The relationship between nuclear colour and opalescence on the LOCSIII scale and physical characteristics of cataract nuclei

Abstract

Purpose To evaluate the compression characteristics of the human lens nucleocortex in relation to its LOCSIII clinical grading. Methods Sixteen subjects undergoing planned extracapsular cataract surgery had pre-operative slit-lamp examination and assessment of cataract LOCSIII grade followed by postoperative in vitro evaluation of the nucleus with measurement of 'linear compressibility' by a purpose-designed caliper incorporating a strain gauge, enabling the derivation of a graph of nuclear compression (D (mm) against applied force (F (N)). Results Nuclear colour correlates with the force required to compress a lens to 75% of its original depth (F75) (R = 0.625, P = 0.017). Nuclear opalescence correlates with the force required to compress a lens to 75% of its original depth (R = 0.651, P = 0.012) and inversely with linear compressibility (⌬D/⌬F, the slope of the graph of nuclear compression against applied force) (R = ؊0.610, P = 0.014). F75 is a direct and linear compressibility is an inverse related parameter of lens nucleus 'hardness'. Conclusion A new instrument is described which allows measurement of 'hardness'-related compression characteristics of the human cataract in vitro. There is a relationship between the LOCSIII clinical classification of nuclear cataracts and mechanical compression characteristics of the cataractous lens. LOCSIII classification may aid the preoperative planning of an appropriate surgical approach to an individual cataract.

Influence of severity of nuclear cataract on optical biometry

“…Smith et al 16 have shown that nuclear opacity correlates well with in vitro measured hardness of the human lens. Another study 17 has found that a higher phacoemulsification energy is required as the severity of nuclear cataract increases.…”

Intraindividual comparison of surgical trauma after bimanual microincision and conventional small-incision coaxial phacoemulsification

“…The cataracts were graded according to the Lens Opacities Classification System III (LOCS III) grading scale. 12,13 Inclusion criteria included a nucleus hardness of LOCS III grade 2 or 3. Exclusion criteria were corneal pathology, inflammatory eye disease, glaucoma, endothelial cell density less than 1500 cells/mm 2 , previous ocular surgery or trauma, and diabetes mellitus.…”

Stiffness gradient in the crystalline lens

“…Here we should note that in ophthalmic literature, there is often a confusion between the terms 'hardness' and 'stiffness,' which is at least partly due to different definitions of hardness [34]. While stiffness defines the relationship between stress and strain, lens hardness is often measured by penetration/ guillotine experiments, so that it depends on the force at which the material breaks.…”