By BJ Lightfoot, OD | PCLI Bellevue, WA
Pacific Cataract and laser Institute
In the USA, nearly 4 million cataract surgeries are performed each year. Many people undergoing treatment have specific visual demands and increasingly heightened expectations for spectacle independence. Fortunately, we have an array of IOL designs to help us achieve the outcomes patients desire. While traditional cataract surgery remains remarkably safe and effective, laser assisted cataract surgery (LACS) offers distinct advantages for patients desiring a greater degree of freedom from glasses.
LACS vs. Traditional Surgery
In 2019 PCLI began incorporating femtosecond laser technology into our cataract practice. The laser we use is the same high-frequency, low-energy instrument our surgeons utilize to create precise LASIK flaps.
The obvious question is, what does LACS do differently than traditional cataract surgery?
Benefits of Laser Incisions
Clear corneal incisions created with the laser have greater architectural stability and reproducibility than those made with a blade. This is achieved through the laser’s custom triplanar wound profile.
Benefits of clear corneal laser incisions include:
distributed quarterly to 2700 optometric physicians Summer 2021
Clear corneal incision made with a blade vs. a laser.
Manual Blade Incision
Laser Triplanar Incision
Benefits of a Precise Capsulorhexis
One of the main advantages of LACS is the ability to consistently create a highly regular and perfectly circular capsulorhexis. Presbyopia-correcting IOLs that employ diffractive optics require near-perfect centration within the capsular bag to function optimally. While a skilled cataract surgeon can consistently make a quality capsulorhexis, some degree of irregularity is unavoidable. Much like trying to draw a circle by hand, there is always variability. This challenge increases when zonules are weak or white cataracts make the capsule challenging to visualize.
A consistent and perfectly circular capsulorhexis facilitates centration of the intraocular lens and reduces the incidence of IOL tilt. This is more critical with presbyopia-correcting IOLs than with monofocal implants and may decrease the prevalence of bothersome dysphotopsias that can occur with presbyopia-correcting IOLs.
The size of a laser-created capsulorhexis can also be modified to accommodate the diameter of the IOL optic. This size-matched approach, coupled with a perfectly circular capsulotomy and a better centered IOL, provides consistent overlap of the anterior portion of the capsule with the optic edge. This ideal alignment also helps to reduce the incidence of posterior capsular opacification.
Benefits of Precision Limbal Relaxing Incisions
Low amounts of uncorrected corneal astigmatism may not bother cataract patients who choose monofocal IOLs, and certainly not if they expect to wear fine-tuning spectacles for best function. However, for those electing to have presbyopia-correcting IOLs, mild residual astigmatism can negatively affect lens implant performance and be a significant source of dissatisfaction. OCT technology coupled with the precision of the femtosecond laser results in LRI formation that is perfect in depth, length, and regularity—far more so than LRIs created manually.
Femtosecond LRIs can treat corneal astigmatism ranging from 0.5 to 1.5D by incising the corneal stroma and flattening the steep meridian. Laser LRIs have shown to be more accurate in addressing corneal astigmatism below 1.25D when compared to toric IOLs. Additionally, laser LRIs can be designed to avoid breaching the overlying corneal epithelium, thereby negating any additional post-operative ocular surface discomfort. If needed, surgeons can titrate the effect of laser LRIs as the eye heals by opening the anterior surface of the corneal epithelium to further reduce astigmatism.
Patients with dense arcus or peripheral corneal scars may not be good candidates, as the femtosecond laser is less capable of forming accurate LRIs in opaque tissue.
Benefits of Nuclear Pre-fragmentation
In cataract surgery, phaco-emulsification is typically used to break down the lens for removal. Ultrasonic energy causes oxidative stress and produces free radicals that can damage the corneal endothelium. This is particularly worrisome when patients have compromised endothelium, as seen post corneal transplant or in cases of Fuch’s endothelial dystrophy. If the cataract is mature and the cornea has significant guttata, the patient may be at increased risk for decompensation secondary to additional phaco energy required to liquefy the cataract.
A skilled cataract surgeon will always employ techniques to minimize the effective phacoemulsification time. With LACS, surgeons can use the laser to pre-treat and fragment the cataract before the capsulorhexis is created. Linear fragmentation patterns segment the nucleus, thereby softening harder, more mature cataracts. This effectively reduces ultrasound energy delivered to the corneal endothelium. Laser pre-fragmentation also reduces the risk of corneal edema in hyperopic patients with shallow anterior chambers.
In addition to being easier on the corneal endothelium, LACS is useful when zonular dehiscence is a concern. For instance, when manual techniques are used in cases with pseudoexfoliation syndrome, phacodonesis may be observed. Weak or missing zonules also increase the risk of intraoperative capsular compromise. Nuclear disassembly with LACS enables surgeons to use less phaco energy, improving the odds of maintaining capsular integrity and thereby better IOL centration.
LACS nuclear disassembly is also helpful with posterior polar cataracts as this type of cataract tends to bond to the posterior capsule. With manual surgery techniques, the incidence of posterior capsule tear can be as high as 36%. Nuclear pre-fragmentation can assist with a gentler and safer dissection from the capsule.
LACS is a non-covered service as determined by Medicare and can only be billed to the patient in specific circumstances.
Medicare only allows patients to pay out-of-pocket for LACS when it is used for:
Most commercial insurers follow Medicare’s guidelines for coverage, so these limitations generally apply across the board.
Looking into the Future
Possible applications of femtosecond laser technology in cataract surgery include refractive index shaping. This advancement has transitioned from preclinical trials to early clinical trials that may allow the refractive index of monofocal lenses already implanted to be altered to correct astigmatism and presbyopia.
Future developments in femtosecond laser software will increase the safety and accuracy of cataract surgery. They may also enable surgeons to provide customized treatment to fit individual patient needs. This evolution, combining cataract and refractive surgery, continues to provide ever-improving options for patients.
If you have questions, feel free to contact any of our optometric physicians. We’re always happy to help.
ABOUT THE AUTHOR
PCLI Bellevue, WA
Cheerful, optimistic and relaxed, BJ Lightfoot’s easy-going manner is a joy to patients and those who work with him. Born and raised in Boise, Idaho, BJ grew up in the suburbs but spent weekends helping on his grandparents’ farm. He enjoys skiing, mountain and road cycling, hiking, backpacking, basketball, travel and guitar. BJ and his wife Kim, an optometric physician, make their home in Seattle, Washington. They have a daughter—Olivia.
BJ Lightfoot, OD
FROM THE EDITOR
For patients needing and desiring a greater degree of precision, laser assisted cataract surgery (LACS) offers distinct advantages. In this issue, my colleague, BJ Lightfoot reviews how premium LACS technology improves visual outcomes for individuals who elect to have astigmatism treatment or presbyopia-correcting lens implants. This option is available at a number of our facilities.
As always, enjoy!
Ami Halvorson, OD
Laser assisted cataract surgery is currently available at our facilities in:
Note from the editor