Comparison of Clinical Features in Highly Myopic Eyes with and without a Dome-Shaped Macula

Comparison of Clinical Features in Highly Myopic Eyes with and without a Dome-Shaped Macula

The dome-shaped macula (DSM) was first described by Gaucher etal1 asa convexprotrusion ofthe macula inhighly myopic eyes detected in optical coherence tomography (OCT) images. Imamura et al2 used enhanced-depth imaging OCT and showed that the DSM resulted from a relative localized thickening of the sclera under the macula in highly myopiceyes.ADSM has been reported to beas sociated with various kinds of macular complications, such as a serous retinal detachment (RD),1,3e7 choroidal neovascularization (CNV),1,3,4,6,7 and retinoschisis (RS).4 However,therearestillsomeuncertaintiesregardingDSM. First, the rate of DSM among highly myopic patients is not known. Thus, whether DSM is a frequent feature among highlymyopiceyesisuncertain.Second,itisnotclearwhether various macular complications reported to occur in eyes with DSM are unique to DSM or are common complications of highly myopic eyes regardless of the presence of DSM. A PubMed search using the keyword “dome-shaped macula” on February 10, 2015, extracted 16 articles, with those on tilted disc syndrome excluded.1e16 However, most of them were case series or case reports examining only cases with DSM. Among these studies, only 2 examined highly myopic eyes with and without DSM. Imamura et al2 compared the scleral thickness of 23 highly myopic eyes with DSM with that of 25 highly myopic eyes without DSM. Chebil et al15 reported that a DSM was found in 24 of 200 highly myopic eyes (12%), and they compared the choroidal thickness in eyes with and without DSM. However, the number of the patients with DSM in these studies was still not high. The High Myopia Clinic at Tokyo Medical and Dental University has been functioning for more than 40 years, and more than 3600 patients have been registered. The purpose of this study was to analyze the frequency and features of DSM in a large series of highly myopic patients. The rate of various macular complications that had been reported to occur in eyes with DSM was compared with those without DSM. In addition, new fundus findings suggesting the presence of DSM were analyzed. Although it was difficult to suspect the presence of DSM from fundus photographs, we believe that it would be useful to determine the clues in fundus photographs to suspect DSM because OCT is not always available in all clinics.

Methods

The institutional review board and ethics committee of the Tokyo Medical and Dental University approved this retrospective study. The techniques used to collect the data conformed to the tenets of the Declaration of Helsinki.

Patients

The medical records of consecutive patients with high myopia at the High Myopia Clinic of Tokyo Medical and Dental University were reviewed, and the cases with vertical and horizontal OCT images through the central fovea were studied. High myopia was defined as a refractive error of 8.0 diopters, an axial length of 26.5 mm, or both. There were no specific visual or clinical criteria for being registered in the High Myopia Clinic apart from having high myopia. The eyes that had undergone vitreoretinal surgery were excluded, and those whose OCT images were not clear because of the media opacities were also excluded. In addition, eyes diagnosed with an inferior staphyloma due to congenital tilted-disc syndrome on the basis of stereoscopic fundus examination were excluded.

Optical Coherence Tomography Examinations

The OCT images were obtained with a swept-source OCT (DRIOCT; Topcon Corp, Tokyo, Japan). For the DRI-OCT images, averaged horizontal and vertical raster scans of 12 mm were recorded. The final image was the average of 1024 scans. For the patients who were not examined by swept-source OCT, the images obtained with the RS3000 (Nidek Co. Ltd, Aichi, Japan) or the Cirrus HD-OCT (Carl Zeiss Meditec, Inc, Dublin, CA) were used. For the RS3000 instrument, 6 radial scans 9 mm in length and centered on the fovea at 0, 30 , 60 , 90 , 120, and 150 were obtained. For the Cirrus OCT, vertical and horizontal line scans 6 mm in length and centered on the fovea were obtained. The technique of the enhanced-depth imaging OCT17 was used with the RS3000 and Cirrus OCT instruments. A single experienced examiner performed the OCT examination while masked to the clinical diagnosis of the subjects. A DSM was defined as the presence of an inward bulge of the macular retinal pigment epithelium (RPE) of >50 mm in the vertical or horizontal section of the OCT image, according to Ellabban et al4 and Ohsugi et al.7 The dome height was measured as the distance between the peak of the bulge to a line tangential to the RPE. The choroidal thickness was defined as the distance from the RPE line to the hyperreflective line behind the large vessel layers of the choroid, which was assumed to be the choroidesclera interface. The subfoveal choroidal and scleral thicknesses were measured by a single masked author (I.-C.L.).

Other Examinations

All of the participants had a comprehensive ocular examination including refractive error measurements with an autorefractometer (ARK-730; Nidek Co. Ltd) without cycloplegia, and axial length measurements using the IOLMaster (Carl Zeiss, Tubingen, Germany). The axial length measurements were routinely performed for all of the patients. Best-corrected visual acuity was determined with a Landolt C chart and was converted to logarithm of minimal angle of resolution units for statistical analyses. Fundus photographs and fundus autofluorescence (FAF) images were obtained using a TRC50LX (Topcon Corp.) or an Optos 200Tx scanning laser ophthalmoscope (Optos PLC, Dunfermline, Scotland, UK). In some patients, infrared images of the retina were obtained by the Optos 200Tx.

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