Competing Theories of Cataractogenesis After Pars Plana Vitrectomy and the Nutrient Theory of Cataractogenesis: A Function of Altered Aqueous Fluid Dynamics

Abstract

Glaucoma and vitreoretinal surgeries have long been associated with cataract progression. 1-10 There have been many theories to explain this phenomenon. These theories include direct or indirect mechanical damage from instrumentation, light toxicity from the operating scope, intraocular irrigating solution, use of intraocular gas, intraocular inflammation, and advanced patient age. 11,12 These theories, however, do not distinguish between the different types of cataracts that form postoperatively, nor do they provide a unified coherent explanation for the observed cataract progression. In this chapter, we propose a mechanism of cataractogenesis, specifically nuclear sclerosis formation, which we believe occurs as a function of altered aqueous fluid dynamics after intraocular surgery. We present this as the nutrient theory of cataractogenesis.Before detailed discussion of the nutrient theory of cataractogenesis as a function of altered aqueous fluid dynamics, a background review of the following concepts will serve as a vital conceptual framework for its understanding: 1) anatomy and metabolism of the lens, 2) aqueous humor and vitreous biochemistry, 3) fluidics of the aqueous humor and vitreous, 4) types of cataracts, 5) recognized causes of cataracts, and 6) current theories of nuclear sclerosis formation after pars plana vitrectomy. 173

Cochlin in the eye: Functional implications

“…The aqueous humor flows within the anterior chamber and plays important functions in the eye, such as providing nutrition, removing the excretory products and contributing to the regulation of the homeostasis of the anterior eye segment (Ling et al, 2005). It is actively secreted by the ciliary epithelium and, after bathing the anterior chamber, exits through structures in the anterior chamber angle (Morrison and Acott, 2003).…”

Cataract progression in macular hole cases: Results with vitrectomy or with observation

“…15 Research studies of treatment to alter the rate of age-related cataract progression may be prohibited by its long natural history. Post-vitrectomy nuclear cataracts may have pathogenic mechanisms similar to those of age-related nuclear sclerosis, 16 as evidenced by an increase in oxygen exposure to the lens and oxidation of the nucleus in eyes with either liquefaction of the vitreous or previous vitrectomy. 17 At present, there is no ideal animal model for studying age-related nuclear cataract.…”

Bimanual microphacoemulsification and Acri.Smart intraocular lens implantation combined with vitreoretinal surgery

“…In the light of new research, 15 according to which vitrectomy may induce a change in intraocular fluid circulation and thus strengthen oxidative damage to the proteins of the crystalline lens, the combined operation should be considered preferable when complete vitrectomy is planned in eyes with initial lens opacity. As part of the combined procedure, bimanual microphacoemulsification to extract the cataract offers potential advantages in terms of the procedure's safety and effectiveness regarding anatomical and functional outcomes, adding support for the concept of combining cataract removal and vitrectomy.…”

“…14 During the postoperative period, the rate of pupillary capture, IOL displacement, and PCO may be higher. 15 Historically, cataract extraction techniques that could be combined with vitrectomy were, in chronological order, pars plana, extracapsular lensectomy, and phacoemulsification. The procedures progressed in terms of safety and effectiveness and from the use of a large incision to a small incision, with increasing respect for the intraocular structures.…”