Phacoemulsification With Intraocular Lens (IOL) Implantation

Modern extracapsular cataract extraction surgery involves the removal of the lens fibers, which form the nucleus and cortex of the cataract, leaving the posterior epithelial capsule to hold the new artificial intraocular lens (IOL) and keep the vitreous humor away from the anterior chamber.[1] Extracapsular techniques of cataract extraction surgery originally involved manual nuclear expression. Phacoemulsification is a mechanically assisted extracapsular technique of cataract extraction surgery.[1, 2]

A cataract is illustrated in the image below.

Cataract illustration.

Phacoemulsification is illustrated in the image below.

Cataract surgery phacoemulsification, phaco, nucleus.

The patient's desire to improve vision is the most common indication for cataract surgery via phacoemulsification with intraocular lens implantation.

If a patient's best corrected visual acuity does not meet government agencies' and industries' minimum standards of visual function for driving tasks, flying, or operating complex equipment, cataract surgery via phacoemulsification with intraocular lens implantation may need to be considered.[1]

Symptoms of cataract

Symptoms of cataract include the following[1] :

• Reduced visual acuity (distant and near objects)

• Daytime glare (sunshine)

• Nighttime glare (street lights or car headlights)

• Distortion of lines (wavy, fuzzy)

• Monocular diplopia

• Altered colors (white objects appear yellowish, bright colors appear bleached)

• Not associated with pain, discharge, or redness of the eye

Signs of cataract

Signs of cataract include the following[1] :

• Reduced visual acuity measured on a Snellen chart or LogMar and near-vision chart

• An abnormally irregular, dim, or absent red reflex is seen when the retina is viewed with an ophthalmoscope at arm's length. Cortical cataracts cause black-spoke-like shadows coming from the edge of the red reflex. Nuclear and posterior capsular cataracts cause a central black shadow across the red reflex.

• Reduced contrast sensitivity can be measured by the ophthalmologist using contrast sensitivity charts.

• Very dense "mature" cataracts causing severely impaired vision present a white pupil.

• Shallowing of the anterior chamber and angles with very dense cataracts are seen with slit lamp examination

• After dilating pupils, slit lamp examination shows whether the cataract is cortical, nuclear, or posterior subcapsular, and allows fundus examination.

• Cataract in children is unusual but may be associated with a white pupil, inability to fix on a target (eg, a light), and the development of a squint.

Low endothelial cell count is a contraindication.

Complication Prevention

Toxic anterior segment syndrome (TASS) is fast becoming a problem for surgeons doing volume surgery in ambulatory surgical centers and hospitals. Its incidence may be avoided with the following:

• Proper use and maintenance of surgical sterilization units

• Meticulous care and sterilization of all surgical instruments

• Avoidance of reusing cannulas

• Washing out Betadine from the surgical field before beginning surgery

• Minimizing the excessive use of intracameral injections (antibiotics, vital dyes, viscoelastics)

Cataract surgery | https://youtu.be/P_9tH1aQTEs

IOL Options | https://youtu.be/_GMxn1VyiNU

Phacoemulsification with Monofocal Implant | https://youtu.be/jgoBQzPm4ek

Phacoemulsification with Toric Implant | https://youtu.be/DuquW4AoNMo

Phacoemulsification with Multifocal Implant | https://youtu.be/2Zl7UI7BJwo

Special devices needed for the procedure are as follows:

• Iris hook

• Pupil stretcher

• Capsular tension ring

Modern extracapsular cataract extraction surgery involves the removal of the lens fibers, which form the nucleus and cortex of the cataract, leaving the posterior epithelial capsule to hold the new artificial intraocular lens (IOL) and keep the vitreous humor away from the anterior chamber.[1]

Ocular lenses

Ocular lenses transmit and refract light to diverge or converge the beam to change the eye's optical power.

Intraocular lenses

Intraocular lenses (IOLs) are plastic lenses that are permanently implanted into the eye, typically at the time of cataract surgery. IOLs also may be injected into patients who retain their native crystalline lens to correct refractive errors.

Phacoemulsification surgical devices

Different manufacturers utilize a peristaltic, Venturi, or a combination of both peristaltic and Venturi systems. Technologic advances have reduced the amount of phaco energy delivered to achieve phacoemulsification. Manipulation of fluid dynamics, surgical tip oscillations, and power delivery leads to shorter surgical times and lesser surgical trauma.

Ophthalmic viscosurgical devices

Cataract surgery is performed in a closed, fluid-filled medium, dependent upon fluid flow. Ophthalmic viscosurgical devices (OVD) are utilized to maintain a safe environment for successful phacoemulsification.

OVDs can best be classified in a system based on zero shear viscosity and relative degree of cohesion or dispersion, as these two factors play essential roles in our surgical use of OVDs.

Higher viscosity cohesives

Higher viscosity cohesives are best used to create and preserve spaces, displace and stabilize tissues, pressurize the anterior chamber, and provide a clear view of the posterior capsule during phacoemulsification. Their disadvantages include rapid removal from the anterior chamber during phacoemulsification or irrigation and aspiration leading to suboptimal endothelial protection, inability to partition spaces, and increased difficulty for removal at the end of the procedure.

Lower viscosity dispersives

Lower viscosity dispersives best are used to protect the endothelium (because it remains adjacent to the corneal endothelium throughout the phacoemulsification) and selectively move, isolate, and partition spaces. Its disadvantages include its inability to maintain spaces or stabilize, and its irregular fracture boundaries, which obscure the view of the posterior capsule.

Anesthesia

Topical and intracameral anesthesia are the preferred routes of delivery in cataract surgery. Other routes of delivery may have their use in specific cases.

Topical anesthesia

Topical anesthesia consists of analgesia. It blocks the production and not the transmission of pain sensation. Motor, thermal, and tactile fibers are not suppressed. It is suitable for cataract surgery because akinesia is not required by phacoemulsification. Safe and effective treatments include repeated eyedrop instillations, gel application, and a drug-soaked sponge.

Ester-bound compounds (tetracaine, proparacaine, benoxinate) have faster and shorter action than amide-bound compounds (lidocaine, bupivacaine, ropivacaine, mepivacaine). Different anesthetic drugs give similar results. The author prefers topical proparacaine eyedrops supplemented with an intracameral delivery of lidocaine. Patient selection or intravenous sedation is less used with experience. Side effects of topical anesthesia consist of immediate and postoperative ocular dryness lasting up to a few weeks.[3, 4]

Intracameral anesthesia

Intracameral injections that are proven safe and effective include intracameral injection of drug dilutions or anesthetic viscoelastic substances. The author prefers to supplement topical proparacaine with preservative-free lidocaine 1% intracameral injection. Intracameral anesthesia has been proven safe for intraocular structures, although its necessity remains controversial.[5]

Peribulbar anesthesia

Peribulbar anesthesia rarely is necessary, except when excessive conjunctival manipulation is performed or when converting to a large incision extracapsular cataract extraction procedure. It is performed using a short 1-inch 25-gauge or 27-gauge needle inserted external to the muscle cone underneath Tenon's capsule. This theoretically is safer than retrobulbar anesthesia since it eliminates the risk for optic nerve injury or intradural injection.

Retrobulbar anesthesia

Retrobulbar anesthesia provides excellent ocular akinesia and anesthesia. This may be used with or without regional anesthesia of cranial nerve VII.

Oral sedation

A light sedative may be taken by mouth to facilitate relaxation during the procedure. The patient is fully awake and can follow verbal commands.

Anxiolysis

A peripheral intravenous line is placed, and very light sedatives are given to decrease anxiety. This is the lightest level of general intravenous anesthesia.

Intravenous sedation

This is similar to anxiolysis GA; however, more intravenous sedatives are given. There is a higher risk for morbidity with this type of delivery due to the potential awakening, which may occur during the procedure once a patient falls asleep.

Laryngeal mask anesthesia (LMA)

Controlled delivery of inhalational and intravenous anesthetics. They are used for surgeries limited to 60-90 minutes. This may be useful in complicated cataract surgeries requiring multiple procedures.

Endotracheal tube anesthesia (ETTA)

Absolute controlled delivery of inhalational and intravenous anesthetics. They are used for surgeries estimated to last longer than 90 minutes.

Temporal

This is the most common position of most surgeons who perform phacoemulsification. The patient is lying supine on a surgical table. The surgeon is seated facing the temporal cornea. This presents the advantage of having better surgical exposure due to the avoidance of the orbital rim superiorly. For a right-hand-dominant surgeon, this would be the standard approach for the left eye. For a left-hand-dominant surgeon, this would be the traditional approach for the right eye.

Superotemporal

This is another common position of surgeons who perform phacoemulsification. The patient is lying supine on a surgical table. The surgeon is seated facing the superotemporal cornea. This presents the advantage of having better surgical exposure due to avoidance of the nose. For a right-hand-dominant surgeon, this would be the standard approach for the right eye. For a left-hand-dominant surgeon, this would be the traditional approach for the left eye.

Superior

More senior surgeons and posterior segment surgeons may be seen performing phacoemulsification using the superior approach. This probably is  retained by habit from transitioning from a superior approach while performing large-incision manual expression extracapsular cataract extraction (ECCE) or retina surgery. The phacoemulsification handpiece usually enters the eye via the temporal or superotemporal cornea, while the second instrument enters the eye via the nasal or superonasal cornea.

Surgical Preparation

After applying topical anesthetic, eyelashes are scrubbed with an antiseptic solution. A facial prep with Betadine follows. Sterile disposable drapes are meticulously applied, and a transparent sterile drape is placed on the eye, ensuring eyelashes are moved out of the surgical field.

The following medications should be stopped 1 week before planned cataract surgery:

• All blood thinners (aspirin, aspilet, clopidogrel, heparin, enoxaparin, ardeparin, danaparoid, warfarin, vitamin E, ginkgo biloba)
• All prostate medications (tamsulosin [Harnal], tamsulosin hydrochloride [Flomax], terazosin hydrochloride [Hytrin], dutasteride [Avodart], dutasteride/tamsulosin [Duodart], finasteride [Proscar], among others)

A preoperative examination is used to determine if there is a need for iris hooks, Malyugin rings, triamcinolone acetonide, Ozurdex dexamethasone implants, and other devices.

Systemic evaluation with or without laboratory diagnostics and cardiopulmonary clearance may be required. Different biometry packages would include the following:

• Optical biometry
• Specular microscopy
• Corneal topography
• Macular optical coherence tomography (OCT)
• Optic nerve OCT
• Dilated color fundus photos

A lid speculum is used to hold the eyelids apart. Surgeons may choose from wire or screw, nasal or temporal, or self-retaining eyelid speculums.

Topical antibiotics or a diluted mixture of antiseptic is used to wash out debris and particulates from the conjunctival fornices. Exposure varies from 30-60 seconds and is followed by generous washing with a balanced salt solution to remove all traces of antiseptic solution from the surgical field.

A 1.2-mm or 15º stab knife is used to fashion a small paracentesis at the peripheral cornea, usually 3-4 clock hours away from the primary surgical incision. This is made along the iris plane and usually is a single-plane stab into the peripheral cornea. Other surgeons who perform phacoemulsification advocate a multiplane approach to enhance self-sealing. With a 1.2-mm stab knife, most second instruments, including bimanual aspirating handpieces, fit snuggly and do not make the wound gape, preventing wound leakage. Intracameral anesthetic injections, vital dye, and viscoelastic injections are performed after the side ports are created.

Scleral tunnel incisions most likely are performed by beginning phacoemulsification surgeons because of the ease of conversion to manual expression extracapsular cataract extraction. The initial advantage presented by a scleral tunnel incision is the avoidance of surgically induced astigmatism. The cumbersome nature of fashioning a scleral tunnel incision has made it fall out of fashion with most phacoemulsification surgeons.

A progressive reduction in incision size and related morbidity has marked the recent history of cataract surgery via phacoemulsification. Increased operating efficiency, improved astigmatism control, and foldable intraocular lens technology have led to increasing use of self-sealing, clear corneal incisions for cataract surgery. Pre-existing corneal astigmatism may be effectively treated during cataract surgery using incisional keratorefractive techniques (limbal relaxing incisions, peripheral penetrating corneal incisions). Additional steps, such as the creation of­­ a supra-incisional penetrating non-perforating corneal incision (Wong incision), have decreased the possibility of wound leaks. Femtosecond lasers that create precise corneal incisions now are available for all phacoemulsification surgeons. They have a unique ability to create a discrete photodisruption of tissue with minimal collateral effects.

The cataract surgery incision is illustrated in the image below.

Cataract surgery incision, (1.9-2.75 mm), corneal incision, limbal incision, clear corneal, small incision, sutureless.

Femtosecond Laser-Assisted Corneal Incisions

Femtosecond laser–assisted corneal incisions before cataract surgery are used to improve the incision location, length, creation, and closure. A single-, double-, or three-plane main corneal incision may be fashioned. One or two side ports may be made. Single or paired limbal relaxing incisions may be created.

A special forceps creates a continuous curvilinear capsulorhexis (CCC, see the image below). CCC has improved intraocular lens stability and centration, which helped reduce posterior capsular opacification and spurred the development of endolenticular nucleofractis techniques. Critical elements of technique for constructing continuous curvilinear capsulorhexis include operating in a deep and stable chamber, initiating the tear in the capsule's center, and grasping the flap to maintain control of the vector of the tear at all times. Using vital dyes has extended the application of continuous curvilinear capsulorhexis to cases with a reduced or absent red reflex. Femtosecond lasers that create precise continuous curvilinear capsulorhexis are now available for all phacoemulsification surgeons.

Cataract surgery capsulotomy, capsulorrhexis, continuous tear.

Femtosecond Laser-Assisted Capsulotomies

Femtosecond laser–assisted capsulotomies, when performed correctly, are almost always free floating. The risk of losing a capsulorhexis edge is eliminated. Capsulotomy size and location may be programmed. When used in white cataracts, incomplete capsulotomy may occur, although the risk of a capsule tear is less.[6]

Cortical cleaving hydrodissection has reduced the need for irrigation and aspiration of cortical material and the rate of posterior capsular opacification. Critical steps of cortical cleaving hydrodissection include injection of a balanced salt solution under the anterior capsule such that a fluid wave traverses the posterior aspect of the lens and decompression of the capsule by depression of the central portion of the lens.

Hydrodelineation means the separation of the epinucleus from the endonucleus to allow the epinucleus to serve as a protective cushion during the manipulation and extraction of the endonucleus.

Nuclear rotation with a second instrument ensures the nucleus is entirely mobile and reduces the possibility of transferring stress to the posterior capsule and zonules during nuclear disassembly.

Most phacoemulsification machines have parameters for power, vacuum, pulse, burst, oscillation levels, and bottle height. These may be set to allow specific phaco procedures to proceed during different steps of phacoemulsification surgery.

Phacoemulsification may be performed in various locations within the eye.

Anterior chamber phacoemulsification affords protection of the capsular bag, zonules, and iris. When a posterior capsular break is present, prolapsing the remaining nucleus into the anterior chamber may be necessary. Since it is nearer to the corneal endothelium, the risk for corneal endothelial loss is higher, despite using viscoelastic for protection.

Iris plane phacoemulsification affords protection of the capsular bag and the corneal endothelium; however, potential injury to the iris may occur if it is inadvertently pulled into the phacoemulsification handpiece.

Posterior chamber phacoemulsification currently is the most common location where surgeons perform phacoemulsification. The increased understanding of proper nucleus rotation and subsequent nuclear disassembly and efficient phacoemulsification machine parameters has increased the safety of phacoemulsification surgery and decreased morbidity, such as posterior capsular rupture (shown below) and endothelial cell loss.

Phacoemulsification is illustrated in the images below.

Cataract surgery phacoemulsification, phaco, nucleus.

Cataract surgery with phacoemulsification cross-section.

Cataract surgery illustration with ruptured posterior capsule.

Anterior vitrectomy for ruptured posterior capsule during phacoemulsification.

One-handed technique

This technique allows the creation of a single corneal incision and the use of a single phacoemulsification handpiece in shaving off each layer of the nucleus and the epinuclear envelope. This is performed with adequate capsulorhexis and nuclear rotation.

Two-handed techniques

Chop techniques substitute mechanical forces for ultrasound energy to disassemble the nucleus, use a high vacuum as an extractive technique to remove nuclear material, and facilitate the achievement of minimally invasive surgery and rapid visual rehabilitation. Bimanual, ultra-small incision cataract surgery and companion IOL technology now are a reality via laser and new ultrasound power modulations.

The divide and conquer technique uses ultrasonic sculpting of a deep central crater and fracturing of segments of a peripheral rim.

Cataract surgery, phacoemulsification, divide and conquer, phaco, chop.

Phaco fracture involves ultrasonic sculpting of grooves and bimanual nucleus cracking into four separate quadrants.

Chip and flip mean sculpting a central bowl until a thin chip of endonucleus remains, whereas crack and flip is a modification of phaco fracture, including hydrodelineation.

Phaco chop requires a firm hold with a high vacuum and a second sharp instrument to divide the nucleus horizontally or vertically.

Investigation of the choo-choo chop and flip technique led to the conclusion that reduction of ultrasound energy is correlated with improvement of visual acuity on the first postoperative day.

Phacoemulsification with laser systems allows a reduction of incision size to 1.5mm.

Surgeons using bimanual microincision phacoemulsification have described improved chamber stability, ability to follow, and greater ease of irrigation and aspiration.

Femtosecond laser-assisted lens fragmentation techniques

Femtosecond laser–assisted lens fragmentation before cataract surgery aims to decrease or eliminate the need for ultrasound energy during nuclear disassembly. For softer nuclei, aspiration techniques may be sufficient. In harder nuclei, ultrasound emulsification still is required.[7] Numerous cutting patterns and algorithms (ie, energy, shot placement, pulse repetition frequency) influence the efficiency of nucleus softening fragmentation.

Cortical material remains attached to the capsular bag after nuclear disassembly and phacoemulsification. A straight irrigation/aspiration handpiece or a bimanual irrigation/aspiration set may be used to remove residual cortex (see the images below). The sub-incisional cortex usually is removed first, followed by superior cortical remnants. The rest are removed in a clock-hour fashion. The capsule is polished with the lowest allowable settings possible. Proper removal of lens epithelial cells prevents posterior capsular opacification and capsular phimosis.

Cataract surgery illustration of cortex and capsule cleanup using IA.

Phacoemulsification with cortex removal. Phaco, aspiration, cataract surgery illustration.

The capsular bag and anterior chamber is reformed with viscoelastic. Preloaded foldable IOLs are now on the market. Most foldable IOLs are loaded onto a cartridge before injection into the capsular bag. They usually go through a sub 2.75 mm corneal slot. Preloaded IOLs decrease surgical time and decrease handling of the lens, thereby theoretically decreasing the risk of introducing contaminants into the eye. IOL lens insertion is illustrated in the images below.

Cataract surgery, lens insertion, 3-piece, IOL, intraocular lens implant, shooter, inserter.

Intraocular lens implant, IOL, 3 piece lens, in the bag.

Intracameral injection

Intracameral antibiotics at the end of surgery now are commonplace due to the statistically significant decrease in morbidity due to postoperative infections.

Test for leaks

Testing for wound leaks at the end of each surgery is essential. Neglecting a leaking wound may lead to a flat chamber and endophthalmitis. A properly constructed corneal incision will be self-sealing. Corneal incision hydration with a balanced salt solution usually provides a tight seal on most corneal incisions. A surgical sponge may be used to check for the egress of anterior chamber fluid. Using fluorescein dye may enhance the visualization of leaks from all incision sites.

Potential postoperative complications include the following conditions:

• Corneal edema

• Descemet's membrane detachment

• Induced astigmatism

• Corneal melting

• Conjunctival ballooning

• Epithelial downgrowth

• Toxic anterior segment syndrome (TASS)

• Flat chamber

• Elevated intraocular pressure

• Intraoperative floppy iris syndrome (IFIS)

• Iridodialysis

• Cyclodialysis

• Ciliary block glaucoma

• Chronic postoperative uveitis

• Retained lens material

• Capsular rupture

• Vitreous prolapse

• Dropped nucleus

• IOL complications (decentration and dislocation, pupillary capture, capsular block syndrome, uveitis-glaucoma-hyphema syndrome, pseudophakic bullous keratopathy, incorrect IOL power, IOL glare, IOL opacification)

• Anterior capsular fibrosis and phimosis

• Posterior capsular opacification

• Hemorrhage (retrobulbar hemorrhage, suprachoroidal effusion, expulsive suprachoroidal hemorrhage, hyphema)

• Endophthalmitis

• Cystoid macular edema

• Uretts Zavala syndrome

• Retinal light toxicity

• Macular infarction

• Retinal detachment

Topical and general anesthesia may be used to promote patient comfort during the procedure. Topical anesthesia consists of analgesia. It blocks the production and not the transmission of pain sensation. Light sedatives and anxiolytics may also be given to facilitate patient comfort and relaxation.

Class Summary

These agents are used in procedures where rapid and short-acting topical ophthalmic anesthetics are required.

Proparacaine (Alcaine, Parcaine)

Has rapid onset of anesthesia that begins within 13-30 sec after instillation. However, has short duration of action of about 15-20 min.

Since prolonged eye anesthesia can eliminate patient's awareness of mechanical damage to, cornea, should not be used outside of the emergency department. Frequent use of anesthetics may retard healing.

Of all topical anesthetics, this is least irritating. Prevents initiation and transmission of impulse at nerve cell membrane by stabilizing and decreasing ion permeability.

Onset of action takes place within 20 sec of application.

Anesthetic effect may last up to 10-15 min.

Tetracaine (Altacaine, TetraVisc, Tetcaine)

By decreasing neuronal membrane's permeability to sodium ions, this agent blocks both initiation and conduction of nerve impulses. Results are inhibition of depolarization, which blocks the conduction of the impulse.

Available in solution and ointment. Onset of action takes place within 30 seconds of application and anesthetic effect may last up to 15-20 min.

Medication stings considerably on application.

Class Summary

These agents are used in procedures where rapid and long-acting topical ophthalmic anesthetics are required. The author prefers to supplement topical proparacaine with preservative-free lidocaine 1% intracameral injection. Intracameral anaesthesia has been proven safe for intraocular structures, although its necessity remains controversial.

Lidocaine (Akten)

Decreases permeability to sodium ions in neuronal membranes. This results in the inhibition of depolarization, blocking the transmission of nerve impulses.

Bupivacaine

Decreases permeability to sodium ions in neuronal membranes. This results in the inhibition of depolarization, blocking the transmission of nerve impulses.

Ropivacaine (Naropin)

Decreases permeability to sodium ions in neuronal membranes. This results in the inhibition of depolarization, blocking the transmission of nerve impulses.

Mepivacaine (Polocaine MPF)

Prevents the generation and conduction of nerve impulses.

Class Summary

These agents are used for their anti-convulsive effects to prevent or treat the convulsions of any origin (e.g. toxicity from the anesthetic agents).

Diazepam (Valium, Diastat)

Depresses all levels of CNS (eg, limbic and reticular formation), possibly by increasing the activity of GABA.

Individualize the dosage and increase it cautiously to avoid adverse effects.

Midazolam (Versed)

Shorter-acting benzodiazepine sedative-hypnotic useful in patients requiring acute and/or short-term sedation. Midazolam is also useful for its amnestic effects.