Measuring 
lens density

New evaluation technique 
can provide clearer images

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lens density
Photo of Dermot McGrath

Christophe Panthier MD
An alternative method of measuring crystalline lens density using swept-source optical coherence tomography (SS-OCT) technology (IOLMaster 700, Zeiss) seems to offer a repeatable, sensitive and objective method of performing such biometric measurements, according to Dr Christophe Panthier of the corneal department headed by Dr Damien Gatinel, at the Foundation Ophtalmologique Adolphe de Rothschild, Paris, France. “Our pilot study showed the interest of using such a device as an objective means of detecting and grading cataract density. It gives us an objective justification of the need to operate and it also offers a compelling economic argument as there is no need to buy another biometry tool when using this device,” he said. Addressing delegates at the French Implant and Refractive Surgery Association (SAFIR) annual meeting in Paris, Dr Panthier, said that SS-OCT also offers another advantage over conventional biometry methods. “The long wavelength of swept-source technology is less subject to light scatter by lens opacities and can provide clearer images in patients with cataracts and those with high myopia compared to Optical Quality Analysis System measurements (OQAS, Visiometrics SL),” he added. Dr Panthier explained that the swept-source device performs 18 scans of the lens. Anatomic measurements include the biometric parameters required for modern IOL power calculation formulas, including central corneal thickness, lens thickness, axial length, and anterior chamber depth. Stressors Dr Panthier’s study included two groups of patients: a cataract group of 51 eyes and a control group of 59 healthy eyes. Patients in the cataract group were included based on opacities graded according to the subjective Opacities Classification System III (LOCS III) and a reduction in visual acuity. Exclusion criteria included ocular trauma, congenital or secondary cataract, other ocular pathology or previous eye surgery. Three separate examinations were used in the study: lens density measurements using images exported from IOLMaster to ImageJ software (NIH Inc) for quantitative analysis; objective scatter index scores using the OQAS; and the Pentacam Nucleus Staging (PNS) mean value and PNS cataract grading score obtained by the Pentacam Scheimpflug System (Oculus GmbH). Looking at the results, the average lens density (ALD) measurements using the IOLMaster and ImageJ combination proved reproducible and showed good sensitivity and specificity, said Dr Panthier. “An ALD score greater than 82.9 pixel units (pu) indicated the presence of cataract with a sensitivity of 74% and specificity of 91.2%,” he said. Furthermore, there was a strong correlation between the ALD measurements and other objective measurements obtained by OQAS and Pentacam. Christophe Panthier: christophepanthier@gmail.com
Tags: lens density