Tutorial
Introduction
The 1960s - The Beginning
The 1970s - Moving Posteriorly
The 1980s - The Capsulorrhexis Era
The 1990s - The Era of Reduced Emulsification Energy
The 2000s - An Era of Alternative Energies and Further Reduction of Ultrasound Energy
Slides
Samuel Masket, MD
In the 1960s, removing a cataract through a 3-mm incision was considered impossible. Doing the "impossible" required a resolution of contradictions which was attained through ingenious application of new technology. As it is now well known, Dr. Charles Kelman's invention for phacoemulsification was inspired by a visit to his dentist where ultrasound energy was used to clean his teeth. But, great ingenuity and perseverance were necessary to move from inspiration to reality. As history has shown, the merger of ingenuity, bioengineering, and surgical technology occurred and phacoemulsification became a viable tool for cataract surgery. However, 35 years ago only Kelman was performing lens emulsification, and IOLs were not available. In the United States, approximately 95% of cataract surgeries are now performed with Kelman phacoemulsification (KPE). Getting from there to here in 35 years mandated a union of surgical technique and industrial technology into a "surgical industrial complex." What has evolved is a highly cost-effective, modern miracle of sight restoration that serves to maintain an independent lifestyle for many elderly patients. This tutorial traces the evolution of ultrasonic small-incision cataract surgery.
When Dr. Kelman began emulsification surgery, corneal physiology was not fully understood, and the fact that corneal clarity was dependent on a healthy (and non-regenerative) corneal endothelium was not well appreciated. Additionally, at that time, neither protective ophthalmic viscosurgical devices (OVDs) nor vitrectomy techniques (other than "open sky") existed. As a result, if the lens nucleus were to become dislocated posteriorly, the eye would, in all likelihood, be functionally lost. As a result, at the outset, maintenance of the posterior capsule was of the utmost importance. Dr. Kelman devised a method to prolapse the nucleus into the anterior chamber (not unlike the present day "phaco flip") for emulsification. This technique required a generous anterior capsulotomy that he performed with a large cystotome in a "Christmas tree" or triangular fashion; the cystotome was then used to impale the nucleus and bring it forward to the anterior chamber in a "tire iron" maneuver under air. Once accomplished, the nucleus was emulsified in the chamber in a one-handed manner. Central to the success of this technique were a dilatable pupil and an anterior capsulotomy that allowed the nucleus to be brought anteriorly out of the capsular bag.
The 1970s - Moving Posteriorly
Kelman resolved the contradictions. However, early adapting surgeons noted that corneal edema was a clinically significant problem and that it was often difficult to maneuver the lens nucleus into the anterior chamber. Variations to the original surgical method were developed by other pioneers particularly Richard (Dick) Kratz, MD, and Robert (Bob) Sinskey, MD. Their concepts involved moving the emulsification action away from the endothelium to protect the cornea and to allow for a more rapid return of clear vision. Then, just as now, as Dr. Osher has taught us, the best measure of surgical quality is a patient's vision in the early postoperative period; protecting the corneal endothelium is central toward that goal.
Dr. Sinskey's concept involved a one-handed method to gently shave or sculpt the nucleus in the posterior chamber after creating a large "can-opener" capsulotomy. Once the lens had been sufficiently debulked, the softer posterior plate could be maneuvered away from the posterior capsule and brought forward through the generous capsulotomy. In this fashion, the posterior capsule was not endangered.
Although Dr. Sinskey's method worked well in his talented hands and corneal clarity was maintained, the posterior capsule was still at risk, particularly owing to the capsulotomy method that could easily allow the anterior capsulotomy to extend peripherally and posteriorly. In response, Dr. Kratz developed the concept of iris plane phacoemulsification. With his method, the superior pole of the lens nucleus was tipped forward and brought to the level of the iris in a two-handed maneuver. Following a generous can-opener anterior capsulotomy a small crater was sculpted in the central nucleus as a first step. Next, in the second step, using a spatula as a lever in the crater (through a sideport incision with the second hand), the nucleus was guided forward by discontinuing fluid inflow and allowing the eye to soften. Manipulating the phaco tip with one hand and using the spatula in the other, the superior pole of the nucleus was freed from the confines of the capsule and brought into the iris plane. In the third step, the nucleus was rotated and gradually chipped away ultrasonically while holding the nuclear remnant above the capsule with the spatula and employing ultrasound to remove the material from the outside in.
Steps to Phaco" instructional program and was disseminated by equipment manufacturers working with an enthusiastic traveling faculty. Indeed, many of today's leading cataract surgeons were members of that original faculty. Working as a group, they not only transitioned many surgeons to KPE, but they also were responsible for development of many innovational surgical techniques.
The Sinskey and Kratz methods "harnessed" phacoemulsification, making it friendlier for the transitioning surgeon, thus allowing more surgeons to adapt it to their practices.
The 1980s - The Capsulorrhexis Era
Technical advances in the early and mid 1980s furthered the surgical science of KPE and brought more surgeons "to the fold." Healon, the first OVD available, eased implantation of IOLs and protected the cornea during KPE. Additionally, however, the capsulorrhexis was developed. This method for continuous tear anterior capsulotomy made KPE safer, as the tendency for the capsulotomy to peripheralize and extend to the posterior capsule was greatly reduced.
But, the capsulorrhexis created a new challenge for the emulsification surgeon. Heretofore, the typical can-opener capsulotomy afforded the opportunity to elevate the lens nucleus or posterior plate with ease, allowing the surgeon to emulsify the lens as one body from the "outside in." On the other hand, a circular capsulorrhexis, unless atypically large, traps the nucleus in the capsule bag, forcing the surgeon to emulsify the lens from the "inside out." As a result, new techniques were needed to solve the puzzle. Because of the difficulty in elevating the entire lens nucleus from the capsule bag, surgeons developed methods to divide the nucleus and bring the subdivisions out of the capsule bag and into the deepest portion of the chamber for safe emulsification. Nuclear subdivision methods were devised as linear, circumferential, or combined forms. Additionally, hydrodissection evolved as means to move and rotate the nucleus within the capsule bag, facilitating the subdivision process (Slide 1). Linear division was described by Howard Gimbel, MD, as "nucleofractis" and John Shepherd, MD, initiated the four-quadrant "divide and conquer" concept, which remains the most commonly practiced form of KPE (Slide 2). I. Howard Fine, MD, introduced circumferential nuclear subdivision for KPE into endonuclear and epinuclear portions with the use of hydrodelineation. His method of "chip and flip" nuclear removal gained popularity among surgeons less comfortable with manual splitting of the lens nucleus.
During this era, KPE gained in popularity, largely due to the evolution of OVDs, foldable IOLs, and workable surgical methods.
The 1990s - The Era of Reduced Emulsification Energy
The premise for, as well as the promise of, small-incision cataract surgery is to provide the patient with a rapid and stable visual outcome, and, as stated above, the best measure for the quality of surgery is the patient's vision in the early postoperative period. Central to that goal is protecting the corneal endothelium with the use of retentive OVDs and exposing the cornea to low amounts of ultrasound energy. Manufacturing technology and surgical techniques developed during the 1990s made the goal of KPE more easily attainable. In my experience, 97% of patients with a variety of nuclear densities in one study group (unpublished data) achieved clear corneas at 1 day after surgery. These results were made possible partly through modulation of emulsification energy in the form of bursts and/or pulses. Further reduction of ultrasound energy was brought about by the use of high vacuum aspiration and nuclear "chopping," using mechanical rather than ultrasonic subdivision of the lens nucleus.
An algorithm for nuclear emulsification exists in which the direct line from chopping to removal of lens fragments represents the shortest path and would require the least energy (Slide 3). However, surgeon preferences or surgical conditions may dictate another and longer course, requiring more ultrasound energy.
The 2000s - An Era of Alternative Energies and Further Reduction of Ultrasound Energy
Recently developed technologies have been adapted in keeping with the theme of reducing ultrasound energy for cataract surgery. Digital "ultra-pulsing" of ultrasound energy, for example, White Star (AMO, Santa Ana, Calif.), is associated with a reduction of the total expended energy and lowered frictional heating of ocular tissue. The latter has led to recent interest in bimanual micro-incision phacoemulsification in which the ultrasound tip is unsleeved and passed through a sub 2-mm incision. Infusion is accomplished through a similar incision with an infusion cannula/chopper.
Additionally, alternatives to ultrasonic lens removal have evolved. Laser lens emulsification with a variety of wavelengths, tip oscillation (Neosonix, Alcon, Ft. Worth, Texas), Sonic Wave (Staar Surgical, Monrovia, Calif.), and pulsed fluids (Aqualase, Alcon), have been deployed with the premise of achieving lens removal without the attendant turbulence associated with ultrasound energy. Although these modalities may serve a role in clear lens replacement surgery or for removal of cataracts at early stages, none of these methods competes favorably with the efficiency of ultrasound for removal of denser cataracts.
Present day cataract surgery is highly evolved from the original concept and provides a remarkable value to price ratio with respect to improved patient lifestyle. It has emerged from the ingenuity and perseverance of Dr. Kelman, the continued development of devices through bioengineering, and the evolution of surgical techniques from many colleagues. None of these elements is insignificant.
This article previously appeared in Cataract & Refractive Surgery Today.