One challenge the surgeon faces in every cataract procedure is the inability to view the structures behind the iris, which means possibly missing cortical remnants at the lens equatorial region or incorrectly positioning an IOL. If zonules rupture during cataract surgery, the extent of damage is also hard to determine because of this visual blockage.
Designed by Bong-Hyun Kim, MD, of Seoul, South Korea, an innovative intraocular mirror (Figure 1) now helps surgeons to visualize the internal structures of the eye, including the iris and corneal endothelial surface. With this device, surgeons can inspect the iris and visualize zonules, the ciliary sulcus, and equator of the nucleus before and during cataract surgery.
Using the intraocular mirror can potentially reduce the rate of intraoperative complications, mainly because surgeons can now visualize what is occurring in the area behind the iris, Dr. Kim explained in an interview with CRST Europe. The mirror also helps to forecast a patient's postoperative course, as surgeons may see what kind of damage is occurring to the cornea because of the reflection and retroillumination the mirror offers. No other tool or device has been reported to effectively demonstrate endothelial cell damage during surgery.The intraocular mirror is also ideal for confirming IOL position, defining areas of zonular dehiscence, or exchanging an IOL.
VISIT TO THE DENTIST
Dr. Kim started designing his intraocular mirror after visiting his friend, a dentist, who Dr. Kim happened to watch using a mirror that allowed complete visualization of the mouth. "At that moment, I was reminded of a situation where I had gotten into trouble during cataract surgery because I could not visualize the structures behind the iris," Dr. Kim said. "I asked to borrow a mouth mirror, and I started to experiment with it in an eye model. I then decided to develop an intraocular mirror."
Dr. Kim spent 1.5 years designing his intraocular mirror, which is now marketed as the BH Kim Intraocular Mirror by Katena Products, Inc. (Denville, New Jersey). The mirror is composed of a head, shank, and handle. A reusable model is already available, and detachable heads will be introduced in the near future (See Detachable Heads Soon Available). The standard 2.5-mm round head is 0.3 mm thick and constructed of highly reflective stainless steel, a variation from what Dr. Kim originally proposed.
"I intended to use glass for the head of the mirror," he said. "But engineers explained that glass was not suitable for intraocular use because of the toxic mercury inside. It is also hard to cut glass into small pieces, and double images are common because of the double reflection from the surface and bottom of the glass."
The intraocular mirror, Dr. Kim said, has certain advantages over an endoscope. First, the instrument is cheaper and does not require any setup time. Second, an additional wound, which induces unnecessary surgical trauma, is sometimes necessary when using an endoscope. "With the intraocular mirror, there is no need to make a different wound," Dr. Kim compared. "The mirror can be inserted into the eye through the main cataract wound. That is why the diameter of the head is 2.5 mm, which is a good size for most cataract wounds."
CLINICAL USES
Clinical uses for the intraocular mirror include ascertaining the position of an IOL (Figure 2), identifying areas with no zonules (Figure 3), aiding in explantation of an opacified IOL (Figure 4), and inspecting for corneal endothelial damage (Figure 5).
Dr. Kim suggests injecting an ophthalmic viscoelastic device (OVD) under the iris before using the intraocular mirror. This step helps to separate structures within the eye and ensure that enough space is available for placement of the mirror behind the iris. An OVD should also be injected into the anterior chamber to allow observation of the corneal endothelium.
"If you do not use an OVD," Dr. Kim warned, "the structures are crowded, and you will have some difficulty identifying the structures and tilting the mirror inside the eye."
During creation of the capsulorrhexis, Dr. Kim's mirror helps to visualize the leading edge of the capsular flap, thus potentially avoiding damage to the zonules.
"As the capsulorrhexis is created, often the anterior capsular flap inadvertently extends peripherally," Dr. Kim said. "The surgeon then must determine the next procedure—either pulling the flap centrally to redirect it or incising the capsule to create a new flap. The intraocular mirror helps the surgeon make the right decision."
The intraocular mirror is also useful before IOL insertion begins to ensure that no cortical remnant is left behind. Once the IOL is ready for insertion, the mirror can be used to properly place the IOL; this is beneficial in patients who have small pupils.
When explanting an opacified IOL, the intraocular mirror helps visualize where the haptics lie, hopefully avoiding zonular breaks that are likely to occur if the position cannot be determined. The key during explantation, Dr. Kim said, is to release the adhesion between the haptics and the capsular bag without damaging the zonules.
This novel device provides surgeons with a safe, quick, and easy method to view the areas of the eye otherwise obstructed by the iris, Dr. Kim said. In the future, the device will also facilitate study for corneal endothelial damage during intraocular surgery.
Bong-Hyun Kim, MD, is the Medical Director of the Seer and Partner Eye Institute, Seoul, South Korea. Dr. Kim states that he has no financial interest in the products or companies mentioned. He may be reached at nunsusul@yahoo.co.kr.
