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Ains-The age-related changes in the biochemical composition of the collagenous matrix of the human lamina cribrosa were investigated. Methods-An age range (3 weeks to 92 years old) of human laminae cribrosae, dissected free of any surrounding structures which contained collagen, were analysed for collagen solubility (n= 58) total collagen content (n=46), proportion of collagen types (n=38), and collagen cross linking (n=30), using hydroxyproline analysis, scanning densitometry of peptides after cyanogen bromide digestion, and high performance liquid chromatography, respectively. Results-Age-related changes included an increase in total collagen and a decrease in the proportion of type III collagen within the lamina cribrosa. The collagen cross link pyridinoline was present at low levels, but demonstrated no trend with age. An age-related increase was found in pentosidine, an advanced glycation product. Conclusion-These changes in collagen composition imply that the mechanical properties of the lamina cribrosa are altered, resulting in a stiffer, less resilient structure with age. Such alterations in structure may contribute to the increased susceptibility of the elderly to axonal damage in chronic open angle glaucoma. (Br_7 Ophthalmol 1995; 79: 368-375)

In order to identify possible risk factors for microbial keratitis the storage cases for contact lenses of 102 asymptomatic lens wearers were tested for contamination by bacteria and free-living amoebae. Of this group 43 had significant counts ofviable bacteria and only 40 had negligible counts. Seven had contamination by acanthamoebae, of whom six also had significant bacterial counts. These results were categorised according to the type of contact lens worn and the lens disinfection method. The high rates of contamination by apathogenic and pathogenic organisms, in particular Acanthamoeba, and the probable support by contaminating bacteria of Acanthamoeba, are discussed.

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SUMMARY Sixty-seven patients with keratoconus were classified according to atopic status. Keratoconus patients with and without atopy did not differ significantly with regard to sex, age of onset, or rate of keratoplasty, but patients with very high IgE levels were more prone to graft rejection. Atopy was less common in patients with unilateral keratoconus, and keratoconus occurred more frequently on the side of the dominant hand. There was a significantly lower frequency of HLA B7 in the keratoconus group than in the controls. No abnormalities of essential fatty acid metabolism were found in keratoconus patients with or without atopy. There was no social class bias in the group. The study included a brother and sister with keratoconus and atopy, and a non-atopic patient whose identical twin did not have keratoconus.

Aims-To investigate changes in the mechanical compliance of ex vivo human lamina cribrosa with age. Methods-A laser scanning confocal microscope was used to image the surface of the fluorescently labelled lamina cribrosa in cadaver eyes. A method was developed to determine changes in the volume and strain of the lamina cribrosa created by increases in pressure. The ability of the lamina cribrosa to reverse its deformation on removal of pressure was also measured. Results-Volume and strain measurements both demonstrated that the lamina cribrosa increased in stiVness with age and the level of pressure applied. The ability of the lamina cribrosa to regain its original shape and size on removal of pressure appeared to decrease with age, demonstrating an age related decrease in resilience of the lamina cribrosa. Conclusions-The mechanical compliance of the human lamina cribrosa decreased with age. Misalignment of compliant cribriform plates in a young eye may exert a lesser stress on nerve axons, than that exerted by the rigid plates of an elderly lamina cribrosa. The resilience of the lamina cribrosa also decreased with age, suggesting an increased susceptibility to plastic flow and permanent deformation. Such changes may be of importance in the explanation of age related optic neuropathy in primary open angle glaucoma. (Br J Ophthalmol 2000;84:318-323) The lamina cribrosa is a lattice-like structure, consisting of successive perforated cribriform plates across the optic nerve canal, through which pass bundles of nerve fibres. The plates are lined by basement membranes and their cores are filled with significant amounts of fibrillar collagens and elastic fibres. During ageing, the constituents of these cribriform plates are altered. [1][2][3][4] It is likely that such changes will alter the mechanical behaviour of the ageing lamina cribrosa and therefore compromise its ability to support the nerve axons that pass through it.The distribution of axonal loss in early glaucoma appears to be related to regional diVerences in architecture of the lamina cribrosa. The superior and inferior regions of the lamina cribrosa, which exhibit greater pore size and less dense connective tissue, are thought to be more susceptible to axonal damage.5 6 The arcuate retinal ganglion cell axons, which pass through these regions, are damaged first in early glaucoma.The cause of glaucomatous axonal damage is unknown; ischaemia and mechanical damage as a result of a raised intraocular pressure or rearrangement of the cribriform plates are among the theories that have been proposed. [7][8][9] Whatever the cause, compression of the lamina cribrosa appears to occur before detectable glaucomatous field loss. 10Age related changes in the lamina cribrosa include increases in the amounts of collagen types I, III, and IV 3 4 within the cribriform plates, which lead to an overall increase in total collagen content. [1][2][3] We have also demonstrated alterations in the ratio of collagen types I and III and an increase in non-enzymatic glyc...

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