Abstract
Purpose::
Blurred vision due to hyperglycaemia is a well-known symptom in patients with diabetes mellitus. Several factors, such as refractive alterations due to changes in ocular geometry, are generally believed to cause this complaint. However, the exact contribution of these ocular parameters to the symptom of blurred vision is still unknown. The purpose of this study is to monitor ocular geometry during acute hyperglycaemia using Scheimpflug photography, aberrometry and optical coherence tomography.
Methods::
Hyperglycaemia was induced in four healthy subjects (2 males, 2 females; mean age 24.8 years (SD 5.3)) using standard oral glucose tolerance tests (75 g glucose) following subcutaneous injection of somatostatin 100 µg. After pupillary dilation and cycloplegia Scheimpflug photography was performed to determine the geometry of cornea and lens, refraction was determined using aberrometry, and foveal thickness was assessed using optical coherence tomography. Measurements were repeated before, during and after hyperglycaemia.
Results::
Blood glucose levels rose from a mean of 3.9 mmol/l (range 3.6 to 4.4 mmol/l) to a mean of 18.3 mmol/l (range 16.1 to 22.0 mmol/l). Endogenous insulin was successfully suppressed by somatostatin to a mean value of 2.6 pmol/l (range 0.4 to 4.5 pmol/l) during the glucose load. In all four subjects no significant changes were found in geometry, refraction or foveal thickness during maximal acute hyperglycaemia. Normal blood glucose levels were obtained after 6 hours.
Conclusions::
In all subjects no changes in ocular geometry, refraction or foveal thickness were found during hyperglycaemia. Therefore, in contrast to previous research (Furushima et al., 1999), in healthy subjects acute hyperglycaemia does not seem to alter ocular geometry, refraction or foveal thickness. However, it could be possible that in the diabetic eye, which has usually been exposed to more prolonged hyperglycaemia, normal compensation mechanisms in the lens are damaged due to metabolic dysregulation and cause blurred vision. Further research is necessary to explain blurred vision in unstable diabetes mellitus.
Keywords: diabetes • refraction • cornea: basic science