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 US Navy medical center

Cataract surgery recently performed, foldable IOL inserted. A small incision and very slight hemorrhage are visible 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.
• The manual small incision cataract surgery (MSICS) technique is an evolution of ECCE (see below) where the entire lens is removed from 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 in 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.[4]

Nucleus of hypermature cataract after ECCE

• Extracapsular cataract extraction (ECCE), (also known as manual 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.[3] 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.[3] After lens removal, an artificial plastic lens (an intraocular lens implant) can be placed in either the anterior chamber or sutured into the sulcus.
  Cryoextraction is a form of ICCE that freezes part of the lens with a cryogenic substance such as liquid nitrogen.[6] In this technique, the cataract is extracted through use of a cryoextractor – a cryoprobe the refrigerated tip of which adheres to the tissue of the lens by local freezing at the contact point, permitting its removal. It is now used primarily for the removal of subluxated lenses.
• Femtosecond laser-assisted cataract surgery has been reported to be safe, and may have less cornea and macula effect than manual phacoemulsification. The laser is used to make the corneal incision, the capsulotomy and to initiate lens fragmentation, which reduces the energy requiremenrts for phacoemulsification.It offers high precision, effective lens fragmentation at lower power levels and good optical quality, but as of 2022 has not been shown to have significant visual, refractive or safety benefit over manual phacoemulsification, and it has a higher cost.[3][7][8]
• Refractive lens exchange is effectively the same procedure used to replace a lens with high refractive error when other methods are not effective. There are risks in addition to cataract procedural risks.[3] A related procedure is the implantation of phakic intraocular lenses in series with the natural lens to correct vision in cases of high refractive errors.[9]

Ophthalmic viscosurgical devices (OVDs) are a class of clear gel like material used in cataract surgery to maintain the volume and shape of the anterior chamber of the eye, and protect the intraocular tissues during the procedure. They were originally called viscoelastic substances, or just viscoelastics. Their consistency allows the surgical instruments to move through them, but when there is low shear stress they do not flow, and retain their shape. OVDs are available in several formulations which may be combined or used individually as best suits the procedure, and are introduced into the anterior chamber at the start of the procedure, and removed at the end. Their tendency to remain coherent helps with removal.[10]

18.5 diopter intraocular lens

After the removal of the cataract, an intraocular lens (IOL) is usually implanted into the eye, either through a small incision (1.8 mm to 2.8 mm) when using a foldable IOL, or through a larger incision, when using a rigid poly(methyl methacrylate) (PMMA) lens. The foldable IOL, made of silicone, hydrophobic, or hydrophilic acrylic material of appropriate refractive power is folded either using a holder/folder, or a proprietary insertion device provided along with the IOL.[11] The lens implant 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 intraocular lens (PCIOL) in patients below 7 months 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. Other designs of multifocal intraocular lens are also available, which focus light from distant as well as near objects, working much like bifocal or trifocal eyeglasses. Preoperative patient selection and good counselling is necessary to avoid unrealistic expectations and post-operative patient dissatisfaction, and possibly a requirement to replace the lenc.[12] Acceptability of these lenses has improved and studies have shown good results in selected patients.

An accommodating lens made by Eyeonics,[13] now Bausch & Lomb, was approved by the US FDA in 2003. The Crystalens has two hinged struts on opposite edges which displace the lens along the optical axis when an inward transverse force is applied to the haptic loops at the outer ends of the struts (the components transferring the movement of the contact points to the device), and it springs back when the force is reduced. It is implanted in the eye's lens capsule, where the contractions of the ciliary body which would focus the eye with the natural lens are used to focus the implant.[14][3]

Monofocal intraocular lenses provide accurately focused vision at one distance only: far, intermediate, or near. Patients who are fitted with these lenses may need to wear eyeglasses or contact lenses for reading or using a computer. These lenses usually have uniform spherical curvature.[15]

The intraocular lenses used in correcting astigmatism have different curvature on two orthogonal axes, as on the surface of a torus, and are called toric lenses. The STAAR Surgical Intraocular Lens was the first such lens developed in the United States and it may correct up to 3.5 diopters. A different model of toric lenses was 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 place the lens to suit the axes to the patient's astigmatism. Intraoperative wavefront analysis, can be used to assist the surgeon in toric lens placement and minimize astigmatic errors.[16]

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.[11] Although most patients can adjust to having implanted monofocal lenses with differing focal length in both eyes, some cannot compensate and may experience blurred vision at both near and far distances. an IOL optimised for distance vision may be combined with an IOL that optimises intermediate vision instead of near vision as a variation of monovision. Bausch and Lomb developed the first aspheric IOLs in 2004, which provide better contrast sensitivity by having their periphery flatter than the middle of the lens. The effectiveness of aspheric IOLs depends on a range of conditions, and they may not always provide significant benefit.[17]

Some IOLs provide ultraviolet and high energy blue light absorbption. The natural crystalline lens of the eye filters these potentially harmful frquencies. According to a few studies though, these lenses have been associated with a decrease in vision quality. A Cochrane review of 2018 found that there is unlikely to be a significant difference in distance vision between blue-filtering and plain lenses, and were unable to identify a difference in contrast sensitivity or colour discrimination.[18]

Another type of intraocular lens is the light-adjustable IOL, which is still undergoing FDA clinical trials. This particular type of IOL is implanted in the eye and then treated with ultraviolet light of a certain wavelength in order to alter the curvature of the lens.[19]

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 existing 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 type is used, the surgeon will need to select the appropriate refractive power of the 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 methods include several formulas including Hagis,[20] Hoffer Q,[20] Holladay 1,[20] Holladay 2,[20] and SRK/T[21], to name a few. There are also free online calculators.[20] A histoty of LASIK surgery requires different calculations to take this into account.[20] Refractive results using traditional power calculation formulas leave patients within 0.5D (diopters) of target (correlates to 20/25 when targeted for distance) in 55% of cases and within 1D (correlates to 20/40 when targeted for distance) in 85% of cases. Developments in intraoperative 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 in eye care. However, as with any type of surgery, some level of risk remains. The cost is another important aspect of these lenses. Although most insurance companies cover the costs of monofocal IOLs, patients may have to pay the price difference if they choose more expensive lenses.

An eye examination or pre-operative evaluation by an eye surgeon is necessary to confirm the presence of a cataract and to determine if the patient is a suitable candidate for surgery. The patient must fulfill certain requirements such as:

• The degree of reduction of vision due, at least in large part, to the cataract should be evaluated. While the existence of other sight-threatening diseases, such as age-related macular degeneration or glaucoma, does not preclude cataract surgery, less improvement may be expected in their presence.[3]
• The eyes should have a normal pressure, or any pre-existing glaucoma should be adequately controlled with medications. In cases of uncontrolled glaucoma, a combined cataract-glaucoma procedure (phaco-trabeculectomy) can be planned and performed.[22]
• The pupil should be adequately dilated using eyedrops; if pharmacologic pupil dilation is inadequate, procedures for mechanical pupillary dilatation may be needed during the surgery.[23]
• Patients with retinal detachment may be scheduled for a combined vitreo-retinal procedure, along with PCIOL implantation.
• It has been shown that patients taking tamsulosin (Flomax), a common drug for enlarged prostate, are prone to developing a surgical complication known as intraoperative floppy iris syndrome (IFIS), which must be correctly managed to avoid the complication posterior capsule rupture; however, prospective studies have shown that the risk is greatly reduced if the surgeon is informed of the patient's history with the drug beforehand, and has appropriate alternative techniques prepared.[24]
• A Cochrane Review of three randomized clinical trials including over 21,500 cataract surgeries examined whether routine preoperative medical testing resulted in a reduction of adverse events during surgery. Results showed that performing preoperative medical testing did not result in a reduction of risk of intraoperative or postoperative medical adverse events, compared to surgeries with no or limited preoperative testing.[25]

The two most commonly used procedures are phacoemulsification and manual small incision cataract surgery (MSICS).

Injector for foldable Intraocular lenses. The incision size for this type is 2.8mm

The surgical procedure in phacoemulsification for removal of cataract involves a number of steps, and is typically performed under an operating microscope. Each step must be correctly performed to achieve the desired result. The steps may be described as follows:

1. Anaesthesia and pupil dilation; Either topical, sub-tenon, peribulbar, or retrobulbar local anesthesia is used, usually causing little or no discomfort to the patient.[26] Topical anesthetic agents are most commonly used and may be placed on the globe as eyedrops prior to surgery and or in the globe during surgery.[27] Local anesthetic injection techniques include sub-conjunctival injections and or injections posterior to the globe (retrobulbar block) to produce a regional nerve block. Intravenous sedation may be combined with the topical and injection techniques. General anesthesia and retrobulbar blocks were historically used for intracapsular cataract surgery, but for small incision surgery and phacoemulsification local and topical anesthesia is in common use.[3]
2. Site preparation by disinfection of the area surrounding the eye, covering the rest of the face, and exposure of the eyeball using an eyelid speculum;
3. Entry into the eye through a minimal incision (corneal or scleral);
4. Injection of ophthalmic viscosurgical devices, also known as viscoelastics, into the anterior chamber to support, stabilize and protect the eyeball, to help maintain eye pressurization, and to distend the lens capsule during IOL implantation.[10]
5. Capsulorhexis; Making a circular opening on the front surface of the lens to access the cloudy lens material within.[28]
6. Hydrodissection; The cataract's outer cortical layer is dissected, by the injection of a fluid wave, from the capsule, the outer-most skin of the cataract.
7. Hydrodelineation; The cataract's outer softer epi-nucleus is separated from the inner firmer endo-nucleus by the injection of a fluid wave. The epi-nucleus serves to protect the cataract's capsule during phacoemulsification of the endo-nucleus.
8. Ultrasonic destruction or emulsification of the cataract after nuclear cracking or chopping (if needed), careful aspiration of the remaining lens cortex (outer layer of lens) material from the capsular bag, capsular polishing (the removal of all epithelial cells from the capsule), if needed;[29]
9. Implantation of the – usually foldable – intraocular replacement lens;[3]
10. Ophthalmic viscosurgical devices removal; The viscoelastic that was injected to stabilize the anterior chamber, protect the cornea from damage, and distend the cataract's capsule during IOL implantation must be removed from the eye to prevent post-operative viscoelastic glaucoma (a severe intra-ocular pressure increase). This is done via suction from the irrigation-aspiration instrument;
11. Wound sealing / hydration (if needed). The incision is sealed by elevating the pressure inside the globe which presses the internal tissue against the external tissue of the incision forcing closed the incision.

1. The pupil is dilated using drops (if the IOL is to be placed behind the iris) to help better visualise the cataract. Pupil-constricting drops are reserved for secondary implantation of the IOL in front of the iris (if the cataract has already been removed without primary IOL implantation). Anesthesia may be placed topically (eyedrops) or via injection next to (peribulbar) or behind (retrobulbar) the eye.[27] Topical anaesthetics are commonly used at the same time as a intracameral lidocaine injection to reduce pain during the operation.[27] Oral or intravenous sedation may also be used to reduce anxiety. General anesthesia is rarely necessary, but may be employed for children and adults with particular medical or psychiatric issues.[27]
2. The operation may occur on a stretcher or a reclining examination chair. The eyelids and surrounding skin will be swabbed with disinfectant. The face is covered with a cloth or sheet, with an opening for the operative eye. The eyelid is held open with a speculum to minimize blinking during surgery. Pain is usually minimal in properly anesthetised eyes, though a pressure sensation and discomfort from the bright operating microscope light is common. The ocular surface is kept moist using sterile saline eye drops or methylcellulose viscoelastic.
3. The discission into the lens of the eye is performed at or near where the cornea and sclera meet (limbus = corneoscleral junction). Advantages of the smaller incision include use of few or no stitches and shortened recovery time.[3] The "small" incision is small in comparison with the earlier ECCE incision, but considerably larger than the phaco incision. The precise geometry of the incision is important as it affects the self-sealing of the wound and can cause astigmatism by distortion of the cornea during healing.[4]
4. A capsulotomy (rarely known as cystotomy) is a procedure to open a portion of the lens capsule, using an instrument called a cystotome.[30] An anterior capsulotomy refers to the opening of the front portion of the lens capsule, whereas a posterior capsulotomy refers to the opening of the back portion of the lens capsule. In phacoemulsification, the surgeon performs an anterior continuous curvilinear capsulorhexis, to create a round and smooth opening through which the lens nucleus can be emulsified and the intraocular lens implant inserted.
5. Following cataract removal, an intraocular lens is usually inserted. After the IOL is inserted, the surgeon checks that the incision does not leak fluid. This is a very important step, since wound leakage increases the risk of unwanted microorganisms gaining access into the eye and predisposing it to endophthalmitis. An antibiotic/steroid combination eye drop is put in and an eye shield may be applied on the operated eye, sometimes supplemented with an eye patch.

Antibiotics may be administered pre-operatively, intra-operatively, and/or post-operatively. Frequently a topical corticosteroid is used in combination with topical antibiotics post-operatively.

Most cataract operations are performed under a local anaesthetic, allowing the patient to go home the same day. The use of an eye patch may be indicated, usually for some hours and while sleeping, after which the patient is instructed to use anti-inflammatory eyedrops to control inflammation and antibiotic eyedrops to prevent infection. Lens and cataract procedures are commonly performed in an outpatient setting; in the United States, 99.9% of lens and cataract procedures were done in an ambulatory setting in 2012.[31]

Occasionally, a peripheral iridectomy may be performed to minimize the risk of pupillary block glaucoma. An opening through the iris can be fashioned manually (surgical iridectomy) or with a laser (called Nd-YAG laser iridotomy). The laser peripheral iridotomy may be performed either prior to or following cataract surgery.

The iridectomy hole is larger when done manually than when performed with a laser. When the manual surgical procedure is performed, some negative side-effects may occur, such as that the opening of the iris can be seen by others (aesthetics), and the light can fall into the eye through the new hole, creating some visual disturbances. In the case of visual disturbances, the eye and brain often learn to compensate and ignore the disturbances over a couple of months. Sometimes the peripheral iris opening can heal, which means that the hole ceases to exist. This is the reason that the surgeon sometimes makes two holes, so ther is a better chance that at least one hole remains open.

After the surgery, the patient is instructed to use anti-inflammatory and antibiotic eye-drops for up to two weeks (depending on the inflammation status of the eye and some other variables). The surgeon will judge, based on each patient's idiosyncrasies, the time length to use the eye drops. The eye will be mostly recovered within a week, and complete recovery should be expected in about a month. The patient should not participate in contact/extreme sports until cleared to do so by the eye surgeon.

As of 2011, cataract surgery is the most frequent surgical procedure in the United States, with 1.8 million Medicare beneficiaries undergoing the procedure in 2004. This rate is expected to increase as the population ages. Cataract surgery following modern procedures is safe and effective, but not entirely free of risk.[40]

Most complications of cataract surgery do not result in long-term visual impairment, but there are some severe complications that can result in irreversible blindness.[40] A survey of adverse results affecting Medicare patients recorded between 1004 and 2006 showed an average rate of 0.5% for one or more severe post-operative complications, with the rate decreasing over the study period by about 20%. The most important risk factors identified were diabetic retinopathy, and a combination of cataract surgery with another intraocular procedure on the same day. 97% of the surgeries in the study were not combined with other intraocular procedures. 3% were combined with retinal, corneal or glaucoma surgery on the same day[40]

"Couching for cataract"; Wellcome Collection illustration of Indian doctors performing the technique.

Couching is the earliest documented form of cataract surgery, and one of the oldest surgical procedures. It is a technique whereby the lens is dislodged, and pushed aside, but mot removed from the eye, thus removing the opacity, but also the ability to focus. Couching was the original cataract surgery and was used for centuries, but it has generally poor outcomes and is currently routinely practiced only in remote areas of developing countries.[44]

Cataract surgery was first mentioned in the Babylonian code of Hammurabi 1750 BCE.[45]

Possibly the first depiction of cataract surgery in recorded history is on a statue from the Fifth Dynasty (2467–2457 BCE).[45] It is further alleged that a "relief painting from tomb number TT 217 in a worker settlement in Deir el-Medina" shows "the man buried in the tomb, Ipuy,... one of the builders of royal tombs in the renowned Valley of the Kings, circa 1279–1213 BC"[46] as he underwent cataract surgery. It is assumed that the couching technique was used.[45]

Galen of Pergamon 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.[47][48] 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.[49]

A form of cataract surgery, now known as "couching", was practised in ancient India and subsequently introduced to other countries by the Indian physician Sushruta (c. 6th century BCE),[50] 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 also 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.[51]

The removal of cataracts by surgery was introduced into China from India, and flourished in the Sui (581–618 CE) and Tang dynasties (618–907 CE).[52]

The removal of cataracts was a common surgical procedure in Djenné[53] (as in many other parts of Africa).[54]

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.[55] However, couching is an ineffective and dangerous method of cataract therapy, and often results in patients remaining blind or with only partially restored vision.[55] For the most part, it has now been replaced by extracapsular cataract surgery and, especially, phacoemulsification.[56]

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 CE.[57] 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".[58] 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.[58] He presented case histories of its use, claiming to have had success with it on a number of patients.[58]^: p318 Extracting the lens has the benefit of removing the possibility of the lens migrating back into the field of vision.[59] A later variant of the cataract needle in 14th-century Egypt, reported by the oculist Al-Shādhili, used a screw to grip the lens. It is not clear, however, how often, if ever, 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.[58]^: p319

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

In 1748, Jacques Daviel was the first modern European physician to successfully extract cataracts from the eye, removing the cataract from the capsule through a corneal incision with about 50% success rate.[42] In America, an early form of surgery known as cataract couching may have been performed in 1611,[60] and cataract extraction was most likely performed by 1776.[61] 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.[62]

King Serfoji II Bhonsle of Thanjavur in India performed cataract surgeries as documented in manuscripts at the Saraswathi Mahal Library in the early 1800s.

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.[63]

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 such as toric lenses for correcting astigmatism.[15] IOLs can be classified as monofocal, toric, and multifocal lenses.[3]

Inracapsular Cryoextraction using a probe tip cooled by liquid nitrogen to freeze the encapsulated lens to the probe was the favored form of cataract extraction from the late 1960s to the early 1980s.[6][64]

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.[65]

Ophthalmic viscosurgical devices (OVDs) were introduced in 1972, and facilitated the procedure as well as improving safety. An OVD is a viscoelastic solution, a gel-like substance used during eye surgery to maintain the shape of eye at reduced pressure and to protect the inside structure and tissues of the eye without interfering with the operation.[42]

Toric intraocular lenses were introduced in 1992 and are used worldwide to correct corneal astigmatism during cataract surgery.[15][42] They have been FDA approved since 1998.[16]

Topical anesthetics were introduced in 1993 by Fischman.[42]

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.[66] As of 2021, approximately 4 million cataract procedures take place annually in the U.S. and nearly 28 million worldwide. That is about 75,000 procedures per day globally.[67]

In the UK the practice of the various National Health Service 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.[68] 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.[69] 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.[70]

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 & Nepal.[71]

Congenital cataracts are a lens opacity which is present at birth. Congenital cataracts occur in a broad range of severity: some lens opacities do not progress and are visually insignificant, others can produce profound visual impairment. Congenital cataracts may be unilateral or bilateral. They can be classified by morphology, presumed or defined genetic cause, presence of specific metabolic disorders, or associated ocular anomalies or systemic findings.[72]

In general, the younger the child, the greater the urgency in removing the cataract, because of the risk of amblyopia. For optimal visual development in newborns and young infants, a visually significant unilateral congenital cataract should be detected and removed before age 6 weeks, and visually significant bilateral congenital cataracts should be removed before age 10 weeks.[72]

Some congenital cataracts are too small to affect vision, therefore no surgery or treatment will be done. If they are superficial and small, an ophthalmologist will continue to monitor them throughout a patient's life. Commonly, a patient with small congenital cataracts that do not affect vision will eventually be affected later in life; generally this will take decades to occur.[73]

The standard of care as of 2015 for pediatric cataract surgery for children older than 2 years is primary posterior intraocular lens implantation. Primary IOL implantation before age 7 months is considered to have no advantages over aphakia.[74] A 2015 study suggests that primary IOL implantation in the 7 month to 2 years old age groups should be considered in children older than 7 months who require cataract surgery.[74]

The capital equipment for phacoemulsification is expensive and requires expert maintenance, and the consumables are also expensive. Quality of outcomes is not sufficiently better than outcomes for manual small incision cataract surgery (MSICS) to justify the difference in cost in a developing world environment.[4]

Most patients suffer from bilateral cataract and although surgery of one eye can restore functional vision, second eye surgery has many advantages. Most patients undergo surgery in both eyes but on separate days. Operating on both eyes on the same day as separate procedures is known as immediately sequential bilateral cataract surgery. This can decrease the number of hospital visits which reduces risk of contagion in an epidemic There are also significant cost savings and faster visual rehabilitation and neuroadaptation. Another indication is significant cataract in both eyes where the person is not a good candidate for having anesthesia and surgery twice. The risk of bilateral simultaneous complications is low.[75][76]