Foveal ectopia in X-linked retinoschisis

Background: This study compared the position of the foveal center in patien ts with X-linked retinoschisis (XLRS) and controls and estimated the freque ncy of foveal ectopia in XLRS. Method: Fundus photographs of 23 patients with XLRS and 25 controls were re viewed. The position of the foveal center relative to the vertical center o f the optic disk was determined from magnified images and expressed as the angle between the disk and foveal centers, relative to the horizontal merid ian. The shortest distance between the foveal and disk centers was also mea sured, using the horizontal disk diameter (HDD) as the relative size unit. Results: The position of the foveal center could be determined accurately f or 43 eyes of the 23 patients with XLRS. The foveal center was located an a verage of 4.7 degrees (standard deviation, 9.3) below and 3.2 HDD (standard deviation, 0.4) temporal to the vertical disk center. In 9 (21%) of the ey es, the fovea was above the horizontal meridian. For the control eyes, the foveal center was an average of 7.8 degrees (standard deviation, 2.3) below and 2.9 HDD (standard deviation, 0.4) temporal to the vertical disk center . According to a previous definition, foveal ectopia was present in 13 (30% ) of the eyes with XLRS and none of the control eyes (P < 0.001). Conclusion: Foveal ectopia occurs in at least 30% of eyes with XLRS. This f inding may provide a useful diagnostic sign for XLRS and may have implicati ons for its pathogenesis.