January 2008




Acting fast to treat congential cataracts

by Matt Young EyeWorld Contributing Editor


Visual deprivation lasting longer than five months may have worse effect on vision

Surgical approach to posterior polar cataract patients includes a careful controlled hydrodelineation to prevent hydraulic perforation at the weakened area of the capsule; new study suggests opacifications like these should be taken out before five months of visual deprivation passes Source: Amar Agarwal, M.D.

Generally speaking, the sooner congenital cataracts are treated, the better for patients’ long-term visual ability. A new study has found more specifically that if in the first months of life, cataract-induced visual deprivation lasts for more than five months, vision will be worse off.

“The present data provide the first evidence that the full development of object feature binding capacities depends on visual input during the first months of life and is particularly susceptible to disturbance if visual deprivation lasts for more than five months,” wrote lead study author Lisa Putzar, psychology, biological psychology and neuropsychology, University of Hamburg, Germany. Ms. Putzar published her study in a recent issue of Vision Research. Even cataract patients who were treated before five months of deprivation didn’t perform as well as controls in some respects. Overall, the study provides a glimpse into the vision of patients many years after they had congenital cataracts and how well they see.

Detrimental cataracts

Ms. Putzar analyzed 14 patients who previously had dense binocular cataracts, dividing them into two groups. The first was treated before six months, were 13 to 48 years old, and had a mean visual acuity of 20/45 in the better eye. The second was treated after six months, were 17 to 33 years old, and had a mean visual acuity of 20/85 in the better eye. A third group of 14 age-matched normal vision controls were tested, as well as a fourth group of 10 visually impaired controls. This fourth group had pattern vision from birth in at least one eye and 20/150 vision in the better eye at the time of testing. Participants were presented with stimuli involving real, illusory, and no contours, and they had to judge quickly whether displays contained contours or not, regardless of whether real. Their reaction times and error rates were recorded. All participants were allowed to wear contact lenses or glasses if visually impaired. “Tests revealed that overall reaction times in the group of normally sighted controls were shorter than in the group of visually impaired controls and in cataract group two,” Ms. Putzar reported. All the groups performed similarly in correctly identifying the stimulus, with group median error rates all below 7%. There were no significant differences in this regard. “In sum, whereas visually impaired controls and cataract patients exhibited similar overall reaction times, cataract patients treated after the age of six months had specific difficulties in perceiving illusory contours, as suggested by the prolonged reaction time differences between illusory and real contours,” Ms. Putzar wrote. “Interestingly, cataract patients treated before the age of six months were indistinguishable from both visually impaired controls and normally sighted controls.”

The subjective experience of how each patient group perceived the visual stimuli was also different. “Asked about their subjective experience with the task, normally sighted controls and visually impaired controls reported the well-known “pop-out effect” for illusory as well as for real contours: squares were detected “on first glance” without the need to sequentially scan the display,” Ms. Putzar reported. “Some cataract patients of group one reported to have occasionally experienced a pop-out effect for illusory contours. By contrast, cataract patients of group two never reported to have perceived a pop-out effect for illusory contours.”

Patients in group two had to search the whole display for clues that an illusory contour was present in the display. That may have been the reason for their prolonged reaction times to detect such contours. It also suggests why error rates were similar—group two simply had to study harder to achieve the same grade, in a sense, Ms. Putzar noted.

Additional experimentation confirmed that cataract patients treated relatively late had trouble identifying illusory contours.

Unilateral worries

While this study tested patients with bilateral cataracts, Mark Packer, M.D., associate clinical professor, Casey Eye Institute, Oregon Health & Science University, Portland, said ironically, patients with unilateral cataract often are worse off visually. “That’s because nerves that go from the eye to the brain will not grow on that [cataract] side,” Dr. Packer said. “That’s what happens when the good eye takes over all the real estate in the brain.” Hence, unilateral congenital cataract is an emergency that needs to be dealt with as soon as possible, within the first three weeks of life, Dr. Packer said. “I would want it taken out as soon as the pediatrician says the child is fine to undergo anesthesia,” he added. Patients can get away with bilateral cataracts a lot longer, Dr. Packer said. He suggested surgery can be delayed six months to even one year of age because both eyes are handicapped, and therefore, one eye will not begin to dominate the other. Still, results of this recent study suggest that waiting—even with bilateral cataracts—may not be ideal if optimal vision is to be reached.

Editors’ note: Ms. Putzar has no financial interests related to her study. Dr. Packer has no financial interests related to his comments.

Contact Information

Packer: 541-687-2110, mpacker@finemd.com

Putzar: (+49)-(0)40/42838-3221, lisa.putzar@uni-hamburg.de

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