Cataract surgery

Cataract surgery, using a temporal approach phacoemulsification probe (in right hand) and "chopper"(in left hand) being done under the operating microscope at a Navy medical center

Cataract surgery recently performed, foldable IOL inserted. Note small incision and very slight hemorrhage to the right of the still dilated pupil.

There are a number of different surgical techniques used in cataract surgery:

• Phacoemulsification (phaco) is the most common technique used in developed countries. It involves the use of a machine with an ultrasonic handpiece equipped with a titanium or steel tip. The tip vibrates at ultrasonic frequency (40,000 Hz) and the lens material is emulsified. A second fine instrument (sometimes called a "cracker" or "chopper") may be used from a side port to facilitate cracking or chopping of the nucleus into smaller pieces. Fragmentation into smaller pieces makes emulsification easier, as well as the aspiration of cortical material (soft part of the lens around the nucleus). After phacoemulsification of the lens nucleus and cortical material is completed, a dual irrigation-aspiration (I-A) probe or a bimanual I-A system is used to aspirate out the remaining peripheral cortical material.
• Manual small incision cataract surgery (MSICS): This technique is an evolution of ECCE (see below) where the entire lens is expressed out of the eye through a self-sealing scleral tunnel wound. An appropriately constructed scleral tunnel is watertight and does not require suturing. The "small" in the title refers to the wound being relatively smaller than an ECCE, although it is still markedly larger than a phaco wound. Head-to-head trials of MSICS vs phaco in dense cataracts have found no difference in outcomes, but shorter operating time and significantly lower costs with MSICS.

Nucleus of hypermature cataract after ECCE

• Extracapsular cataract extraction (ECCE): Extracapsular cataract extraction involves the removal of almost the entire natural lens while the elastic lens capsule (posterior capsule) is left intact to allow implantation of an intraocular lens.[1] It involves manual expression of the lens through a large (usually 10–12 mm) incision made in the cornea or sclera. Although it requires a larger incision and the use of stitches, the conventional method may be indicated for patients with very hard cataracts or other situations in which phacoemulsification is problematic.
• Intracapsular cataract extraction (ICCE) involves the removal of the lens and the surrounding lens capsule in one piece. The procedure has a relatively high rate of complications due to the large incision required and pressure placed on the vitreous body. It has therefore been largely superseded and is rarely performed in countries where operating microscopes and high-technology equipment are readily available.[1] After lens removal, an artificial plastic lens (an intraocular lens implant) can be placed in either the anterior chamber or sutured into the sulcus.
• Femtosecond laser-assisted cataract surgery has been shown to have no visual, refractive or safety benefit over manual phacoemulsification.[2][3]

Cryoextraction is a form of ICCE that freezes the lens with a cryogenic substance such as liquid nitrogen.[4] In this technique, the cataract is extracted through use of a cryoextractor — a cryoprobe whose refrigerated tip adheres to and freezes tissue of the lens, permitting its removal. Although it is now used primarily for the removal of subluxated lenses, it was the favored form of cataract extraction from the late 1960s to the early 1980s.[5]

• Intraocular lens (IOL) implantation: After the removal of the cataract, an IOL is usually implanted into the eye, either through a small incision (1.8 mm to 2.8 mm) using a foldable IOL, or through an enlarged incision, using a PMMA lens. The foldable IOL, made of silicone or acrylic material of appropriate power is folded either using a holder/folder, or a proprietary insertion device provided along with the IOL. The lens implanted is inserted through the incision into the capsular bag within the posterior chamber (in-the-bag implantation). Sometimes, a sulcus implantation (in front or on top of the capsular bag but behind the iris) may be required because of posterior capsular tears or because of zonulodialysis. Implantation of posterior chamber IOL (PCIOL) in patients below 1 year of age is controversial due to rapid ocular growth at this age and the excessive amount of inflammation, which may be very difficult to control. Optical correction in these patients without intraocular lens (aphakic) is usually managed with either special contact lenses or glasses. Secondary implantation of IOL (placement of a lens implant as a second operation) may be considered later. New designs of multifocal intraocular lens are now available. These lenses allow focusing of rays from distant as well as near objects, working much like bifocal or trifocal eyeglasses. Preoperative patient selection and good counselling is extremely important to avoid unrealistic expectations and post-operative patient dissatisfaction. Acceptability for these lenses has become better and studies have shown good results in selected patients.

In addition, there is an accommodating lens that was approved by the US FDA in 2003 and made by Eyeonics,[6] now Bausch & Lomb. The Crystalens is on struts and is implanted in the eye's lens capsule, and its design allows the lens' focusing muscles to move it back and forth, giving the patient natural focusing ability.

Artificial intraocular lenses (IOLs) are used to replace the eye's natural lens that is removed during cataract surgery. These lenses have been increasing in popularity since the 1960s, but it was not until 1981 that the first U.S. Food and Drug Administration (FDA) approval for this type of product was issued. The development of IOLs brought about an innovation as patients previously did not have their natural lens replaced and as a result had to wear very thick eyeglasses or some special type of contact lenses. Presently, IOLs are especially designed for patients with different vision problems. The main types of IOLs that now exist are divided into monofocal and multifocal lenses.

A cataract surgery. Dictionnaire Universel de Médecine (1746-1748).

The monofocal intraocular lenses are the traditional ones, which provide vision at one distance only: far, intermediate, or near. Patients who choose these lenses over the more developed types will probably need to wear eyeglasses or contact lenses for reading or using the computer. These intraocular lenses are usually spherical, and they have their surface uniformly curved.

The multifocal intraocular lens is one of the newest types of such lenses. They are often referred to as "premium" lenses because they are multifocal and accommodative, and allow the patient to visualize objects at more than one distance, removing the need to wear eyeglasses or contact lenses. Premium intraocular lenses are those used in correcting presbyopia or astigmatism. Premium intraocular lenses are more expensive and are typically not covered, or not fully covered, by health insurance, as their additional benefits are considered a luxury and not a medical necessity. An accommodative intraocular lens implant has only one focal point, but it acts as if it is a multifocal IOL. The intraocular lens was designed with a hinge similar to the mechanics of the eye's natural lens.

The intraocular lenses used in correcting astigmatism are called toric, and have been FDA approved since 1998. The STAAR Surgical Intraocular Lens was the first such lens ever developed in the United States and it may correct up to 3.5 diopters. A different model of toric lenses is created by Alcon and may correct up to 3 diopters of astigmatism. In order to achieve the most benefit from a toric lens, the surgeon must rotate the lens to be on axis with the patient’s astigmatism. Intraoperative wavefront analysis, such as that provided by the ORA System developed by Wavetec Visions Systems, can be used to assist the doctor in toric lens placement and minimize astigmatic errors.

Cataract surgery may be performed to correct vision problems in both eyes, and in these cases, patients are usually advised to consider monovision. This procedure involves inserting in one eye an intraocular lens that provides near vision and in the other eye an IOL that provides distance vision. Although most patients can adjust to having implanted monofocal lenses in both eyes, some cannot and may experience blurred vision at both near and far distances. IOLs that emphasize distance vision may be mixed with IOLs that emphasize intermediate vision in order to achieve a type of modified monovision. Bausch and Lomb developed in 2004 the first aspheric IOLs, which provide better contrast sensitivity by having their periphery flatter than the middle of the lens. However, some cataract surgeons have questioned the benefits of aspheric IOLs, because the contrast sensitivity benefit may not last in older patients.

Some of the newly-launched IOLs are able to provide ultraviolet and blue light protection. The crystalline lens of the eye filters these potentially harmful rays and many premium IOLs are designed to undertake this task as well. According to a few studies though, these lenses have been associated with a decrease in vision quality.

Another type of intraocular lens is the light-adjustable one which is still undergoing FDA clinical trials. This particular type of IOL is implanted in the eye and then treated with light of a certain wavelength in order to alter the curvature of the lens.

In some cases, surgeons may opt for inserting an additional lens over the already implanted one. This type of IOLs procedures are called "piggyback" IOLs and are usually considered an option whenever the lens result of the first implant is not optimal. In such cases, implanting another IOL over the existent one is considered safer than replacing the initial lens. This approach may also be used in patients who need high degrees of vision correction.

No matter which IOL is used, the surgeon will need to select the appropriate power of IOL (much like an eyeglass prescription) to provide the patient with the desired refractive outcome. Traditionally, doctors use preoperative measurements including corneal curvature, axial length, and white to white measurements to estimate the required power of the IOL. These traditional methods include several formulas including Hagis, Hoffer Q, Holladay 1, Holladay 2, and SRK/T, to name a few. Refractive results using traditional power calculation formulas leave patients within 0.5D of target (correlates to 20/25 when targeted for distance) or better in 55% of cases and within 1D (correlates to 20/40 when targeted for distance) or better in 85% of cases. Recent developments in interoperative wavefront technology such as the ORA System from Wavetec Vision Systems, have demonstrated in studies, power calculations that provide improved outcomes, yielding 80% of patients within 0.5D (20/25 or better).

Statistically, cataract surgery and IOL implantation seem to be procedures with the safest and highest success rates when it comes to eye care. However, as with any other type of surgery, it implies certain risks. The cost is another important aspect of these lenses. Although most insurance companies cover the costs of traditional IOLs, patients may need to pay the price difference if they choose the more expensive premium ones.

Galen of Pergamon (c. 2nd century CE), a prominent Greek physician, surgeon and philosopher, performed an operation similar to modern cataract surgery. Using a needle-shaped instrument, Galen attempted to remove a cataract-affected lens.[17][18] Although many 20th century historians have claimed that Galen believed the lens to be in the exact center of the eye, Galen actually understood that the crystalline lens is located in the anterior aspect of the human eye.[19]

A form of cataract surgery, now known as 'couching' (a dangerous method of dislodging the lens with a sharp object, yielding blindness in 70% of cases, and very little improvement in the rest), was found in ancient India and subsequently introduced to other countries by the Indian physician Sushruta (ca. 3rd century CE[20][21]), who described it in his work the Compendium of Sushruta or Sushruta Samhita. The Uttaratantra section of the Compendium, chapter 17, verses 55–69, describes an operation in which a curved needle was used to push the opaque phlegmatic matter (kapha in Sanskrit) in the eye out of the way of vision. The phlegm was then blown out of the nose. The eye would later be soaked with warm clarified butter and then bandaged. Here is translation from the original Sanskrit:

vv.55-56: Now procedure of surgical operation of ślaiṣmika liṅganāśa (cataract) will be described. It should be taken up (for treatment) if the diseased portion in the pupillary region is not shaped like half moon, sweat drop or pearl: not fixed, uneven and thin in the centre, streaked or variegated and is not found painful or reddish.

vv. 57-61ab: In moderate season, after unction and sudation, the patient should be positioned and held firmly while gazing at his nose steadily. Now the wise surgeon leaving two parts of white circle from the black one towards the outer canthus should open his eyes properly free from vascular network and then with a barley-tipped rod-like instrument held firmly in hand with middle, index and thumb fingers should puncture the natural hole-like point with effort and confidence not below, above or in sides. The left eye should be punctured with right hand and vice-versa. When punctured properly a drop of fluid comes out and alsoe there is some typical sound.

vv. 61bc-64ab: Just after puncturing, the expert should irrigate the eye with breast-milk and foment it from outside with vāta-[wind-]alleviating tender leaves, irrespective of doṣa [defect] being stable or mobile, holding the instrument properly in position. Then the pupillary circle should be scraped with the tip of the instrument while the patient, closing the nostril of the side opposite to the punctured eye, should blow so that kapha [phlegm] located in the region be eliminated.

vv. 64cd-67: When pupillary region becomes clear like cloudless sun and is painless, it should be considered as scraped properly. (If doṣa [defect] cannot be eliminated or it reappears, puncturing is repeated after unction and sudation.) When the sights are seen properly the śalākā [probe] should be removed slowly, eye anointed with ghee and bandaged. Then the patient :should lie down in supine position in a peaceful chamber. He should avoid belching, coughing, sneezing, spitting and shaking during the operation and thereafter should observe the restrictions as after intake of sneha [oil].

v.68: Eye should be washed with vāta-[wind-]alleviating decoctions after every three days and to eliminate fear of (aggravation of) vāyu [wind], it should also be fomented as mentioned before (from outside and mildly).

v.69: After observing restrictions for ten days in this way, post-operative measures to normalise vision should be employed along with light diet in proper quantity.[22]

The removal of cataracts by surgery was also introduced into China from India, and flourished in the Sui (AD 581–618) and Tang dynasties (AD 618–907).[23]

The first references to cataract and its treatment in Europe are found in 29 AD in De Medicinae, the work of the Latin encyclopedist Aulus Cornelius Celsus, which also describes a couching operation.

Couching continued to be used throughout the Middle Ages and is still used in some parts of Africa and in Yemen.[24] However, couching is an ineffective and dangerous method of cataract therapy, and often results in patients remaining blind or with only partially restored vision.[24] For the most part, it has now been replaced by extracapsular cataract surgery and, especially, phacoemulsification.[25]

The lens can also be removed by suction through a hollow instrument. Bronze oral suction instruments have been unearthed that seem to have been used for this method of cataract extraction during the 2nd century AD.[26] Such a procedure was described by the 10th-century Persian physician Muhammad ibn Zakariya al-Razi, who attributed it to Antyllus, a 2nd-century Greek physician. The procedure "required a large incision in the eye, a hollow needle, and an assistant with an extraordinary lung capacity".[27] This suction procedure was also described by the Iraqi ophthalmologist Ammar Al-Mawsili, in his Choice of Eye Diseases, also written in the 10th century.[27] He presented case histories of its use, claiming to have had success with it on a number of patients.[27] Extracting the lens has the benefit of removing the possibility of the lens migrating back into the field of vision.[28] A later variant of the cataract needle in 14th-century Egypt, reported by the oculist Al-Shadhili, used a screw to produce suction. It is not clear, however, how often this method was used as other writers, including Abu al-Qasim al-Zahrawi and Al-Shadhili, showed a lack of experience with this procedure or claimed it was ineffective.[27]

In 1748, Jacques Daviel was the first modern European physician to successfully extract cataracts from the eye. In America, an early form of surgery known as cataract couching may have been performed in 1611,[29] and cataract extraction was most likely performed by 1776.[30] Cataract extraction by aspiration of lens material through a tube to which suction is applied was performed by Philadelphia surgeon Philip Syng Physick in 1815.[31]

In 1949, Harold Ridley introduced the concept of implantation of the intraocular lens which permitted more efficient and comfortable visual rehabilitation possible after cataract surgery.[32]

In 1967, Charles Kelman introduced phacoemulsification, a technique that uses ultrasonic waves to emulsify the nucleus of the crystalline lens in order to remove the cataracts without a large incision. This new method of surgery decreased the need for an extended hospital stay and made the surgery ambulatory. Patients who undergo cataract surgery hardly complain of pain or even discomfort during the procedure. However patients who have topical anesthesia, rather than peribulbar block anesthesia, may experience some discomfort.

According to surveys of members of the American Society of Cataract and Refractive Surgery, approximately 2.85 million cataract procedures were performed in the United States during 2004 and 2.79 million in 2005.[33]

In India, modern surgery with intraocular lens insertion in government- and NGO-sponsored Eye Surgical camps has replaced older surgical procedures. In rare cases, infections have caused blindness among some of the patients in mass free eye camps in India.[34]

In the UK the practice of the various NHS healthcare providers in referring people with cataracts to surgery varied widely as of 2017, with many of the providers only referring people with moderate or severe vision loss, and often with delays.[35] This is despite guidance issued by the NHS executive in 2000 urging providers to standardize care, streamline the process, and increase the number of cataract surgeries performed in order to meet the needs of the aging population.[36] The national ophthalmology outcomes audit in 2019 found five NHS trusts with complication rates between 1.5% and 2.1%, but since the first national cataract audit in 2010, there had been a 38% reduction in posterior capsule rupture complications.[37]