| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
From the Department of Optometry and Vision Sciences, The University of Melbourne, Victoria, Australia.
PURPOSE. Recent investigations have suggested that scleral thinning in mammalian eyes with axial myopia is a consequence of the loss of scleral tissue, rather than the redistribution of existing tissue as the eye enlarges. The present study investigated whether further changes in the distribution and metabolism of scleral tissue occur during the process of recovery from axial myopia. Scleral glycosaminoglycan (GAG) synthesis and content as well as scleral dry weight changes were monitored as indicators of remodeling in myopic and recovering tree shrew sclerae.
METHODS. Myopia was induced in tree shrews by monocularly depriving them of pattern vision. Some animals then had the occluder removed and were allowed to recover from the induced myopia for periods of 1, 3, 5, 7, and 9 days. Newly synthesized GAGs were radiolabeled in vivo with [35S]sulfate. Sulfate incorporation and total GAG content in the sclera was measured through selective precipitation of GAGs from proteinase K digests with alcian blue dye. Dry weights of the sclerae were also determined. Changes in ocular refraction and eye size were monitored using retinoscopy, keratometry, and ultrasonography.
RESULTS. Eyes developing myopia showed a significant reduction in scleral GAG synthesis, particularly in the region of the posterior pole (-36% ± 7%) compared with contralateral control eyes. Scleral dry weight was also significantly reduced in these eyes (-3.7% ± 1.2%). In recovering eyes, significant changes in GAG synthesis were apparent after 24 hours of recovery. After 3 days of recovery, significantly elevated levels of GAG synthesis were found (+79% ± 15%), returning to contralateral control eye values after 9 days of recovery. Interocular differences in scleral dry weight were shown to follow a similar pattern to that observed for GAG synthesis.
CONCLUSIONS. Active remodeling, resulting in either the loss or replacement of scleral tissue and not passive redistribution of scleral tissue, is associated with changes in eye size during both myopia development and recovery. Regulatory changes in scleral metabolism can be rapidly evoked by a change in visual conditions and the direction of regulation is related to the direction of change in eye size.
This article has been cited by other articles:
|
|
 |
|
  W. Shen and J. G. Sivak Eyes of a Lower Vertebrate Are Susceptible to the Visual Environment Invest. Ophthalmol. Vis. Sci., October 1, 2007; 48(10): 4829 - 4837. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. G. Moring, J. R. Baker, and T. T. Norton Modulation of Glycosaminoglycan Levels in Tree Shrew Sclera during Lens-Induced Myopia Development and Recovery Invest. Ophthalmol. Vis. Sci., July 1, 2007; 48(7): 2947 - 2956. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Schippert, E. Burkhardt, M. Feldkaemper, and F. Schaeffel Relative Axial Myopia in Egr-1 (ZENK) Knockout Mice Invest. Ophthalmol. Vis. Sci., January 1, 2007; 48(1): 11 - 17. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. A. McBrien, R. Metlapally, A. I. Jobling, and A. Gentle Expression of Collagen-Binding Integrin Receptors in the Mammalian Sclera and Their Regulation during the Development of Myopia Invest. Ophthalmol. Vis. Sci., November 1, 2006; 47(11): 4674 - 4682. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Troilo, D. L. Nickla, J. R. Mertz, and J. A. S. Rada Change in the Synthesis Rates of Ocular Retinoic Acid and Scleral Glycosaminoglycan during Experimentally Altered Eye Growth in Marmosets Invest. Ophthalmol. Vis. Sci., May 1, 2006; 47(5): 1768 - 1777. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Zhou, E. F. Rappaport, J. W. Tobias, and T. L. Young Differential Gene Expression in Mouse Sclera during Ocular Development Invest. Ophthalmol. Vis. Sci., May 1, 2006; 47(5): 1794 - 1802. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. T. Siegwart Jr and T. T. Norton Selective Regulation of MMP and TIMP mRNA Levels in Tree Shrew Sclera during Minus Lens Compensation and Recovery Invest. Ophthalmol. Vis. Sci., October 1, 2005; 46(10): 3484 - 3492. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. I. Jobling, M. Nguyen, A. Gentle, and N. A. McBrien Isoform-specific Changes in Scleral Transforming Growth Factor-{beta} Expression and the Regulation of Collagen Synthesis during Myopia Progression J. Biol. Chem., April 30, 2004; 279(18): 18121 - 18126. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. R. Phillips and N. A. McBrien Pressure-Induced Changes in Axial Eye Length of Chick and Tree Shrew: Significance of Myofibroblasts in the Sclera Invest. Ophthalmol. Vis. Sci., March 1, 2004; 45(3): 758 - 763. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Chakravarti, J. Paul, L. Roberts, I. Chervoneva, A. Oldberg, and D. E. Birk Ocular and Scleral Alterations in Gene-Targeted Lumican-Fibromodulin Double-Null Mice Invest. Ophthalmol. Vis. Sci., June 1, 2003; 44(6): 2422 - 2432. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Gentle, Y. Liu, J. E. Martin, G. L. Conti, and N. A. McBrien Collagen Gene Expression and the Altered Accumulation of Scleral Collagen during the Development of High Myopia J. Biol. Chem., May 2, 2003; 278(19): 16587 - 16594. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. T. Siegwart Jr and T. T. Norton The Time Course of Changes in mRNA Levels in Tree Shrew Sclera during Induced Myopia and Recovery Invest. Ophthalmol. Vis. Sci., July 1, 2002; 43(7): 2067 - 2075. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. A. Austin, C. Coulon, C.-Y. Liu, W. W.-Y. Kao, and J. A. Rada Altered Collagen Fibril Formation in the Sclera of Lumican-Deficient Mice Invest. Ophthalmol. Vis. Sci., June 1, 2002; 43(6): 1695 - 1701. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. A. McBrien, L. M. Cornell, and A. Gentle Structural and Ultrastructural Changes to the Sclera in a Mammalian Model of High Myopia Invest. Ophthalmol. Vis. Sci., September 1, 2001; 42(10): 2179 - 2187. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. T. Siegwart Jr and T. T. Norton Steady State mRNA Levels in Tree Shrew Sclera with Form-Deprivation Myopia and during Recovery Invest. Ophthalmol. Vis. Sci., May 1, 2001; 42(6): 1153 - 1159. [Abstract] [Full Text]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
