Search

Confocal microscopy (CM) of keratoconus is reviewed. In the Manchester Keratoconus Study (MKS), slit scanning CM was used to evaluate 29 keratoconic patients and light microscopy (LM) was performed on two of the keratoconic corneas post-keratoplasty. The findings of the MKS are compared with other CM studies. Consideration of the differences between studies of cell counts is confounded by the use of different experimental controls. A consensus exists among studies with respect to qualitative observations. The epithelium appears more abnormal with increasing severity of keratoconus. In severe disease, the superficial epithelial cells are elongated and spindle shaped, epithelial wing cell nuclei are larger and more irregularly spaced and basal epithelial cells are flattened. Bowman's layer is disrupted and split in the region of the cone and intermixed with epithelial cells and stromal keratocytes. Stromal haze and hyper-reflectivity observed with CM correspond with apical scarring seen with the slitlamp biomicroscope (SLB). Hyper-reflective keratocyte nuclei are thought to indicate the presence of fibroblastic cells. Increased haze detected with CM is found with LM to be due to fibroblastic accumulation and irregular collagen fibres. Dark stromal bands observed with CM correlate with the appearance of Vogt's striae with SLB. Desçemet's membrane appears normal with both CM and LM. Some evidence of endothelial cell elongation is observed with CM. The application of CM to ophthalmic practice has facilitated a greater understanding of medical and surgical approaches that are used to treat keratoconus. This review offers new perspectives on keratoconus and provides a framework, against which tissue changes in this visually debilitating condition can be studied in a clinical context in vivo using CM.

Purpose: To evaluate the corneas of keratoconic subjects using in vivo confocal microscopy., Methods: Slit scanning confocal microscopy was used to evaluate the central cornea of one eye of each of 29 keratoconic subjects (mean age 31 +/- 10 years; range 16-49 years). Quantitative aspects of corneal morphology were compared against data from control subjects., Results: Compared with normal control corneas, epithelial wing cell nuclei were larger (p < 0.0001) and epithelial basal cell diameter was larger (p < 0.05) in the keratoconic cornea. Many of the keratoconic corneas investigated showed increased levels of stromal haze and reflectivity, which appeared to be related to the presence of apical scarring on slit lamp examination. A grading scale was devised to quantify the levels of haze. This scale was shown to provide a measure of the level of scarring present. The anterior keratocyte density (AKD) and posterior keratocyte density were 19% lower (p < 0.0001) and 10% lower (p = 0.004) than in controls, respectively. The reduction in AKD was significantly associated with three factors: a history of atopy, eye rubbing and the presence of corneal staining. The mean endothelial cell density in keratoconus was 6% greater than that of normal controls (p = 0.05). The level of endothelial polymegethism was shown not to be different between keratoconic subjects and matched controls (paired t-test: t = 1.82, p = 0.08)., Conclusions: Confocal microscopy demonstrates significant quantitative alterations of corneal morphology in keratoconus.

Objective: To compare morphologic features of keratoconus as observed in vivo with a slit scanning confocal microscope and in vitro using light microscopy., Methods: Slit scanning confocal microscopy (CM) was used to evaluate the central cornea of 29 keratoconic subjects (mean age, 31 +/- 10 years; range, 16-49). Light microscopy (LM) examination was performed on 2 of the keratoconic corneas post-keratoplasty., Results: With CM, the epithelium appeared more abnormal with increasing severity of keratoconus. In severe disease, the epithelium displayed the following characteristics: superficial cells were elongated and spindle shaped, wing cell nuclei were larger and more irregularly spaced, and basal cells were flattened. These findings were confirmed by LM. Images obtained using CM revealed disruption to Bowman's layer and the occasional presence of epithelial cells and stromal keratocytes. This was shown with LM to be due to breaks in Bowman's layer. Stromal haze and hyperreflectivity observed with CM corresponded with apical scarring seen on slit-lamp biomicroscopy. Hyperreflective keratocyte nuclei observed with CM are thought to indicate the presence of fibroblastic cells seen with LM. Increasing levels of haze detected with CM were found with LM to be due to fibroblast accumulation and irregular collagen fibers. Descemet's membrane appeared normal with both CM and LM. Evidence of endothelial cell elongation was apparent in 1 subject with CM., Conclusions: The current study confirms the application of CM for assessing morphologic alterations to the epithelium, Bowman's layer, and stroma in keratoconus. Many of the tissue changes observed with CM could be reconciled with observations made using LM. This work provides a framework against which tissue changes in keratoconus can be studied in a clinical context in vivo using CM.