Table 1
Alterations seen in the aging cornea
| Characteristic | Result of change | |
|---|---|---|
| (1) Changes in shape and optical properties | (i) Steepening of keratometry and a shift from with the rule to against the rule astigmatism38 39 | |
| (ii) Transparency is unaffected in central cornea in absence of scar or degeneration40 | ||
| (iii) Collagen intramolecular and interfibrillar spacing increases—possibly via increased protein glycation41 42 | ||
| (iv) Increased thickness of Descemet’s membrane | ||
| (2) Corneal degenerations (influenced by environmental and genetic factors) | (i) Cornea farinata | |
| (ii) White limbus girdle | ||
| (iii) Mosaic degeneration | ||
| (iv) Deep crocodile shagreen | ||
| (v) Hassall–Henle bodies | ||
| (vi) Arcus senilis | ||
| (3) Physical properties | (i) Resistance to infection reduced | |
| (ii) Failure to upregulate ICAM-1 and reduced inflammatory cell infiltration43 | ||
| (iii) Reduced phagocytically active cells after infection44 | ||
| (iv) Decline in high energy metabolism45 | ||
| (v) Increased tear contact time46 | ||
| (vi) Increased epithelial permeability to flourescein47 | ||
