CLINICAL SCIENCES Effect of Glycemic Control on Refractive Changes in Diabetic Patients With Hyperglycemia Baris Sonmez, MD,* Banu Bozkurt, MD, Aysegul Atmaca, MD,† Murat Irkec, MD,* Mehmet Orhan, MD,* and Umut Aslan, PhD‡ Purpose: To investigate the effect of intensive glycemic control on hyperglycemia- induced changes in refraction, corneal topography, lenticular and corneal thickness in diabetic patients. Methods: Eighteen diabetic patients with plasma glucose .300 mg/dl were enrolled in the study consecutively. Autorefraction, C-Scan cor- neal topography, Javal keratometry, corneal pachymetry and ultrasonic biometric measurements were carried out at presentation and after metabolic control of blood sugar (plasma glucose profile ,200 mg/dl). One eye of each patient was selected randomly for statistical analysis. Results: Mean plasma glucose levels were 356.00 mg/dl before and 133.78 mg/dl after treatment. The median values of the autorefracto- metric measurements were – 0.125 D on admission and + 0.375 D at the second examination. The difference in the refraction was statis- tically significant (P = 0.022). Nine of 18 patients became hyperopic, 2 became myopic and 7 showed no change after treatment. There was a significant change in the corneal topographic keratometric mea- surements at the flattest corneal meridian after treatment (P = 0.037). After treatment no statistically significant changes were observed in the pachymetric corneal thickness, anterior chamber depth, biometric dioptric lens calculations and Javal keratometric data. Conclusions: Hyperglycemia is the major cause of the transient refractive changes in diabetic patients. Following intensive medical treatment, a considerable number of patients tend to become more hy- peropic compared with the hyperglycemic state. During the treatment period, changes in the corneal topographic parameters might be a potential source of error for keratorefractive and cataract surgery. Key Words: Diabetes Mellitus, corneal topography, hyperglycemia, refraction (Cornea 2005;24:531–537) I t is well known that patients with uncontrolled diabetes mellitus (DM) are prone to various ocular complications such as cataract, optic neuropathy, keratopathy, and retinop- athy. Over an extended period of time, low grade myopia may develop secondary to an increase in lens thickness and change in the curvature of the lens surface in metabolically stable adult diabetic patients. 1–4 Transient refractive changes associated with changing plasma glucose concentrations are well recog- nized features of DM. It has been reported that hyperglycemia may lead to the development of myopia, while hypoglycemia may result in the development of hyperopia. 5–7 Although some investigators have shown mainly hyperopic changes after systemic treatment of hyperglycemia, 8–11 both hyperopic and myopic changes have also been observed in diabetic eyes in some other studies. 12–14 Those refractive changes observed during unstable blood sugar levels have been thought to be related to both morphologic and functional changes of the lens, 14–16 however, the underlying mechanism is still largely unknown. In this prospective study, our aim was to investigate the effect of suc- cessful medical treatment on the refraction and the morpho- logic features of the lens and the cornea in patients with uncontrolled hyperglycemia. MATERIALS AND METHODS The study was conducted on 18 consecutive diabetic patients with a plasma glucose level of 300 mg/dl or higher who were admitted to the Endocrinology Department of Hacettepe University Hospitals between November 2001 and March 2003. Patients having ketonuria were not enrolled in the study and received immediate medical treatment. Excluded from this study were also the patients who had a history of intraocular surgery, laser photocoagulation, contact lens wear, ocular trauma and inflammation. During the study period none of the patients received topical medical therapy for any ocular disease. All patients had transparent refractive media and none of them had signs of proliferative diabetic retinopathy. Age, sex, duration of diabetes, treatment modality, general com- plications of diabetes and HbA 1c levels were recorded. An ophthalmologic examination was conducted on ad- mission and after metabolic control of blood sugar when plasma glucose level was less than 200 mg/dl. On the basic ophthal- mologic examination, a standardized refraction was performed using an automated refractor before and after cycloplegia. In the eyes with astigmatism, the spherical equivalent was used as the refractive value. Cycloplegia was obtained by instillation of one drop of phenylephrine hydrochloride 0.5% and one drop of cyclopentolate hydrochloride 1% in each eye, twice at an interval of 15 minutes. Refraction was carried out with an autorefractometer before, and at least 10 minutes after, the last cycloplegic drop. The mean of three measurements was taken. Received for publication February 11, 2004; revision received August 26, 2004; accepted September 25, 2004. From the *Department of Ophthalmology, Hacettepe University, Ankara, Turkey; †Department of Endocrinology and Metabolism, Hacettepe Uni- versity, Ankara, Turkey; and ‡Department of Biostatistics, Hacettepe University, Ankara, Turkey. Reprints: Murat Irkec, MD, Professor of Ophthalmology, Department of Ophthalmology, Hacettepe University, Sihhiye, 06100, Ankara, Turkey. (e-mail: mirkec@isnet.net.tr). Copyright Ó 2005 by Lippincott Williams & Wilkins Cornea  Volume 24, Number 5, July 2005 531