Phakic IOLs: what could go wrong?

The popularity of phakic IOLs in both cataract and refractive surgery has soared in recent years with lens manufacturers all joining the race to develop better lenses with improved outcomes and fewer complications. Although phakic IOLs are considered the ideal tools for the correction of high ametropias, because of their excellent accuracy and predictability, stability of refraction from day one and independence of tissue healing, they have, unfortunately, been marred by reports of certain complications throughout their development history. These complications include corneal decompensation, chronic inflammation, iris atrophy (pupil distortion), cataract and glaucoma. Here, António Marinho, MD, PhD discusses the influence of phakic IOLs on cataract and glaucoma development.

For the purpose of this article, Dr Marinho refers specifically to his experience with the following phakic IOLs:

Posterior chamber phakic IOLs:

Anterior chamber iris-supported phakic IOLs:

Lens complications

Posterior chamber phakic IOLs

Specifically, posterior chamber phakic IOLs have long been associated with the development of cataract because of their close proximity to the natural lens. This complication may be attributable to poor surgical technique during implantation or it could simply be caused by the presence of the phakic IOL in the eye for a long period of time.

When considering cataracts caused as a consequence of poor surgical technique, this generally results if pressure is exerted onto the natural lens or the natural lens is touched during implantation. This may happen as the IOL is positioned in the posterior chamber, particularly when introducing the haptics behind the iris.

Cataracts caused in this way generally have the following characteristics:

In general, this is related to surgeon experience, with incidence of this complication usually declining with increased confidence, knowledge and experience.

More significantly are those cataracts that develop as a consequence of the presence of the IOL in the eye following implantation. These cataracts are fairly typical and are characterised as follows:

The aetiology of these anterior, subcapsular cataracts has been considered in the past, with the most accepted theory describing them as metabolic cataracts. The theory states that, if the IOL sits on the natural lens and prohibits the free circulation of aqueous humour around the anterior surface of the natural lens, the lens will be inadequately nourished and hence an anterior subcapsular opacification will develop.