Vitrectorhexis versus forceps posterior capsulorhexis in pediatric cataract surgery.

This study was done to compare the results of posterior continuous curvilinear capsulorhexis created using forceps with those created using vitrector in eyes suffering from congenital cataract. Vitrectorhexis term was first used by Wilson et al in 1999. [1] Fifty eyes with congenital and developmental cataract were included in this study. The posterior capsulorhexis was created using utrata forceps in 17 eyes or through a vitrector in 33 eyes. Forceps capsulorhexis was performed before IOL implantation, while vitrectorhexis was performed after IOL implantation in the bag. The results of both the surgery were compared using the following criteria: incidence of extension of rhexis, ability to achieve posterior rhexis of appropriate size, ability to implant the IOL in the bag, the surgical time, and learning curve. Vitrectorhexis after IOL implantation was an easy to learn alternative to manual posterior continuous curvilinear capsulorhexis in pediatric cataract surgery. It was more predictable and reproducible, with a short learning curve and lesser surgical time.

Performing posterior continuous curvilinear capsulorhexis (PCCC) has historically been a challenge. Traditionally, forceps have been used to perform PCCC. It has a long learning curve and achieving the appropriate sized opening still remains a challenge. Vitrectorhexis is an alternative to manual PCCC. The purpose of this study was to compare the results of manual PCCC with vitrectorhexis while performing posterior capsulorhexis in pediatric cataract surgery.

Methods

A prospective analysis of 50 consecutive pediatric cataract surgeries with posterior capsulorhexis was done. These surgeries were done between December 2010 and June 2011 by a single surgeon. Alcon INFINTI® Vision System Phacoemulsification Machine was used in all the cases. The sample was collected by incidental cum purposive method. The age group of the patients was between 1 and 8 years. Seventeen eyes underwent Manual PCCC (Group A) and 33 Eyes underwent Vitrectorhexis (Group B). Cases with fibrosed posterior capsule and traumatic cataracts with ruptured anterior or posterior capsule were excluded. Eyes that had received a capsulotomy using other than a vitrectorhexis or manual capsulorhexis or without IOL insertion were excluded from the study. Anterior capsulorhexis was done manually in all the cases.

The initial steps of surgery till cortical aspiration were same in both groups. While performing manual PCCC, the anterior chamber was filled with methylcellulose, taking care that the surface of posterior capsule was more or less flat. Too concave posterior capsule would make it difficult to properly visualize the PCCC edge. After an initial nick in the center of the posterior capsule, high molecular weight ocular viscosurgical device like sodium hyaluronate 1% was injected in the Berger's space between the posterior capsule and the anterior vitreous phase. This would prevent entanglement of the vitreous fibres in the capsular forceps if there was disturbance in anterior vitreous phase. The leading edge of the PCCC would be gripped and re-gripped with an aim to achieve a PCCC diameter of about 4 mm. After completing the PCCC anterior vitrectomy was done with settings of 800 cuts per minute and aspiration of 150 mm Hg. End point of vitrectomy would be when the posterior capsule remnant falls back with a smooth margin. After a good anterior vitrectomy, the IOL would be inserted in the bag with the leading haptic being pushed in the bag, and the trailing haptic dialed into it. A single piece acrylic hydrophobic IOL (Acrysof® SN60AT) was used in most of the cases after manual PCCC due to the ease of insertion and manipulation in the bag.

In cases where vitrectorhexis was performed, the IOL was first implanted in the bag. In this case, multipiece acrylic hydrophobic IOL (Sensar AR40e or Acrysof® MN60AC) was implanted in all but 2 of the surgeries. In those two cases single piece acrylic hydrophobic IOL (Acrysof® SN60AT) was used. After IOL implantation, the main incision site was sutured using single 10 0 nylon suture. The IOL was implanted before vitrectorhexis with presumption that the rhexis margin would be ragged, thereby risking posterior rhexis extension during IOL implantation. Then the vitrector was introduced behind the IOL optic with port down and the irrigation cannula was kept in anterior chamber. The settings of vitrectomy were a cut rate of 800 per minute and aspiration of 100-150 mm Hg. Once the opening was made in the posterior capsule, the port was turned anterior so that the enlargement could be done under visualization. Once an appropriate sized posterior capsulotomy was achieved, anterior vitrectomy was done by moving the vitrector in the center of the opening. Then with the cutter off, the instrument was gently brought back in the anterior chamber and IOL optic manipulated back in the bag. The instruments were withdrawn from the eye and side ports and main port hydrated till the eyeball was normotensive. This procedure of vitrectorhexis was preferred over pars plana vitrectomy with vitrectorhexis, as the surgeon was a trained anterior segment surgeon, not performing regular pars plana vitrectomy. Moreover, this technique would avoid additional three incisions in the eye for similar result.

Results

As per the details in Table 1 the average age of patients was 3.7 years (range 3 months to 8 years). The average age of Group A was 3.38 years and Group B was 3.86 years. In Group A, 10 cases were operated in right eye and 7 in left eye. In Group B 15 were operated in right eye and 18 in left eye. There was extension of the PCCC in 2 (11.76%) of the 17 cases (4th and 12th case) in Group A. and in 3(9.09%) of the 33 (2nd, 7th, and 16th) cases in Group B. Of the three PCCC extensions in Group B, first two occurred with aspiration setting of 150 mm Hg. After that aspiration was brought down to 100 mm Hg and only 1 extension occurred in the remaining 26 cases. Another significant aspect was that the surgeon had been practicing manual PCCC for the last 7 years and the 33 cases of vitrectorhexis where his first 33 cases. Considering this fact, vitrectorhexis had a much faster learning curve. The size of anterior rhexis was about 6- 6.5 mm in both the methods; it made insertion of the vitrector behind the lens optic easier. In two cases of vitrectorhexis, the anterior rhexis has to be enlarged after making in nick with Vannas scissor, to facilitate easy insertion of vitrector behind the bag. In 17 of the manual PCCC cases, three multipiece IOL had to be placed in sulcus, two due to extension of the posterior rhexis and one due to large PCCC. In the vitrectorhexis group, all IOLs were placed in the bag irrespective of the extension of the posterior rhexis. Surgical time in the manual rhexis group averaged to 26 min, while that of the vitrectorhexis group was 17 min.

Table 1

Patient details relevant to the study

Discussion

In 2007, Wilson and colleagues,[2] found out that vitrectorhexis is well suited for use in children less than 6 years of age due to their highly elastic anterior lens capsule. In 2009, Hazirolan and colleagues,[3] concluded that both the techniques for anterior and posterior capsulorhexis are comparable in terms of corneal edema, anterior chamber reaction, and visual axis clarity. Surprisingly, that was the only study published for vitrector being used for posterior capsulorhexis. Andreo, Trivedi and Neuhann et al concluded that the manual CCC offered greater resistance to capsule tearing than the vitrectorhexis and also revealed a more smooth, regular edge. It therefore remains the gold standard. However, the vitrectorhexis displayed more than adequate resistance to unwanted anterior capsule tears when used for IOL insertion through capsulotomy sizes currently used in clinical practice.[456]

In this study it is evident that inspite of having good experience in manual PCCC, the predictability and reproducibility of the procedure were average, where as in the vitrectorhexis group, in a small number of cases, both the factors increased significantly. Initial two cases of posterior rhexis extension were probably due to higher aspiration setting of the cutter (150 mm Hg), which improved once the aspiration was brought down to 100 mm Hg. IOL implantation in the bag is desirable in small children, which was achieved in 100% of the cases in vitrectorhexis group, irrespective of the extension of the rhexis margin. Also, the surgical time was significantly reduced from average 26 to 17 min. The obtained t value 9.68 is greater than P value (2.014) at 0.05 level. Thus, there is a significant difference between the surgical time taken in group A and group B. In the three cases where the posterior vitrectorhexis extended, care was taken that the lens haptic was perpendicular to the area of extension. The wound was gently hydrated and the lens was found to be nicely centered in the postoperative visits.

The limitations of the study were a small sample size, lack of randomization of the sample and unequal size of the samples. The Group B was deliberately kept larger as the surgeon wanted to study the learning curve of a new procedure that he was trying. Long-term result of the new procedure is yet to be seen.

Conclusion

Vitrectorhexis after IOL implantation is an easy to learn alternative to manual PCCC in pediatric cataract surgery. It is more predictable and reproducible, with a short learning curve and lesser surgical time.