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Dysphotopsia and functional quality of vision after implantation of an intraocular lens with a 7.0 mm optic and plate haptic design

Bonsemeyer, Małgorzata Kalina MSc; Becker, Eckhard MD; Liekfeld, Anja MD, PhD

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Journal of Cataract & Refractive Surgery: January 2022 - Volume 48 - Issue 1 - p 75-82
doi: 10.1097/j.jcrs.0000000000000735
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A successful outcome of a cataract treatment comprises an indefectible surgical technique, spot-on intraocular lens (IOL) selection, and maximal postoperative visual and functional result. The most important, however, is patient satisfaction, which depends not only on the visual acuity and possible spectacle independence but also on the freedom of any undesired optical images. Dysphotopsia may be the major source of patient dissatisfaction, lowering the quality of daily life.1 These unwanted light artifacts may be perceived even after uneventful cataract surgery.

Positive dysphotopsia (PD) occurs directly postoperatively as halos, flashes, and glares or light streaks in up to 67% of patients, with reduction in its incidence to 0.2% to 2.2% within a year.2–5 It can be seen from an angle and disappear at an attempt to focus on it, which may give the patient a disturbing feeling.6 PD is considered to be caused by a sharp truncated IOL edge causing light reflection and scattering rather than refraction, surface-related secondary internal IOL–fundus reflections, and peripheral light focusing due to direct projection of light rays missing the IOL onto the retina without striking the optic.7–9 Functionally, smaller optic diameter has also been connected with an increased incidence of glare.10 Besides IOL design, anatomical risk factors such as low corneal power, large pupils exposing IOL edges, the size of the iris–IOL gap, and younger age have been identified as well.2,3,11

The therapy of PD includes an observational approach, Nd:YAG laser posterior capsulotomy, an IOL exchange, or secondary sulcus-fixated IOL.3,12

Negative dysphotopsia (ND) is perceived as a crescent-shaped shadow in the peripheral temporal field of vision in 15.2% of pseudophakic patients directly after the cataract surgery, reducing its incidence to 3.2% within a year.13 The extent of the shadow may rapidly change because of quick pupil dynamics, and the image behind the shadow is repeated and enlarged. Altogether, this could give a misleading motion perception in the temporal visual field.6

There are 2 main theories about the etiology of ND: it is either a result of an illumination gap between light rays still refracted and already missing the IOL, or a projection of the edge of anterior capsulorhexis through the IOL onto the retina.14,15 High IOL refraction index or anatomical factors such as small photopic pupils, presence of the functional nasal retina extending anteriorly enough to perceive the artifacts, or greater alpha and kappa angles have been reported as contributing to ND.14,16 Makhotkina also pointed out other risk factors such as shorter axial length (AL), younger age, postoperative increase in the anterior chamber depth (ACD), higher IOL power, and higher corrected distance visual acuity (CDVA).17,18

When no resolution of ND occurs as a result of neuroadaptation, IOL exchange, reverse optic capture, or secondary sulcus-fixated piggyback IOL have been recommended as the strategies of surgical treatment of persistent complaints. Still, no fully effective approach has been found as yet.15,17–19

Given the complexity of PD and ND, including contradictory theories about their etiology and treatment, it is a great challenge to find a solution to this problem. Regarding patient satisfaction, safety, and risk of consecutive surgeries as part of further treatment, it is of key importance to focus on developing a preventive strategy against dysphotopsia. Therefore, the purpose of this study is to determine the impact of an IOL with a 7.0 mm optic diameter and plate-haptic design compared with an IOL with a 6.0 mm optic diameter and C-loop haptic design on the incidence of dysphotopsia and visual functions after the cataract surgery.

METHODS

Following the tenets of the Declaration of Helsinki, a prospective monocentric randomized patient-blinded comparative clinical study was planned, and an approval from the local ethics committee was obtained. Provided detailed information about the purpose of the trial, patients with indication for cataract surgery were voluntarily recruited and gave written consent. The inclusion criteria required senile cataract, no history of ocular surgeries or trauma, and age under 78 years. Patients with corneal astigmatism greater than 1.0 diopter (D) or relevant coexisting ocular comorbidities such as age-related macular degeneration, diabetic retinopathy, uncontrolled glaucoma, pseudoexfoliation syndrome, zonular weakness, uveitis, or amblyopia were excluded.

One hundred twenty eyes (86 patients) underwent slitlamp examination with biomicroscopy in pupillary dilation and preoperative measurements including biometry (IOL Master 500 or 700; Carl Zeiss Meditec AG), keratometry and corneal topography (Keratograph 4/70670; Oculus Optikgeräte GmbH), pupillometry in photopic, mesopic, and scotopic conditions (PupillX; Mediol), uncorrected distance visual acuity (UDVA), subjective and objective CDVA, subjective and objective spherical equivalent (SER), and intraocular pressure (IOP).

All eyes were preoperatively randomly divided into 2 groups, each receiving single-piece foldable hydrophilic acrylic aspheric IOL with a refractive index of 1.46 and with 2 different haptic designs and optic sizes (Figure 1). Group 1 received an IOL with a 7.0 mm optic diameter and plate haptics (Aspira-aXA; HumanOptics AG). Group 2 received an IOL with a 6.0 mm optic diameter and C-loop haptics (Aspira-aA). The size of a single optic–haptic junction shoulder is 4.28 mm (70°) and 2.69 mm (51.4°) for Aspira-aXA and Aspira-aA, respectively. In both IOLs, the posterior surface has a 360° lens epithelial cell barrier designed to prevent cell migration (Figure 1, side view), which reduces the effective optic diameter to 6.5 mm for the Aspira-aXA and to 5.5 mm for the Aspira-aA IOL. The outer side of the lens epithelial cell barrier presents a sharp optic edge (Figure 1) (personal communication with HumanOptics, April 28, 2021).

Figure 1.
Figure 1.:
IOL designs in Group 1 with a 7.0 mm optic diameter (left) and Group 2 with a 6.0 mm optic diameter (right). Courtesy of HumanOptics AG.

Cataract surgeries were performed under local topical anesthesia using the standard phacoemulsification technique with computer assistance (Zeiss Callisto eye 3.6.1). A clear corneal incision of 2.5 to 3.0 mm and a capsulorhexis of 6.5 mm and 5.5 mm for Groups 1 and 2, respectively, depending on the optic size, were performed. The IOLs were implanted with the use of Multiject (Medicel AG) or Accuject 2.2 (Medicel AG) injectors for 6.0 mm and 7.0 mm optics, respectively. The positioning of the optic–haptic junction was random in both groups. Clear corneal incision was performed from anatomically and ergonomically most accessible site, taking into consideration the steepest corneal meridian, and the IOL was rotated if needed to achieve the best centration dictated by the axis of the capsular bag. No intraoperative complications were reported.

Standard early postoperative examinations took place partly in the referring facilities. The study protocol included 3 follow-ups: 1 month, 3 months, and 12 months postoperatively, consisting of objective examinations and a questionnaire. UDVA, subjective and objective CDVA, subjective and objective SER, IOP, slitlamp examination in medical mydriasis to verify IOL centration and possible posterior capsule opacification, keratometry with corneal topography (Keratograph 4/70670), and, additionally, in the second and third follow-up, monocular contrast sensitivity (CS) (Functional Vision Analyzer; Stereo Optical Co., Inc.) in photopic (85 cd/m2) and mesopic (3 cd/m2) conditions for 1.5, 3, 6, 12, and 18 cycles per degree (cpd) were measured. Mesopic vision and glare sensitivity (Mesotest II; Oculus Optikgeräte GmbH) were assessed in 35 eyes from Group 1 and in 50 eyes from Group 2 in month 12 examination. During each follow-up, the patients were given a questionnaire (Supplemental Figure 1, https://links.lww.com/JRS/A410) to evaluate their satisfaction with the surgery outcome on a scale from 1 to 10 points (1 being excellent and 10 being very poor) and the degree of spectacle dependence for distant, intermediate, and near vision on a 4-degree scale ranging from never (0), sometimes (1), often (2), to always (3). Further questions referred to perception of PD in the form of glare sensitivity at daytime or nighttime and halos around light sources at daytime or nighttime. Regarding ND, a question about noticing a crescent-formed shadow limiting the peripheral field of vision was asked. All answers could be located on a 4-degree scale regarding frequency (from never [0], sometimes [1], often [2], to always [3]) and extent (not at all [0], little [1], moderately [2], or strongly [3]) of complaints. The answers were tabulated into numerical figures for statistical reasons. To exclude binocular perceptions, patients were instructed that each questionnaire concerned the particular examined eye.

Sample size calculation was conducted with G*Power program (v. 3.1.9.4. for Windows; Heinrich Heine University Düsseldorf) with the following input parameters: power = 0.8, alpha = 0.05, effect size d = 0.5, and 2-tailed. The statistical analysis was executed with IBM SPSS Statistics v. 24.0 (IBM Corp.). Although binocular implantations were allowed in the study protocol, the prerequisite for independent samples for each eye for statistical analysis was made. The data were analyzed as nominal, ordinal, and metric values. Chi-square, t, Mann-Whitney U, and Wilcoxon tests were used for the analysis.

RESULTS

Demographic and Anatomical Data

A total of 120 eyes of 86 patients were recruited for the study. Group 1 with a 7.0 mm optic comprised 57 eyes of 43 participants, and Group 2, with a 6.0 mm optic, comprised 63 eyes of 43 participants. Three patients from Group 1 and 1 patient from Group 2 dropped out the study.

There was no difference between the groups regarding the distribution of sex and eye laterality, AL, pupil size in photopic, scotopic, and mesopic conditions, white-to-white distance, ACD (measured with IOL Master), lens thickness, central corneal thickness, IOP, or calculated IOL power. Pupil dynamics was assessed as a difference between pupil diameters in scotopic and photopic conditions preoperatively, revealing no significant difference between the groups (Supplemental Table 1, https://links.lww.com/JRS/A411).

The distribution of photopic pupils ≤3.0 mm was the same in both groups: 6 cases (10.5%) in Group 1 and 7 cases (11.5%) in Group 2 (P = .869). Scotopic pupils ≥5.5 mm were found in 21 cases (36.8%) in Group 1 and in 31 cases (50.0%) in Group 2 (P = .148). White-to-white distance of at least 11.8 mm was found in 35 eyes (61.4%) in Group 1 and in 40 eyes (63.5%) in Group 2 (P = .813). Three cases (5.3%) in Group 1 and 3 cases (4.8%) in Group 2 had ACD flatter than 2.5 mm (P = .900).

Visual Acuity, Refraction, and Spectacles

Preoperative UDVA and subjective CDVA were the same in both groups, whereas preoperative subjective SER was significantly larger in Group 2 compared with Group 1 (+1.01 ± 1.71 and −0.14 ± 2.12, respectively; P = .001). Postoperatively, the UDVA in month 1 follow-up was greater in Group 1 compared with Group 2 (0.08 ± 0.08 and 0.13 ± 0.14, respectively; P = .021 after Bonferroni correction). The subjective cylinder power measured in the first follow-up was, however, of no difference between the groups (Group 1 mean −0.40 ± 0.35 D, Group 2 mean −0.44 ± 0.37 D, P = .506). No other differences between the groups in further follow-ups were measured (Supplemental Table 2, https://links.lww.com/JRS/A411). For the calculation of postoperative UDVA and SER, 1 eye from Group 1 with myopic target refraction was excluded.

Comparing the values from month 1 and month 12 follow-ups within a group, significant differences were observed in Group 2: the UDVA and SER increased (P values after Bonferroni correction 0.027 and 0.042, respectively). Within Group 1, no significant changes regarding UDVA, CDVA, or SER were measured (Supplemental Table 2, https://links.lww.com/JRS/A411).

Analyzing the subjective monocular spectacle dependence, the need for reading spectacles in Group 1 was lower compared with Group 2, reaching significant levels in month 12 follow-up (Supplemental Table 3, https://links.lww.com/JRS/A411). Regarding far and intermediate distances, there was no difference between the groups.

Dysphotopsia

One month postoperatively, there were 3 cases (5.4%) of ND in Group 1 and 13 cases (20.6%) in Group 2 (P = .015). Three months postoperatively, 2 eyes (3.6%) from Group 1 and 8 eyes (12.7%) from Group 2 still had ND (P = .073). In the last month 12 follow-up, there were no cases of ND in Group 1 and 2 cases (3.2%) in Group 2 (P = .183), both of which were described as totally undisturbing (Figure 2).

Figure 2.
Figure 2.:
General incidence of negative dysphotopsia with time in both groups: Significant reduction in negative dysphotopsia in Group 1 (blue) compared with Group 2 (orange) measured during the first examination (P < .05) marked with asterisk. Values in percent. ND = negative dysphotopsia

Analyzing daytime and nighttime glare and halos together as general PD, a significantly lower incidence was measured during month 1 follow-up in Group 1 (18 cases [31.6%]) compared with Group 2 (33 cases [52.4%]) (P = .021). In month 3 follow-up, PD were perceived by 14 eyes (24.6%) in Group 1 and 24 eyes (38.1%) in Group 2 (P = .111). One year postoperatively, PD were present in 5 cases (9.3%) in Group 1 and in 14 cases (22.6%) in Group 2, showing a 2.4-fold reduction in PD in Group 1 compared with Group 2 (P = .053) (Figure 3).

Figure 3.
Figure 3.:
General incidence of positive dysphotopsia with time in both groups: Significant reduction in positive dysphotopsia in Group 1 (blue) compared with Group 2 (orange) measured during the first examination (P < .05) marked with asterisk. Values in percent. PD = positive dysphotopsia

Comparing results of each question about PD and ND separately between the groups, the frequency and extent values for each type of dysphotopsia were lower or the same in Group 1 compared with Group 2 (with exception of nighttime halo in month 12 follow-up), with significant P values reached for the frequency of ND in the first examination (P = .048 after Bonferroni correction). Daytime glare was the most common type of dysphotopsia reported throughout the study (Tables 1 and 2).

Table 1. - Frequency of Positive and Negative Dysphotopsia in Both Groups in All 3 Follow-ups.
Dysphotopsia
Month 1 Month 3 Month 12
Group 1 Group 2 Group 1 Group 2 Group 1 Group 2
Glare
 Day 0.29 ± 0.53 0.60 ± 0.94 0.25 ± 0.48 0.54 ± 0.93 0.15 ± 0.53 0.19 ± 0.51
 Night 0.13 ± 0.38 0.25 ± 0.51 0.13 ± 0.38 0.25 ± 0.67 0.00 ± 0.00 0.05 ± 0.28
Halo
 Day 0.05 ± 0.23 0.32 ± 0.86 0.04 ± 0.19 0.11 ± 0.36 0.02 ± 0.14 0.02 ± 0.13
 Night 0.07 ± 0.26 0.30 ± 0.80 0.09 ± 0.29 0.22 ± 0.63 0.06 ± 0.23 0.08 ± 0.27
ND 0.09 ± 0.44* 0.30 ± 0.69* 0.07 ± 0.42 0.21 ± 0.63 0.00 ± 0.00 0.03 ± 0.18
ND = negative dysphotopsia
Mean values with SD based on the answer scale from 0 to 3 points from the questionnaire given, all median values = 0.00. Significant P value (after Bonferroni correction) for comparison between the groups within particular follow-up marked with asterisk.

Table 2. - Extent of Positive and Negative Dysphotopsia in Both Groups in All 3 Follow-ups.
Dysphotopsia
Month 1 Month 3 Month 12
Group 1 Group 2 Group 1 Group 2 Group 1 Group 2
Glare
 Day 0.27 ± 0.59 0.65 ± 0.99 0.23 ± 0.47 0.47 ± 0.82 0.09 ± 0.45 0.16 ± 0.41
 Night 0.14 ± 0.48 0.19 ± 0.50 0.13 ± 0.38 0.24 ± 0.64 0.00 ± 0.00 0.03 ± 0.18
Halo
 Day 0.02 ± 0.13 0.14 ± 0.50 0.02 ± 0.13 0.06 ± 0.31 0.00 ± 0.00 0.02 ± 0.13
 Night 0.05 ± 0.23 0.16 ± 0.52 0.05 ± 0.23 0.16 ± 0.52 0.04 ± 0.27 0.00 ± 0.00
ND 0.05 ± 0.30 0.19 ± 0.50 0.04 ± 0.27 0.08 ± 0.28 0.00 ± 0.00 0.00 ± 0.10
ND = negative dysphotopsia
Mean values with SD based on the answer scale from 0 to 3 points from the questionnaire given, all median values = 0.00. No significant P values for comparison between the groups within particular follow-up reached.

Within Group 1, no significant changes in the frequency or extent of dysphotopsia were measured between month 1 and month 12 follow-ups. Within Group 2, the frequencies of daytime and nighttime glare, and daytime halo significantly lowered (P values after Bonferroni correction .006, .027, and .039, respectively) (Table 1). The same observation was made within Group 2 for the extent of daytime and nighttime glare, nighttime halo and ND (P values after Bonferroni correction .003, .039, .042, and .018, respectively) (Table 2).

Contrast Sensitivity

The mean CS calculated for all 5 spatial frequencies (1.5 to 18 cpd) was the same in both groups 3 and 12 months postoperatively, in all 4 light conditions (Supplemental Table 4, https://links.lww.com/JRS/A411).

In month 3 follow-up, the photopic CS with and without glare was the same for all measured spatial frequencies in both groups. At the same time point in mesopic conditions, CS without glare for 3 cpd and with glare for 6 cpd was higher in Group 2 (P values .035 and .012, respectively). Statistically significant differences in CS in month 12 follow-up between Groups 1 and 2 for all light conditions and spatial frequencies are depicted in Figure 4.

Figure 4.
Figure 4.:
Monocular contrast sensitivity in both groups in photopic and mesopic conditions, with and without glare, in month 12 follow-up: Scores given in logarithmic values. Norm values for age >60 years from: Hohberger et al.20 Legend to all graphs on the left top side. Significant differences in contrast sensitivity for particular spatial frequencies in particular light conditions marked with asterisks.

Mesotest

The mesopic vision and glare sensitivity in month 12 follow-up showed no difference between the groups: 16 cases (45.7%) in Group 1 and 26 cases (54.2%) in Group 2 showed maximal values (P = .770). The maximal glare sensitivity was reached in 4 eyes (11.4%) in Group 1 and 8 eyes (16%) in Group 2 (P = .649).

Positive Dysphotopsia and Contrast Sensitivity

No influence of PD on CS values in all light conditions and spatial frequencies was observed in the second follow-up, irrespective of the IOL design. In month 12 follow-up, patients with PD revealed lower photopic CS without glare for 1.5 and 3 cpd (P = .005 and .036, respectively) and lower photopic CS with glare for 3 cpd (P = .047). In mesopic conditions with glare, patients with PD showed higher values for 18 cpd (P = .013).

Preoperative Anatomical Factors and Incidence of Dysphotopsia

Irrespective of the IOL design, cases with persistent ND in the last examination revealed significantly younger age compared with those without ND (59.00 ± 5.66 and 68.82 ± 6.25 years, respectively; P = .029). No significant differences for other measured parameters were detected (Supplemental Table 5, https://links.lww.com/JRS/A411).

Between the cases with and without persistent PD in month 12 follow-up, irrespective of the IOL design, significant differences in AL (23.61 ± 0.90 and 23.20 ± 0.77 mm, respectively; P = .040) and pupil dynamics (1.55 ± 0.69 and 1.14 ± 0.55 mm, respectively; P = .006) were found (Supplementary Table 6, https://links.lww.com/JRS/A411).

Patient Satisfaction

The degree of general patient satisfaction showed lower numbers (meaning higher satisfaction) in Group 1 compared with Group 2, reaching a statistically significant difference in month 3 follow-up (median 1.00 and 2.00 points, respectively; P = .006) (Supplemental Table 7, https://links.lww.com/JRS/A411). Within each group, the satisfaction levels remained unchanged throughout the study.

Anterior Capsule Contraction

In the last follow-up, slight anterior capsule contraction developed in 2 cases (3.7%) in Group 1 and 5 cases (8.1%) in Group 2, showing a 2-fold lower incidence, however reaching no statistical significance (P = .443). As all the cases represented still very good levels of visual acuity, satisfaction, and no dysphotopsia, no treatment was required.

DISCUSSION

The results of this study suggest that the IOL design with a 7.0 mm optic and plate haptics reduces both PD and ND. These findings are similar to those available in the literature referring to approaches reducing ND up to 4 weeks postoperatively.21,22 Clinically concluding, the incidence, frequency, and partially extent of dysphotopsia were lower throughout the whole study in Group 1; however, they reached statistically significant values between the groups only in month 1 follow-up.

The process of neuroadaptation had a larger impact in the group with a 6.0 mm optic and C-loop haptic IOL design (showing significant reduction of dysphotopsia with time), whereas dysphotopsia rates remained low and almost unchanged with time in the 7.0 mm optic and plate haptic IOL design group. This could explain the statistical significance of dysphotopsia reduction between the groups only in the first follow-up, as previously reported for ND.21 The obtained data suggest that the IOL design with a 7.0 mm optic reduces dysphotopsia from the early postoperative course before slower, and in this context minor, neuroadaptation. Possibly because of the preventive IOL effect, the disturbance with dysphotopsia in this group was lower from the very beginning; thus, there was also less need for slower neuroadaptation. From a clinical point of view, earlier freedom from dysphotopsia that took place in Group 1 provides higher patient satisfaction and so earlier readiness for the cataract surgery of the fellow eye, if indicated. This relieves the patient from the uncomfortable transitional phase between the surgeries that may include, for instance, cyanopsia or lack of proper spectacles.

The IOL design does not seem to have an effect on the mean CS, mesopic vision, or glare sensitivity. The peak CS occurring between 3 and 6 cpd as a possible predictive factor for everyday functioning was higher in the cases with a 6.0 mm optic IOL design.23 Nevertheless, the design with a 7.0 mm optic achieved very good CS values comparable with high norms for the age group in this study, and the general level of satisfaction was higher than that in the 6.0 mm optic group (reaching significant levels in month 3 follow-up), which might indicate that freedom from dysphotopsia is subjectively more important for the patient than the highest CS results. Furthermore, the IOL design with a 7.0 mm optic seems to enable a quicker stabilization of the final visual acuity and refraction. However, it is not to be excluded that the higher UDVA in the first follow-up had an impact on the lower incidence of dysphotopsia, which might be a limitation of this study. In the group with a 7.0 mm optic IOL design, SER remained slightly more myopic compared with the group with a 6.0 mm optic IOL design, which might be confirmed by a significantly lower subjective need for reading spectacles among these cases. This could also influence the higher degree of satisfaction in this group.

The data from this study confirm the incidence of ND and early PD reported in the literature.2,13 Regarding the incidence of persisting PD, however, higher numbers were found. In both groups in the last follow-up, there were cases of PD with no degree of disturbance (2 of 5 in Group 1 and 3 of 14 in Group 2), which, if excluded, would decrease the general PD incidence. In addition, it could be concluded that when asked the same questions about dysphotopsia throughout the study, the patients became more sensitized to the symptoms and gave more positive answers. Also, the known discrepancy between self-declared and enquired dysphotopsia might have affected our results.18 Of all the photic phenomena analyzed in this study, the most common, intense, and persisting in both groups was glare at daytime. This could be due to reaccustoming to normal light conditions after years of cataract development and general higher activity of patients during the day rather than at night together with stronger light sources present at daytime comparing with nighttime, which could trigger dysphotopsia.

The comparison of preoperative anatomical data revealed some significant differences, which could serve as predictive factors for dysphotopsia. In the first place, patients with persistent ND symptoms were of younger age. These data confirm the findings of Makhotkina and could be explained by a higher degree of awareness of dysphotopic symptoms, criticism, and expectations of younger patients.18 Our results also demonstrated longer AL and greater pupil dynamics among cases with persistent PD. To the authors' knowledge, this is the first report presenting these features as possible predictive risk factors for PD.

The idea of enlarged optic as a solution against dysphotopsia has been discussed since its first reports in the literature. Tester hypothesized that it would reduce PD, but with no statistical significance in the results, as in this study.4 A higher incidence of both PD and ND in the IOL with smaller optic has also been clinically proven.24 Finally, the discrepancy in the size of the crystalline lens and implanted IOL has been lately reported as the primary cause of ND.25

Holladay previously described the effect of enlarged optic working against PD in ray-tracing analysis.7 Later, this theory was also extended onto ND, stating that a larger optic diameter would affect both the missing and refracted rays similarly and move the shadow gap.14 Anteriorizing the shadow gap onto already nonfunctional retina or illuminating it are currently claimed as solutions against ND.26 On the other hand, the horizontal or inferotemporal haptics orientation has also been reported to reduce ND, as the optic–haptic junction refracts at very large angles or totally reflects light missing the optic.21,22,26 As a result, the illumination gap remains, yet it is not recognizable anymore because its peripheral boundary is removed from the retina. We cannot confirm this mechanism as the haptics orientation was random in both study groups. Moreover, a particular haptics orientation or even a local modification of the IOL edge may lose their function because of IOL rotation or dislocation.26 The IOL design with a 7.0 mm optic and plate haptics has a larger extent of optic–haptic junction (ca. three-fourth of the IOL circumference) compared with the design with a 6.0 mm optic and C-loop haptics (almost one-third of the IOL circumference) and may generally serve a larger “antidysphotopic surface,” probably less dependent on a particular orientation. However, our results also showed reduction in PD, which is why we believe that the enlarged optic diameter is here of key importance (to the authors' knowledge, there are no available ray-tracing data about the influence of the optic–haptic junction on PD).

We hypothesize that if both the shadow and light missing the IOL create nonphysiological images, they should both be excluded from the functional retina possibly by anteriorizing. In this matter, using an enlarged optic seems to be a plausible solution to perceive a continuous, closer to physiological, nonconstricted retinal image. In addition, an optic larger than scotopic and mesopic pupil size should also reduce PD by preventing direct lens edge exposure and internal rays reflection.

Further analysis, including optical modeling using the IOL design with a 7.0 mm optic diameter and plate haptics from this study, is therefore required to investigate our hypothesis based on the obtained promising clinical data. It should be verified whether using the IOL design with a 7.0 mm optic would cause light to miss the optic, at which peripheral retinal angle it would be projected, whether it would have an impact on peripheral vision, and whether particular orientation of the used plate haptics would be of antidysphotopic advantage for both PD and ND. The limitations of our study also include a relatively small number of participants, lack of wavefront analysis, and different haptic types in both IOL designs. There is no Aspira-aXA model with a 6.0 mm optic available. This is why we decided to use a comparable design with C-loop haptics for the control group because it is made of the same materials and has been chosen as a trusted and well-verified one, providing very good results for the control group.

The IOL design with a 7.0 mm optic has also several other advantages. Large optic reduces the risk of posterior capsule opacification development and enables a wider capsulorhexis, which even in the case of capsule contraction should keep a large enough clear central optic zone.27 Clinically, the size of a 7.0 mm optic may mimic the crystalline lens better than the standard 6.0 mm optic and so contribute to pseudophakic retinal view without IOL edge disturbance. In addition, it requires significantly less IOP elevation during scleral indentation and, consequently, less intraocular stress compared with the 6.0 mm optic.28 These advantages are particularly relevant for the diagnosis and treatment of peripheral retinal pathologies and diabetic patients. Technically, the implantation using a classic well-mastered surgical method is not problematic, with no need for starting a new learning curve. The in-the-bag implantation allows multifocal and toric variants. Moreover, the larger optic does not raise the risk of postoperative inflammation, surgically induced astigmatism, or loss of corneal endothelial cell density.29 Finally, in this study, no intraoperative complications occurred.

To the authors' knowledge, this is the first report on the influence of the IOL design with a 7.0 mm optic and plate haptics on the functional quality of vision after cataract surgery. The used IOL design reduces dysphotopsia and provides good CS, as well as good and stable visual acuity and refraction, together with high general patient satisfaction. Considering its clinical and technical advantages, it is an attractive choice among the wide variety of available IOLs, most of all in the aspect of preventing dysphotopsia.

WHAT WAS KNOWN

  • Dysphotopsia appears to be caused by an idiosyncratic reaction of anatomical factors, particular IOL design, and implantation technique.
  • No fully effective treatment of dysphotopsia has been reported, and a preventive strategy is needed.
  • IOLs with a smaller optic diameter have caused higher rates of dysphotopsia.

WHAT THIS PAPER ADDS

  • An IOL design with a 7.0 mm optic and plate haptics reduced both positive and negative dysphotopsia and provided good visual performance in terms of stable visual acuity and refraction, contrast sensitivity, mesopic vision, and glare sensitivity.
  • Longer axial length and greater pupil dynamics might serve as predictive risk factors for positive dysphotopsia.

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