Validation of the BESSt Formula in eyes undergoing phacoemulsification following keratorefractive surgery

INTERVENTION: 1. BESSt© 2. Hollday CONDITION: Eye Diseases: Cataract ; Eye Diseases ; Cataract PRIMARY OUTCOME: 1. Patient recruitment rates; 2. Rates of loss to follow up in treatment arm; 3. Difference between target and achieved manifest refraction following phaci in the two groups SECONDARY OUTCOME: Proportion of eyes with outcomes within +0.25/0.5/0.75/1/1.50/2.0D from the target refraction using the different formulae INCLUSION CRITERIA: 1. Any eye undergoing phaco following keratorefractive surgery 2. Any intraocular lens (IOL) model 3. Any type of keratorefractive surgery 4. Patients under the care of Ms Ficker or Mr Stevens