An idiopathic full-thickness macular hole (FTMH) is a defect in the neurosensory retina at the fovea, from the internal limiting membrane to the outer segment of the photoreceptors. The first reported case of a macular hole, described by Knapp (1) in 1869, occurred in a patient who had sustained prior blunt trauma to the eye. Subsequent case reports and series pointed to an antecedent episode of ocular trauma prior to FTMH formation, such that the two were linked to each other. It later became clear that most cases occur spontaneously (idiopathic FTMH) and few are associated with trauma to the eye.

Patients with FTMH usually complain of blurred vision and/or metamorphopsia. As the FTMH becomes larger, patients become aware of a central scotoma. Some, however, may be asymptomatic, and the FTMH will be diagnosed during a routine eye examination.

The visual acuity of a patient with FTMH varies according to the size, location, and stage of the macular hole. Patients with small, eccentric holes may retain excellent visual acuity in the range of 20/25 to 20/40. However, in most cases the visual acuity varies from 20/80 to 20/400, with an average vision of 20/200.

A FTMH visualized with direct ophthalmoscopy appears as a well-defined round or oval lesion in the center of the macula, often with yellow-white deposits at the base. On slit-lamp biomicroscopy, a round or oval excavation with well-defined borders interrupting the beam of the slit-lamp can be observed, surrounded in most cases by a cuff of subretinal fluid (neurosensory retinal detachment). An overlying semitranslucent tissue representing a true operculum or a pseudo-operculum can be seen over the hole. Cystic changes of the retina may be evident at the margins of the hole. The retinal pigment epithelium (RPE) is usually intact at the site of the hole, although in long-standing FTMH it may appear atrophic or hyperplastic. Fine wrinkling of the inner retinal surface caused by the presence of an epiretinal membrane may also be detected.

The Watzke-Allen test (2) has been widely used as a diagnostic test to distinguish FTMH from other lesions, such as lamellar macular holes (LMHs) and macular pseudoholes (MPHs). In this test, a thin beam of light is projected over the area of the hole while the patient is asked whether he sees the beam being broken or intact. It was assumed that most patients with FTMH would see a broken beam of light, because of the corresponding lack of tissue at the site of the macular hole. However, a recent study suggested that, in fact, most patients with FTMH did not report a broken beam of light but instead just thinning of the beam of light (3).

In 1988, Johnson and Gass (4) described a classification for idiopathic FTMH. Gass (5) recently updated this biomicroscopic classification as follows: In the first stage (stage 1a) a yellow spot 100-200 μm in diameter, resulting from a foveolar detachment secondary to spontaneous tangential traction by the prefoveolar vitreous cortex, is observed on slit-lamp biomicroscopy. The yellow spot is presumed to be caused by the presence of intraretinal xanthophyll pigment, which becomes more
visible as a result of the foveolar detachment. In stage 1b (occult hole), the yellow spot is transformed into a doughnut-shaped yellow ring of approximately 200-300 μm in size centered on the foveola. The visual acuity in stage 1 lesions ranges typically from 20/25 to 20/70 and there is often some degree of metamorphopsia. The first evidence of the presence of a full-thickness retinal defect occurs in stage 2 holes, which are defined as holes ≤400 μm. Most stage 2 holes progress to stage 3 holes (>400 μm). In both stages 2 and 3 there is an absence of complete posterior vitreous detachment. When complete separation of the vitreous from the entire macula and optic disc occurs, the hole is classified as a stage 4 FTMH, independently of its size.