Bag-in-lens in young eyes
Tips and tricks for successful implantation of the bag-in-the-lens IOL.
The bag-in-the-lens (BIL) intraocular lens has many characteristics that make it ideal for children with cataracts and the learning curve with the technique is fairly smooth for an experienced cataract surgeon, Sorcha Ní Dhubhghaill told the ESCRS/WSPOS symposium at the 38th Congress of the ESCRS.
“The BIL prevents posterior capsule opacification PCO and visual axis re-opacification. The method also guarantees excellent centration and, by trapping the capsular bag, we can also prevent rhexis phimosis. Moreover, the lens has been designed with a view to being quite exchangeable and interoperable, something that is particularly helpful for the paediatric population,” said Prof Ní Dhubhghaill MB, PhD, FEBOS-CR, Antwerp University Hospital, Edegem, Belgium.
She explained that the BIL IOL is a hydrophilic acrylic implant with a central 5.0mm optic and elongated oval-shaped haptics that are perpendicular to each other and between which is an inter-haptic groove. To implant the lens the surgeon first creates an anterior posterior capsulorhexis and uses the haptics to clasp the leaves of the two capsulorhexis edges together within inter-haptic groove.
“By trapping the peripheral lens epithelial cells between these grooves, we can see that although they continue to grow and form a Soemmering’s ring, they remain confined to the very periphery of the lens. Eventually that forms a kind of donut around the IOL and the visual axis remains clear and the lens is made more stable by this additional Soemmering’s ring support,” Prof Ní Dhubhghaill said.
She added that although the posterior capsule is generally removed in paediatric cataract procedures, with standard IOLs the lens epithelial cells can still migrate across the back of the lens and opacify the visual axis. Performing YAG laser procedures in such cases can be very challenging.
Several case series of paediatric patients who have undergone successful implantation of the BIL have demonstrated that the visual axis remains clear of visual axis re-opacification throughout 10 or more years of follow-up. In addition, because of the success of the lens in preventing PCO, it has become the IOL of choice in adult cataract patients at the Antwerp University Hospital.
Mastering the technique
Because of the BIL IOL’s unique and unconventional design, surgeons must adapt their technique in three specific respects to implant it successfully. They are the anterior capsulorhexis (ACCC), posterior capsulorhexis (PCCC) and lens insertion. For a skilled surgeon, the learning curve usually takes around 25 cases, she said.
To accommodate the BIL IOL, the capsulorhexis has to be 5.0mm in diameter. To ensure precision, a flexible ring-shaped calliper can be inserted after filling the anterior chamber with an ophthalmic viscosurgical device (OVD). An external Eye Cage device can then be used to align the calliper with the Purkinje reflexes and the limbus. An additional injection of OVD will then stabilise the anterior chamber for performance of the capsulorhexis. The cataract can then be removed using standard technique, which in paediatric cases generally requires only simple aspiration.
Following cataract extraction, the anterior rhexis serves as a guide to ensure that the posterior capsulorhexis matches its dimensions and centration. The surgeon should first create a central puncture in in the posterior capsule and inject an OVD into the space of Berger, which serves as circular cushion that pushes back the anterior hyaloid face and prevents vitreous prolapse.
“Before performing the posterior capsulorhexis, make sure the capsular bag is emptied of any OVD so that it will be very flat, which makes it easier to control the vectors of force when you’re making your rhexis. What you don’t want is a capsular bag that bows downward because it will make performing the capsulorhexis less controlled.
“The posterior capsulorhexis starts with a small scratch to puncture the posterior capsule in a sideways rather than a downward motion to avoid touching the anterior hyaloid face. Inject OVD into the hole created to make the cushion of OVD just a little bit wider than the anterior capsulorhexis, which should tamponade the vitreous body. Sometimes it is necessary to dissect the anterior hyaloid face away from adhesions there to free the posterior capsule,” said Prof Ní Dhubhghaill.
Upon completion of the posterior capsulorhexis, the IOL is then injected into the anterior chamber followed by an injection of OVD over the lens to stabilise it and push it flat down against the anterior and posterior capsules. Once it is in position, the lens is tilted to catch the edges of the two capsular leaves beneath one of the posterior haptics and the remaining capsule is gently teased with a sliding motion to capture the rest of the capsule within the groove. With one final push the second posterior haptic is secured beneath the two rhexes.
In paediatric cases, Miostat is then injected to prevent optic-haptic capture and an iridotomy is performed to prevent pupillary block, she added.
Sorcha Ní Dhubhghaill: firstname.lastname@example.org