IOL Glare and Dysphotopsia
In addition to lens decentration and opacification of the IOL or capsule, glare can result when the diameter of the IOL optic is smaller than the diameter of the scotopic pupil. Optics with a square-edge design and multifocal IOLs are more likely to produce glare and halos, even when well centered. When the pupil is dilated, spherical aberration may cause some degree of distortion or glare under scotopic conditions even when the iris covers the edge of the lens optic. Aspheric IOLs may reduce some of these phenomena and improve contrast sensitivity. Although spherical aberration of the cornea varies in the population and changes with keratorefractive surgery, various aspheric and spherical IOLs can be matched to the degree of corneal asphericity (see Chapter 9).
Patients with diffractive or refractive multifocal IOLs are more likely to experience glare, decreased contrast sensitivity, or loss of desired multifocality with minor IOL decentration, altered pupil diameter or position, or posterior capsule opacity. An accommodating lens may vault anteriorly (a condition known as Z syndrome) because of misplaced haptics or asymmetric capsular contraction. This syndrome can often be managed by posterior capsulotomy, but the lens may need to be surgically repositioned or explanted. Toric IOLs must be located on a precise axis for maximal astigmatic correction. These lenses may need to be repositioned if they are placed improperly or rotate postoperatively. Refer to Chapter 9 for further discussion of toric IOLs, including risk factors for postoperative toric IOL rotation.
Dysphotopsias are abnormal visual symptoms related to light rays interacting with IOL optics (see BCSC Section 3, Clinical Optics). Current research indicates that a central neuroadaptive component may also be involved in patient perceptions of dysphotopsia.
Positive dysphotopsia is
described as glare, streaks, flashes, arcs, or halos of light in the midperiphery
more common with truncated square-edge IOLs and those manufactured from higher-index materials, as well as with multifocal IOLs
Negative dysphotopsia is
described as an arcuate dark or dim crescent-shaped region, usually in the temporal visual field
likely to occur in the routine setting of a PCIOL centered in the capsular bag with the anterior capsule edge overlapping the lens optic
possible with any type of IOL placed within the capsular bag
more common with acrylic, square-edge optics with a higher index of refraction
In susceptible eyes, temporal light rays may interact with the nasal lens edge and overlying anterior capsule, causing a shadow (penumbra) on the nasal retina. This effect is more common with a miotic or nasally located pupil and may be relieved with dilation or by blocking light from the temporal side.
Although negative dysphotopsia symptoms are common in the early postoperative period (approximately 15% of all patients), they improve over time in most patients, presumably because of neuroadaptation or anterior capsule opacification. Only approximately 3% of patients report symptoms at 1 year postoperatively. Thus, initially, observation is advised. For patients with prolonged symptoms and compromised vision, surgery may be necessary. In most cases, repositioning of the optic anterior to the capsulorrhexis by reverse optic capture through the capsulorrhexis (with the haptics in the capsular bag) or sulcus fixation of an appropriate PCIOL is successful. However, when reverse optic capture is performed at the time of initial IOL implantation with cataract surgery, the reported rate of posterior capsule opacification requiring Nd:YAG laser posterior capsulotomy by 3 months postoperatively is 100%. Implantation of a piggyback IOL in the ciliary sulcus, partial nasal anterior capsulotomy, or truncation of the nasal optic within the capsular bag has also been successful in some cases.
Masket S, Fram NR, Cho A, Park I, Pham D. Surgical management of negative dysphotopsia. J Cataract Refract Surg. 2018;44(1):6–16.
Werner L. Glistenings and surface light scattering in intraocular lenses. J Cataract Refract Surg. 2010;36(8):1398–1420.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.