Neodymium: YAG laser for anterior capsulotomy

Neodymium: YAG laser for anterior capsulotomy Frederick A. Richburg, M.D. Fresno, California

ABSTRACT A technique using the Meditec OPL-3 YAG laser for anterior capsulotomy just prior to planned extracapsular cataract surgery is presented. A review of 1,108 cases showed this technique to have a low complication rate. Compared to conventional anterior capsulotomies, it is the author's opinion that this method gives increased operative control, shortens time in the operating room, and is a help with in-the-bag intraocular lens placement. Key Words: anterior capsulotomy, extracapsular cataract extraction, iris bleeding, iris miosis, Nd:YAG laser

The anterior capsulotomy is an essential part of a successfully performed extracapsular cataract extraction (ECCE). Complications during this step can cause rupture of the posterior capsule, rupture of zonules, vitreous loss, and dislocation of the nucleus. Irregular edges may make in-the-bag placement of an intraocular lens (IOL) impossible. Furthermore, if the anterior chamber collapses during the caps ulotomy, trauma to the iris may cause miosis, while corneal injury results in endothelial cell loss. Corneal trauma can also occur when small pieces of capsule left floating freely in the chamber become adherent to the cornea and cause corneal edema. Because there is no clearly superior method or instrument used to perform an anterior capsulotomy, the techniques and instruments are numerous. Several different knives are used; e.g., the Sato knife, the Huber ruby knife, needle knives, irrigating cystotome, bent 25- or 30-gauge needles, and others. 1,2,3 The Gills technique employs specially designed scissors. 4 More recently, ultrasonic knives and rotating knives have been developed to perform the anterior capsulotomy.5,6 A list of procedures done with these instruments includes the Christmas tree capsulotomy, skewer technique, trap-door incision, various slit or discission caps ulotomies, and the postage stamp or can-opener capsulotomy, which can be made in many different shapes. 7,8 I describe a technique, which was first reported by Dr. Aron-Rosa,9 using the YAG laser for anterior capsulotomy.

SUBJECTS AND METHODS Between November 27, 1982, and November 1984, 1,108 patients, aged 10 through 99 years, had laser opening of the anterior capsule 10 to 15 minutes prior to planned ECCE. Intraocular lenses were inserted in 1,075 patients (97%). Neither topical anesthesia nor a contact lens was used for this procedure. Each patient was given oral sulindac 150 mg (Clinoril®), diphenhydramine hydrochloride 100 mg (Benadryl@), and doxycycline monohydrate 100 mg (Vibramycin ®). Topical phenylephrine hydrochloride (Neo-Synephrine®) and tropicamide l.0% (Mydriacyl®) were administered to the eye to receive surgery. Thirty-five minutes before surgery they were given a 4-cc retrobulbar injection of 0.75% bupivacaine hydrochloride (Marcaine ®), 0.5% lidocaine hydrochloride (Xylocaine®), and 0.5 cc hyaluronidase (Wydase®), followed by ocular pressure with a super pinky (Gill's technique). Just prior to going to the operating room, the patients were seated at the Meditec OPL-3 mode-locked Nd:YAG laser slitlamp. (See Table 1 for specifications.) Minus 3 was added to the operator's emmetropic correction in the slitlamp objectives through which the ReNe beam was focused on the anterior capsule. This was necessary with our laser because its inner lens system is set to produce optical breakdown 0.5 mm behind the point of maximal ReNe focus. By adding -3 to the objectives this point is moved posteriorly about 0.5 mm, making it coincide with the center of focus of the YAG laser beam and

Reprint requests to Frederick A. Richburg, M.D., 1680 East Herndon Avenue, Fresno, California 93710. 372

AM INTRAOCULAR IMPLANT SOC J-VOL 11, JULY 1985

Table 1. Specifications for the Meditec OPL-3 neodymium:YAG laser.

1-1.5 mm

Wavelength:

1,064 nm

Output energy:

3.7 mJ

Pulse method:

mode-locked with passive dye cell

Pulse train:

7 pulses per train

Spot size:

50

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{-tm

Cone angle:

.

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point of optical breakdown. Because patients were given a retrobulbar injection and ocular pressure with a super pinky, the cornea became stippled, dry, and covered with mucus at times. Artificial tears or saline drops were applied to the cornea and wiped away with a cotton applicator to keep the cornea clean and moist. A nurse held the patient's head firmly against the slitlamp chin rest and forehead band, while the surgeon held the eyelids open. The slitlamp articulating arm and microscopic objectives were centered on the patient's optical axis, thus making all laser shots coaxial. The first laser shot was fired with the HeN e focused just anterior to the anterior capsule, with the capsule itself in sharp focus. If it was on the capsule, a microcut or a whitening of a small dot appeared on the capsule. If the shot was slightly deep, an air bubble was created underneath the capsule. In the latter situation, the next shot was pulled backward slightly, cutting the capsule and allowing the bubble to escape. If the shot was anterior to the capsule, a spark could be seen in the anterior capsule. Once on target, the laser was fired in rapid succession, placing the shots in a D-shaped pattern approximately 1.5 mm from the iris for 360 degrees. The effect of optical breakdown and its reaction on the capsule was watched very closely, not the HeNe. The HeNe was of secondary importance at this point in the procedure. I attempted to leave no more than a 0.2-mm bridge between each shot and frequently the shots coalesced spontaneously, actually allowing the capsule to curl up. The minimal diameter of one shot in the anterior capsule was about 0.2 mm. The entire procedure required 50 to 300 shots and took one to three minutes. Most cases required 150 to 200 shots. Variation in corneal clarity and capsular integrity appeared to be the reason for using more shots in some cases. Because the size of the patient's dilated pupil allowed an anterior capsulotomy of only 6 mm to 7 mm, and the size of a typical nucleus was 8 mm to 9 mm, I have found that radial relaxing incisions made with five to ten laser shots in each quadrant aided in a smooth delivery of the nucleus and controlled splitting of the peripheral capsule (Figure 1).

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Fig. 1.

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(Richburg) Laser shots are placed 1.5 mm from the iris border. Four relaxing incisions at the 1:30, 4:30, 7:30, and 10:30 positions allow controlled cracking of the capsule during delivery of the nucelus out of the capsular bag.

Postoperatively, all patients were treated with acetazolamide 125 mg (Diamox®) every six hours for 24 hours. In six cases (0.5%) the laser was not used because of corneal scars and severe corneal guttata.

RESULTS Additional cuts with a cystotome were required in 12 of 1,108 cases (0.1 %). Unintended bleeding of the iris occurred in six of the last 901 cases (0.7%). The cornea was hi tin three eyes (0.3%). No sequelae were seen six hours later in any of these 21 cases. DISCUSSION There are many ways to perform an anterior capsulotomy, which is usually a simple procedure taking less than one to two minutes. Nonetheless, the very fact that there are different methods for this procedure illustrates that there is no single technique that works every time. A complicated anterior capsulotomy converts a smooth surgical procedure into a complex problem. In my experience, when the technique of anterior capsulotomy presented here was applied properly, surgery was much easier because the anterior caps ulotomy was nearly perfect, and it was a simple matter to reach in and remove the entire piece of capsule that had been cut away. All capsular tags were completely out of the field. They could not plug up the aspiration tip or phacoemulsifier, nor could they adhere to the cornea and cause corneal edema. In my experience, it was easier to slip loops of an IOL behind sharp, well-delineated capsular flaps. When these incisions were properly placed, i.e., with a YAG laser, capsular fixation was easily achieved. Our operating room records indicate that this procedure decreased

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the time in the operating room by one to four minutes on the average since there was no need to do an operative caps ulotomy. One of the best indications for laser anterior capsulotomy is an eye with posterior pressure and/or a very soft cataract, i. e., congenital cataracts, traumatic cataracts, and mature cataracts. In these eyes, one can do a 360-degree anterior capsulotomy by starting the laser cuts inferiorly and quickly working up the sides and then across superiorly. I start inferiorly and work quickly in these cases because with each shot in a white, mature cataract the lens cortical material extrudes, appearing like a tiny waterfall coming out through the capsule; as the liquid cortex accumulates in the inferior anterior chamber, it obstructs laser function and the surgeon's vision. Subluxated cataracts on which one wishes to do an ECCE are also excellent cases for this procedure, in order to avoid the zonular stress of pulling with a knife or needle. 10 Several complications can occur with this procedure, but to date none in this series have been significant. The most severe complication would occur if the surgeon did not correctly calculate the point of optical breakdown and performed a posterior capsulotomy while trying to do an anterior capsulotomy. In this situation it is possible to dislocate the nucleus into the posterior chamber. We had vitreous loss in one case where it is conceivable that the posterior capsule was damaged prior to removal of the nucleus. We have not seen any cases with a posteriorly dislocated nucleus. Iris bleeding, the most common complication, is caused by hitting directly on or close to (1 mm or less depending on the power of the shot) the iris with the laser, whose shot or shock waves cause the bleeding. This problem, which occurred in six cases, can be avoided by keeping all shots 1.5 mm away from the iris. This type of bleeding can be easily controlled by placing a finger on the globe to increase intraocular pressure (lOP). Patient movement is the most common reason for hitting the wrong spot with the laser. It is also possible to hit the cornea during the procedure, particularly when a patient moves backward. Miosis can also occur when one hits the iris or when a shock wave gets too close to the iris. I have seen this in several cases but it has never been a Significant problem. Severe glaucoma can be a complication of doing laser anterior caps ulotomies several hours prior to surgery. In November 1982, I did two laser capsulotomies with the same basic technique but planned to do the cataract surgery the next morning, 16 hours later. The patients developed severe pain and lOPs of 60 mm Hg and 70 mm Hg five to six hours. after their laser capsulotomies. Medical treatment did not adequately reduce the lOP. To relieve the pressure, I performed emergency cataract surgery nine hours after the capsulotomies. Both patients have final visual acuities 374

of 20/20 and no optic disc cupping at 18 months postoperatively. I now do anterior capsulotomies 10 to 15 minutes prior to opening the eye. However, Drews 11 has described a technique that allows him to perform anterior capsulotomies the day before surgery. It is possible to cause a dislocation of the nucleus into the anterior chamber when an exceptionally large capsulotomy is performed on an otherwise soft cataract; however, I have found that surgery immediately afterwards eliminates the seriousness of this kind of complication. If one is going to use this technique for anterior capsulotomy, the patient must be medically cleared for surgery. Endothelial cell loss with subsequent bullous keratopathy and the need for penetrating keratoplasty may be a complication of some types of capsulotomy. I have not observed any specific trends with this laser technique. I have done four corneal transplants in the 1,108 cases described, three of which had low preoperative endothelial cell counts and severe corneal guttata. Aron-Rosa12 has reported that there is no Significant change in the endothelial cell count with a picosecond laser when doing anterior capsulotomies. I am evaluating our patients further for endothelial cell loss due to laser shots. Doing an anterior capsulotomy is similar to trying to cut a hole in an egg. Sometimes one can accomplish this very simply with a postage-stamp-type technique; however, at other times the egg will crack, causing problems. Large capsular cracks or tears can cause vitreous loss and displacement oflOLs and their loops when rotating the lens with a hook. This can lead to decentration, tilting, or dislocation of the posterior chamber IOL. This cracking can also occur with the YAG laser, but its effects are minimal in proportion to the gross cracks that result from using various knives. CONCLUSION A technique for anterior capsulotomy is presented and my experience with 1,108 cases reported. This new technique needs further evaluation regarding the status of the endothelium. The incidence of complications such as significant bleeding in the iris, iris miosis, and laser shot hitting the cornea have been discussed. Postoperative increased lOP has not been a problem. I do not advocate that one purchase a YAG laser to perform anterior capsulotomies, but for those who already have one for posterior capsulotomies, this paper presents another use for it. I do not consider this a separate procedure but rather part of the routine ECCE. The YAG laser is one more tool that can be used for an anterior capsulotomy; only time will tell where it fits in the technology of cataract surgery. REFERENCES 1. Huber C, Dubois R: A ruby cystotome. Am Intra-Ocular Implant Soc J 7:378-379, 1981

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2. Johnson SH, Kratz RP: A short, angled, irrigating cystitome. Am Intra-Ocular Implant Soc J 8:372, 1982 3. Pohjanpelto P: Watertight entry with a bent disposable needle for anterior capsulotomy. Am J Ophthalmol 97:529-530, 1984 4. Lyle WA: A new phacoemulsification technique for in-the-bag IOL placement. Am Intra-Ocular Implant Soc J 9:461-463, 1983 5. Mendez A: Anterior capsulotomy with ultrasound cystotome. Am Intra-Ocular Implant Soc J 10:363-364, 1984 6. Clayman HM, Parel J-M: The capsule coupeur for automated anterior capsulectomy. Am Intra-Ocular Implant Soc J 10:480-482, 1984 7. Hecht SD, McCarthy EF Jr: The skewer technique for anterior capsule remnants. Ophthalmic Surg 15(7):583-584, 1984

8. Welch DW, Stephenson GS: The "trap door" anterior caps ulotomy technique for extracapsular cataract extraction with posterior chamber intraocular lens implantation in the capsular bag. Am Intra-Ocular Implant Soc J 8:59-60, 1982 9. Aron-Rosa D: Use of a pulsed neodymium-Yag laser for anterior capsulotomy before extracapsular cataract extraction. Am Intra-Ocular Implant Soc J 7:332-333, 1981 10. Woodward PM: Anterior capsulotomy of dislocated lenses in Marchesani syndrome using a Nd:YAG laser. Am Intra-Ocular Implant Soc J 10:215-217, 1984 11. Drews RC: Anterior capsulotomy with the neodymium:YAG laser: Results and opinions. Am Intra-Ocular Implant Soc J 11:240-244, 1985 12. Aron-Rosa D: Use of a pulsed picosecond Nd:YAG laser in 6,664 cases. Am Intra-Ocular Implant Soc 10:35-39, 1984

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