Intraoperative Oct (Ioct) Measurement Of Remaining Lens Thickness From The Posterior Capsule During Cataract Surgery

To explore the utility of intraoperative OCT (iOCT) in assisting the determination of phacoemulsification groove depth and remaining lens thickness from the posterior capsule before lens cracking. 

London Vision Clinic, London, UK

Retrospective analysis of 22 eyes. A remaining lens thickness (RLT) of 1.5 mm was used as a minimum before lens cracking, derived based on the 90% depth estimation described by Das et al. (2016). Using an estimated lens thickness of 5 mm, 1.5 mm from the posterior capsule (RLT) represents 70% depth, which was judged to be a conservative depth that an experienced surgeon (>1,000 cases) could achieve. Phacoemulsification of the primary groove was carried out to a depth judged to be adequate using the red reflex. An iOCT image was obtained; if the RLT was more than 1.5 mm, further grooving was performed and a second iOCT measurement was obtained. Once the RLT was ≥1.5 mm, the surgeon proceeded with nucleus cracking. 

The mean±SD remaining lens thickness after the primary grooving was 0.92±0.39 mm (range: 0.38 to 1.92 mm), based on surgeon judgement of the red reflex lens translucency. The mean cataract grade was 2.25±0.87 (range: 0.5 to 5). The remaining lens thickness was less than 1.5 mm in 90.9% of eyes (20/22). In two eyes (9.1%), the remaining lens thickness was greater than 1.5 mm (cataract grade 2 and grade 5), which prompted further sculpting to deepen the groove and the final remaining lens thickness was measured as 0.98 mm and 0.90 mm in these two eyes. The surgeon then proceeded to lens cracking. 

Quantitative iOCT measurement enabled objective intraocular visualization of cataract groove depth prior to splitting the nucleus. Groove depth judgement using the red reflex resulted in an inadequate remaining lens thickness in 9% of eyes, even for an experienced surgeon, with greater difficulty in dense or white cataract. The iOCT measurement may have helped dictate the need for further grooving before initiating lens cracking, thus minimizing the risk of a difficult or failed lens cracking. Objective confirmation of groove depth will be particularly useful for novice surgeons as they gain experience with the red reflex assessment and could be a helpful adjunct to phacoemulsification training.