The purpose of the proposed research is to develop a model of myopia that could be used to evaluate treatment techniques for ultimate application to humans. Our preliminary experiments have indicated that defocus of the retinal image in domestic chicks for the first three weeks of life results in an increase in the diameter of the globe of the eye that is suggestive of myopia.
The specific aims of the proposed research are to replicate our preliminary findings using more precisely defined optical devices and then to use behavioral techniques to assess the degree of myopia. The myopia will be calculated from a comparison of the far point of accommodation in treated and untreated chicks. Visual acuity and intensity difference thresholds will be determined in order to assess whether the defocussing procedure has produced impairments of visual information processing either in the retina or centrally. If myopia is present in the chicks, an attempt will be made to correct the defect by interposing an optometric trial lens between the cornea and the target. Finally, an attempt will be made to evaluate the hypothesis that a cause of myopia is intensive and prolonged inspection of the spatial properties of visual stimuli close to the near point of accommodation by comparing the eyes of untreated subjects in visual acuity tests with the eyes of another group of chicks that have had equivalent experience with a test of comparable difficulty, but in which the spatial properties of the stimulus are irrelevant. The advantages of such a model are (1) very low expense, (2) very rapid development and (3) suitability for the evaluation of mechanical and surgical treatments for myopia, such as orthokeratosis, radial keratotomy, keratomileusis, hydrogel lenticular implantation, etc.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY004742-04
Application #
3259211
Study Section
Visual Sciences B Study Section (VISB)
Project Start
1983-07-01
Project End
1987-05-31
Budget Start
1986-07-01
Budget End
1987-05-31
Support Year
4
Fiscal Year
1986
Total Cost
Indirect Cost
Name
University of Maryland College Park
Department
Type
Schools of Arts and Sciences
DUNS #
City
College Park
State
MD
Country
United States
Zip Code
20742
Jones, B E; Thompson, E W; Hodos, W et al. (1996) Scleral matrix metalloproteinases, serine proteinase activity and hydrational capacity are increased in myopia induced by retinal image degradation. Exp Eye Res 63:369-81
Hodos, W; Kuenzel, W J (1993) Thermal gradients in the eyes of lid-sutured chicks. Curr Eye Res 12:479-87
Porciatti, V; Hodos, W; Signorini, G et al. (1991) Electroretinographic changes in aged pigeons. Vision Res 31:661-8
Hodos, W; Miller, R F; Fite, K V (1991) Age-dependent changes in visual acuity and retinal morphology in pigeons. Vision Res 31:669-77
Hodos, W; Erichsen, J T (1990) Lower-field myopia in birds: an adaptation that keeps the ground in focus. Vision Res 30:653-7
Hodos, W; Revzin, A M; Kuenzel, W J (1987) Thermal gradients in the chick eye: a contributing factor in experimental myopia. Invest Ophthalmol Vis Sci 28:1859-66
Hodos, W; Fitzke, F W; Hayes, B P et al. (1985) Experimental myopia in chicks: ocular refraction by electroretinography. Invest Ophthalmol Vis Sci 26:1423-30