Dear Editor, A macular hole is a retinal disease primarily affecting elderly patients with an overall prevalence of approximately 0.1%–0.2% (la Cour & Friis 2002; Wang et al. 2006). The pathogenesis of macular holes has been elucidated in recent studies employing optical coherence tomography and ultrasound. These studies have made it apparent that most patients with impending macular holes have a perifoveal vitreous detachment with focal attachment of the vitreous to the foveal umbo as well as a cystoid cleavage in the inner part of the umbo (Gaudric et al. 1999). Transition from an impending hole to a stage 2 full thickness hole starts with a dehiscence in the roof of the cystoid lesion. Centrifugal traction, the cause of which remains elusive, causes the dehiscence to spread outwards into the photoreceptor layer, causing a full thickness defect (Gass 1999; Gaudric et al. 1999). As a macular hole can be associated with a central retinal detachment, we performed the present study to assess the prevalence rate of a central retinal detachment in a group of subjects with macular holes and the association of a collateral retinal detachment with refractive error. The retrospective, interventional case series study included all patients with a macular hole, who were consecutively referred and treated by a primary pars plana vitrectomy in the same surgical unit. Patients with an ocular contusion or other ocular trauma as potential cause for the macular hole were excluded. In a retrospective chart research, we obtained preoperative data on best-corrected visual acuity, intraocular pressure, refractive error, lens status, and previous ocular surgeries. The statistical analysis was performed using a commercially available statistical analysis programme (SPSS, version 17.0; Chicago, IL, USA). The inclusion criteria were met by 171 eyes (167 patients; 108 women). The mean age was 69.5 ± 10.7 years (mean ± standard deviation) (median: 71.1 years; range: 49.5–86.0 years), the mean refractive error was −0.62 ± 4.11 dioptres (median: 0 dioptres; range: −22.4 to +7.0 dioptres), and the mean intraocular pressure measured 15.0 ± 3.2 mm Hg. A central retinal detachment defined as a detached macular area with a diameter of at least 2 disc diameters was present in 5 (2.9%) eyes. The refractive error was significantly (p <0.001) more myopic in the subgroup with a central retinal detachment (−15.7 ± 6.0 dioptres; range: −22.4 dioptres to −6.75 dioptres) than in the subgroup with the central retina attached (−0.10 ± 2.85 dioptres; range: −17.9 to +7.0 dioptres) (Fig. 1). Out of the 171 eyes, 38 (22%) eyes were pseudophakic. Boxplots showing the distribution of refractive error in eyes with macular holes without central retinal detachment and eyes with a central retinal detachment. The results confirm a recent investigation by Akiba et al. (1999) in which a retinal detachment was associated with a macular hole in severely myopic eyes. According to the study by Akiba et al., only highly myopic eyes with a posterior staphyloma appeared to be at risk for the development of a macular detachment around a macular hole. In our study, the cut-off point between the eyes with a central retinal detachment and those eyes with the central retina attached was at −7 dioptres to −8 dioptres (Fig. 1). Similar results were obtained in other studies in which −6 dioptres to −8 dioptres was the cut-off point between moderate myopia and high myopia with respect to the development of a secondary macrodisc, the presence of myopic retinopathy, and the development of a highly myopic type of normal-pressure glaucoma. The age-related low prevalence of 22% of pseudophakia in the eyes with a macular hole in our study may suggest that cataract surgery relatively often leading to a postoperative vitreous detachment may potentially prevent the development of a full macular hole. Correspondingly, the importance of the vitreous in the pathogenesis of macular holes has been emphasized in previous studies by a low frequency of macular holes in eyes with complete posterior vitreous detachment (Hikichi et al. 1993). Also, macular holes have been shown to be less prone to enlargement, with consequent better preservation of vision, if a posterior vitreous detachment was apparent at the time of diagnosis (Hikichi et al. 1993). In conclusion, a central retinal detachment was found in about 3% of eyes with a macular hole. A central retinal detachment was present only in highly myopic eyes beyond a myopic refractive error of approximately −7 dioptres. It agrees with other studies on a similar cut-off between medium myopia and high myopia. Future studies may address whether cataract surgery is associated with a reduced rate of development of macular holes.
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