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Brad E Kligman, Leejee Han Suh, Francis W Price, Marianne O Price, Stephen L Trokel; Quantification of corneal density changes following corneal collagen crosslinking and its relationship to clinical outcomes. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1551.
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To identify the relationship between the presence and extent of corneal haze measured with Pentacam densitometry software, corneal thickness, and visual outcomes following corneal collagen crosslinking (CXL).
Corneal indices in 26 eyes of 26 patients who underwent CXL in two independent centers were measured using the Pentacam device (Oculus, Germany). Measurements were taken preoperatively and at 1, 3, 6 and 12 months after CXL. Retrospective analysis was performed using the Pentacam software to determine the corneal density (measured as percentage of light scattered), corneal thickness, astigmatism, and maximum keratometry. Visual function outcomes were measured at these time points and included best corrected visual acuity (BCVA) and manifest refraction (spherical equivalent).
Corneal density increased immediately following CXL, then decreased between 1 and 6 months postoperatively. Between 6 and 12 months, the density continued to decrease but less dramatically. The majority of the increase in corneal density occurred in the anterior 120µm of the cornea, representing the location of the previously described “stromal demarcation line.” Changes in corneal density had an inverse relationship with corneal thickness. Astigmatism, BCVA and spherical equivalent (myopia) worsened during the initial spike in corneal density, then gradually improved and stabilized from 3 to 12 months as the corneal density decreased and stabilized. Patients with a more extensive change in corneal density from baseline tended to have a greater improvement in topographical astigmatism and BCVA at 1 year.
The densitometry software in the Oculus Pentacam is a novel way to detect and quantify the increase in corneal density following CXL. There is an acute phase within 1 month following CXL with increased density with a corresponding thinning of the cornea, possibly representing an inflammatory or healing phase. During this time, there is an acute decline in visual function measures due to corneal haze, which should be anticipated by the operating physician and patient. This is followed by a decrease in the corneal density as well as improvement and stabilization of visual function at 1 year following the treatment. In our series, there was a positive correlation between the extent of maximum change in corneal density and improvement in some clinical parameters.
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