INFLUENCE OF INTRAOCULAR LENS HAPTIC DESIGN ON REFRACTIVE ERROR
Savini G, Barboni P, Ducoli L, et al1
ABSTRACT SUMMARY
Savini et al evaluated the influence of IOLs' haptic design on the refractive prediction error for cataract patients. The investigators used the same devices to measure corneal power and axial length in 110 eyes implanted with a three-piece AcrySof IOL (MA60AC) and 84 eyes implanted with a single-piece AcrySof IOL (SA60AT; both from Alcon). They assessed the median absolute error and mean absolute error in refraction prediction (ie, the difference between expected and actual refraction) 1 month postoperatively using the Haigis, Hoffer Q, Holladay 1, and SRK/T formulas.
With all of the formulas, the median absolute error was lower with the three-piece IOL. The median absolute error ranged between 0.15 D (Haigis and Holladay 1) and 0.19 D (SRK/T) with the three-piece IOL and between 0.23 D (Haigis) and 0.30 D (SRK/T) with the single-piece IOL. With all of the formulas, a higher percentage of eyes with the three-piece IOL were within ±0.25 D and ±0.50 D of the target refraction.
DISCUSSION
The ophthalmic industry has endeavored to establish a gold-standard IOL platform. One-piece IOLs have become the platform of choice for multifocal/bifocal and toric lenses. Compared with three-piece IOLs, single-piece lenses can be inserted through smaller incisions (up to 1.8 mm vs 2.75 mm), and their placement inside the capsular bag is more predictable and less traumatic. It is important to note that most IOLs that fit through small incisions (1.8-2.2 mm) are made of a hydrophilic acrylic material, which is associated with a high percentage of posterior capsular opacification as well as opacification of the optical zone, leading to a severe decrease in visual acuity.2,3
Klamann et al reported that 1.8-mm incisions result in statistically significantly less surgically induced astigmatism than 2.2-mm (P = .046) and 2.75-mm (P = .017) incisions. There was no significant difference between the 2.2-mm group and the 2.75-mm group in the study.4 According to Prinz and colleagues, both single- and three-piece IOLs have comparable rotational stability, suggesting the latter is a viable toric IOL option.5
The study by Savini et al is limited by its short follow-up period (1 month), but the higher percentage of eyes within the target refraction in the three-piece IOL group highlights the strength of the haptic design of these lenses. They resist capsular contraction, preventing further forward axial movement caused by haptic compression force decay in the first few postoperative days. In conclusion, a three-piece IOL is a very good option for cataract patients. It outperformed the refractive predictability of the single-piece IOL with minimal clinical differences between the two lenses.1
COMPARISON OF THE ANTERIOR CAPSULOTOMY EDGE CREATED BY MANUAL CAPSULORHEXIS AND TWO FEMTOSECOND LASER PLATFORMS: SCANNING ELECTRON MICROSCOPY STUDY
Al Harthi K, Al Shahwan S, Al Towerki A, et al6
ABSTRACT SUMMARY
The authors compared the anterior capsular edge of manual (n = 10) and laser capsulotomies created with the LenSx Laser (Alcon; n = 9) or the Victus Femtosecond Laser Platform (Bausch + Lomb Technolas; n = 10). They used scanning electron microscopy (SEM) to evaluate irregularities of the capsule's edge using angular moment and contrast.
On SEM, the surfaces of the edge created by both lasers showed marked irregularity compared with the smooth edge of the manual capsulotomy. The angular second moment and contrast measures for both lasers differed significantly from those obtained for the manual capsulorhexis (P < .001). There was no difference between the lasers in angular second moment and contrast measures. The angular second moment showed only a weak negative correlation with increasing laser power, whereas contrast showed a weak positive correlation with increasing power.
DISCUSSION
Although surgeons face oppressive marketing, they must balance the pros and cons of laser cataract surgery for patients. SEM suggests that the laser compromises the resistance of the capsular edge, increasing the risk of anterior capsular tears during intraocular maneuvers, especially in eyes with hard nuclei where excessive manipulation is mostly required. Abel et al reported that anterior capsular tears occurred in 1.84% of eyes in the laser group (n = 1,852) and 0.22% of eyes in the manual group (n = 2,228; P < .0001).7
Capsulotomies created with the laser result in superior centration and size, more predictable effective lens position, and a lower incidence of posterior capsular opacification.8 Still, the clinical relevance of these differences when compared to that of a capsulorhexis performed manually by an experienced surgeon is questionable.8,9 Harthi et al elucidate the morphological modifications associated with cutting the lens capsule, and the results of their study should be used to improve laser cataract surgery so that the edges are more smooth with minimal structural damage. n
Section Editor Edward Manche, MD
• director of cornea and refractive surgery at the Stanford Eye Laser Center, Stanford, California
• professor of ophthalmology at the Stanford University School of Medicine, Stanford, California
• edward.manche@stanford.edu
Daniela M. V. Marques, MD, PhD
• medical director at the Marques Eye Institute, São Paulo, Brazil
• medical collaborator in the Research Department of the Cataract Sector of the Federal University of São Paulo
• +55 11 99252 1925; dradaniela@marqueseye.com.br
• financial disclosure: none acknowledged
Frederico F. Marques, MD, PhD
• medical director at the Marques Eye Institute, São Paulo, Brazil
• medical collaborator in the Research Department of the Cataract Sector of the Federal University of São Paulo
• +55 11 98292 3082; drfrederico@marqueseye.com.br
• financial disclosure: none acknowledged
1. Savini G, Barboni P, Ducoli P, et al. Influence of intraocular lens haptic design on refractive error. J Cataract Refract Surg. 2014;40(9):1473-1478.
2. Li Y, Wang J, Chen Z, Tang X. Effect of hydrophobic acrylic versus hydrophilic acrylic intraocular lens on posterior capsule opacification: meta-analysis. PLoS One. 2013;8(11):e77864.
3. Jorge Pde A, Jorge D, Ventura CV, et al. Late opacification in hydrophilic acrylic intraocular lenses: analysis of 87 eyes in a random sample of 102 patients. J Cataract Refract Surg. 2013;39(3):403-407.
4. Klamann MK, Gonnermann J, Maier AK, et al. Smaller incision size leads to higher predictability in microcoaxial cataract surgery. Eur J Ophthalmol. 2013;23(2):202-207.
5. Prinz A, Neumayer T, Buehl W, et al. Rotational stability and posterior capsule opacification of a plate-haptic and an open-loop-haptic intraocular lens. J Cataract Refract Surg. 2011;37(2):251-257.
6. Al Harthi K, Al Shahwan S, Al Towerki A, et al. Comparison of the anterior capsulotomy edge created by manual capsulorhexis and 2 femtosecond laser platforms: scanning electron microscopy study. J Cataract Refract Surg. 2014;40(12):2106-2112.
7. Abell RG, Darian-Smith E, Kan JB, et al. Femtosecond laser-assisted cataract surgery versus standard phacoemulsification cataract surgery: outcomes and safety in more than 4,000 cases at a single center. J Cataract Refract Surg. 2015;41(1):47-52.
8. Nagy ZZ. New technology update: femtosecond laser in cataract surgery. Clin Ophthalmol. 2014;8:1157-1167.
9. Kovács I, Kránitz K, Sándor GL, et al. The effect of femtosecond laser capsulotomy on the development of posterior capsule opacification. J Refract Surg. 2014;30(3):154-158.
