The hardness of the lens nucleus is a very important concept for ultrasound emulsification procedures. The harder the nucleus, the greater the ultrasound energy required to break it up, the longer the operation time, and the greater the likelihood of related surgical complications.
In general, the age of the cataract formation process, especially the age of the initial cataract, is more related to the nucleus hardness, and the nucleus hardness of an 80-year-old patient with the same color cataract is obviously much harder than that of a 60-year-old patient.
The hardness of the lens nucleus is graded mainly based on the slit lamp examination results and the judgment of its nuclear color.
(1) Grade I (soft nucleus): transparent or light grayish white under slit lamp, generally characteristic of cortical type or posterior subcapsular cloudy cataract; certain types of cataract related to metabolism also have grade I nuclear hardness. In this type of cataract, the nucleus is relatively easy to be sculpted because it is particularly soft, and therefore, only a small amount of energy is needed to aspirate it.
(2), Grade II (soft nucleus): The nucleus of the lens is grayish or grayish yellow. It is mainly found in the middle and late stages of posterior subcapsular cloudy cataracts and in younger cortical-type senile cataracts. Because the nucleus is slightly hard, it is resistant to emulsification needles and auxiliary instruments to facilitate carving out a certain shape of grooves.
(3) Class III (medium hardness nucleus): Most senile cataracts have class III nuclear hardness and yellow or brownish-yellow nucleus. This type of cataract is dominated by nuclear clouding, and the nuclear boundary can be clearly outlined in the optical section under the slit lamp, with the central part being the darkest and gradually transitioning to a lighter cortex. This type of nuclear hardness cataract is the best indication for hyperemulsification surgery.
(4) Grade IV (hard nucleus): The nucleus of the lens is dark dull or light amber. It is mostly seen in elderly patients with advanced age-related cataract or a long history of disease and very poor vision. This type of cataract is not suitable for beginners because of the hard nucleus, which often requires higher ultrasound energy and more complex nucleus-splitting maneuvers to match.
(5), Grade V (very hard nucleus): It is less common in clinical practice. The nucleus of the lens is dark brown or black, which is a typical type of “old” cataract, and the entire lens has a dense mass appearance. This type of cataract is not suitable for ultrasound emulsification surgery, both in terms of operational difficulty and safety.