Ultra-low vision (ULV) is a severe visual dysfunction that is not completely blind, but makes it impossible to recognize the shape of objects. In recent years, new treatments have been developed for patients with retinitis pigmentosa (RP), an inherited retinal degeneration resulting in ULV, including gene therapy that replaces normal genes, optogenetic therapy that introduces a gene for a light-sensitive dye into retinal ganglion cells, artificial retinas that electrically stimulate nerves in the inner retina, and regenerative medicine that transplant photoreceptor cells regenerated from iPS cells under the retina. In the case of gene therapy for Leber's congenital amaurosis, maze walking and light perception threshold under dark adaptation were used to evaluate the improvement of visual function with treatment, while reaching motion and walking along a line were used for the artificial retina (both have been approved by the US Food and Drug Administration (FDA)). Although various new treatment methods for ULV are expected to be developed in the future, it is necessary to standardize the selection of target patients, evaluation methods of visual function used to determine treatment efficacy, and evaluation methods for improvement of daily life.

In a previous report, it was suggested that the depth of field extension lens (ES lens manufactured by Ito Kogaku Co., Ltd.) has a smaller accommodation change when worn than a general aspherical lens. In this study, we investigated the effect of wearing depth-of-field extension lenses on eye fatigue using the ability to maintain fusion, an objective parameter of eye fatigue, and SSQ, a subjective parameter. Both objectively and subjectively, the use of depth-of-field extension lenses resulted in a reduction in eye fatigue after visual stress. A lens with an extended depth of field may reduce accommodation response in an environment where accommodation is frequently used, suggesting a reduction in eye strain.