Eccentric capsulorhexis and postoperative dysphotopsia following phacoemulsification

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.

Negative dysphotopsia: the enigmatic penumbra

PURPOSE

To determine the cause of negative dysphotopsia and the location, appearance, and relative intensity of such images in pseudophakic eyes.

SETTING

Baylor College of Medicine, Houston, Texas, USA.

DESIGN

Reporting available data addressing a specific clinical question.

METHODS

Negative dysphotopsia was simulated using the Zemax optical design program. The nominal values for the pseudophakic eye model were as follows: IOL power, 20.0 diopters (D); corneal power, 43.5 D; Q value, -0.26; axial IOL depth behind pupil, 0.5 mm; external anterior chamber depth (corneal vertex to iris plane), 4.0 mm; optic diameter, 6.0 mm; pupil diameter, 2.5 mm.

RESULTS

From the first ray-tracing simulation, analysis of the image for the nominal parameters showed 2 annuli (ring-shaped) shadows. The inner annulus shadow was located from a retinal visual field angle of 86.0 to 100.0 degrees (width 14.0 degrees), and the outer annular shadow was located from 105.9 to 123.3 degrees (width 17.4 degrees). Superimposing the inner annulus on the human visual field showed that the shadow would be apparent only temporally, where it is within the limits of the visual field and functional retina. The patient would perceive this as a temporal dark crescent-shaped partial shadow (penumbra).

CONCLUSIONS

Primary optical factors required for negative dysphotopsia are a small pupil, a distance behind the pupil of 0.06 mm or more and 1.23 mm or less for acrylic, a sharp-edged design, and functional nasal retina that extends anterior to the shadow. Secondary factors include a high index of refraction optic material, angle α, and the nasal location of the pupil relative to the eye's optical axis.

FINANCIAL DISCLOSURE

Drs. Zhao and Reisin are employees of and Dr. Holladay is a consultant to Abbott Medical Optics, Inc. No author has a financial or proprietary interest in any material or method mentioned.

Comparison of pseudophakic dysphotopsia with Akreos Adapt and SN60-AT intraocular lenses

PURPOSE

To determine the relative incidence of unwanted light images with the AcrySof SN60-AT intraocular lens (IOL) (Alcon) and the Akreos Adapt (Bausch & Lomb) IOL.

SETTING

The Eye Clinic, Sir Charles Gairdner Hospital, Nedlands, Australia.

METHODS

In a prospective randomized study of 61 patients who had cataract surgery, the relative incidence of unwanted light images with 2 biconvex acrylic double square-edged IOLs, the SN60-AT and Akreos Adapt, was compared. Patients were followed at 1 week and for a minimum of 6 weeks. At both follow-ups, patients were asked to rate their experience of dysphotopic phenomenon according to a set of questionnaire criteria. The Mann-Whitney test was used to analyze the ordinal data.

RESULTS

All 61 patients were interviewed at both stages of follow-up. The mean follow-up was 8 weeks +/- 2 (SD). At 1 week, there was significantly more dysphotopsia (positive and negative) with the SN60-AT IOL (37.5%) than with the Akreos Adapt IOL (24.1%) (P = .042). Significantly more patients with the SN60-AT IOL reported negative dysphotopsia at 1 week only. At 8 weeks, the incidence of positive and negative dysphotopsia declined to 31.3% and 20.7% in the SN60-AT group and Akreos Adapt group, respectively, and there was no longer a statistically significant difference between the 2 groups.

CONCLUSIONS

More patients with the SN60-AT IOL than with the Akreos Adapt IOL reported dysphotopsia. One week postoperatively, the difference was significant. The difference was primarily a result of the higher incidence of negative dysphotopsia with the SN60-AT IOL. At 8 weeks, the incidence of all types of light phenomena was significantly lower in both groups.

Case report: pseudophakic dysphotopsia simulating Bagolini glasses

A case is reported of a 68-year-old patient who had undergone uneventful cataract surgery and intraocular lens implantation. She reported the perception of a binocular cross simulating that seen with Bagolini striated glasses, especially with streetlights at night. It is suggested that this phenomenon was caused by posterior capsular folds.

Severe photic phenomenon

A 69-year-old man who had uneventful bilateral cataract surgery with visual acuity of 20/15 without correction presented with severe dysphotopsia. Treatment with brimonidine (Alphagan) or pilocarpine did not resolve the symptoms. A multipiece silicone intraocular lens was piggybacked into the sulcus, and the patient no longer reported dysphotopsia.