Purchase this article with an account.
Sandra Gisbert Martinez, Frank Schaeffel; M to L cone ratios determine eye size in chicks. Invest. Ophthalmol. Vis. Sci. 2018;59(9):694.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Based on a hypothesis by Prof. Jay Neitz, Seattle, proposed at the International Myopia Conference in Tuebingen in 2010, we have tested whether the abundance and the ratio of Long wavelength-sensitive (L) to Middle wavelength-sensitive (M) cones may affect eye size and development of myopia in chickens.
14 chickens were treated with frosted plastic diffusers in front of one eye for a period of 7 days to induce deprivation myopia. Ocular dimensions were measured by A-scan ultrasonography at the beginning and at the end of the treatment and development of refractive state was tracked using infrared photorefraction. At the end of the treatment period, L and M cone densities and ratios were analyzed in retinal flat mounts from both myopic and control eyes, using the red and yellow oil droplets as markers. Because large numbers of cones were counted (>10,000), software was written in Visual C++ written for automated cone detection and density analysis.
(1) On average, 9.7±1.7D of deprivation myopia was induced in 7 days (range from 6.8D to 13.7D) with an average increase in axial length by 0.65±0.20mm (range 0.42mm to 1.00mm), (2) the increase in vitreous chamber depth was correlated with the increase in myopic refractive error, (3) absolute M and L cone densities were variable among individual animals. Average central M cone densities were 10498 cells/mm2; L cone densities: 9574 cells/mm2; peripheral M cone densities: 6343 cells/mm2; peripheral L cones: 5735 cells/mm2). (4) Cone densities were highly correlated in both eyes of each animal (p<0.01 in all cases), (5) the most striking finding was that ratios of M/L cones were significantly correlated with vitreous chamber depths and refractive states in the control eyes with normal vision, both in the central and peripheral retinas (p<0.05 to p<0.01), (6) however, M/L cone ratio had no predictive power for the amount of deprivation myopia that was previously induced.
M and L cone densities and their ratios are probably genetically determined in each animal. The lower the M/L cone ratio in an animal, the deeper the vitreous chambers and the more myopic were the refractions in control eyes. Therefore, M/L cone ratios may determine the set point of emmetropization. Individual deprivation myopia was not dependent on M/L cone ratios. How M/L cone ratios affect set point and eye size needs to be clarified in future studies.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
This PDF is available to Subscribers Only