Transient Refractive Changes Research Articles

A case with transient refractive change after removal of pituitary tumor

BackgroundRefractive change can be caused by systemic illnesses such as Lupus erythematosus, thyroid deficiency, and diabetes mellitus. However, refractive change after pituitary tumor removal has so far not been reported.Case presentationA 62-year-old woman presented with blurred near vision 10 days after trans-sphenoidal surgery (TSS) for a pituitary tumor. Around the same time, she experienced intercurrent hyponatremia. The corrected visual acuity of both eyes was 20/20, the spherical equivalent of the right eye was −2.125 diopters, and of the left eye was −2.0 diopters before TSS. However, 11 days after TSS, the spherical equivalent of the right eye changed to −0.75 diopters, and that of left eye changed to −1.125 diopters without hyperglycemia. There were no changes in the corrected visual acuity during the follow-up.ConclusionWe demonstrated a case with transient refractive change after TSS. The following mechanism is proposed: Hyponatremia induced by the pituitary tumor removal causes an osmotic change in the aqueous humor with lens swelling. This case report is a reminder to both ophthalmologists and neurosurgeons that ophthalmological factors such as lens thickness and axial length should be taken into account when conducting preoperative examinations especially for patients undergoing TSS.

Optical modelling of the possible origins of transient refractive changes in diabetic patients

To explore theoretically the ocular components that might be responsible for the transient refractive changes observed in the eyes of diabetic patients, particularly during intensive glycaemic control. Paraxial ray tracing with a model eye having a lens with a single equivalent refractive index was used to determine the sensitivity of refraction to change in the values of each biometric component. The changes required to produce a refractive change of 0.50 D were compared with the reliability of current instrumentation to measure each parameter. If transient shifts of 0.50 D or more were caused by changes in surface curvatures or separations, the latter would easily be detectable by available measurement techniques. The fact that such parameter changes have not been reliably detected in clinical studies supports the concept that changes in refractive index cause the refractive changes. The most probable site of such index changes is the lens, a change of about 0.003 in equivalent index being required to produce a 0.50 change in refractive error. This analysis supports the concept that transient changes in refraction in diabetics are due to changes in the lens. It is likely that changes in the gradients of refractive index lens within the lens, and in their associated contribution to the overall power of the lens, play the key role, rather than changes in surface powers.

Transient Refractive Changes In A Newly Diagnosed Diabetic-ACase Report

Hyperglycemia is the most frequently observed sign of diabetes and is considered the etiologic source of diabetes complication both in the body and in the eye. Changes in refraction are very common in diabetic patients and sometimes, it could be the first sign to the existence of the condition. Transient hyperopic changes are highly dependent on the magnitude of plasma glucose concentrations and rapid correction of hyperglycemia is strictly correlated with complete recovery of refraction. To account for this phenomenon, the sorbitol production via the polyol pathway with over hydrationof the lens has beenconsidered, aswell asachange inthe refractive index of the lens. Refractive corrections or alterations are to be discouraged until plasma glucose levels have normalized.

Effect of Glycemic Control on Refractive Changes in Diabetic Patients With Hyperglycemia

To investigate the effect of intensive glycemic control on hyperglycemia- induced changes in refraction, corneal topography, lenticular and corneal thickness in diabetic patients. Eighteen diabetic patients with plasma glucose >300 mg/dl were enrolled in the study consecutively. Autorefraction, C-Scan corneal 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. Mean plasma glucose levels were 356.00 mg/dl before and 133.78 mg/dl after treatment. The median values of the autorefractometric measurements were - 0.125 D on admission and + 0.375 D at the second examination. The difference in the refraction was statistically 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 measurements 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. 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 hyperopic 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.

Diabetic myopia--is it lens-induced? An oculometric study comprising ultrasound measurements.

An oculometric study has been performed to evaluate features possibly being responsible for a (permanent) shift towards myopia in eyes of diabetics, a trend apparent from previous clinical investigations. Having excluded cases of transient refractive change associated with poor metabolic control, we are dealing with adult subjects with stable refractive levels, also including cases of adult-onset myopia. Out of 62 diabetic and 48 non-diabetic eyes (age 17-23, diabetes duration 2-38 years) a careful matching according to age, sex and refraction provided 26 eye-pairs from 52 subjects for analysis. In 23 matched pairs there was low myopia. The lenses of diabetics appeared significantly thicker than in non-diabetics (mean difference 0.2 mm), and a higher lens power came close to significance. Corneal curvature, anterior chamber depth and axial length did not differ. A subsequent analysis of degree of lens thickness increase in diabetics revealed a positive correlation with diabetes duration. A thicker lens does not of necessity imply a higher lens power, but from the present data this is the most likely explanation of diabetic myopia in adults.