Successful anterior capsulotomy benefits the other steps of cataract surgery. This is not easy to achieve without sufficient experience, however, particularly in congenital and hypermure cataracts. A number of techniques have been developed to simplify the procedure.1–3 This study was designed as a preliminary animal trial to test the feasibility of an enzymatic method for anterior capsulotomy in humans.
The local ethics committee gave approval for the study. Collagenase Type XI (Sigma C-9407) was used. The solution was prepared at 1 mg/mL concentration in 20 mmol TRIS HCI plus 1 mmol CaCl2 at pH 7.2.
Five adult rabbits (2.0 to 2.5 kg) were killed by deep ether anesthesia, and the eyes were enucleated. Five eyes were used as control, and 5 comprised the study subjects. Corneas and irises were excised from the eyes. The study included 2 techniques. For the first, 3 μg of the enzyme was applied with a micropipette. The anterior surface of the lens was dried with a sponge, after which saline and the enzyme solutions were applied to the control and study groups. The eyes were incubated at 37°C with 95% humidity for 30 minutes. The eyes were then washed with saline.
For the second technique, 1 μg of the enzyme and saline solution was applied with a specially designed loop-shaped tool (4.0 mm diameter) to the eyes as described for the first technique. After dipping the loop into the enzyme solution, it was pressed lightly against the dried lens surface for 1 second, creating a wet circle. The eyes were kept in the incubator for 15 minutes.
No changes were observed in the control group. For the first technique, signs of digestion started within a few minutes, increasing and reaching a maximum at 30 minutes. At 30 minutes, the capsule disappeared with its full thickness; however, the edge of the digested capsule was rough and irregular (Figure 1). For the second technique, lens thickness decreased from one-half to one-fourth with slight variations. No full thickness digestion was observed at any area at the 15-minute point.
Although a complete capsulotomy was achieved with the first technique, the desired effect, ie, a localized weakening in the capsule, was achieved with the second, allowing an easy capsulorhexis. The edge of the digested area was fragile and rough in the first trial. Although this method obviates a capsulorhexis, the weakness of capsulotomy line may pose potential problems. For example, small indentations may lead to unwanted radial tears. Using the second method, the capsulorhexis line is weakened by restricted local application of the enzyme, after which the capsule can be easily torn using the capsulorhexis method.
Enzymatic digestion may represent a new method for capsulotomy. This preliminary study is the first to put the idea to test. Further studies, especially ones using human cadaver eyes, are essential to clarify the value of this technique.
Adnan Cinal MD
Gurkan Ozturk MD
Ahmet Demirok MD
Murat Özdemir MD
Suleyman Ozen MD
Hanefi Ozbek MD
Tekin Yasar MD
Saban Simsek MD
1. Gassmann F, Schimmelpfennig B, Kloti R. Anterior capsulotomy by means of bipolar radio-frequency endodiathermy. J Cataract Refract Surg 1988; 14:673-676
2. Brierley L. Vacuum capsulorhexis. J Cataract Refract Surg 1995; 21:13-15
3. Michalos P, Avila EN. “Capsulocopis”: a new surgical instrument and method for capsulotomies. Ophthalmic Surg Lasers 1996; 27:476-478