|Year : 2018 | Volume
| Issue : 2 | Page : 53-56
Wave front aberrations and patient satisfaction of aspheric intraocular lenses
Ismail A.N Omar
Department of Ophthalmology, Faculty of Medicine, Minia University, Minia, Egypt
|Date of Submission||09-Mar-2018|
|Date of Acceptance||16-May-2018|
|Date of Web Publication||30-Aug-2018|
Ismail A.N Omar
Department of Ophthalmology, Faculty of Medicine, Minia University, El-Minya 61111
Source of Support: None, Conflict of Interest: None
Aim The aim was to study postoperative wave front higher order aberrations of eyes implanted with aspheric intraocular lens (IOL) in comparison with those with standard spherical IOL and to assess the subjective satisfaction in relation to both IOL designs.
Patients and methods The study included 40 patients with bilateral cataract. Patients were enrolled in a prospective comparative case series from December 2013 till January 2015. All patients underwent a complete preoperative assessment. Phacoemulsification was done for all patients in both eyes. Aspheric IOL (Acrysof IQ SN60WF) was implanted in the right eye and standard spherical IOL (AcrySof SA60AT) in the left eye. Wave front examination was done at 3 months postoperatively to measure the higher order aberrations. A questionnaire was used to record the patients’ satisfaction regarding the two IOL designs.
Results There were no significant differences between the two IOLs regarding the postoperative visual acuity or the mean refractive spherical equivalent. Spherical aberrations were significantly lower in the aspheric IOL group, with only 35% of the patients reported that it was the best eye. There were no significant differences in other aberrations.
Conclusion Aspheric IOLs and standard IOLs have the same visual outcome regarding visual acuity. However, aspheric IOLs induced significantly less spherical aberrations. Aspheric IOL gave better qualitative visual functions in some patients especially during night.
Keywords: aberrations, aspheric, intraocular lens, wave front
|How to cite this article:|
Omar IA. Wave front aberrations and patient satisfaction of aspheric intraocular lenses. J Egypt Ophthalmol Soc 2018;111:53-6
| Introduction|| |
The aim of modern cataract surgery and new intraocular lens (IOL) is to improve visual function besides restoration of visual acuity .
Spherical aberration of the human eye is a combination of the positive spherical aberration of the cornea ,,, and the negative spherical aberration of the crystalline lens ,. They compensate each other, resulting in low spherical aberration in the young eye ,,.
With aging, the optical properties of the crystalline lens change ,, and the lens’s spherical aberration becomes more positive and increases the total spherical aberration of the eye and results in decreased ocular optical quality ,,.
Quantification of total ocular aberrations was made easy after the adoption of wave front technology. This led to better understanding of how to correct ocular aberrations by customized IOL, aiming for better vision quality .
Standard spherical IOL can degrade image quality, increasing the spherical aberration of the optical system. The light rays at the peripheral zones of a positive lens are refracted with larger angles and intersect the optical axis closer to the lens than the paracentral rays, producing positive spherical aberration . Thus, conventional spherical IOLs usually increase the positive spherical aberration in the eye following cataract extraction ,. Aspheric IOL designs compensate for the corneal spherical aberrations by inducing negative spherical aberration, so they can optimize image quality .
The purpose was to study postoperative wave front higher order aberrations (HOAs) of eyes implanted with aspheric IOL in comparison with those with standard spherical IOL, and to assess the subjective satisfaction in relation to both IOL designs.
| Patients and methods|| |
The study included 40 patients with bilateral age-related cataract. Patients were enrolled in a prospective comparative study from December 2013 till January 2015. All patients had clear cornea, normal intraocular pressure, and corneal astigmatism not more than one diopter.
Exclusion criteria were pediatric cases, patients with corneal opacities or irregularities, dry eye, amblyopia, eyes with previous surgery, high myopia, glaucoma, and diabetes mellitus. Moreover, patients with anisometropia were excluded, as this may affect the visual acuity results. For fear of IOL tilt or decentration, cases with pseudoexfoliation syndrome were excluded too.
The study was explained in detail preoperatively to patients, and written consents were signed by them. The study was designed respecting the expected ethical aspects. It was performed according to the Declaration of Helsinki 1975, as revised in 2008 and approved by the Institutional Review Board and Medical Ethics Committee of Minia University.
This study was single blinded because studied patients did not know which eye will be implanted with the aspheric IOL to avoid bias during the questionnaire. However, they were informed that one eye will have aspheric IOL and the other standard IOL.
Preoperatively, all patients underwent complete ophthalmic examination, including uncorrected visual acuity and best-corrected visual acuity (BCVA) measurements, slit-lamp biomicroscopy, applanation tonometry, fundus examination, and biometry with IOL calculation.
Bilateral phacoemulsification was planned for all patients with 2-week interval between both eyes. All surgeries were performed by the same phacoemulsification machine and all patients were targeted for emmetropia. The surgical technique included peribulbar anesthesia, limbal upper corneal incision, adjusted central capsulorhexis of ∼5.5 mm in size, hydrodissection and hydrodelineation, phacoemulsification of the nucleus, bimanual irrigation/aspiration of the cortical matter, IOL implantation in the capsular bag with an injector, and hydration of the wounds.
All patients had implanted aspheric IOL (Acrysof IQ SN60WF; Alcon Laboratories Inc., Fort Worth, Texas, USA) in the right eye, and standard spherical IOL (AcrySof SA60AT; Alcon Laboratories Inc.) in the left eye. So, they were divided into two equal groups: group A with aspheric IOL and group B with standard IOL.
Postoperatively, all patients were examined by slit-lamp to ensure that the IOL is central, no pigments on its surfaces, and no anterior or posterior capsular folds or opacification.
The patients were examined after surgery by 3 months for assessment of the refractive state using autorefractometer and visual acuity with the illiterate E chart.
Wave front aberrations were measured with Shack–Hartmann aberrometry (I-Design) under mesopic conditions. At least three measurements were taken per eye, and the mean values of the Zernike coefficients were calculated for spherical aberrations, coma, and trefoil.
All patients were asked to answer the following questionnaire, 3 months postoperatively:
- Do you feel now any difference in vision at daytime? If yes, which eye?
- Do you feel now any difference in vision at night? If yes, which eye?
- Do you see haloes around bright light or in the streets at night? If yes, which eye?
- Do you feel any difference while seeing colors? If yes, which eye is better?
Collected data were tabulated and analyzed using the SPSS (statistical Package for the Social Sciences; SPSS Inc., Chicago, Illinois, USA) program for windows version 20. Variables were calculated as mean and SD. A P value less than 0.05 was considered statistically significant.
| Results|| |
Overall, 80 eyes of 40 patients with bilateral cataract met the inclusion criteria of this study. They were 24 (60%) female patients and 16 (40%) male patients. The mean age was 52.3±4.43 years, ranging between 42 and 59 years.
The patients were divided into two equal groups: group A (aspheric IOL) and group B (standard IOL).
All surgeries were successful with no complications affecting the pupil size, shape, or IOL centration. No cases of anterior or posterior capsular opacification were reported.
Preoperatively, there was no statistically significant difference between the two groups regarding the mean refractive spherical equivalent or BCVA ([Table 1]).
Data analysis detected no significant postoperative changes between both groups regarding BCVA, MSRE, root mean square of HOA, coma, and trefoil. Significant reduction of the spherical aberrations was reported in group A ([Table 2]).
Fourteen (35%) patients reported more satisfaction with the right eye (the eye with aspheric IOL) whether in day or night vision. However, 12 (30%) patients showed only better night vision in the right eye. The remaining 14 (35%) patients showed no difference between the two eyes. There was no difference between both the eyes regarding haloes or color vision (P>0.05 in both).
| Discussion|| |
This study was conducted on patients undergoing bilateral cataract surgery. Every patient included in the study had clinically and visually significant cataract, which required phacoemulsification; preoperative wave front analysis was not applicable because cataract interfered with obtaining a valid wave front image. Therefore, the study was concerned with intraindividual postoperative aberration changes between both eyes.
Preoperatively, the excluded cases were those with anisometropia, or any other structural difference between both eyes, such as anisocoria and corneal changes, as they may affect image quality during wave front examination. Therefore, there were no statistically significant preoperative differences between both groups in BCVA and mean refractive spherical equivalent.
As the capsulorhexis size may affect the wave front images or induce aberrations, its size was planned to be the same in both eyes.
This is the first study to use the I-Design aberrometer, which depends upon the Shack–Hartmann aberrometry principle. Previous studies used the same principle to evaluate the aspheric IOLs, but they used aberrometers from different manufacturers ,,,.
The wave front aberrations of the patients were measured 3 months after surgery, to give enough time for stability of the eye conditions, especially corneal wound healing.
While measuring the postoperative spherical equivalent and BCVA in both studied groups, no statistically significant differences were found. This supports the previous studies which reported that both IOL types give the same visual outcome, which was not the case in the wave front aberrations.
On studying postoperative wave front examination results, the spherical aberrations in the aspheric IOL group were significantly less than those in the standard IOL group. This met the results of previous studies comparing aspheric IOLs with spherical ones from different types of manufacturers ,,,,,,,,,. So, irrespective of the IOL type, aspheric IOLs reduce the postoperative spherical aberrations when compared with the standard IOLs.
Studies done by Karolinne et al. , Rocha et al. , and Sandoval et al. , on the same IOLs used in this study found a significant difference in the total HOA, but the difference was marginally significant in the current study.The questionnaire in this study may give a clue that spherical aberrations mainly affect night vision as 65% of patients reported more satisfaction with the eye implanted with aspheric IOL during night.
Regarding the root mean square values of the coma and trefoil, no statistically significant differences were reported between both groups, which were not the results many other authors reported. This supports that aspheric IOLs provided lower spherical aberration values, without interfering with coma and other terms of HOAs ,,,.
In conclusion, aspheric IOL design depends on its implantation in eyes with normal relation between corneal and lenticular spherical aberrations, so it will not be suitable to use it in eyes with abnormal HOAs. Preoperative wave front analysis should be done in every patient with cataract, but it is limited by bad image quality obtained in patients with cataract.
Aspheric IOLs and standard IOLs have the same visual outcome regarding visual acuity, but aspheric IOLs have the advantage of less spherical aberrations. Aspheric IOL gives better qualitative visual functions in some patients especially during night.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]