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ORIGINAL ARTICLE
Ahead of print publication  

Visual outcomes and higher-order aberrations in eyes implanted with hybrid extended depth of focus intraocular lens


1 Department of Cataract and Refractive Surgery, Kenia Eye Hospital, Mumbai, Maharashtra, India
2 Department of Ophthalmology, Kenia Foundation, Mumbai, Maharashtra, India
3 Department of Clinical Research, Kenia Medical and Research Foundation, Mumbai, Maharashtra, India

Date of Submission06-Dec-2021
Date of Acceptance26-Feb-2022
Date of Web Publication22-Aug-2022

Correspondence Address:
Onkar H Pirdankar,
Kenia Medical and Research Foundation, Rizvi Nagar, Corner of Milan Subway, Mumbai - 400 054, Maharashtra
India
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/tjo.tjo_16_22

  Abstract 


PURPOSE: To study the visual outcomes and higher order aberrations in eyes implanted with Hybrid EDOF IOL, particularly in Indian eyes.
MATERIALS AND METHODS: This is retrospective case series where subjects aged between 40-65 years and were implanted with LUCIDIS IOL by single surgeon were included. Subjects with Pre surgery corneal astigmatism > 1.50 D, corneal guttae, IOP >22mmHg, any ocular Co morbidities, Intra or post operative complication were excluded. At 1 month follow up, uncorrected visual acuities at distance (UCDVA), intermediate (UCIVA) and near (UCNVA), refraction were recorded. Internal Higher order aberrations and strehl ratio for a fixed pupil of 4mm and 6mm were calculated using NIDEK OPD Scan. Monocular defocus curve was obtained at 4 meter logMAR chart.
RESULTS: Total of 55 eyes of 35 patients with mean±SD age of 58.50±7.49 years were evaluated. 89.09% of the eyes achieved visual acuity of 6/6. 49.09% could read N10 font at intermediate distance without any correction and 85.45% of the eyes had uncorrected near visual acuity of N6. Around 67% of the eyes did not require any refractive correction whereas around 26% of the eyes required correction upto ±0.25D. The defocus curve showed that visual acuity also ranges from 0.05 logMAR to 0.2 logMAR for Plano to -3.00D respectively. Mean±SD Strehl ratio at 4 and 6 mm pupil size was 0.06±0.04 and 0.02±0.02 respectively.
CONCLUSION: Hybrid EDOF IOL such as LUCIDIS provides excellent vision at all distances. This could be attributed to IOL design which is spherical aberration neutral lens.

Keywords: Extended Depth of Focus IOL, higher order aberrations, visual outcomes



How to cite this URL:
Kenia VP, Kenia RV, Mudaliya L, Pirdankar OH. Visual outcomes and higher-order aberrations in eyes implanted with hybrid extended depth of focus intraocular lens. Taiwan J Ophthalmol [Epub ahead of print] [cited 2022 Sep 28]. Available from: https://www.e-tjo.org/preprintarticle.asp?id=354279




  Introduction Top


Advancement in lifestyle has increased the requirement for unaided visual acuity at all distances. Cataract surgical advances have also progressed from topical anesthesia to near neutral incisions whereas advances in intraocular lenses to give continuous range of vision and good contrast. Monofocal intraocular lens (IOL) provides vision only for a particular distance whereas multifocal or trifocal IOLs provide vision at discrete foci.[1],[2] Multifocal or trifocal IOLs are available in refractive, diffractive, or refractive-diffractive design. Refractive IOLs are pupil-dependent whereas loss of energy is the main drawback of diffractive designs. Extended depth of focus (EDOF) IOLs creates single elongated focal point instead of multifocal foci as available with multifocal or trifocal IOLs. There are various types of EDOF IOLs available and based on optical designs, have been classified as pure and hybrid EDOF. Pure EDOF IOLs are based on spherical aberration or pinhole effect which is responsible for the depth of focus for continuous vision, whereas hybrid EDOF IOLs are the combination of bifocality and EDOF and are categorized as diffractive, refractive, or diffractive refractive IOLs.[3] EDOF IOL provides better uncorrected far, intermediate visual acuity, contrast sensitivity, and higher satisfaction in eyes with preoperative astigmatism <1.50 D as compared to presbyopia-correcting IOLs such as bifocal IOLs, panfocal, and trifocal IOLs.[4],[5]

An advance refractive aspheric hybrid EDOF IOL, LUCIDIS (SAV-IOL, Switzerland), which is manufactured using instant focus and pseudo non-diffractive beam (PNDB) patented technology. The IOL has an optical diameter of 6 mm with 360° square edge design and closed-loop haptics. The IOL is made up of hydrophilic acrylic and available in power range from + 5.00D to + 30.0D in 0.50D step with addition of + 3.00 D. A previous study as reported similar visual and refractive outcomes in eyes with LUCIDIS IOL to that of trifocal IOL in refractive lens exchange patients.[6] LUCIDIS IOL has also demonstrated good safety profile with low complication rate.[7] However, to the best of our knowledge, there is no report that describes the detailed evaluation of higher-order aberrations in eyes implanted with LUCIDIS IOL. Hence, our aim is to study the visual outcomes and higher-order aberrations in eyes implanted with hybrid EDOF IOL, particularly in Indian eyes.


  Materials and Methods Top


This is retrospective case series where records of participants implanted with LUCIDIS IOL were analyzed. The study was reviewed and approved by the Institutional Ethics Committee of Kenia Medical and Research Foundation (ECR/1088/Inst/MH/2018, Approval Number: 2021/006, Approval Date: February 22, 2021) and was conducted in accordance with tenets of the Declaration of Helsinki. Participants aged between 40 and 65 years and were implanted with LUCIDIS IOL by single surgeon were included in this study. Participants with presurgery corneal astigmatism >1.50 D, corneal guttae, intraocular pressure (IOP) >22 mmHg, any ocular comorbidities, intra-or postoperative complication, Chang–waring chord, Angle Kappa >0.5 mm, Ix and Iy (Shift of corneal apex toward iris center) >0.8 mm, cases where IOL master 700 not possible, and those with lost to follow-up were excluded from this study.

Surgical planning

In all patients, IOL master 700 was used for ocular biometry and IOL power calculation. IOL power was calculated using the Universal II Barrett's formula. All patients had small incision phacoemulsification with IOL implantation performed by the same single surgeon (VPK). The VERION image-guided system was used for surgical planning of incision placement and capsulorhexis guide. Clear corneal temporal incision of 2.8 mm was made. Capsulorhexis of 5.5 mm was created with VERION-guided visual axis centered was created. After phacoemulsification, the IOL was implanted in the capsular bag.

Immediate postoperative assessment

All patients were examined after 12 h of surgery to rule out any intraoperative or immediate surgical complication. Uncorrected visual acuity, noncontact IOP, and slit-lamp examination will be performed during the same visit. All patients were prescribed standard postoperative medical care treatment. Postoperative treatment consisted of moxifloxacin 0.5% eye drop four times a day for 1 week, prednisolone acetate 1% eye drop three times a day for 1 month with weekly tapering, and carboxymethylcellulose 4 times a day for 1 month.

Visual outcome details

All patients were evaluated at 1-month follow-up. Uncorrected distance (UCDVA), intermediate (UCIVA), and near (UCNVA) visual acuities were recorded. Intermediate visual acuities were recorded at 80 cm, whereas near visual acuities were recorded at 40 cm using N notations. Distance visual acuities and refraction were noted. Internal higher-order aberrations for a fixed pupil size of 4 mm and 6 mm were calculated using NIDEK OPD Scan (Nidek. Co. Ltd) to understand the impact of HOA at different pupil sizes with a LUCIDIS IOL.[8],[9] NIDEK OPD scan uses dynamic skiascopy-based ocular aberrometry and Placido disk corneal topography to obtain wavefront data. Image quality metrics such as Strehl ratio were obtained using NIDEK OPD Scan for a fixed pupil size of 4 mm and 6 mm.[9] Strehl ratio describes the intensity of the actual point spread function (PSF) to the intensity of the diffraction-limited PSF.[10],[11] To obtain monocular defocus curve, the defocus lenses ranging from −300 to +2.00 D (in 0.5 steps) were placed over distance refraction in random order and participants' visual acuity were measured using 4 m logMAR chart. For statistical analysis, the average defocus curve across all patients was obtained by plotting the mean visual acuities at each defocus ranging −3.00–+ 2.0D (in 0.50D steps).[2],[12],[13]

Statistical analysis

Data were entered in Microsoft Excel (Microsoft Corporation) and analyzed using Minitab 17 Software (Minitab LLC, State University, PA, USA). The mean and standard deviation (SD) were calculated for continuous variables and proportions for the categorical variables. Chi-square goodness-of-fit was used to evaluate the difference between categorical variables.


  Results Top


Total of 55 eyes of 36 patients with the mean ± SD age of 58.50 ± 7.49 years was evaluated. Thirty-eight eyes of 19 patients had bilateral implantation and 17 had unilateral implantation. There were 18 males whereas 18 were females. Of 55 eyes, 32 were right eyes and 23 were left eyes. The preoperative mean ± SD of IOP, axial length, K1, and K2 were 16.06 ± 2.75 mmHg, 23.68 ± 1.04 mm, 43.52 ± 1.16 diopter (D), and 44.00 ± 1.23 diopter, respectively. The preoperative spherical error ranging between − 12.00D and + 4.00D (Median: 0.5D) whereas cylindrical component was ranging between − 2.50D and + 0.75D (Median: 0.0D). The preoperative spherical equivalent refraction was ranging between – 12.75D and + 4.25D (Median: 0.25D).

Visual outcomes

89.09% of the eyes achieved visual acuity of 6/6 and 10.91% had visual acuity of 6/9 [Figure 1]a (Chi-square goodness-of-fit, Chi-square: 33.61, P < 0.001). Most of the patients (49.09%) could read N10 font at intermediate distance without any correction. 25.45% could read N12 font where N8 and N18 fonts were readable in 12.73% of the cases each at intermediate distance [Figure 1]b (Chi-square goodness-of-fit, Chi-square: 19.4, P < 0.001). 85.45% of the eyes had uncorrected near visual acuity of N6 and 9.09% could read N8 font at near distance [Figure 1]c (Chi-square goodness-of-fit, Chi-square: 107.86, P < 0.001). Around 67% of the eyes did not require any refractive correction, whereas around 26% of the eyes required correction up to ± 0.25D. Only 7% required a refractive correction >0.25 but < 0.75 diopters. [Figure 2] describes the distribution of preoperative corneal astigmatism and postoperative spectacle astigmatism. The defocus curve shows that LUCIDIS IOL provides the continuous vision from Plano to −3.00D corresponding to the range of vision from infinity to 33 cm. The visual acuity also ranges from 0.05 logMAR to 0.2 logMAR for Plano to − 3.00D, respectively. [Figure 3] describes the mean monocular defocus curve. Total as well as third-order aberrations arising due to internal component at 4 mm and 6 mm fixed pupil size were noted. Aberrations at 6 mm pupil size were three times greater than that of 4 mm pupil size [Figure 4]. The mean ± SD Strehl ratio at 4 and 6 mm pupil size was 0.06 ± 0.04 and 0.02 ± 0.02, respectively.
Figure 1: a-c Uncorrected distance, intermediate and near visual acuity

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Figure 2: Distribution of preoperative corneal astigmatism and postoperative spectacle astigmatism

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Figure 3: Monocular defocus curve

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Figure 4: Internal higher-order aberrations for 4 mm and 6 mm pupil

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Monocular versus binocular visual outcomes

A subgroup analysis was conducted on 38 eyes of 19 patients who had bilateral implantation. Monocularly, 88.9% and 11.1% of the eyes had uncorrected distance visual acuity of 6/6 and 6/9, respectively, whereas binocularly, all patients (100%) could read 6/6 for distance without any correction. Similarly, for near vision, 86% could read N6, 8% could read N8, and 6% had N12 visual acuity without any correction, whereas binocularly, all cases (100%) could read N6. At intermediate distance, monocularly, 19%, 53%, 17%, and 11% had visual acuity of N8, N10, N12, and N18, respectively, whereas binocularly 28%, 50%, and 22% read N8, N10, and N12 print size without any correction.


  Discussion Top


Over the years, many techniques have been tried to overcome presbyopia and near vision postcataract surgery such as monovision, multifocality, and EDOF. The present study describes the visual outcomes of LUCIDIS EDOF IOL, a hybrid EDOF. EDOF delivers good functional vision at far and intermediate distance. To enhance the range of vision beyond intermediate distance, hybrid EDOF technology has been incorporated. LUCIDIS is a nondiffractive hybrid EDOF IOL having an addition of +3.00D which uses pseudo nondiffracting beam which provides elongated focal points such as axicons to deliver EDOF.[14] With LUCIDIS IOL, most of the patients achieved excellent visual acuity for all distances. Those who had UCDVA of 6/9 improved to 6/6 with correction of spherical equivalent ranging of ± 0.50D. None of our patients complained of glare and haloes. This could be attributed to the absence of diffractive rings and smooth transition blend of distance and near intermediate zone causing no dysphotopsia suggesting ease of night driving, computers, and reading activities in dim light. A study conducted by Ozulken et al., have reported that reading small print, reading a newspaper or book, and driving at night was significantly better with the LUCIDIS IOL.[6]

Trifocal IOL corrects distance, intermediate, and near vision at specific focal points only and leaves a gap of uncorrected vision between these focal points.[2] On the other hand, EDOF provides continuous range of vision thus providing better far and intermediate vision as well as better contrast compared to multifocal IOL. Various daily activities predominantly require intermediate vision for computer work, viewing car speedometer, identifying food in plate, kitchen work, etc. Latest EDOF IOLs have been designed to provide better and comfortable vision at intermediate distance.

EDOF IOL provides better depth of focus and uninterrupted vision across far and intermediate distances; however, the latest EDOF IOL such as LUCIDIS reduces the gap between near and intermediate focal points, thus provide uninterrupted vision for near to intermediate which is a unique feature. EDOF can be achieved by various ways such as diffraction, spherical aberrations, and pseudo nondiffractive beam (PNDB). EDOF achieved using diffractive rings can cause dysphotopsia. EDOF using increase in spherical aberrations, results in lower image quality, lower light intensity, and poor near vision (Ref), whereas EDOF using PNDB works similar to axicon[14] where it provides elongated focal point of continuous intensity over a longer distance along optical axis and thus increases the depth of focus. PNDB derived EDOFs is larger, broader, good light intensity, and good image quality. LUCIDIS IOL uses PNDB technology where constructive wavefront interference enhances the quality and intensity of light through aspheric IOL provides EDOF.

We noted excellent binocular uncorrected distance, near and intermediate visual acuity as compared to monocular suggesting the edge of bilateral implantation over monocular, and this could be explained by binocular summation. The effect was seen for all distances. Neuroadaptation is another factor which could be a time-consuming process and could be subject-dependent and needs a consideration, especially in multifocal IOL;[3] however, our patients did not report any complaints of halos or glare this could be attributed to the nondiffractive optics of LUCIDIS IOL.

Contrast sensitivity, higher order aberrations along with image quality metrics such as modulation transfer function (MTF), Strehl ratio have been used to evaluate the outcomes of cataract surgery.[1],[9],[15],[16],[17] In the present study, we have reported HOA and Strehl ratios at 4 and 6 mm pupil size. It is important to note that all wavefront errors do not induce equivalent effect on visual functions.[18] Previous studies such as Gillmann and Mermoud and Aref et al. have reported the combined mean ± SD RMS of 0.119 ± 0.049 μm and 0.147 ± 0.054 μm, respectively, in eyes implanted with LUCIDIS IOL and did not report the individual aberration values with respect to specific pupil size.[7],[19] Furthermore, the errors that are concentrated near the pyramid affect the visual functions more than errors that are near the edge of the pyramid. For example, spherical aberration reduces visual acuity more than quadrafoil and hence we have reported the spherical aberrations.[18] In the present study, the spherical aberration induced due to IOL were – 0.10 and 0.03 microns for 6 mm and 4 mm pupils, respectively, suggesting near neutral spherical aberration optics in LUCIDIS IOL. This also suggests that the existing spherical aberration does not contribute to the EDOF.

Furthermore, we noted that the aberrations at 6 mm pupil size were approximately threefolds the aberrations at 4 mm pupil size. A previous study of EDOF IOL has also reported similar findings[8] where four-time increase in HOA were noted at 6 mm pupil size as compared to 4 mm. EDOF IOL Provides better contrast than trifocal IOL.[20] A study by Aref et al. 2019 reported that mean contrast sensitivity measured using Pelli-Robson chart is 1.5 log contrast unit in eyes implanted with LUCIDIS IOL.[19] However, due to the retrospective nature of the study, we are unable to report measures of contrast sensitivity or image quality metrics such as MTF. However, understanding these factors could provide more insight on the IOL image quality.


  Conclusion Top


Thus to conclude, hybrid EDOF IOL such as LUCIDIS provides excellent vision at all distances. This could be attributed to IOL design which is spherical aberration neutral lens.

Financial support and sponsorship

Nil.

Conflicts of interest

The authors declare that there are no conflicts of interests of this paper.



 
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