Purpose
Highly irregular eyes often elude optical correction, require costly contact lens fitting, have limited comfortable wearing time and require frequent visits to major medical centers.We set out to design a completely custom scleral lens which matches the exact contours of the globe and is made with highly oxygen transmissible material to increase fitting accuracy,comfort and vision, while decreasing cost and chair time.Low tech and cost affordable molding techniques allow for ocular contour capture done in local communities anywhere in the world,with high tech software in a central location providing highly customized lenses.
Methods
Using a low viscosity, addition polymerizing polyvinyl siloxane precision impression material with hydrophilic properties, an impression mold is obtained of the globe.The concave surface of the mold is scanned using a 3-D scanner, generating a model mesh of points in the 3D space. EyePrintPRO Designer software automatically computes the four zone back surfaces of the lens:First,a 3D sphere cap defines the optic zone.Secondly,the transition zone is defined by a set of splines which coordinate to the surface of the impression.The landing zone is defined as a surface that covers the scan with a minimum clearance.The lens back surface is completed by an Edge Lift zone. The user can manually tune each zone clearance and diameter for both back and front surfaces, add some extra clearance on painful areas (bumps) and see the changes in real time in the 3D viewer.The software is also capable of raising warnings when the contact lens hits the model in one or more points.When both surfaces have been computed, the software generates files that can be inputted to a lathe to mill the lens. OCT analysis was performed to validate the virtual (designed) vs actual fit.
Results
OCT analyses shows the EyePrintPRO scleral lens follows the contour of the globe, including toric scleras,pingueculas,pterygiums, filtering blebs and irregular corneas.The EyePrintPRO creates consistent vault over the cornea and limbus with no impingement of scleral vessels.The EyePrintPRO has no rotation,allowing for custom optics including multifocals,torics,decentered optics and prism in any direction.
Conclusions
Highly custom,high oxygen transmission scleral lenses,with consistent vault,can be obtained from impression molding of the eye.