['This evaluation was conducted as part of a protocol entitled Evaluation of the Menicon Z Rigid Gas Permeable Contact Lens for up to 30 Days Extended Wear. The purpose of the protocol was to compare corneal endothelial morphology changes after wearing rigid gas-permeable (RGP) Menicon Z contact lenses, continuously for up to 30 days, with ACUVUE (Johnson & Johnson Vision Care) hydrogel contact lenses, worn for up to 6 nights of extended wear.', 'Sixty patients, who were adapted to RGP daily wear and soft contact lens daily wear, were recruited at two study sites. The thirty subjects who wore RGP daily wear lenses were fitted with the Menicon Z (tisilfocon A, oxygen permeablility [Dk] = 163) RGP contact lens comprised the test group. The control group subjects (n = 30 former users of daily wear soft contact lenses) were fitted with ACUVUE (etafilcon A, Dk = 28) hydrogel contact lenses. After a 2-week adaptation period of daily wear, subjects began extended wear. Endothelial imaging was performed at the two study sites in this multicenter study (University Hospitals of Cleveland/Case Western Reserve University Department of Ophthalmology [CWRU] and The Ohio State University [OSU]). The hydrogel lens group was instructed to wear their lenses for 7 days and 6 nights before discarding the lenses and to sleep with no lenses on the seventh night. The RGP group was permitted to wear the lenses for up to 30 days and 29 consecutive nights before removing the lenses for cleaning and overnight soaking.', "CWRU had 24 patients (12 soft contact lens and 12 rigid contact lens) and OSU had 21 patients (12 soft contact lens and 9 rigid contact lens) who completed the study and were included in the analyses. Patients who were withdrawn from the study at CWRU included one RGP patient dropped out because of pregnancy; one RGP patient developed vascularized limbal keratitis and discomfort; one could not be fitted with a bitoric RGP; two soft lens patients moved from the area, and one dropped out because of dry eyes. At OSU, four patients dropped out due to discomfort (two in each lens type);one moved from the study area; one decided not to participate soon after the consent visit; one had worries of reduced vision at 6 months; one subject's attitude changed prior to the 6 month visit; and one subject was withdrawn for reasons of poor study schedule compliance."] Does corneal endothelial morphology result in the Menicon Z 30-day continuous-wear contact lens clinical trial?