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PRK can improve visual acuity in adult amblyopic eyes
The procedure may improve visual function in eyes resistant to traditional treatments, investigators say.
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PRK may improve visual acuity in adult amblyopic eyes previously thought to be resistant to traditional methods of treatment, according to a recent study.
“Adults wishing to undergo refractive surgery may undertake such procedures despite an amblyopic eye thought to be refractory to visual rehabilitation by conventional methods, such as spectacles and contact lenses,” said Nicola Rosa, MD, and colleagues at the University of Naples in Italy.
The researchers set out to assess whether PRK could lead to improvement in adult amblyopic patients because they wanted to explore the “proven significant neural plasticity” in adults with and without amblyopia. Traditional thinking suggests that only infants have a visual system malleable enough to correct conditions such as amblyopia, so work in this field with adults is limited, they said.
“Few articles deal with the use of refractive surgery to correct amblyopia in adult patients,” the authors said.
Improved BCVA
The study was a noncomparative case series in which 38 amblyopic eyes of 36 adult patients aged 20 to 59 years underwent PRK for a mean spherical equivalent attempted correction of –6.38 D.
According to the researchers, 30 eyes had compound myopic astigmatism, one eye had myopia, five eyes had mixed astigmatism, and two eyes had hyperopia. BCVA ranged from 0.2 to 0.7 lines.
The eyes were treated with either the Nidek EC 5000 or Schwind Esiris laser. No other amblyopia therapy, such as occlusion, was used postoperatively.
Dr. Rosa and colleagues reviewed patients’ refraction preoperatively and at 1, 3 and 6 months postop. The researchers used linear regression analysis to assess correlations between the difference in BCVA and the amount of treatment, astigmatic changes, achieved correction, preop BCVA, age and difference in refraction between the two eyes.
At 1 month postop, the mean spherical equivalent was 1.52, and BCVA ranged between 0.2 and 1.2 lines, with 22 of 36 eyes gaining one or more lines. At 3 months postop, the mean spherical equivalent was 1.18, and BCVA ranged between 0.15 and 1.15 lines, with 22 of 27 eyes gaining one or more lines. At 6 months postop, the mean spherical equivalent was –1.17, and BCVA was between 0.25 and 1.3 lines, with 21 of 23 eyes showing one or more lines of improvement and 17 of 23 eyes showing two or more lines of improvement.
The researchers said there were no complications, and none of the patients lost BCVA.
No statistically significant correlation was found between the improvement in BCVA and the other parameters of the study.
No concrete explanation
The improvement in BCVA could have resulted from the elimination of visual impairments such as minification and aberrations caused by the use of glasses in myopic eyes, the researchers said. They also speculated that improvement may have been due to an actual reduction of amblyopia, which suggests that adult amblyopic eyes may have a functional reserve uncovered when visual acuity in the fellow eye suddenly deteriorates.
“In post-refractive surgery cases, a sharper image in the operated eye could force the patients to use their hitherto lazy eye,” the authors wrote.
The researchers said that they could not prove whether post-PRK visual improvement was due to one of the suggested factors or a combination of them. They also noted that it was impossible to speculate on other visual functions such as binocular function as they relate to amblyopia.
“Longer follow-up in this kind of patient could prove or disprove the idea that the use of the amblyopic eye could show future improvements, as recent improvement in adult amblyopic eyes after active perceptual learning treatment has been shown,” the authors said.
The findings of the study are not meant to suggest that PRK should be performed in young children to improve visual function or that refractive surgery can cure amblyopia, they added.
For Your Information:
- Nicola Rosa, MD, and colleagues can be reached at the Dipartimento di Oftalmologia, Il Università degli Studi di Napoli, Via Pansini 5, 80100 Napoli, Italy; +39-081-566-6781; fax: +39-081-566-6775; e-mail: nicola.rosa@unina2.it.
Reference:
- Lanza M, Rosa N, et al. Can we utilize photrefractive keratectomy to improve visual acuity in adult amblypic eyes? Ophthalmology. 2005;112:1684-1691.
- Jared Schultz is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses geographically on Europe and the Asia-Pacific region.