Multi-component IOL

May 1, 2014

In this article, Dr Portaliou discusses a new multi-component adjustable lens that may be the answer paediatric ophthalmologists have been waiting for.

During the last decade, advances in the ophthalmological field have made their way into the everyday clinical practice of paediatric ophthalmology as well. Nevertheless, despite the technological advances and constant improvements in surgical techniques and intraocular lens (IOL) technology, cataract surgery in children remains challenging3 and presupposes a customized approach and a highly skilled surgical team to ensure an optimum result.

One of the most crucial steps - decisions when performing paediatric cataract surgery - is the choice between aphakia or IOL implantation. Aphakia can be devastating for the young patient due to the necessity for a high hyperopic correction. However, the type of IOL to implant and the dioptric power of the IOL used are critical to avoid extreme refractive surprises and other complications postoperatively.

The available options when performing cataract surgery in children are aphakia followed by immediate contact lens fitting versus primary IOL implantation. In children that have completed their 2nd year of life, IOL implantation is the preferred approach but surgeons still remain hesitant to implant an IOL in infants and children under the age of 2. The advantages of IOL implantation are numerous such as amblyopia prevention, lower rate of certain complications and higher compliance if contact lens fitting is impossible.

Despite the advantages, deciding on the IOL type and power remains challenging as the anatomy of children's eyes is unique in certain aspects. Children's ocular system is still developing and, therefore, is in a dynamic state, one that makes precision of measurements uncertain. Children's eyes are characterized by steeper corneas, shallower anterior chamber depth and shorter axial length4 making correct biometry and accurate IOL calculations almost impossible.

Predicting the refractive change of young patients over time is another challenge for paediatric ophthalmologists. Trivedi et al.5 have concluded that there is a continuous myopic shift in refraction as age advances and suggested that the greatest change in axial length occurs during the first 2 years of life. In particular, there is a rapid growth of 0.62 mm/month during the first 6 months and sequentially a 0.19 mm/month in the time frame between the 6th and 18th month of life. The growth continues with a much lower rate (0.01 mm/month) until adulthood. Of course these general rules do not always apply as the natural variance in growth of the eye is unpredictable. Most surgeons aim for residual hyperopia when implanting an IOL, expecting a myopic shift during the growth process that will lead to emmetropia by the age of 18 years. Others aim for a slight myopia that will facilitate children's near vision and possibly prevent amblyopia. No direct guidelines are available and, therefore, each surgeon is relying on his/her personal experience rather than a well established algorithm.

The type of IOL to implant is an important issue as well. In the bag implantation is preferable and polymethyl methacrylate (PMMA) the material of choice. Certain investigators have suggested the use of multifocal IOLs in children.6 Tassignon's7 'bag-in-the-lens' surgical approach is a technique in which the anterior and posterior capsules are placed in the groove of a specially designed IOL after a capsulorrhexis of the same size is created in both the anterior and posterior capsules. The principle behind this IOL design is to ensure a clear visual axis by mechanically tucking the two capsulorrhexes into the IOL groove, thereby preventing any migration of proliferating lens epithelial cells and thus preventing posterior capsule opacification.