Effect of muscarinic agents on sclera fibroblast and their role in myopia 1

1 I. Introduction 1.1 Myopia Myopia has reached epidemic proportions in Singapore (Rajan et al 1994, Saw et al 1996). Myopia is 1.5 to 2.5 times more prevalent in adult Chinese residing in Singapore than similarly aged European-derived populations in the United States and Australia where the sociodemographic associations are similar (Wong et al 2000). In the United States 25% of children become myopic and it affects 15-20% of the adult population (Sperduto et al 1983, Hirsch and Weymouth 1990). Optically, myopia is defined as a mismatch between the refractive optics and the length of the eye that causes an image to be focused in front of the retina leading to an out of focus image. High myopia is an important cause of visual disability (Klein et al 1995). It has been noted as the cause of blindness due to the many associated complications, such as retinal break, retinal detachment and myopic retinopathy. Myopia also places a burden on society and on the individual. The cost of glasses, contact lenses and refractive surgery has been estimated to be $13 billion annually (Sheedy 1996). Quality of life issues associated with myopia are also considerable. Myopia limits career choices, social interaction and in underdeveloped countries, myopes may not have corrective choices. Despite the high prevalence and associated social and economic costs of correcting myopia, we know little about the etiology of myopia. 1.1.1 Refractive development Human studies have found that myopia results from axial elongation of the sclera that is not corrected by a concommitant change in corneal curvature. At birth, the cornea and lens are sharply curved so the focal plane is short. As the eye matures, the axial length increases, rapidly at first during the “infant” high growth period and then slowly during the “juvenile” slow elongation period (Sorsby et al 1961). Growth moves the retina away from the cornea and toward the focal plane so that eventually the axial length matches the focal plane, producing an emmetropic eye that focuses distant objects without accommodation. In some cases, the axial length becomes longer than the focal plane, so the image of distant object is focused in front of the retina causing blurring. The eye is approximately 17mm long at birth. From birth to age 6, the eye grows by approximately mm. During this period there will be a loss of 4D of corneal power, and 20D of lens power. Through the process of emmetropisation, the distribution of refractive error becomes narrow and the prevalence of myopia is only 2% at age 6. During the next years, the average eye will grow approximately a millimeter. The prevalence of myopia during this time will increase more than seven fold, to 15% by 15 years of age (Mutti et al 1996). Gross and Wickman (1995) concluded that both emmetropisation and juvenile onset myopia are best explained by a retinal image-mediated biochemical mechanism that modulates eye growth. However, the nature of this growth mechanism has not been elucidated. The emmetropisation mechanism in chickens and tree shrews appear to require visual signals to guide the elongation of the eye. If the focal length is artificially lengthened by wearing a minus-power lens, the eye will elongate until the axial length approximately matches the amount of increase in imposed focal length (Irving et al 1991, Siegwart et al 1993). When the eyes are deprived of form vision with a translucent diffuser, there is no visual image to indicate that the appropriate axial length has been reached. In this situation, elongation continues unchecked, moving the retina past the focal plane (PickettSeltner et al 1988, Wallman et al 1987). If humans have an emmetropisation mechanism similar to that demonstrated in animals, juvenile-onset myopia may occur if a child inherits a dysfunctional emmetropisation mechanism. It is not clear if dysfunction occurs in photoreceptors, in the communication of an unknown signal to the sclera, or in some intrinsic control of sclera growth. This suggests that there may be an emmetropisation feedback loop, and this becomes disrupted in myopia. Several studies have found pharmacological treatments that reduce axial elongation in animal models (Stone et al 1989, McBrien et al 1993, Rohrer et al 1993, Seltner et al 1993), and there are current clinical trials testing some of these in children. 1.1.2 Genetic influences Several lines of evidence point to a role of genetics in the development of myopia. Monozygotic twins tend to resemble each other more closely in refractive error than dizygotic twins. Estimates of heritability (proportion of phenotypic variance explained by heredity) for myopia obtained from monozygotic twins were higher than dizygotic twins (Minkovitz et al 1993,Teikari et al 1988), suggesting a genetic influence. A family history of myopia is associated with the likelihood of developing myopia, although this could also be a result of visual habits such as amount of reading from parents. A greater prevalence of myopia exists among the children of myopic parents than among the children of non-myopic parents. According to the Orinda longitudinal study, prevalence of myopia in children with two myopic parents is 30-40% whereas it is reduced to 20-25% in children with one myopic parent and to S transition of mammalian cells. J Cell Biochem. 1994;54:379-386 209. Reuther GW, Pendergast AM. The roles of 14-3-3 proteins in signal transduction. Vitam Horm. 1996;52:149-75. 210. Richler A, Bear JC. Refraction, nearwork and education: a population study in Newfoundland. Acta Ophthalmol(Copenh). 1980;58:468-478. 211. Robb RM. Refractive errors associated with hemangiomas of the eyelids and orbit in infancy. Am J Ophthalmol 1977;83:52-8. 212. Roberts AB and Sporn MB. Physiological actions and clinical applications of transforming growth factor beta (TGF-beta). Growth factors 1993;8:1-9. 213. Roberts AB and Sporn MB. The transforming growth factor beta In :Sporn MB and Robers AB (eds). Handbook of experimental pharmacology, 1990;90:419-472. 214. Roberts, A.B., Heine UI, Flanders KC, Sporn MB (1990) Transforming growth factor-beta. Major role in regulation of extracellular matrix. Ann N Y Acad Sci. 1990, 580: 225-32. 215. Roeb E, Graeve L, Hoffman R, Decker K, Edwrds D, Heinrich P. Regulation of tissue inhibitor of metalloproteinase gene expression by cytokines and dexamethasone in rat hepatocyte primary cultures. Hepatology 1993;18:1437-1442. 150 216. Rohrer B, Negishi K, Tao J, Stell WK. A role for basic fibroblast growth factor(bFGF) in the visually guided regulation of eye growth in the chick. IOVS. 1993;34(Suppl):1209 abstract 2489. 217. Rohrer B, Stell WK. Basic fibroblast growth factor(bFGF) and transforming growth factor-beta(TGF-beta) act as stop and go signal to modulate postnatal ocular growth in the chick. Exp Eye Res. 1994;58:553-562. 218. Rudd CE, Janssen O, Prasad KV, Raab M, da Silva A, Telfer JC, Yamamoto M. src-related protein tyrosine kinases and their surface receptors. Biochim Biophys Acta. 1993;1155:239-66. 219. Sainsbury JRC, Needham GK, Farndon JR, Malcolm AJ, Harris AL. Epidermal growth factor receptor status as predictor of early recurrence of and death from breast cancer. Lancet 1987;1:1398-1402. 220. Sampson WG. Role of cycloplegia in the management of functional myopia. Tr Am Acad Ophthalmol Otolaryngol. 1979;86:695-697. 221. Sato Y. Aturocrinological role of bFGF on tube formation of fascular endothelial cells in vitro. Biochem Biophy Res Comm. 1991;180:1098-1102 222. Saw SM, Chua WH, Wu HM, Yap E, Chia KS, Stone RA. Myopia: gene- environment interaction. Ann Acd Med Singapore. 2000;29:290-297. 223. Saw SM, Katz J, Schein OD, Chew SJ, Chan TK. Epidemiology of myopia. Epidemiology Rev. 1996;18:175-187. 224. Schaeffel F, Bartman M, Hagel G et al. Studies on the role of the retinal dopamine/melatonin system in experimental refractive errors in chickens. 1995;35:1247-1264. Vision Res. 151 225. Schaeffel F, Howard HC. Mathematical model of emmepropisation in the chicken. J Opt Soc Am. 1988;5:2080-2086. 226. Schreiber AB, Liberman TA, Lax I, Yarden Y, Schlessinger J. Biological role of epidermal growth factor receptor clustering. J Biol Chem. 1983; 258:846-853. 227. Seko Y, Shimokawa H, Tokoro T. Expression of bFGF and TGF-beta2 in experimental myopia in chicks. IOVS. 1995;36:1183-1187. 228. Seko, Y., Shimokawa H, Tokoro T. In vivo and in vitro association of retinoic acid with form-deprivation myopia in the chick. Exp Eye Res. 1996, 63 (4): 443-52. 229. Seko, Y., Shimokawa, H., Shimizu, M. and Tokoro, T. In vivo and in vitro association of retinoic acid with form-deprivation myopia in chicks. IOVS, 1995;36, (Suppl.) 3510 230. Seko, Y., Tanaka, Y., and Tokoro, T. Influence of bFGF as a potent growth stimulator and TGF-β as a growth regulator on scleral chondrocytes and scleral fibroblasts in vitro. Ophthalmic Res. 1995, 27: 144-52 231. Seltner RLP, Tao J, Rohrer B, Stell WK. A role for vasoactive intestinal polypeptide(VIP) in growth and form-deprivation myopia(FDM) in the chick eye. IOVS. 1993;34(Suppl); 1210 abstract 2490. 232. Shapiro A, Yanko L, Nawratzki I et al. Refractive power of premature children at infancy and early childhood. Am J Ophthalmol. 1980;90:234-238. 233. Sheedy JE. What is the role of glasses in optometry ? Optom Educ. 1996;21:111- 113. 234. Sherman SM, Norton TT, Casagrande VA. Myopia in the lid sutured tree shrew. Brain Res. 1977;124:154-157. 152 235. Shi NY, Floyd-Smith G. Protein kinase C-delta mRNA is down-regulated transcriptionally and post-transcriptionally by 12-O-tetradecanoylphorbol-13-acetate. J Biol Chem. 1996;271:16040-6. 236. Shih YF, Chen CH, Chou AC, Ho TC, Lin LL, Hung PT. Effect of different concentrations of atropine on controlling myopia in myopic children. J Ocul Pharmacol Ther 1999;15:85-90. 237. Shotwell AJ. Plus lens, prism, and bifocal effects on myopia progression in military students. Part III. Am J Optom. 1984;61:112-117 238. Siegwart JT, Norton TT. Refractive and ocular changes in tree shrews raised with puts or minus lenses. IOVS. 1993;34(Suppl):1208 abstract 2482. 239. Siegwart JT, Norton TT. Regulation of the mechanical properties of tree shrew sclera by the visual environment. Vision Res. 1999;39:387-407. 240. Sievers J, Hausman B, Unsicker K, Berry M. Fibroblast growth factors promote the survival of adult rat retinal ganglion cells after transection of the optic nerve. Neurosci Lett. 1987;76:157-162 241. Siow YL, Kalmar GB, Sanhera JS, Tai G, Oh SS, Pelech SL. Identification of two essential phosphorylated threonine residues in the catalytic domain of Mekk1. Indirect activation by Pak3 and protein kinase C. J Biol Chem. 1997;272:7586-94. 242. Sirakawa F, Mizel SB. In vitro activation and nuclear translocation of NF-kappa B catalyzed by cyclic AMP-dependent protein kinase and protein kinase C. Mol Cell Biol. 1989;9:2424-30. 243. Sivak JG, Barrie DL, Callender MG, Doughty MJ, Seltner RL, West JA. Optical causes of experimental myopia. In: Myopia and the control of eye growth(Ciba foundation 153 symposium 155, Bock G, Widdows K eds), John Wiley & Sons Ltd, Chichester, 1990;160177. 244. Smith EL 3rd, Bradley DV, Fernandes A, Boothe RG. Form deprivation myopia in adolescent monkeys. Optom Vis Sci. 1999;76:428-432. 245. Smith EL 3rd, Hung LF, Kee CS, Qiao Y. Effects of brief period of unrestriced vision on the development of form-deprivation myopia in monkeys. IOVS. 2002;43:291299. 246. Smith EL 3rd, Hung LF. Form-deprivation myopia in monkeys is graded phenomenon. Vision Res. 2000;40:371-381. 247. Smith EL, Fox DA, Duncan GC. Refractive error changes in kitten eyes produced by chronic on-channel blockade. IOVS. 1985:26(suppl):331. 248. Sommers D, Kaiser-Kupfer MI, Kupfer C. Increased axial length of the eye following neonatal lid suture as measured with A-scan ultrasonography (Abstract). IOVS. 1978;17:S295. 249. Sorsby A, Benjzmin B, Sheridan M, Stone J, Leary GA. Refraction and its components during the growth of the eye from the age of three. Med Res Counc Spec Rep Ser. 1961;301:1-67. 250. Sorsby A, Leary GA. A longitudinal study of refraction and its components during growth. London, England: Her Majesty’s Stationery Office;1970. 251. Sperduto RD, Siegel D, Roberts J, Rowland M. Prevalence of myopia in the United States. Arch Ophthalmol. 1983;101:405-407 252. Sporn MB and Roberts AB. Transforming growth factor beta: recent progress and new challenges. J of Cell Biol. 1992;119:1017-1021. 154 253. Stachowiak MK, Moffet J, Maher P, Tucholski J, Stachowiak EK. Growth factor regulation of cell growth and proliferation in the nervous system. A new intracrine nuclear mechanism. Mol Neurobiol. 1997;15:257-283. 254. Stone RA, Laties AM, Raviola E, Wiesel TN. Increase in retinal vasoactive intestinal polypeptide after eyelid fusion in primates. Proc Natl Acad Sci USA. 1988;85:257-260. 255. Stone RA, Lin R Laties AM, Iuvone PM. Retinal dopamine and form deprivation myopia. Proc Natl Acad Sci USA. 1989;86:704-706. 256. Stone RA, Lin T, Laties AM. Muscarinic antagonist effects on experimental chick myopia. Exp Eye Res. 1991;52:755-758. 257. Tay MT, Au Eong KG, Ng CY, Lim MK. Myopia and education attainment in 421,116 young Singaporean males. Ann Acad Med Singapore. 1992;21:785-791. 258. Teikari JM, Kaprio J, Koskenvuo MK, et al. Hereditability estimate for refractive errors: A population –based sample of adult twins. Gen Epidemiol. 1988; 5:171-181. 259. Tigges M, Tigges J, Fernandes A, Eggers HM, Gammon JA. Postnatal axial eye elongation in normal and visually deprived rhesus monkeys. IOVS. 1990;31:1035-1046. 260. Tokoro T, Suzuki K. Changes in ocular refractive components and development of myopia during seven years. Jpan J Ophthalmol.1969;13:27-34. 261. Tokoro T. Experimental myopia in rabbits. IOVS. 1970;9:926-934. 262. Totani L, Piccoli A, Pellegrini G, Di Santo A, Lorenzet R. Polymorphonuclear leukocytes enhance release of growth factors by cultured endothelial cells. Arteriorscler Thromb 1994;14:125-132. 155 263. Tredici TJ. Role of orthokeratology : a perspective. Ophthalmology. 1979;86:698-705 264. Troilo D, Gottlieb MD, Wallman J. Visual deprivation causes myopia in chicks with optic nerve section. Curr Eye Res 1987;6:993-999. 265. Troilo D, Judge SJ. Ocular development and visual deprivation myopia in the common marmoset (Callithrix jacchus). Vision Res. 1993;33:1311-1324. 266. Troilo D, Wallman J. Experimental emmetropisation in chicks. IOVS 1988;29 (suppl)76. 267. Vainikka S. Fibroblast growth factor receptor shows novel features in genomic structure, ligand binding and signal transduction. EMBO. 1992;11:4273-4280. 268. von Noorden GK, Crawford MLJ. Lid-closure and refractive error in macaque monkeys. Nature 1978;272:53-54. 269. von Noorden GK, Lewis RA. Ocular axial length is unilateral congenital cataracts and blepharoptosis. IOVS 1987;28:750-752. 270. Walicke P, Cowan WM, Keno N, Baird A, Guillemin R. Fibroblast growth factor promotes survival of dissociated hippocampal neurons and enhances neurite extension. Proc Natl Acad Sci. 1986;83:3012-3016 271. Wall man J . Nature and nurture of myopia. Nature. 1994;371:201-202 272. Wallman J, Adams JI. chicks:Susceptibility, Developmental aspects of experimental myopia in recovery and relation to emmetropisation. Vision Res. 1987;27:1139-1163. 273. Wallman J, Gottlieb MD, Rajaram V, Fugate-Wentzek LA. Local retinal regions control local eye growth and myopia. Science 1987;237:73-77. 156 274. Wallman J, Turkel J, Trachtman J. Extreme myopia produced by modest changes in early visual experience. Science. 1978;201:1249-1251. 275. Wallman J, Wildsoet C, Xu A et al. Moving the retina: Choroidal modulation of refractive state. Vision Res 1995;35:37-50. 276. Wells JA. Structural and functional basis for hormone binding and receptor oligomerization. Curr Opin Cell Biol. 1994;6:163-73. 277. Werner S, Weinberg W, Liao X, Peters KG, Blessing M, Yuspa SH, Weiner RL, Williams LT. Targeted expression of a dominant negative FGF receptor mutant in the epidermis of transgenic mice reveals a role of FGF in keratinocyte organisation and differentiation. EMBO. 1993;12:2635-2643. 278. Werner S. Differential splicing in the extracellular region of fibroblast growth factor receptor generates receptor variants with different ligand binding specificities. Mol Cell Biol. 1992;12:82-88. 279. Wess J, Bonner TI, Dorje F, Brann MR. Delineation of muscarinic receptor domains offering selectivity of coupling to guanine nucleotide binding proteins and 2nd messengers. Mol Pharmacol. 1990;38:517-523 280. Wiesel TN, Raviola E. Increased in axial length of the macaque monkey eye after corneal opacification. IOVS 1979;18:1232-1236. 281. Wiesel TN, Raviola E. Myopia and eye enlargement after neonatal lid fusion in monkeys. Nature. 1977;266:66-68. 282. Wildsoet C, Wallman J. Choroidal and scleral mechanisms of compensation for spectacle lenses in chicks. Vision Res 1994;35: 157 283. Wildsoet CF, Pettigrew JD. Kainic acid induced eye enlargement in chickens differential effects on anterior and posterior segments. IOVS. 1988;29:311-319. 284. Wildsoet CG, McBrien NA, Clark IQ. Atropine inhibition of lens-induced effects in chick: evidence for similar mechanisms underlying form deprivation and lens induced myopia. IOVS. 1994;35:S2068. 285. Woessner JF. The matrixmetalloproteinase family in : Parks WC Mecham RP, eds. Matrix metalloproeinases. San Diego; Academic Press; 1998:1-14 286. Wojtowicz-Praga SM, Dickson RB, Hawkins MJ. Matrix metalloproteinase inhibitors. Invest New Drugs. 1997;15:61-75. 287. Wolfman A, Macara IG. Elevated levels of diacylglycerol and decreased phobolester sensitivity in ras- transformed fibroblasts. Nature. 1987;325:359-361 288. Wong TY, Foster PJ, Hee J, Ng TP, Tielsch JM, Chew SJ et al . Prevalence and risk factors for refractive errors in adult Chinese in Singapore. IOVS. 2000;41:24862494. 289. Wu YR. DNA collagen and uronic acid in form deprivation myopia. IOVS. 1990;31:S254. 290. Yarden Y, Ullrich A. Growth factor receptor tyrosine kinases. Ann Rev Biochem. 1988; 57:443-478. 291. Yayon A, Klagsbrun M, Exko JD, Leder P, Ornitz DM. Cell surface, heparin-like molecules are required for binding of basic fibroblast growth factor to its high-affinity receptor. Cell 1991;64:841-848. 292. Yen MY, Liu JH, Kao SC, Shiao CH. Comparison of the effect of atropine and cyclopentolate on myopia. Ann Ophthalmol. 1989;21:180-187 158 293. Yen MY, Liu JH, Kao SC, Shiao CH. Comparison of the effect of atropine and cyclopentolate on myopia. Ann Ophthalmol. 1989;21:180-182. 294. Yinon U, Koslowe KC, Label D, Landshman N, Barishak YR. Lid suture myopia in developing chicks:optical and structural considerations. Curr Eye Res. 1983;2:877-882. 295. Yinon U, Koslowe KC. Hypermetropia in dark reared chicks and the effect of lid suture. Vision Res 1986;26:999-1005. 296. Yinon U, Rose L, Shapiro A. Myopia in the eye of developing chicks following monocular and binocular lid closure. Vision Res 1980;20:137-141. 297. Yinon U. Myopia induction in animals following alteration of the visual input during development: a review. Curr Eye Res 1984;3:677-690. 298. Young FA, Leary GA, Baldwin WR et al . The transmission of refractive errors within Eskimo families. Am J Optom Arch Am Acd Optom. 1969;46:676-685. 299. Young FA. The effects of restricted visual space on the primate eye. Am J Ophthalmol. 1961;52:799-806. 300. Yu AE, Hewitt RE, Kleiner DE, Stetler-Stevenson WG. Molecular regulation of cellular invasion-role of gelatinase A and TIMP-2. Biochem Cell Biol. 1996;74:823-831 301. Zachary I, Rozengurt E. Focal adhesion kinase (p125fak); a point of convergence in the action of neuropeptides, integrins and oncogenes. Cell. 1992;71:891-894. 302. Zadnik K, Satariano WA, Mutti DO et al. The effect of parental history of myopia on children’s eye size. JAMA.1994;271:1323-1327. 303. Zadnik K, Mutti DO, Friedman NE, Adams AJ. Initial cross-sectional results from the Orinda Longitudinal Study of Myopia. Optom Vis Sci.1993; 70:750-758. 159 304. Zadnik K, Mutti DO. How applicable are animal myopia models to human juvenile onset myopia. Vision Res. 1995;35:1283-1288 [...]... deprivation in chick and in rhesus monkey (Stone et al 19 89 ,19 91, Iuvone 19 91) In chicks, normalisation of retinal dopamine correlated with recovery from myopia (Pendrak et al 19 97) Use of atropine Historically atropine was used because it is a cycloplegic agent in human antagonising the mAChRs of the cilliary muscle It also reduces axial elongation in deprivation models of myopia (McBrien et al 19 93, Stone.. .11 19 56, Kalina 19 69, Fledelius 19 76, Shapiro et al 19 80, Kushner 19 82, Koole et al 19 90, Gallo et al 19 91, Fledelius 19 93) Johnson and colleagues (19 82) have described axial myopia in one eye in one sibling of a pair of identical twins, which had a posterior subcapsular cataract Von Noorden and Lewis (19 87) examined 10 young patients who had unilateral cataracts and in seven out of ten cases the involved... monkey and dopamine was decreased in both chick and monkey (Iuvone et al 19 89, Stone et al 19 88 ,19 89) A recent study found that glucagon-containing amacrine cells respond differentially to the sign of defocus and may mediate lens-induced changes in ocular growth refraction (Fischer et al, 19 99) Local application of the dopamine agonist, apomorphin blocked the axial elongation that ordinarily follows... (VIP) in the control of eye growth (Schaeffel et al 19 95, Stone et al 19 88) 13 1. 1.9 Pharmacology of myopia Several studies have reported the modulation of the effect of pharmacological agents on experimental myopia Raviola and Wiesel (19 85) found that atropine had no effect in the rhesus macaque, but prevented axial elongation in the stump-tailed macaque Wildsoet and Pettigrew (19 88) have shown that intravitreal... (TNF-α) (Moses 19 97, Wojtowicz-Praga et al 19 97) 18 1. 2.2 Sclera fibroblast control Sclera cells are the final effectors in a complex signal cascade leading to axial elongation Several studies have established the effectiveness of atropine in decreasing the progression of axial length in humans and in experimental myopia, however the mechanism is still elusive Atropine may act directly on sclera fibroblasts... range between 51 kd and 66 kd (Kerlavage et al 19 87, Ashkenazi et al 19 88) 1. 2 Sclera Alteration in visual experiences can increase scleral growth, leading to axial elongation and myopia (Hodos et al 19 84, March-Tootle et al 19 89, Sherman et al 19 77, Tigges et al 19 90, Wallman et al 19 78, Wiesel et al 19 77, Yinon et al 19 80) It has been reported that the cartilaginous part of the sclera of form deprived... elongation (Wallman et al 19 78, Norton et al 19 90) Active sclera growth is a primary event in the axial elongation therefore control of the sclera fibroblast may lead to a possible therapy for myopia prevention or decreasing the development of myopia 17 1. 2 .1 Matrix Metalloproteinases (MMPs) Evidence has been obtained that the sclera extracellular matrix (ECM) remodelling of the sclera is part of. .. al 19 91) In the case of chicks, the ciliary muscle is striated and therefore is innervated via nicotinic rather than muscarinic cholinergic receptors (McBrien et al 19 93) Therefore the effect of 14 atropine must have been exerted on the retina or directly on the sclera Indeed, there is evidence that atropine inhibits cellular proliferation of sclera chondrocytes and extra cellular matrix production... pirenzepine, may slow axial elongation in both experimental and clinical myopia (Cottrial et al 19 96) Pharmacological treatment of myopia and its potential widespread application raise a number of questions Experimental myopia leads to an increase in ECM production and accumulation of proteoglycans within the cartilaginous sclera while fibrous sclera was opposite as similarly observed in monkey and tree... response of sclera fibroblasts to atropine A culture system for sclera fibroblasts will be developed and used to test the effect of atropine on proliferation, receptor activity and intracellular signal transduction pathways To test the overall hypothesis, the following specific phenomena will be studied 1 The presence of muscarinic receptors in sclera fibroblasts (SF) 2 The response of SF to muscarinic agents . apomorphin blocked the axial elongation that ordinarily follows visual deprivation in chick and in rhesus monkey (Stone et al 19 89 ,19 91, Iuvone 19 91) . In chicks, normalisation of retinal dopamine. myopia, specifically VIP was increased in monkey and dopamine was decreased in both chick and monkey (Iuvone et al 19 89, Stone et al 19 88 ,19 89). A recent study found that glucagon-containing. explained as the effect of a reduction in pattern vision. Raviola and Wiesel (19 85) went on to examine the effects of optic nerve section on lid suture myopia. In one stump tailed macaque myopia