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Large bore phaco tip, femto laser lens fragmentation reduce effective phaco time
Phacoemulsification techniques have led to smaller incision sizes with increased wound stability, elimination of corneal sutures, and reduction or elimination of surgically induced corneal astigmatism. Corneal clarity and optimal vision after cataract surgery are dependent on many factors, most importantly the status of the corneal endothelium, and causing the least amount of endothelial damage during phacoemulsification is a priority for all cataract surgeons. Phaco tip trauma and mechanical contact of lens nuclear fragments are considered principal causes of endothelial damage. Other factors include age of the patient, anterior chamber depth, axial length, lens thickness, phacoemulsification time and power, infusion volume, effective phacoemulsification time and postoperative ocular inflammation.
The combination of femtosecond laser techniques with phacoemulsification is rapidly changing the field of cataract surgery. Femtosecond laser pretreatment of the cataractous lens has been shown to significantly reduce the effective phacoemulsification time and, hence, cause less potential iatrogenic injury to the corneal endothelium. Further optimization of lens fragmentation patterns and improved surgical techniques can also decrease potential corneal endothelial cell loss during cataract surgery.
In this column, Drs. Gollamudi and Crothers describe using a large bore phaco tip combined with femtosecond laser nuclear fragmentation. Continued long-term evaluation is needed to establish safety, reproducibility and efficacy of this cataract surgery modification.
Thomas “TJ” John, MD
OSN Surgical Maneuvers Editor
Subba R. Gollamudi
We now have in our armamentarium tools and technology capable of making even the most complex surgeries routine. Together, we began looking for ways to minimize effective phacoemulsification time (EPT), and thus ultrasound energy, to reduce the risk of trauma inside the eye and collateral damage to the endothelium, iris or capsule. Our supposition was that if we fragmented the cataract into cubes with the femtosecond laser before beginning emulsification, we could aspirate the cubes faster using a larger phaco tip. Could we use less or no ultrasound energy during emulsification and rely more on the machine fluidics?
Technique
We carried out a study to test our questions. The surgical protocol began by taking preoperative measurements and inputting them into the LRI Calculator (Abbott Medical Optics). These figures were then input into the femtosecond laser interface, adjusting settings to the patient’s custom parameters. Patients receiving femtosecond laser-assisted cataract surgery were docked to the Catalys precision laser system (AMO) for lens fragmentation. Incisions were created, and the capsulotomy was completed. Gollamudi then performed hydrodissection and hydrodelineation using the specialized Akahoshi combo prechopper (Asico) to cleave the nucleus into halves and quarters. Using the peristaltic pump on the WhiteStar Signature phacoemulsification system (AMO), Gollamudi grasped one of these quarters and pulled it into the iris plane and out of the capsular bag. He then flipped the pump immediately to Venturi mode to aspirate and emulsify the chunks as they flew toward the phaco port. He then repeated the process for the other pieces of the nucleus. After removing the cataract, intraoperative measurements with the ORA system aberrometer (WaveTec Vision) were taken to verify IOL power and placement before insertion.
Gollamudi then inserted an IOL, which was selected based solely upon the particular needs of the individual patient. He recommended the Tecnis monofocal (AMO) for standard surgery. For multifocal or premium lens patients, he placed the AcrySof IQ toric (Alcon), the Tecnis multifocal (AMO), the AcrySof IQ ReStor (Alcon) or the Crystalens (Bausch + Lomb).
The study
Studies have demonstrated a reduction in EPT using either an optimized phaco tip size or femtosecond laser lens softening, but there is little published information regarding the effect of phaco tip bore size on such softened lenses. Our study attempted to answer the question, “What is the effect of phaco tip diameter on EPT in femtosecond laser-assisted cataract surgery?”
This prospective single-surgeon study evaluated 80 eyes separated into four study groups:
1. No femtosecond laser-assisted cataract surgery with small bore phaco tip (21-gauge Abbott Laminar flow tip, 30° curved, 0.56 mm internal diameter)
2. No femtosecond laser-assisted cataract surgery with large bore phaco tip (20-gauge MST/Dewey tip, 30° bent, 0.7 mm internal diameter, 0.9 mm outer diameter)
3. Femtosecond laser-assisted cataract surgery with small bore phaco tip
4. Femtosecond laser-assisted cataract surgery with large bore phaco tip
All groups were limited to cataracts between the grades of 2 and 4 and standardized phacoemulsification settings using the WhiteStar Signature system. The femtosecond laser-assisted groups received standard lens softening patterns and capsulotomy using the image-guided Catalys laser system.
Results
The large bore needle with the femtosecond laser produced the lowest energy input. There was a statistically significant reduction in EPT when comparing the use of the large bore phaco tip with the use of the small bore phaco tip (Figure).
Source:Gollamudi SR
Our study results were consistent with previous studies that showed a decrease in EPT when using a larger bore phaco tip. Femtosecond laser cataract fragmentation also indicated a trend in decreasing the EPT, although in our study, this did not reach the level of statistical significance.
By combining the technology of three distinct pieces of specialized equipment —femtosecond laser for lens fragmentation into cubes, large bore tip to increase aspiration and bring fragments to the safety zone in the center of the eye, and the fluidics of switching easily between Venturi and peristaltic modes — we are able to increase the level of efficiency.
Conclusion
Although it seems clear from other studies that femtosecond laser-assisted cataract surgery decreases EPT, our results highlight the importance of specific factors, such as phaco tip diameter, in achieving maximum reduction in EPT. Further research aimed at evaluating the relationship between phaco tip size and spacing within lens fragmentation patterns and its effect upon EPT seem indicated with larger sample sizes so as to more accurately reveal all significant factors in optimizing EPT in femtosecond laser-assisted cataract surgery.
References:
Abell RG, et al. Ophthalmology. 2013;doi:10.1016/j.ophtha.2012.11.045.
Conrad-Hengerer I, et al. J Cataract Refract Surg. 2012;doi:10.1016/j.jcrs.2012.07.023.
Crothers A, et al. Effect of phaco tip with large bore size on ultrasound energy in eyes that had femtosecond laser nuclear fragmentation. Presented at: American Society of Cataract and Refractive Surgery meeting; April 27, 2014; Boston.
Pereira AC, et al. J Cataract Refract Surg. 2006;doi:10.1016/j.jcrs.2006.05.006.
Walkow T, et al. J Cataract Refract Surg. 2000;doi:10.1016/S0886-3350(99)00462-9.
For more information:
Subba R. Gollamudi, MD, specializes in cataract, cornea and refractive surgery and is the medical director and managing partner of Eye Specialty Group in Memphis, Tenn. He can be reached at Eye Specialty Group, 825 Ridge Lake Blvd., Memphis, TN 38120; email: drsubbagollamudi@esg.md.
Andrew W. Crothers, MD is a cornea, cataract and refractive surgeon at Eye Specialty Group in Memphis, Tenn. He can be reached at Eye Specialty Group, 825 Ridge Lake Blvd., Memphis, TN 38120; email: drandrewcrothers@esg.md.
Edited by Thomas “TJ” John, MD, a clinical associate professor at Loyola University at Chicago and in private practice in Oak Brook, Tinley Park and Oak Lawn, Ill. He can be reached at 708-429-2223; email: tjcornea@gmail.com.
Disclosure: Gollamudi is a consultant for Abbott. Crothers and John have no relevant financial disclosures.