APR 23, 2012
This large retrospective study found that the amount of postoperative astigmatism following pediatric cataract surgery is lower with clear corneal incisions, compared with scleral tunnel incisions. However, the difference in the magnitude of astigmatism is well within the interobserver variability of the estimate of the astigmatic error of 0.25 to 0.50 D.
Subjects were 138 children (218 eyes) aged between six months and 12 years who had cataract extraction with IOL implantation using either clear corneal or scleral incisions. All patients had surgery at a single center and were followed for at least six months..
Although there was a slight increase in the amount of astigmatism in the scleral group over time, it was not statistically significant (p=0.26). In the corneal incision group, the amount of astigmatism decreased significantly with time (p<0.001). The difference in astigmatism between the two groups was comparable at one month postop (p=0.90), while it was significantly lower with clear corneal incision at three (p=0.03) and six months (p=0.01). With-the-rule astigmatism was the most common form in both groups.
The authors suggest two possible explanations for the regression in astigmatism: the ocular tissues in children exhibit a high degree of elasticity, so the tissue tension may spread evenly to neighboring areas, reducing the amount of astigmatism. Also, as the globe continues to grow and becomes more spherical, the amount of astigmatism diminishes.
The authors note that the magnitude of astigmatism does not vary with age. After considering other parameters such as sex, IOL position, axial length, etc, so as to be sure that there were no other confounding factors in the results, they conclude that the site of incision was the only factor that was statistically significant.