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Positioning of acrylic IOL decreases negative dysphotopsia
Several factors, including individual anatomical features, IOL factors and neuroadaptation, likely play a role in creating negative dysphotopsia.
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The incidence of negative dysphotopsia after cataract surgery was reduced by positioning the optic-haptic junction of a one-piece acrylic IOL lens inferotemporally, according to a study of five groups of eyes implanted with IOLs.
Conversely, compared with a silicone IOL, a one-piece acrylic IOL appeared to cause a higher incidence of negative dysphotopsia when implanted in the vertical position.
Principal investigator Bonnie A. Henderson, MD, an OSN Cataract Surgery Board Member, said that most of her patients who experience negative dysphotopsia “have perfectly performed, uncomplicated cataract surgeries.”
Henderson began pursuing the notion of attempting to block the light from the inferotemporal quadrant due to a referred patient “who was able to eliminate the symptoms entirely when she used her hand to block the light originating from her inferotemporal quadrant,” she said. “The patient also noticed that the symptoms disappeared when she tilted her chin up and looked down — in other words, effectively using her lower lid to block light originating from the inferior quadrant.”
As a result, Henderson and colleagues experimented by blocking different clock hours around various patients’ eyes and determining those positions that had any effect on the negative dysphotopsia shadow.
“Because of these observations, I started wondering if there was a connection between the angle of the light entering the eye, hitting the edge of certain types of IOL and the development of the negative dysphotopsia shadow,” Henderson told Ocular Surgery News.
Five groups of eyes
The prospective study, published in the Journal of Cataract and Refractive Surgery, divided 418 eyes of 305 patients into five groups: a silicone IOL implanted inferotemporally (39 eyes), a silicone IOL implanted vertically (60 eyes), a one-piece acrylic IOL implanted with the optic-haptic junction inferotemporally (163 eyes), a one-piece acrylic IOL implanted with the junction vertical (114 eyes) and bilateral inferotemporal implantation of a one-piece acrylic IOL (42 eyes).
“Although we studied the incidence of negative dysphotopsia for both acrylic and silicone IOLs, the study was only for the acrylic lens,” Henderson said. “The control group consisted of eyes with the acrylic IOL placed with the optic-haptic junction in the 12 o’clock and 6 o’clock positions.”
There was a 2.3-fold decrease in the incidence of negative dysphotopsia when positioning the optic-haptic junction of an acrylic IOL inferotemporally.
“This significant difference between the control group and the study group was seen as early as the first postoperative day,” Henderson said. “However, the difference was no longer significant in the longer follow-up periods.”
Neuroadaptation
Henderson said it is unclear whether neuroadaptation that allows most patients to ignore negative dysphotopsia occurs within 1 week or up to 1 month, or whether the mechanism of persistent negative dysphotopsia is different from the mechanism for early symptoms.
On the other hand, Henderson firmly believes there is a combination of factors — individual anatomical features, IOL factors and neuroadaptation — “that must be present to create the negative dysphotopsia symptoms,” she said.
Although placing the optic-haptic junction of a one-piece acrylic IOL inferotemporally suggests a lower incidence of negative dysphotopsia symptoms, “it is important to keep in mind that the benefit was short-lived,” Henderson said. “This positioning does not appear to protect from the long-term persistent symptoms that plague many patients.”
Henderson now places all non-toric acrylic IOLs with the optic-haptic junction in the inferotemporal position.
“This has not eliminated negative dysphotopsia symptoms but does appear to have decreased the incidence of early and even long-term complaints. I will continue to elicit symptoms from my patients and track the observations,” she said. – by Bob Kronemyer
- Reference:
- Henderson BA, et al. J Cataract Refract Surg. 2016;doi:10.1016/j.jcrs.2016.08.020.
- For more information:
- Bonnie A. Henderson, MD, can be reached at Ophthalmic Consultants of Boston, 52 Second Ave., Suite 2500, Waltham, MA 02451; email: bahenderson@eyeboston.com.
Disclosure: Henderson reports no relevant financial disclosures.