Commentary: Femtosecond laser assisted cataract surgery in cataract with phakic intraocular lenses in situ.

Phakic intraocular lenses (pIOLs) are used for the surgical correction of moderate to high myopia and have similar efficacy, enhanced precision, and safety when compared with corneal ablative procedures.[1] Cataractogenesis in cases with pIOLs in situ may be attributed to surgical trauma, extremely shallow vault, disturbances in aqueous outflow, or age-related senile cataract.[2]

Phacoemulsification in cases with pIOLs in situ is surgically challenging as pIOLs need to be explanted in addition to emulsifying the nucleus and implanting a new foldable IOL. The pupil may constrict after pIOL explant, complicating subsequent capsulorhexis and nuclear fragmentation. Furthermore, the iris is often floppy in high myopes. The presence of pIOLs does not significantly affect axial length measurements by optical biometry; however, care must be taken to use the appropriate IOL power calculation formula as many eyes have higher axial lengths. The type of IOL is based on the axial length (expand series of IOLs may be needed in cases with extremely long axial length) and length of incisions (large sutured corneal incisions in cases with rigid iris-claw pIOLs may preclude toric or multifocal IOL implantation).

Femtosecond laser-assisted cataract surgery (FLACS) has added to the armamentarium of surgical techniques for cataract extraction and it is increasingly being used in the management of challenging and complex cataract cases. The authors have described the successful use of FLACS in a case with posterior chamber pIOL in situ.[3] They manually adjusted the laser treatment zone to avoid laser delivery to the implantable collamer lens (ICL) and observed accumulation of cavitation bubbles beneath the ICL hampering successful nuclear fragmentation.

FLACS has successfully been performed in cases with both iris-claw pIOLs and posterior chamber pIOLs in situ.[4] The advantages of FLACS include the creation of precise well-centered capsulotomies, self-sealing corneal incisions, and prefragmented nuclear pieces. Femtosecond laser pretreatment allows safe completion of phacoemulsification even in cases that experience pupillary constriction after pIOL explant.

Rigid iris-claw pIOLs are conventionally explanted via a large superior incision, followed by suturing the incision and performing phacoemulsification through a second temporal clear corneal incision. Alternatively, we have described a modified technique of FLACS wherein the temporal haptic of iris-claw pIOL is disenclavated and the optic is shifted nasally to allow completion of phacoemulsification without explanting the rigid pIOL. Subsequently, the iris-claw pIOL is explanted after enlarging the same corneal incision, thereby minimizing the number of incisions.[4]

Femtosecond laser technology has its unique set of challenges in cases with pIOL in situ. First, the presence of a pIOL during femtosecond laser planning interferes with the automated detection of anterior and posterior lens capsules, and the planned treatment zone often encompasses the pIOL. It is essential to manually adjust the treatment zone, and various modifications in laser parameters have been suggested for optimal results including increasing the depth and vertical spot spacing of capsulotomy as well as increasing the safety zones of anterior and posterior lens capsules during nuclear fragmentation.[345]

The second issue with the use of femtosecond laser technology is the entrapment of cavitation bubbles in the closed space between the posterior surface of pIOL and the anterior lens capsule. The effect is observed more in cases with shallow vaults and subsequently less space to allow dispersion of the cavitation bubbles. Dense accumulated cavitation bubbles hamper effective penetration of femtosecond lasers and may result in incomplete nuclear fragmentation.[345] Nuclear fragmentation is usually effective in cases with rigid iris-claw pIOLs, as the adequate vault allows dispersion of cavitation bubbles.

To conclude, FLACS may be safely used in cases with pIOL in situ, with the creation of well-centered free-floating capsulotomies. The laser treatment planning requires manual adjustments, and cavitation bubbles may hamper effective nuclear fragmentation, especially in cases with shallow vaults.