COMMENTARY

Can the Riddle of the Negative Dysphotopsia Be Solved?

William W. Culbertson, MD

Disclosures

September 28, 2012

Negative Dysphotopsia: The Enigmatic Penumbra

Holladay JT, Zhao H, Reisin CR
J Cataract Refract Surg. 2012;38:1251-1265

The Dark Arc Rises

Negative dysphotopsia is a dark crescent-shaped area that is perceived by patients in the temporal visual field 5%-15% of the time following cataract surgery, predominately with "in-the-bag" placement of square-edged acrylic intraocular lenses (IOLs). This phenomenon is very annoying to some patients and has been a source of speculation among ophthalmologists as to its optical etiology and the various remedies to eliminate it in these symptomatic patients.[1,2,3] Proposed causes have included a scotoma resulting from the projection of the square edge of the IOL or of the edge of the anterior capsule onto the peripheral retina. Treatments, including piggyback IOLs, exchange of the IOL with a curved-edged silicone IOL, anterior capsulotomy, and pharmacologic pupil constriction or dilation, have not resulted in consistent improvement in patients' symptoms. Thus, without a clear understanding of the optical source of dysphotopsia, effective prevention and/or correction of this phenomenon has been elusive.

Study Summary

Holladay and colleagues used a ray-tracing technique in a mathematical model eye, the Zemax optical design program (Radiant Zemax, LLC; Redmond, Washington). They investigated the effect of varying the anatomic and optical parameters, including the diameter and position of the pupil in various lighting conditions, the index of refraction of the IOL, the curvature of the edge of the IOL, the depth of the anterior chamber, the anterior-posterior position of the IOL, the optical and visual axis, the axial length, and the anterior extent of the functioning retina in the nasal part of the globe.

Much of what they found has been consistent with anecdotal observations of surgeons and has confirmed the suspected etiology of the effect. The model showed that less obliquely oriented light rays entering the pupil at an acute angle from the temporal side of the eye would be refracted posteriorly if these light rays struck the periphery of the IOL; and rays with an even greater oblique angle would not enter the eye at all, leaving an optical void accounting for a dark crescent-shaped void in the temporal field -- the negative dysphotopsia.

By manipulating various anatomic and IOL variables in the model, they found that predisposing factors for a negative dysphotopsia could include square-edged IOLs composed of acrylic material with a high index of refraction, an increased depth of the position of the IOL behind the pupil, a small pupil diameter, and a nasal position of the pupil relative to the visual axis and with anterior extension of functioning retina in the nasal pars plicata region of the retina. These theoretical conclusions were consistent with some of the clinical observations and theories presented previously in the literature.

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