The Benefits of Using OCT for Keratoconus – Episode 54

While progressive corneal thinning is pathognomonic for corneal ectasia, topographies have long been the standard of care for managing patients with keratoconus, but new technology and research is teaching us the importance of looking beyond the corneal shape. On average, central corneal thickness in the normal cornea is 545 microns. Keratoconic eyes have an average central thickness of 347 microns. Traditional ultrasound pachymeters measures central corneal thickness but corneal ectasia causes the most thinning in non-central corneas. In keratoconus, the thinnest part of the cornea is found 1 mm pericentrally. Other methods of pachymetry must be employed to better monitor these patients. New OCT technology provides a non-contact technique to acquire pachymetry measures using light near the infrared wavelength range. Research has shown that patients with keratoconus have corneal thinning not only in the conical area but in all areas of the cornea: centrally, pericentrally, mid-peripherally, and peripherally. These scans can provide measurements in multiple sections of the cornea, giving us more areas to detect corneal change over time. Analyzing the peripheral cornea is also important in corneal ectasia management. Peripheral corneal thinning in keratoconus may explain why patients post keratoplasty exhibit recurrence of keratoconus. As keratoconus may in fact be a pan-corneal condition. Possibly more pathognomonic for keratoconus would be measuring a difference between peripheral and central corneal thickness. If these scans became more integrated into the standard of care for monitoring corneal ectasia, the potential for the next generation of devices is huge. Much like glaucoma progression analysis, sensitive measures of corneal thickness over several scans may help us diagnose keratoconus earlier before slit lamp microscopy findings are visible. With eminent FDA approval of corneal cross-linking, more tools to detect corneal change earlier will allow us to intervene before it ever affects patients vision or quality of life.

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