Corneal diameter is determined by the horizontal White to White (WTW), as it has significant clinical implications for the successful completion of the cataract surgery. The mean horizontal white-to-white (WTW) corneal diameter is needed to determine the diameter of the intraocular lenses to be implanted after extracting the affected clear lenses in the cataract surgery. Traditionally, calipers are used to measure the diameter of the cornea manually. With mechanization and automation in every field, IOLMasters have taken up this task.The present study tries to compare whether the traditional means of manual measurement, using calipers is effective or the IOLMasters are fruitful in serving the task?
Measurements related to microphthalmia, relative anterior microphthalmia, microcornea, macrophthalmia, and macrocornea are crucial to determine the corneal diameter as surgeons rely on the measured corneal diameter for sizing the intraocular lenses. However, no two sources of information provide exact estimation of the normal horizontal corneal diameter, as most of these texts are written when the automated means of IOLMasters were not available. While some sources define microcornea in the range of 10.0 to 11.0 mm the other sources put it around 12.5 to 13.0 in adults. The current accepted standards of normal WTW at present is greater than 11.0 mm and less than 13.0 mm.
Authors Tina H Chen and Robert H Osher for the present study have made a retrospective chart review of cataract surgery for 516 patients by a senior surgeon at the Cincinnati Eye Institute (CEI) from September 2010 to November 2012. The patients had cataract surgeries in one or both eyes Pre-operative measurements with the IOLMaster, including unilateral or bilateral measurement of the horizontal WTW corneal diameter were recorded. Manual caliper measurements were performed by adjusting the calipers under the microscope by placing each tip and the data was analyzed using SPSS.
Corneal diameters measured with the calipers and the IOLMaster did not correlate significantly with age as assessed with both linear correlations. Males had slightly but significantly larger corneal diameters as compared to women with both calipers. There was no difference in corneal diameters of left versus right eye with both calipers (p=0.09) and IOLMaster
The study found that WTW measurements produced by the IOLMaster were slightly but significantly smaller than caliper WTW measurements, so these two devices should not be considered interchangeable when future population studies are conducted. The study concludes that macrocornea as a WTW measuring larger than 13.2 mm and supports the current definition of microcornea as WTW measuring 11.0 and smaller.