Dysphotopsia: a multifaceted optic phenomenon

Preparation and Stability Study of an Injectable Hydrogel for Artificial Intraocular Lenses

Currently available intraocular lenses (IOLs) on the market often differ significantly in elastic modulus compared to the natural human lens, which impairs their ability to respond effectively to the tension of the ciliary muscles for focal adjustment after implantation. In this study, we synthesized a polyacrylamide-sodium acrylate hydrogel (PAH) through the cross-linking polymerization of acrylamide and sodium acrylate. This hydrogel possesses excellent biocompatibility and exhibits several favorable properties. Notably, the hydrogel demonstrates high transparency (94%) and a refractive index (1.41 ± 0.07) that closely matches that of the human lens (1.42). Additionally, it shows strong compressive strength (14.00 kPa), good extensibility (1400%), and an appropriate swelling ratio (50 ± 2.5%). Crucially, the tensile modulus of the hydrogel is 2.07 kPa, which closely aligns with the elastic modulus of the human lens (1.70-2.10 kPa), enabling continuous focal adjustment under the tension exerted by the ciliary muscles.

Modified technique for sutured scleral fixated intraocular lens in a patient with post-traumatic aniridia and aphakia: a case report

BACKGROUND

A modified surgical technique of sutured scleral fixated intraocular lens (SSF-IOL) was applied in a patient with post-traumatic aniridia and aphakia.

CASE PRESENTATION

A 51-year-old man was referred to our clinic with decreased vision (finger count) in his right eye. This patient had previously undergone primary repair of the ruptured globe and pars plana vitrectomy to manage ocular trauma in the same eye. On presentation, the best corrected visual acuity in his right eye was 20/40. The slit lamp examination of his right eye revealed loss of total iris and lens. Corneal endothelial cell density was 1462 cells/mm2. Fundoscopic examination of the right eye revealed a retinal attachment. For IOL implantation, a rigid poly methyl methacrylate IOL was used with a 2-point scleral fixation performed using a polypropylene suture. One year postoperatively, the uncorrected distance visual acuity was 20/32, and the manifest refraction was - 0.5/-1.5 × 130 (20/20). Pentacam revealed that the astigmatism of the anterior corneal surface and the total cornea was 1.1 D (axis: 59.8°) and 1.0 D (axis: 35.6°), respectively. The horizontal (3°-183°) cross-section image displayed an IOL with a 1° tilt and 0.425 mm decentration. The patient reported no dysphotopsia or photophobia and was satisfied with the visual results. OPD-scan III revealed that higher-order aberrations in the right eye were slightly higher than those in the left eye. No suture-related or other serious complications were observed.

CONCLUSION

The modified SSF-IOL technique can offer improved visual quality for patients with aniridia and aphakia by ensuring proper IOL positioning and reducing astigmatism.

Use of the perceptual point-spread function to assess dysphotopsias

Nowadays many patients are choosing EDOF or multifocal lenses for replacement of natural lens in cataract surgery. This can result in issues such as presence of dysphotopsias, namely halo and glare. In this work, we propose a new perimetry method to describe dysphotopsias in far-field region in a presence of bright, point-like light source. We constructed a custom device and designed measurement procedure for quantitative measurement of dysphotopias in the center of visual field and used it to examine patients with mild cataracts or implanted IOLs. Our approach may help in establishing an objective method to study and compare dysphotopsias.

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.

Incidence and causes of negative dysphotopsia after uncomplicated cataract surgery - A randomized clinical trial

Purpose:

The purpose of this study is to find incidence of negative dysphotopsia (ND) in eyes undergoing clear corneal phacoemulsification and identify its causes including corneal wound hydration and type of intraocular lens (IOL).

Methods:

In this randomized clinical trial, consenting adult patients undergoing phacoemulsification were randomized to receive a hydrophobic (Alcon Acrysof^® SN60WF) or a hydrophilic acrylic IOL (CT Asphina^® 603P, Carl Zeiss Meditec) in a 1:1 ratio. At time of surgery, eyes were again randomized in 1:1 fashion to receive stromal wound hydration or not (n = 80 each in four groups). Primary outcome measure was the incidence of ND between eyes receiving stromal hydration versus no hydration. Those with ND were observed for 5 years after surgery.

Results:

Of the 320 eyes, 29 (9.06%) reported ND of which 24 (83%) were transient. Eyes with wound hydration had significantly higher proportion of ND (n = 21/160, 13%) compared to no hydration (n = 8/160, 5%) (P = 0.01). Additionally, eyes with wound hydration were three times more likely to experience ND (odds ratio = 3.29, 95% CI = 1.3–8.2, P = 0.01). Majority of eyes (20/21, 95%) with ND after hydration had it transiently while half (4/8, 50%) of those with ND without wound hydration had it persistently at 6 weeks (P < 0.001) and continued to experience ND for 5 years but did not request intervention.

Conclusion:

ND occurred in 9% cases with majority being transient. Corneal wound hydration led to significant higher likelihood of experiencing transient ND. Those with persistent ND for more than 6 weeks (1.5%) continue to experience ND for at least 5 years.

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.

The Effects of a Senofilcon A Contact Lens With and Without a Photochromic Additive on Positive Dysphotopsia Across Age

OBJECTIVE

The visual effects of wearing a photochromic contact lens (test) were directly compared with a nonphotochromic contact lens (control). Positive dysphotopsia (halos, starbursts) and intraocular scatter (behaviorally determined) were assessed. Both younger and middle-aged subjects were evaluated to examine the influence of age.

METHODS

Fifty-four subjects (18-62 years) were tested using a contralateral design. Subjects were fit with a photochromic contact lens on one eye and a nonphotochromic contact lens on the other eye, randomly assigned. Testing occurred with and without photochromic activation (darkened) by use of a violet activator (365 nm, half-bandwidth 20 nm). The extent of dysphotopsia (halos and spokes) was measured using an aperture (∼4 mm) that created a bright point source of light 45 inches from the plane of the eye. Between the point source and subject, a centering precision caliper was used to measure lateral spread. Two-point thresholds were determined by measuring the minimum distance between two points of broadband xenon light.

RESULTS

The photochromic contact lens produced smaller halo diameters than the control contact lens, both activated (41% on average) and inactivated (21% on average), and age strata was a significant factor (P<0.001) with the older group showing a greater reduction. The photochromic contact lens produced smaller starburst diameters than the control contact lens, both activated (37% on average) and inactivated (23% on average), and age strata was a significant factor (P=0.001) with the older group showing a greater reduction. The two-point thresholds were reduced (25% activated, 9% inactivated) on average but the age effect was not significant (P<0.10).

CONCLUSIONS

The senofilcon A lens with photochromic additive reduced the extent of positive dysphotopsia compared with the same lens without the additive, regardless whether the lens was activated or not. The visual benefit was greatest with the older subjects.

Targeted Lens Pitting to Treat Negative Dysphotopsia

PURPOSE

To describe a patient with negative dysphotopsia who underwent a novel non-invasive technique that uses the Nd:YAG laser to induce nasal light scattering through targeted lens pitting.

METHODS

Case report.

RESULTS

Symptoms of negative dysphotopsia resolved after targeted lens pitting.

CONCLUSIONS

Targeted lens pitting with Nd:YAG laser is a potential technique that may help treat negative dysphotopsia in a manner that preserves intraocular anatomy. Further study is warranted to explore targeted lens pitting in both patients with and without prior retinal surgery as a treatment for negative dysphotopsia. [J Refract Surg. 2021;37(3):212-214.].

Measures of visual disturbance in patients receiving extended depth-of-focus or trifocal intraocular lenses

The degree of visual disturbance associated with a particular model of intraocular lens (IOL) depends on several factors, including IOL optic, material, and mechanics. Characterization of visual disturbance profiles is paramount for informing clinical IOL selection. Although many studies evaluating presbyopia-correcting IOLs include subjective assessment of visual symptoms, the types of patient-reported outcome measures (PROMs) used to capture these outcomes are inconsistent across studies, complicating data contextualization. Furthermore, some tools produce more meaningful results than others. This review presents a discussion on the scientific literature published on the subjective and semiobjective (halo and glare simulator, light-distortion analyzer, vision monitor, and halometers) methods used to assess visual disturbances in patients implanted with trifocal or extended depth-of-focus IOLs, highlighting their advantages and limitations. It underscores the importance of between-study comparisons and the need for standardized PROMs in clinical IOL research to provide more accurate information for IOL selection.

Illusions, hallucinations, and visual snow

Illusions and hallucinations are commonly encountered in both daily life and clinical practice. In this chapter, we review definitions and possible underlying mechanisms of these phenomena and then review what is known about specific conditions that are associated with them, including ophthalmic causes, migraine, epilepsy, Parkinson's disease, and schizophrenia. We then discuss specific syndromes including the Charles Bonnet syndrome, visual snow syndrome, Alice in Wonderland syndrome, and peduncular hallucinosis. The scientific study of illusions and hallucinations has contributed significantly to our understanding of how eye and brain process vision and contribute to perception. Important concepts are the distinction between topologic and hodologic mechanisms underlying hallucinations and the involvement of attentional networks. This chapter examines the various ways in which pathological illusions and hallucinations might arise in relation to the phenomenology and known pathology of the various conditions associated with them.

Future Intraocular Lens Technologies

The future of intraocular lens (IOL) technology has already begun with a number of recent innovations. The postoperative change of refractive power will lead to a customized fine-tuning that provides patients with the individual vision they expect and with as much spectacle independence as possible. The latest-generation (2.0) Light-Adjustable Lens (RxSight) was recently introduced into clinical practice, with the first results being very encouraging. Other methods of altering the power of an already implanted IOL are under development. The same can be said about the correction of presbyopia, the so-called last frontier in refractive surgery. Extended depth-of-focus IOLs have been introduced, as has the technology of the pinhole IOL. The latter has therapeutic potential beyond the refractive aspect and has already proven helpful in cases of iris defects and irregular corneas. Several technologies are currently being tested to achieve-finally-an accommodative IOL. One such concept uses the (remaining) strength of the ciliary muscle, whereas another is triggered by the pupil reaction when shifting focus from far to near. Not an IOL itself, but rather a high-tech innovation that so far has mostly been implanted during cataract surgery, is a microelectronic sensor that measures habitual intraocular pressure (IOP) at any given time and promises to revolutionize the management of glaucoma patients. The last generation of this device (Eyemate; Implandata Opthalmics Products GmbH) is implanted during small-incision cataract surgery; the latest development is an even smaller sensor that will be inserted suprachoroidally before, in the near future, such a device will be part of a capsular ring. These IOP sensors are a prime example that IOL technology will continue to be a driving force in ophthalmology, with a positive impact far beyond cataract surgery.

Comparison of three different presbyopia-correcting intraocular lenses

Objective (aim): to test the refractive and visual outcomes and the quality of vision after the bilateral implantation of three different multifocal intraocular lenses (MIOLs) in patients with age-related cataract. Methods: In this retrospective, comparative study including 90 eyes of 45 cataract patients, bilateral implantation of either the hydrophilic trifocal Liberty® 677MY capsular bag IOL, the hydrophilic AT LISA® tri 839M lens, or the hydrophobic AcrySof® IQ PanOptix® IOL was performed during routine cataract surgery. Refractive outcomes, visual acuities (VA) for far, intermediate and near distances, as well as visual quality, dysphotopic events and spectacle use were evaluated six months postoperatively. Results: VA curves were similar for the three MIOLs, however the Liberty lens seemed to be superior for far and near, while AT LISA tri provided somewhat better VA in the intermediate range. Refractive correction was the most effective with the Liberty IOL (p=0.0131). Dysphotopic phenomena were usually perceived in low light conditions. Their frequency was lower with the AT LISA tri and Liberty lenses. Symptoms were significantly less disturbing for patients implanted with the Liberty lens, two-thirds of AT LISA tri and Liberty patients, while only 57% of PanOptix patients achieved spectacle independence. Conclusions: All examined MIOLs were found to be safe and efficient in presbyopia-correction of cataract patients, however different models had different advantages. The vision preferences of each patient should always be taken into consideration when choosing a MIOL, and the possible occurrence of dysphotopic events should be also clearly communicated in each case. Abbreviations: ACD = Anterior chamber depth, ANOVA = Analysis of variance, AXL = Axial length, CDVA = Corrected distance visual acuity, CYL = Cylinder; Cylindric refraction, D = Diopter, IOL = Intraocular lens, K1; K2 = Keratometry values, MIOL = Multifocal intraocular lens, n = Number of cases, n.a. = Not applicable, Postop = Postoperative, QoV = Quality of Vision, SD = Standard deviation, SEQ = Spherical equivalent, SPH = Sphere; Spherical refraction, UDVA = Uncorrected distance visual acuity, UIVA = Uncorrected intermediate visual acuity, UNVA = Uncorrected near visual acuity, VA = Visual acuity.

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.

Individual differences in visual function

A significant proportion of research on the visual system focuses on general principles that apply to samples and/or populations. Many questions, however, are more suited to the specific characteristics of an individual. The visual system, like most systems of the body, is extremely variable with respect to function and susceptibility to disease. Understanding this variation is an important avenue to better measurement, disease prevention and treatment.

Photopsia

'Photopsia' describes the symptom of visual disturbances that are typically flash-like, sudden in onset and brief, and occurring without light entering the eye. Patients reporting photopsia often pose a diagnostic challenge, given the wide range of possible neurological and ophthalmological causes. We review the common causes of photopsia, discuss the assessment and workup of this symptom, and stress the importance of close interdisciplinary liaison to help with its diagnosis and management. We discuss a patient with acute zonal occult outer retinopathy to illustrate these points.

The Effects of Blue Light-Filtering Intraocular Lenses on the Protection and Function of the Visual System

Filtration of high-energy short-wave visible light (blue light) to improve vision and protect against damage has evolved both in aquatic animals and terrestrial species. In humans, pigments in the inner layer of the macula absorb wavelengths between 400 and 520 nm and function to improve visual performance. In patients who undergo cataract surgery, replacing cataractous lenses with artificial intraocular lenses (IOLs) that do not mimic normal healthy adult lenses could result in preventable negative visual effects, including glare disability. Blue light-filtering (BLF) IOLs were designed to filter short-wave light in addition to ultraviolet light and mimic the natural crystalline lens. Current studies indicate that BLF IOLs may provide protection from blue light-induced retinal damage and slow the development and progression of age-related macular degeneration. Additionally, BLF IOLs have been shown to improve chromatic contrast, reduce photostress recovery time, reduce glare disability and discomfort, and generally improve visual performance under glare conditions. Although a number of concerns have been raised about the relative risks versus the benefits of BLF IOLs, recent studies reported no adverse effects on visual function or contrast under photopic conditions, no long-term effects on color vision, and no detrimental effects on circadian rhythms with BLF IOLs. Based on the current understanding of the field, evidence suggests that BLF IOLs would be returning the eye to a more natural state compared with non-BLF lenses.

The Efficacy of Questionnaire-based Evaluation in Determining the Incidence of Recent Pseudophakic Dysphotopsia

Background: Dysphotopsias are optical side effects experienced by patients who underwent cataract surgery. This unwanted photic phenomenon has gained ground and is a major postoperative concern. Visual acuity is not sufficient in evaluating the postoperative visual function.

The aim of this study was to determine the efficacy of using a preexistent questionnaire in determining the presence of dysphotopsia.

Material and method: We conducted a prospective study, using the modified Visual Function Index (VF-14) and the Ocular Surface Disease Index (OSDI) surveys, completed on patients that underwent uncomplicated phacoemulsification with intraocular lens implantation between November 2016 and November 2017. Patients included in the study had no known ocular comorbidities and had no other possible postoperative explanation for these visual phenomena. Three weeks after the surgery, the questionnaire was filled up by one individual examiner.

Results: Of the 50 patients considered, 37 patients met all the inclusion criteria and were successfully enrolled in the study, with a mean age of 75.88 years. Dysphotopsia phenomena were present in 13.51% of cases; 60% of these patients described the presence of positive dysphotopsia, and 40% complained of temporal shadows. The best corrected visual acuity was over 0.8 in 75.67% of the cases.

Conclusion: Although there is no objective test to diagnose this early postoperative complication, pseudophakic dysphotopsia should not be overlooked and additional chair time is needed.