologists&rsquo; (ICO) Scientific Committee</em></li>
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	<a href="http://www.imt.ie/clinical/2013/10/second-sight-of-the-elderly.html">http://www.imt.ie/clinical/2013/10/second-sight-of-the-elderly.html</a></p>
