A cataract is a clouding of the lens inside the eye, causing vision loss that cannot be corrected with glasses. Most cataracts are associated with the aging process and are common among the elderly. In cataract surgery, the lens inside your eye that has become cloudy is removed and replaced with an artificial lens (called an intraocular lens, or IOL) to restore clear vision.
Phacoemulsification and IOL have ushered in a new era of cataract surgery. Innovation in IOL design and Phacoemulsification instrumentation have potentiated improved surgical outcomes, reduced perioperative morbidity and increased likelihood of spectacle independence by many folds.
The first recorded history of cataract surgery is from 600 BC (by Sushruta of India) is by couching. Then the concept of aspirating out the cataractous lens, rather than pushing it inside, was introduced by Ammar Abu Ali of Egypt. In 1747, Jacques Daviel of France was the first to perform extracapsular cataract surgery. It did not become very popular because of many inadequacies and complications. Samuel Sharp in 1753 was among the first to perform ICCE. This technique passed through many stages including the Smith technique of tumbling, Aruga forceps, cryotherapy and erysiphake. Gradually ECCE also went through more maturation.
Charles Kelman introduced Phacoemulsification in 1967. Since then, there have been significant improvements in fluidics, energy delivery, efficiency and most importantly, safety of the procedure. The major advantage of Phacoemulsification is that it reduces morbidity from cataract surgery by reducing incision size with subsequent fast recovery and decreased complication risk, especially endophthalmitis.
A major advancement in cataract surgery has been the invention of IOLs that can be implanted to replace the extracted cataractous lens. Casamata was perhaps the first to implant an IOL way back in 1795. Modern PMMA lens was first implanted by Harold Ridley in 1949, which was a rigid one. Subsequent IOLs were made of silicone and acrylic which was flexible and hence could be folded and injected through a smaller incision.
To make cataract surgery safer, OVDs & ophthalmic viscosurgical devices have played significant role. From HPMC to dispersive OVDs like viscoat and to cohesive OVDs like Healon, OVDs have led to dramatic improvement in safety of surgery and minimize damage to ocular structures. OVDs are the most important advances in safety of modern cataract surgery.
Capsular staining enhances visualization and has further improved safety. This is especially useful in all conditions wherever red reflex is dull because of any reason. Trypan blue is the most popular out of all the available options.
Femtosecond laser is another advancement in making cataract surgery safer and predictable. It (1) makes rhexis of desired shape and size even in highly intumescent cataract or in the one with very weak zonules (2) does segmentation of nucleus much easy which makes the task much easier in very hard, posterior polar or zonular deficiency.
In recent years our understanding of the optical aberrations of normal human eye, cataractous eye and the eye which has undergone refractive surgery has undergone some change. Newer corneal imaging techniques like Sheimpflug imaging, placido disc, video kertography and anterior segment OCT have enhanced our understanding of shape and functionality of cornea. The positive corneal aberrations can now be compensated with negative spherical aberrations of newly designed aspheric lenses. These new lenses also enhance contrast sensitivity.
Almost conquering presbyopia has also been a milestone in advancement of cataract surgery. Multifocal IOLs, accommodating IOLs & trifocal IOLs are the new harbingers of new dawn. Array, Restor, Tecnis multifocal and Panoptix are some of the new IOLs. These multifocal IOLs have persistent drawback of potential for patients to see halos or glare for weeks to months after surgery.
However, it has been observed that these symptoms decrease with time as people learn to disregard these with passage of time. Another drawback is decrease in contrast sensitivity, especially in dim light. Patient selection with multifocal lenses is important. Patients with high expectations, large astigmatism, zonular weakness or retinal disease, may not be good candidates. Advent of Toric lenses is really a boon in neutralizing preexisting corneal astigmatism; hence better spectacle free vision. Limbal relaxing incisions on cornea, which are given in the peripheral depth of cornea to neutralize mild to moderate astigmatism is also a new advent to reduce astigmatism.
Eyhance is a new monofocal lens which gives very good intermediate vision and very good contrast sensitivity.
Crystalens (Baush & Lomb) and Synchrony are the accommodating IOLs. Another promising technology is a ‘light adjustable lens’ made of photosensitive silicon material wherein residual refractive error can be corrected by shining UV light on the IOL through dilated pupil, a few weeks post-operatively.
How cataract surgery has been made further safe in patients with zonular weakness, CTR made of PMMA can be put in the bag and stretch it to facilitate better centration and stability of IOL. Ring segments like Cionne’s ring can also be fixated in the bag and stretched to sclera to support and centralize the bag in subluxated bags.
About the Author:
Dr. Umesh Harkuni, MS (Ophthalmology)
Consultant, KLES Dr. Prabhakar Kore Hospital & MRC Belagavi.
