Simultaneous defocus integration during refractive development

Yan Yin Tse, Siu Yin Lam, Jeremy A. Guggenheim, Chuen Lam, King Kit Li, Quan Liu, Chi Ho To

Research output: Journal article publicationJournal articleAcademic researchpeer-review

63 Citations (Scopus)


PURPOSE. To determine the effects of simultaneously presented myopic and hyperopic defocus on the refractive development of chicks. METHODS. A novel form of dual-power lens was designed. Normal chicks 7 to 8 days of age were fitted with a dual-power lens over one eye and a piano lens over the fellow (control) eye. Dual-power lenses of +20/-10, +10/-10, +5/-10, and plano/-10-D were tested, along with +10/-10-D lenses having differing ratios (50:50, 33.67, and 25:75) of surface area devoted to each power. Ocular refraction and axial ocular component dimensions were assessed after 6 days of lens wear, by retinoscopy and high-frequency ultrasound, respectively. In a separate experiment designed to test the effect of dual-power lens wear on the refractive development of myopic eyes, chicks were fitted with a dual-power +10/-10-D lens for 6 days, after myopia had been induced by 6 days of -10-D lens wear. RESULTS. For each of the dual-power lenses tested, the refractive end point of the treated eye was found to lie between the two optical powers of the lens (but with the response weighted in favor of the effect of myopic defocus). Refractive development appeared to be modulated by the sign, dioptric magnitude, and relative contribution (relative contrast) of the imposed optical defocuses through an integrative mechanism. Chicks with myopia induced by -10-D lens wear recovered when treated with a +10/-10-D dual-power lens. CONCLUSIONS. The chick retina can discern both the sign and the magnitude of optical defocus. Chick eyes were able to integrate blur cues from simultaneously presented images focused either side of the photoreceptors and to modulate their refractive development accordingly. This implies that the complex nature of defocus in the visual environment may play a critical role in the pathogenesis of myopia. The results suggest a rational method for arresting or reversing the development of myopia, which may be useful in the treatment of human myopia if the primate retina is also capable of responding to simultaneously presented opposing defocus cues.
Original languageEnglish
Pages (from-to)5352-5359
Number of pages8
JournalInvestigative Ophthalmology and Visual Science
Issue number12
Publication statusPublished - 1 Dec 2007

ASJC Scopus subject areas

  • Ophthalmology


Dive into the research topics of 'Simultaneous defocus integration during refractive development'. Together they form a unique fingerprint.

Cite this