Abstract
Abstract: :
Purpose: Kroeger and Binder (Brit J Ophthalmol 2000; 84: 890-893) reported that accommodation was reduced in human subjects when they read in monochromatic blue compared to red light. In contrast, emmetropization in chickens did not seem to compensate for chromatic defocus (385nm versus 665nm; Rohrer et al, J Physiol 1992; 449: 363-376). The apparently different response of accommodation and emmetropization to chromatic defocus was studied again in both humans and chickens because it may provide new insight into the interactions of both. Methods: Refractions of 5 emmetropic subjects were recorded with the PowerRefractor (Choi et al, OVS 2000; 77: 537-548) while they were reading at 3D target distance in light of 6 different quasi-monochromatic spectral compositions (between 430nm and 655nm). Refractions of 10 chickens were also measured while the wavelength of the room light was restricted to either 430nm or 615nm. In addition, 10 animals were reared at the same wavelengths for 2 days and their refractive states subsequently determined either in complete darkness or in the monochromatic light. Ambient illuminance was adjusted according to the photopic spectral sensitivity functions in all cases, using ND filters. Results: Our results confirmed the initial observation by Kroeger and Binder that there is about 0.8D less accommodation at 480nm than at 655nm (p<0.0001; paired t-test). Also chickens accommodated 1.040.76D less in the blue than in the red (p<0.0001). After rearing in blue light for 2 days, their refractive states were 1.411.00D more hyperopic than in the red (p<0.0001). The induced changes in accommodation and, later, in refractive states were not significantly different from each other Conclusion: Chromatic aberration produces small but predictable shifts in accommodation in humans and both in accommodation and refractive states in chickens and humans. The fact that these effects were not seen in the first study by Rohrer et al, may result from either insufficient resolution of the refracting device or from the fact that near UV light was used rather than 480nm. It is difficult, however, to explain the changes in refractive states as a consequence of lags of chromatic accommodation.
Keywords: 304 accommodation • 397 emmetropization • 481 myopia