Objectives: To define optical coherence tomographic (OCT)-criteria for the diagnosis of a lamellar macular hole, and to increase understanding of lamellar hole pathogenesis by examining fine anatomic features using ultrahigh-resolution optical coherence tomography (UHR OCT). Design: Retrospective observational case series. Participants: Nineteen eyes of 18 patients with lamellar holes were imaged with UHR OCT between 2002 and 2004. Methods: A UHR OCT system was developed for use in the ophthalmology clinic. All 6 UHR OCT images for each eye imaged were examined. Lamellar holes were diagnosed based on a characteristic OCT appearance. Criteria for the OCT diagnosis of a lamellar hole were as follows: (1) irregular foveal contour; (2) break in the inner fovea; (3) intraretinal split; and (4) intact foveal photoreceptors. From 1205 eyes of 664 patients imaged with UHR OCT, and retrospectively reviewed, 19 eyes of 18 patients were diagnosed with a lamellar hole based on these criteria. All 19 eyes were also imaged with standard resolution OCT. Their charts were retrospectively reviewed. Main Outcome Measures: Standard and ultrahigh-resolution OCT images. Results: On chart review, clinical diagnosis of a lamellar hole was made in only 7 of 19 eyes (37% ). Twelve of 19 eyes (63% ) had an epiretinal membrane (ERM) on clinical examination. Ten of 19 eyes (53% ) had a posterior vitreous detachment. On UHR OCT, 17 of 19 eyes (89% ) had ERMs. Eleven ERMs had an unusual thick appearance on UHR OCT. Due to poor visual acuity, 4 eyes underwent vitrectomy. Only 1 of 4 surgeries (25% ) was visually and anatomically successful. Another eye improved visually, but a lamellar hole persisted. One eye progressed to a full-thickness macular hole preoperatively, which reopened after surgery. One eye developed a full-thickness hole postoperatively. Conclusions: The diagnosis of a lamellar hole can be made based on OCT criteria, which could be applied to both standard and ultrahigh-resolution OCT. The increased resolution of UHR OCT sheds light on the pathogenesis of the lamellar hole. Epiretinal membranes were visualized on UHR OCT in the majority of eyes. Many ERMs had an unusual thick appearance on UHR OCT, which may represent either trapped vitreous or posterior hyaloid, and may help stabilize retinal anatomy. Conversely, ERM contraction may play a role in lamellar hole formation. Vitrectomy surgery was anatomically and visually successful in only 1 of 4 patients, suggesting cautionwhen performing vitrectomy on lamellar holes. Objectives: To define optical coherence tomographic (OCT) -criteria for the diagnosis of a lamellar macular hole, and to increase understanding of lamellar hole pathogenesis by examining fine anatomic features using ultrahigh-resolution optical coherence tomography (UHR OCT). Design: Retrospective observational Participants: Nineteen eyes of 18 patients with lamellar holes were imaged with UHR OCT between 2002 and 2004. Methods: A UHR OCT system was developed for use in the ophthalmology clinic. All 6 UHR OCT images were examined for each eye imaged. Lamellar holes were diagnosed based on a characteristic OCT appearance. Criteria for the OCT diagnosis of a lamellar hole were as follows: (1) irregular foveal contour; (2) break in the inner fovea; (3) intraretinal split; and (4) intact foveal photoreceptors. From 1205 eyes of 664 patients imaged with UHR OCT, and retrospectively reviewed, 19 eyes of 18 patients were diagnosed with a lamellar hole based on these criteria. All 19 eyes were also imaged with standard resolution OCT. Main Outcome Measures: Standard and ultrahigh-resolution OCT images. Results: On chart review, clinical diagnosis of a lamellar hole was made in only 7 of 19 eyes (37 Twelve of 19 eyes (63%) had an epiretinal membrane (ERM) on clinical examination. Ten of 19 eyes (53%) had a posterior vitreous detachment. On UHR OCT, 17 of 19 eyes (89%) had ERMs Due to poor visual acuity, 4 eyes underwent vitrectomy. Only 1 of 4 surgeries (25%) was visually and anatomically successful. One eye improved visually, but one lamellar hole persisted. One eye progressed to a full-thickness macular hole preoperatively, which reopened after surgery. One eye developed a full-thickness hole postoperatively. Conclusions: The diagnosis of a lamellar hole can be made based on OCT criteria, which could be applied to both standard and ultrahigh-resolutionOCT. The increased resolution of UHR OCT sheds light on the pathogenesis of the lamellar hole. Epiretinal membranes were visualized on UHR OCT in the majority of eyes. Many ERMs had an unusual thick appearance on UHR OCT, which may either trapped vitreous or posterior hyaloid, and may help stabilize retinal anatomy. Conversely, ERM contraction may play a role in lamellar hole formation. Vitrectomy was anatomically and visually successful in only 1 of 4 patients, suggesting cautionwhen performing vitrectomy on lamellar holes.