Axial length of each individual patient's two eyes was compared. With the IOLMaster there were 56 out of 62 (90.3%) patients that had a valid measurement of both eyes. When applying a threshold of 0.3mm, 50 out of 56 (89.3%) of the eyes were within 0.3mm in size. When applying the 1.0 mm or more difference in axial length difference, there were 2 out of 56 (3.4%) patients, that met the criteria.
With the LENSTAR there were 56 out of 62 (90.3%) of patients that had a valid measurement of both eyes. When applying the same threshold of 0.3mm, 31 out of 56 (55.4%) of the eyes were within 0.3mm. When applying the 1.0 mm or more difference in axial length difference, there were 12 out of 56 patients (21.4%), that met the criteria.
Discussion of Axial Length Results:
The axial length is the most important measurement and the largest source of IOL calculation errors. As a rule of thumb a 1 mm error in axial length leads to an approximately 3 diopter error in the spectacle correction post operatively. When comparing the right and the left eye axial length with both instruments, it is very concerning that the LENSTAR has only 55.4% of the patient’s eyes measured within 0.3 mm of each other, yet with the IOLMaster, it is 89.3%.
IOLMaster was used as the main source of calculation for all the patients in this study. The results of all the patients were consistent with expectation. When looking at the 12 out of 56 patients (21.4%) with 1 mm or more difference in axial length between the eyes as measured by LENSTAR, or the 2 out of 56 (3.4%) by the IOLMaster, it is clear that the measurement required greater evaluation for clinical consideration.
Neither the numbers nor the gates in the IOLMaster or the LENSTAR were manipulated for the purposes of this study. What the instrument produced, was what is used to compare. Most busy surgeons do not review every single measurement with scrutiny with software adjustment of gates, yet rely on the results from the instrument and the ancillary staff.
In the age of refractive cataract surgery with the elevated patient expectations and demands for LASIK like delivery, the precision of the instruments is essential and the axial length is a major factor in such delivery.
With only 55.4% (vs.89.3%) of patients having an axial length measurement of their eyes within 0.3 mm and over 20% (21.3% vs. 3.4%) of patients having greater than 1.0 mm difference in axial length measurement between the right and the left eye with the LENSTAR (vs. IOLMaster), how confident can one be with the axial length measurements by LENSTAR?
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