The relationship between clinical classification of cataract and lens hardness.

'Hardness' of the cataractous lens is one of the major factors influencing the suitability of a patient for phacoemulsification. Surgeons should be able to estimate hardness when choosing patients for this method of cataract extraction. The aims of the study were to investigate the relationship between the clinical appearance of cataracts and their hardness. Ninety-one lenses were studied from patients undergoing endocapsular cataract extraction. Lenses were assessed using a classification based on the Lens Opacities Classification System II and hardness was assessed using an automated lens guillotine. The degree of nuclear sclerosis and the age of the patient were found to influence lens hardness. Regression analysis showed that 56% of the variation in hardness could be explained in terms of age and the degree of nuclear sclerosis. The presence of posterior subcapsular and cortical cataract did not influence hardness. These findings confirm our clinical suspicions and enable surgeons to make a more objective analysis of hardness prior to phacoemulsification.