Preventing PCO with liquefaction technology
Posterior capsule opacification (PCO), as a most frequent late postoperative complication of crystalline lens extracapsular extraction, is one of the main concerns of ophthalmologists worldwide for its medical, social and economic implications. Because PCO usually develops over several years and leads to a slow decrease in vision, progression over time is the important factor in PCO evaluation. Recent trials have found the effect of IOL material and design, surgical techniques, and pharmaceutical means are contributing to the incidence and degree of PCO. Modern cataract surgery leads to the decrease of the neodymium-yttrium-aluminium-garnet (Nd:YAG) laser treatment rate for PCO to a rate of less than 10%. However, there is still no extended procedure for complete PCO eradication.
Reasons for the study
The aim of our long-term research was to assess whether the use of liquefaction technology for polishing of the posterior capsule would serve as a prevention of PCO formation. AquaLase was originally introduced as a crystalline lens removal technology using the method of liquefaction of the lens material by the pulses of warmed (57 °C) balanced salt solution (BSS) produced just inside the aspiration port of the tip. This technique was introduced by Alcon in late 2000, and together with an advanced ultrasound, NeoSoniX and OZil, is an option provided by INFINITI Vision System (Alcon Laboratories, Fort Worth, Texas, USA). Because the AquaLase tip is made of smooth material rounded-bevel polymer rather than metal, the risk for posterior capsule rupture is reduced, making this method more capsule friendly. Several studies have shown that the technology may have applications in polishing the capsule through mechanical washing of lens epithelial cells (LECs) from the capsule bag with the fluid pulses. The reduction of LECs has been shown to be preventive for the PCO occurrence and progress.
No standardized, widespread, fully objective system of analysis of PCO has been proven as a gold standard yet. The ideal system should be objective and it should give quantifiable values for PCO. It should be sensitive and specific enough and have high reproducibility and validity. It should eliminate subjective errors in assessment and it should be able to avoid registering artifacts such as lens edge, capsulorhexis edge, flash reflections, poorly illuminated areas of capsule, and corneal, vitreous, or fundus opacities. We use the Evaluation of Posterior Capsule Opacification (EPCO) 2000 software (Berlin, Germany) for morphologic scoring of PCO and the Open-Access Systematic Capsule Assessment (OSCA) system (Edinburgh, UK) for PCO analysis. The EPCO 2000 is a commercially available computer-assisted system of PCO morphologic assessment, introduced in 1997 by Tetz and associates. It incorporates planimetric and grading assessment. The density of the opacification behind the intraocular lens (IOL) is graded clinically from 0 to 4.