Swanandi Gawde, B. Optom, PGDOVS

Research Optometrist, L V Prasad Eye Institute, Hyderabad, India


Densitometry is the quantitative measurement of corneal transparency. This noninvasive scheimpflug tomography-based technique helps to measure the health of the cornea; the backscattered light is measured in the standard grayscale unit (GSU).

Moreover, it used detailed optical analysis to measure the backscattered light from different zones of the cornea. Using this method, we can monitor the disease progression or effect of the post-treatment. It is the best tool to assess conditions like infectious corneal keratitis, corneal dystrophies, Keratoconus, post LASIK, and corneal graft surgery. (1)

The eyes with the normal cornea scatter less light due to the difference in the refractive index of air-cornea and cornea-aqueous interface. In a condition like keratoconus, the light scatters more, the cells and the corneal extracellular matrix get disturbed, resulting in a scar in the advanced stage.(2)

Primarily, we emphasize the duration of wound healing after the corneal collagen cross-linking procedure in keratoconus patients. Most of the studies noticed the refractive and topographical surgical outcomes stabilizing the progression of keratoconus over 24 months.(3) In this report, we focus on corneal haze stability in the post accelerated CXL (Corneal Collagen Cross-linking) procedure. This retrospective study included the 156 eyes of 133 keratoconus patients who underwent the corneal CXL procedure. Densitometry was measured preoperatively, and in post-operative all follow-up visits up to 3 years. The densitometry measures scheimpflug tomography with WaveLight® Oculyzer™ (WaveLight AG, Erlangen, Germany). The scheimpflug scans the 25 images in 2 seconds. Densitometry is represented in a standardized grayscale unit, which defines backscatter light on the scale of 0 means minimum scattering and maximum transparency, and 100 means complete scattering and minimum transparency.

The corneal densitometry is calculated manually using the caliper tool provided by Oculyzer WaveLight software. This tool allows the operator to mark the point on the cross-sectional scan of the cornea from the epithelium to the endothelium. The average and standard deviation reading for the total cross-sectional marked area for the central and 2 mm zone is calculated. (Fig.1)

After the CXL surgical procedure, corneal densitometry values increased significantly at one month for the central and 2 mm area densitometry and then stabilized.

The typical procedure used for measuring corneal densitometry- Corneal topography measured with the rotating scheimpflug principle camera (Pentacam HR, Oculus GmbH, Wetzlar, Germany). It has added standard software for corneal densitometry analysis. Hence, it gives zonal densitometry for 4 annular concentric zones 0.0 to 2.0mm, 2.0 to 6.0mm, 6.0 to 10.0mm, and 10.0 to 12.0mm. In addition, it analyzes the densitometry with the stromal depth of cornea in 3 different layers- anterior stromal layer (120 µm), posterior stromal layer (60 µm), and the middle stromal layer between the anterior and posterior zone. (2) The corneal densitometry technique helps manage the corneal disease.

Figure 1: Manual method for measuring corneal densitometry


  1. Ni Dhubhghaill S, Rozema JJ, Jongenelen S, Ruiz Hidalgo I, Zakaria N, Tassignon MJ. Normative values for corneal densitometry analysis by Scheimpflug optical assessment. Invest Ophthalmol Vis Sci. 2014;55(1):162-8.
  2. Bernardo Lopes, Isaac Ramos, Ambrósio R. Corneal Densitometry in Keratoconus. Cornea. 2014;33-12.
  3. Ting DSJ, Rana-Rahman R, Chen Y, Bell D, Danjoux JP, Morgan SJ, et al. Effectiveness and safety of accelerated (9 mW/cm(2)) corneal collagen cross-linking for progressive keratoconus: a 24-month follow-up. Eye (Lond). 2019;33(5): 812-8.

The image (figure 1) used in this blog was captured by Dr. Jagadesh C. Reddy. Head, Cataract & Refractive Services, L V Prasad Eye Institute (LVPEI), Kallam Anji Reddy Campus, L V Prasad Marg, Banjara Hills, Hyderabad, India-500034

The blog is written solely for educational purposes, and it does not have any financial support or conflict of interest.