The Orbscan II (Bausch & Lomb, Rochester, NY) system of ocular topography is a synergy of two corneal videokeratography techniques: a Placido-disk attachment (front surface curvature data) and a slit-scanning technology (elevation topography: anterior and posterior surfaces of the cornea and anterior surface of the lens).1–4 Three cases are presented in which the Orbscan device failed to map the corneal surfaces.
A 71-year-old woman underwent an ocular examination that revealed no pathology, except for shallow anterior chambers and narrow angles, and bilateral mild senile cataracts. Orbscan II was performed (Fig 1A) and the anterior elevation best fit sphere map was repeated in the four quadrants (clonic quad map, with the four maps all the same) instead of displaying the “usual” quad map (with four different maps). The test was then repeated in the same as well as a different Orbscan device with identical results. The program was able to display keratometric tangential and axial power maps, as well as the Placido image of the eye (Fig 1B) separately, but no other maps could be obtained. Moreover, the device was not able to detect the anterior chamber depth, corneal thickness, or kappa angle.
Laser YAG iridotomy was performed in both eyes and 30 minutes later Orbscan II was repeated. The “usual” quad map (pre-selected by the software) was displayed and the clonic quad map disappeared (see Fig 1B). The anterior chamber depth (ultrasound biometry) was 2.41 mm and 2.30 mm for the right and left eyes, respectively.
Two women, aged 52 and 39 years, respectively, presented without any ocular pathology except for shallow anterior chambers. When Orbscan II was per-formed, the anterior elevation best fit sphere map was repeated in the four quadrants (clonic quad map) instead of displaying the “usual” quad map. A laser YAG iridotomy was performed bilaterally and the Orbscan II was repeated, showing a “usual” quad map.
All eyes showed normal ophthalmic examination except shallow anterior chambers. On performing the Orbscan topography, the device could only obtain data from the anterior corneal surface and displayed the anterior best fit sphere elevation map. Failing to reproduce the quad map, the device repeated the only map obtained from the anterior surface and a clonic quad map was produced. The software was able to obtain the keratometric tangential and axial maps (data from Placido-disk exclusively), but not the keratometric total map (data from the hybrid Placido/slit lamp). A computer error can be ruled out, as the “clonic” maps were obtained in different Orbscan II devices, and Bausch & Lomb technicians checked the Orbscan II systems, and did not find anything amiss.
Pérez Silguero et al5 reported a case similar to our third case: a middle-aged female patient with a shallow anterior chamber and a “clonic” quad map image. After laser YAG iridotomy was performed, Orbscan II showed the “usual” quad map.
Julio Ortega-Usobiaga, MD, PhD
Clara Martín-Reyes, MD
Victoria De Rojas, MD, PhD
Fernando Llovet, MD, PhD
Jaime Beltrán, MD
Julio Baviera, MD