Influence of the intraocular lens optic–haptic junction on illumination of the peripheral retina and negative dysphotopsia

Modified "C" Haptic Intraocular Lens Orientation and Negative Dysphotopsia

Phacoemulsification is the standard of care in cataract surgery in the developed world, with patients having high expectations regarding visual results. Postoperative dissatisfaction due to negative dysphotopsia (ND) ranges from rare to very frequent; its etiology is unclear, and it affects postoperative satisfaction. Since one of the most frequently used strategies to avoid ND is related to intraocular lens (IOL) haptic orientation, we conducted a prospective interventional study that enrolled 197 patients who underwent standard phacoemulsification. All patients had a one-piece hydrophobic acrylic IOL implanted; in one group, the haptics were placed in any meridional axis except inferotemporal (IT) meridians, and in the other group, the IOL was implanted with the haptics in an IT position. Our results showed no statistically significant differences between groups when analyzing the correlation between the position of IOL haptics and the presence of ND in week one and month one. Also, pupillary diameter showed no statistically significant differences between patients with or without ND. Despite some studies claiming that haptic orientation prevents ND, we found that haptic orientation does not correlate with ND incidence and that ND decreases from day 1 to month 1. Our results support previous findings on the decrease in ND over time and that haptic orientation should not be considered an intraoperative strategy to avoid this unwanted phenomenon.

Optical modeling of the entire visual field of the eye

Vision is rarely evaluated scientifically at very large visual angles, despite being used continuously in everyday life. Furthermore, raytrace calculations indicate that peripheral optical properties are different for a pseudophakic eye, and even though this is rarely noted by patients, it is probably the cause of bothersome "negative dysphotopsia." Simplified paraxial parameters that characterize the basic properties of phakic and pseudophakic eyes are collected together here as a baseline, and then raytracing is used to show that input angles of about 60°, which correspond to obstruction by the nose, eyebrow, and cheek, illuminate a retinal hemisphere. At larger angles in the temporal direction, the image with an intraocular lens (IOL) reaches a limit due to vignetting at about a 90° input angle to the optical axis, in comparison to 105° with the Gullstrand-Emsley eye model, and 109° for the most realistic gradient index crystalline lens model. Scaling the far peripheral vision region more accurately may lead to benefits relating to intraocular lenses, diseases of the peripheral retina, widefield fundus images, and myopia prevention.

Dysphotopsias or Unwanted Visual Phenomena after Cataract Surgery

Dysphotopsias are unwanted visual phenomena that occur after cataract surgery. They represent some of the most common reasons for patient dissatisfaction after uncomplicated surgery for cataract phacoemulsification with in-the-bag intraocular lens (IOL) implantation. Depending on the form of the optical phenomenon and the effect it poses on vision, dysphotopsias are divided into positive and negative type. Positive dysphotopsias are usually described by patients as glare, light streaks, starbursts, light arcs, rings, haloes, or flashes of light. Negative dysphotopsias are manifested as an arc-shaped shadow or line usually located in the temporal part of the visual field, similar to a temporal scotoma. In addition to their different clinical manifestations, positive and negative dysphotopsia also have different risk factors. Even though up to 67% of patients may experience positive dysphotopsia immediately after surgery, only 2.2% of the cases have persistent symptoms up to a year postoperatively. Surgical intervention may be indicated in 0.07% of cases. The incidence of negative dysphotopsias is up to 26% of all patients; however, by one year postoperatively, the symptoms usually persist in 0.13 to 3% of patients. For both types of dysphotopsia, preoperative patients' education, accurate preoperative diagnostics, and use of an appropriate IOL design and material is mandatory. Despite all these measures, dysphotopsias may occur, and when noninvasive measures fail to improve symptoms, a surgical approach may be considered.

Randomized Controlled Trial of IOL Orientation for Dysphotopsia

PURPOSE

To evaluate whether orientation of the optic-haptic junction of an intraocular lens (IOL) during cataract surgery could decrease the incidence and/or severity of positive and negative dysphotopsia.

DESIGN

Prospective, randomized controlled trial.

METHODS

163 patients (326 eyes) in a private practice scheduled to have bilateral implantation of a Tecnis monofocal IOL (ZCB00) (Johnson & Johnson Vision, Santa Ana, CA) were randomly assigned to have the optic-haptic junction positioned vertically, horizontally, superonasally or inferonasally. Patients with known visual field defects or best corrected vision less than 20/80 were excluded. Patients were surveyed for positive and negative dysphotopsia symptoms at 1 week and 4-6 weeks after surgery. Patients were blinded to the orientation while researchers were not. Data was analyzed to compare the differences in positive and negative dysphotopsia incidence and severity.

RESULTS

IOL oriented vertically in 82 eyes (25.2%), horizontally in 72 eyes (22.1%), superonasally in 94 eyes (28.8%), and inferonasally in 78 eyes (23.9%). Significant difference noted between orientations in incidence of negative dysphotopsia at 1 week postoperatively (p = 0.019) and 4-6 weeks postoperatively (p = 0.002). Patients in the superonasal group had the worst outcome at both time periods, and the horizontal group had the best outcome at 4-6 weeks. No differences were noted for positive dysphotopsia incidence or severity.

CONCLUSIONS

The orientation of the optic-haptic junction of a monofocal IOL was significantly associated with incidence of negative dysphotopsia after surgery, with the horizontal orientation performing best at 4-6 weeks.

Effect of a 7.0 mm intraocular lens optic on peripheral retinal illumination with implications for negative dysphotopsia

PURPOSE

To use optical modeling to compare a 6.0 mm and 7.0 mm intraocular lens (IOL) optic diameters on peripheral retinal illumination with implications for negative dysphotopsia.

SETTING

Mayo Clinic, Rochester, Minnesota, and Simpson Optics LLC, Arlington, Texas.

DESIGN

Model eye.

METHODS

Ray-tracing software was used to simulate retinal illumination from an extended light source for a pseudophakic eye with in-the-bag biconvex IOLs (refractive index [n] = 1.46 and 1.55) and a 2.5 mm pupil. Ray-tracing diagrams and simulated retina illumination profiles were compared using the 6.0 mm and 7.0 mm optic diameter IOLs. Retinal locations were scaled to relative visual angles from 70 to 110 degrees horizontally.

RESULTS

A 7.0 mm optic (n = 1.46) expands the image field by 2.8 degrees compared with a 6.0 mm optic. High-angle input light misses a 7.0 mm optic at a larger visual angle than a 6.0 mm optic, shifting illumination of the peripheral retina by this light anteriorly by 5.6 degrees. Consequently, a region of nonilluminated peripheral nasal retina is enlarged and shifted peripherally using a 7.0 mm optic (visual angle, 86.3 to 96.3 degrees) compared with a 6.0 mm optic (visual angle, 83.5 to 90.7 degrees). Similar illumination changes were seen modeling a 1.55 n IOL.

CONCLUSIONS

A narrow dark region in the nasal retina when using a 6.0 mm optic is changed to a broader, more peripheral dark region when using a 7.0 mm optic. An extended, more peripheral dark nasal region may make a temporal shadow less bothersome and explain lower negative dysphotopsia rates using a 7.0 mm optic.

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

PURPOSE

To determine the impact of IOL with 7.0 mm optic and plate haptic design on incidence of dysphotopsiae and visual functions after cataract surgery.

SETTING

Day-care clinic.

DESIGN

A prospective monocentric randomized patient-blinded comparative clinical study.

METHODS

Following preoperative measurements, patients underwent cataract surgery with implantation of two IOL designs - with 7.0 mm optic and plate haptics (group 1) or with 6.0 mm optic and C-loop haptics (group 2). In month 1, 3 and 12 follow-ups patients were examined, answered a questionnaire regarding satisfaction, spectacle dependence, frequency and extent of positive and negative dysphotopsiae, and underwent contrast sensitivity, mesopic vision and glare sensitivity testing. The data were analyzed as nominal, ordinal and metric with Chi-Square, Mann-Whitney-U, Wilcoxon and t-tests.

RESULTS

Group 1 comprised 57 eyes (43 patients) and group 2 comprised 63 eyes (43 patients). Corrected distance visual acuity was the same between groups throughout the study. Group 1 showed significantly lower incidence of positive and negative dysphotopsiae in month 1 follow-up (p=0.021 and 0.015, respectively) and a higher satisfaction rate in month 3 follow-up (p=0.006). Mean contrast sensitivity and mesopic vision with and without glare were the same in both groups. Positive dysphotopsiae cases in month 12 follow-up revealed lower photopic contrast sensitivity (p=0.005, 0.036 and 0.047, respectively), longer AL and greater preoperative pupil dynamics (p=0.04 and 0.06).

CONCLUSIONS

The IOL design with 7.0 mm optic diameter and plate haptics reduces dysphotopsiae, provides good visual acuity, contrast sensitivity, mesopic vision with and without glare and high patient satisfaction.

Pseudophakic negative dysphotopsia and intraocular lens orientation: a prospective double-masked randomized controlled trial

PURPOSE

To determine whether horizontal orientation of the intraocular lens optic-haptic junctions has an effect on the incidence of pseudophakic negative dysphotopsia.

METHODS

Single-centre prospective double-masked randomized controlled trial. 220 eyes of 201 participants undergoing routine cataract surgery were randomized to receive their intraocular lens either orientated with the optic-haptic junctions at 180° ('horizontal') or without manipulation following implantation (control). Patients were excluded according to age (<19 and > 99 years), coexisting eye disease affecting visual function and insufficient cognitive function to complete the study. In the fourth postoperative week, a telephone interview was conducted to determine rates of negative dysphotopsia. The data were analysed to provide the relative risk of negative dysphotopsia with horizontal orientation of the intraocular lens (IOL) optic-haptic junctions compared with standard treatment.

RESULTS

Orientating the IOL optic-haptic junctions horizontally halved the incidence of pseudophakic negative dysphotopsia in the fourth postoperative week (9/110 in the intervention group; 18/110 in the control group; RR: 0.50, 95% confidence interval: 0.235-1.064, p = 0.072). The overall incidence of negative dysphotopsia was 12.2% (27/220 participating eyes). No intraoperative adverse effects of intraocular lens rotation were reported.

CONCLUSION

The simple intraoperative manoeuvre of rotating the intraocular lens to orientate the optic-haptic junctions at 180° may be a safe and effective measure to reduce the risk of developing postoperative pseudophakic negative dysphotopsia in the first postoperative month. This is the first report that demonstrates the benefit of horizontal optic-haptic junction positioning to be sustained beyond the first postoperative day.

Pseudophakic Dysphotopsia: Review of Incidence, Cause, and Treatment of Positive and Negative Dysphotopsia

We reviewed the literature concerning positive dysphotopsia (PD) and negative dysphotopsia (ND) regarding cause, incidence, and clinical and surgical management. In addition, we summarized our surgical experience in managing dysphotopsia. A PubMed review, limited to English language articles, yielded 149 citations; multifocal (diffractive optic) and phakic intraocular lens (IOL) dysphotopsia were excluded. Overall, 39 articles were determined to be relevant for the objectives of this investigation. Regarding PD, 7 articles corroborated that the cause of PD is related primarily to internal reflection of oblique light rays that strike the square (truncated) edge of the IOL and are reflected onto the retinal surface. No round-edged foldable IOLs are available in the United States at this time, although IOLs modified with a round anterior edge and square posterior edge show a trend toward decreased incidence of PD. High index of refraction (I/R), surface reflectivity, and IOL optic design are additional causative factors for PD. Regarding the authors' surgical experience, changing the optic material to have a lower I/R improved PD symptoms in the large majority of patients. The cause of ND seems to be multifactorial and less well understood, with some disparity between clinical and laboratory findings. Four articles that explore using ray-tracing optical modeling suggest an "illumination gap," in which some temporally incident light rays to the nasal retina pass anterior to the IOL and some are refracted posteriorly by the IOL, resulting in a gap and resultant temporal shadow. However clinically, ND is associated invariably with well-centered in-the-bag IOLs. Other implicating factors include nasal anterior capsule override, haptic orientation, large-angle κ value, and high hyperopia. Persistent ND has been treated successfully or reduced with reverse (anterior) optic capture, sulcus IOL placement, piggyback IOLs, and neodymium:yttrium-aluminum-garnet nasal capsulectomy. Two articles reference a new optic edge designed to capture the anterior capsulotomy, mimicking reverse optic capture. Persistent dysphotopsia after cataract surgery is a significant cause for patient dissatisfaction. The cause and management of both ND and PD are of significance, and new IOL designs and alternative surgical strategies may help to mitigate these unintended side effects of IOL implantation.