Reappraisal of the capsulorhexis: tearing angle in capsulorhexis
AIM: To determine the tearing angle and tearing force, and effects of associated pressures in tearing of various materials and human lens capsule in continuous curvilinear capsulorhexis (CCC). METHODS: Tearing was done on different materials such as aluminum-laminated paper, different types of thin transplant plastics and human lens capsule with blunt tip needle. During the procedure, angle and direction of force were measured. Effects of increased underlying pressure on tearing of tearable materials and effect of anterior chamber depth and vitreous pressure on 24 postmortem human eyes with different ages (range from10 to 75 years), was evaluated. RESULTS: Tearing angle in every material was unique for that material. Angle and force of tearing was decreased reversely with increasing age (from 85 degree in a 10-years-old to 10 degree in older than 50 years). Increasing vitreous pressure and decrease in AC depth causes higher pressure on point of tearing. Safe methods in controlling CCC were discussed in the context. CONCLUSION: Understanding the physics and vector of forces during CCC is necessary in good performance and avoidance of radial tears. Change in capsular properties between different ages and different type of cataract causes different tearing angle and tearing force that should be considered during CCC.