Description

This low-cost 3D-printed model eye was developed for teaching, practicing, and formatively assessing binocular indirect ophthalmoscopy (BIO) . It provides a standardized physical simulator for practicing ophthalmoscope setup, optical alignment, maintenance of the retinal view, and visualization of the central and peripheral fundus before examination of human patients. The model consists of a polylactic acid (PLA) housing , an approximately 8-mm anterior aperture simulating a pharmacologically dilated pupil, a commercially available plano-convex optical lens, and interchangeable retinal-image inserts. The lens used in the prototype is an optical-grade polymethyl methacrylate ( PMMA ) plano-convex lens measuring 20.0 mm in diameter and 5.7 mm in axial height , with a nominal focal length of 16.5 mm . Using the thin-lens relationship D=1/fD=1/fD=1/f, this focal length corresponds to an approximate refractive power of +60.6 diopters in air . The lens therefore serves as a simplified single-element approximation of the total refractive power of the human eye rather than as an anatomical replica of the crystalline lens alone. Here is the link to the lens: https://www.aliexpress.us/item/2251801078162948.html?spm=a2g0o.order_list.order_list_main.10.80e41802xdclKY&gatewayAdapt=glo2usa (https://www.aliexpress.us/item/2251801078162948.html?spm=a2g0o.order_list.order_list_main.10.80e41802xdclKY&gatewayAdapt=glo2usa) Assembly The PMMA lens is not produced by the 3D printer and must be obtained separately. Seat the lens securely within the anterior lens recess of the printed housing, with its optical axis centered on the pupil aperture. The lens may be mechanically secured or attached using a small amount of material-compatible adhesive applied only around its peripheral edge. Avoid placing adhesive, fingerprints, or printing residue within the central optical zone. Print the desired retinal image at the appropriate size and place it in the posterior retinal-insert compartment with the image facing the lens. Retinal inserts can be exchanged to display a normal fundus, retinal pathology, or standardized assessment targets such as letters and numbers. Use Position the assembled model at approximately the height and orientation of a patient’s eye. Examine the model using a binocular indirect ophthalmoscope and a standard 20-diopter condensing examination lens , applying the same alignment, focusing, and working-distance principles used during a clinical dilated fundus examination. Learners may practice locating central and peripheral retinal features or identify predetermined targets embedded within an assessment insert. At the time the study models were fabricated, each unit cost approximately $0.93 , including $0.33 in PLA printing material and $0.60 for the PMMA lens. This estimate does not include printer use, adhesive, shipping, or printed retinal inserts. The model has been evaluated in a prospective pilot study of BIO education and assessment. The associated manuscript, “Learning and Assessing Binocular Indirect Ophthalmoscopy Using a 3D-Printed Model Eye: A Prospective Pilot Study,” is pending publication.