Osteogenesis imperfecta (OI) is a rare connective tissue disorder caused by mutations in the type I collagen genes, COL1A1 and COL1A2, and is characterised by low bone mass and bone fragility. In this study, we explored the relationship between type 1 collagen genes and the quantitative trait central corneal thickness (CCT). CCT was measured in a cohort of 28 Australian type I OI patients and mean CCT was found to be significantly lower compared to a normal population (P < 0.001). We then investigated CCT and corneal collagen fibril diameter and density in a mouse model of OI with a col1a2 mutation. Mean CCT was significantly lower in mutant mice (P = 0.002), as was corneal collagen fibril diameter (P = 0.034), whilst collagen fibril density was significantly greater in mutants (P = 0.034). Finally, we conducted a genetic study to determine whether common single nucleotide polymorphisms (SNPs) in COL1A1 and COL1A2 are associated with CCT variation in the normal human population. Polymorphism rs2696297 (P = 0.003) in COL1A1 and a three SNP haplotype in COL1A2 (P = 0.007) were all significantly associated with normal CCT variation. These data implicate type 1 collagen in the determination of CCT in both OI patients and normal individuals. This provides the first evidence of quantitative trait loci that influence CCT in a normal population and has potential implications for investigating genes involved in glaucoma pathogenesis, a common eye disease in which the severity and progression is influenced by CCT.
Increasing AAC pressure and corneal drying reduced the graft thickness at a very predictable rate. Adequate corneal thinning can be achieved by increasing the pressure in the AAC by closing the clamp followed by removal of the residual corneal epithelium and repeated drying with a cellulose spear for 5 to 10 minutes, depending on the initial corneal thickness. This method is simple and is both suitable for use in the eye bank and by the surgeon.
Eyes affected with orbital plexiform neurofibroma, a hallmark of neurofibromatosis type 1, appear to be associated with increased axial length and myopia. This is of particular importance in children, to diagnose and treat unilateral high myopia early and prevent anisometropic amblyopia.
Subconjunctival Loa loa wormLoa loa (African eye worm) is a subcutaneous nematode that infects several million people in the rainforest belt of western and central Africa. 1 Characteristic clinical features include passage of adult filarial worms across the eye (subconjunctival or in anterior chamber) or Calabar swellings.A 42-year-old man, who had migrated to Australia from Nigeria 2 years previously, presented with the sensation of something crawling over his right eyeball. On examination there was right conjunctival injection and a subconjunctival worm was seen moving in the inferior fornix (Figure 1). Visual acuity was 20/20 bilaterally and the remainder of the ophthalmic examination was unremarkable. General physical examination was also normal with no evidence of lymphedema or subcutaneous swellings. There was no history of Calabar swellings. Blood, urine, and stool investigations were unremarkable except for an eosinophilia of 1.18 Â 10 9 /l (normal range 0.50-1.02) in the differential leukocyte count. Thick blood smears of blood taken at 12:00 noon showed microfilariae (Figure 2). A 5.8 cm long live worm was removed after making an incision in the temporal conjunctiva under topical anesthesia (Figure 3). The worm was fixed in 70% alcohol and then cleared in warm (55 8C) lactophenol for 10 minutes. Following clearing, the worm was series transferred to glycerin through graded glycerin concentrations in lactophenol (25%, 50%, 75%, and 85%), all done at 55 8C for 10 minutes. The worm was mounted in glycerin. Microscopical images and line drawings were produced of the key morphological features to confirm the identification of a gravid female Loa loa (Figures 2, 4, and 5). The patient was treated with 400 mg oral albendazole for 3 weeks and oral
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