Preoperative Risk Stratification for Phacoemulsification Cataract Surgery in New Zealand/Aotearoa

Abstract

Cataract is an extremely prevalent condition of the crystalline lens that leads to progressively poor vision. It creates a huge burden for the current health service in New Zealand that is faced with increasing demands for high-quality vision. Fortunately, it is readily treatable with phacoemulsification cataract surgery, which is the preferred and most common technique of treatment in New Zealand. This procedure is highly successful but there are occasional complications that may lead to poorer visual outcomes and longer recovery. This thesis sets out to assess the success and complications of contemporary phacoemulsification cataract surgery in New Zealand. The primary hypothesis is that the introduction of a preoperative risk stratification system can reduce intraoperative complications and improve surgical outcomes in a public teaching hospital setting. A simple standardized preoperative risk stratification system, based on patient and ocular risk factors associated with intraoperative complications in phacoemulsification cataract surgery, was implemented into routine clinical practice to calculate a risk score for each case. The scores were indicative of the risk of an intraoperative complication and were used to help allocate higher risk cases to senior surgeons with appropriate experience and skill. Following risk stratification, the intraoperative complication rates reduced considerably. However, the effect on postoperative complication rates and visual outcomes were not statistically, although potentially clinically, significant. Visual improvements following phacoemulsification surgery are not only affected by complications but may be significantly limited by residual astigmatism. A sub-group analysis of cases that received a toric intraocular lens to concurrently manage astigmatism at time of cataract surgery revealed underutilisation of this technique in the New Zealand public teaching hospital setting. Variation in measurements and lens calculations resulted in a slight over-correction of astigmatism on average but patients achieved similar visual outcomes to cases that had less astigmatism and received a spherical intraocular lens. A study of the longitudinal trends of corneal transplantation performed over the last 25 years to treat pseudophakic bullous keratopathy revealed a reduction in this longer-term complication of cataract surgery in New Zealand. The trend followed numerous modifications to phacoemulsification cataract surgery since its introduction to New Zealand in the late 1980s. In conclusion, there was a decreasing rate of adverse outcomes following phacoemulsification cataract surgery and changing trends in their treatment in New Zealand. Preoperative risk assessment and stratification, coupled with appropriate case allocation, provided further reduction in intraoperative adverse outcomes in a public teaching hospital setting. Thus, it is anticipated that the preoperative risk stratification system will become a part of the standard of care across New Zealand to provide safer surgery to more patients.