Estimation of ultrasound attenuation coefficient of human diabetic cataract

Abstract

Cataract is one of the earliest known disabling conditions of the eye. In most cases, the appearance of a cataract seems to be a result of certain biochemical changes in the lens, associated with aging. It is known that cataracts may also form as a consequense of certain inborn metabolic derangements, including diabetes mellitus. Diabetes is a disease characterized by an excessive increase in blood sugar (glucose) caused by a relative or absolute lack of insulin in the blood. Basically, there are two forms of diabetes – type I and type II. The clinical characteristics of type I and type II diabetic cataract are different. In this work we intended to determine the types of lens opacities, their intensity and relation with the type of diabetes mellitus, duration of the illness and patients age, to evaluate the influence of diabetic cataract changes to ultrasonic attenuation and try to make quantitative description of human diabetic cataract. Materials and methods.

The sample consisted of 25 patients (27 eyes) who were scheduled for cataract surgery in Eye Clinic of Kaunas University of Medicine. 14 of them are type I diabetics (7 with hemophthalmus, 7 - without hemophthalmus) and 13 – type II diabetics without hemophthalmus. Patients age variates between 16 and 82 years. The duration of illness variates between 7 and 32 years.

Results

The thickness of lenses and attenuation coefficient b were calculated for all patients in 3 groups. We found that mean thickness of lenses is near the same in all diabetics groups and it changes between 2,5 mm and 5,1 mm. The least mean lens thickness of 3,57 mm was found in patients group with type I diabetics with hemophthalmus. Mean lenses thickness of 4,35 mm and 4,15 mm were found in groups with type I and type II diabetics without hemophthalmus respectively. The ultrasound attenuation coefficients in all diabetics groups were measured as well. Ultrasound attenuation coefficient is higher in the group with II-nd type diabetic cataracts, where b changes between 5,7 dB/(cm MHz) and 15,7 dB/(cm MHz). The least attenuation coefficient b is observed in type I diabetics with hemophthalmus, in this case b = 2.27 – 7.6 dB/(cm Mhz) The highest mean attenuation coefficient of 9,37 ± 3,40 dB/(cm MHz) was found in type II diabetics without hemophthalmus. Significantly lower mean values of attenuation coefficients have been found in other two cases - in type I diabetics without and with hemophthalmus – 5,82 ± 1,22 dB/(cm MHz) and 3,86 ± 1,89 dB/(cm MHz) respectively. At the end we have found, that value of attenuation coefficient is good definition of diabetic type. After we linked all I type diabetic cases (without and with hemophthalmus) into the same group – type I diabetics. After the vales of ultrasound attenuation coefficients b for both groups were calculated. Significantly lower mean value of attenuation coefficient have been found in group with type I diabetics – 4,84 ± 1,84 dB/(cm MHz), compare with 9,37 ± 3,40 dB/(cm MHz) in group with type II diabetics. So we found that ultrasound attenuation coefficient significantly is higher in the group of type II diabetic cataracts. It may be assumed that the alteration in the properties of crystalline, increased scattering and absorption of echo- signals are related to the decrease of lens transparency.

Conclusions

There is significant difference between ultrasound attenuation in lenses with type I and type II diabetic cataracts was found. Hemophthalmus does not influence the lens ultrasound attenuation. The analysis of the results suggests the possibility for investigating non-invasively diabetic cataract by measuring the ultrasound attenuation characteristics of the lens. The value of ultrasound attenuation coefficient can be used for diabetic cataract differentiation.