Abstract
Background: One of the leading causes of preventable blindness is cataract affecting approximately 18 million people worldwide. Twenty per cent of cataract operations worldwide are performed on people with diabetes mellitus (PDM).Aim: The aim of this review article is to analyse the scientific literature relating to visual changes associated with diabetes mellitus (DM) in pseudophakic, aphakic and phakic people, and to discuss the consequences of these changes for optometrists.Method: A literature search was conducted on PubMed, the University of KwaZulu-Natal Libraries and Google Scholar databases from August 2017 to August 2018.Results: Acute and chronic hyperglycaemia in DM causes myopia in phakic PDM, whilst in aphakic PDM it causes a hyperopic shift in refraction. It has been reported that contrast sensitivity and visual acuity are affected by changes in blood glucose. People with DM have increased central corneal thickness as compared to non-diabetics, whilst only the posterior corneal curvature is affected by hyperglycaemia in PDM. No evidence exists on the effects of glycaemic changes in pseudophakes.Conclusion: It should be noted that high blood glucose level (BGL) induces transient myopia and hyperopia in chronic phakic PDM and aphakic PDM, respectively. All refractive procedures, including prescription of spectacles, corneal refractive procedures and lens extraction, should be deferred until normalisation of BGL in phakic and pseudophakic PDM, as higher sugar levels affect corneal curvature and thickness and overall vision.
Highlights
One of the leading causes of preventable blindness is cataract affecting approximately 18 million people worldwide.[1]
There are no significant changes in the overall anterior corneal curvature before and after glycaemia control in phakic people with diabetes mellitus (PDM);[14,15] there is evidence of significant change in the flattest corneal meridian.[16] http://www.avehjournal.org
Refractive error is influenced by changes in corneal thickness, corneal curvature, lenticular thickness and axial length or a combination of all of these.[11]
Summary
One of the leading causes of preventable blindness is cataract affecting approximately 18 million people worldwide.[1]. Diabetes mellitus is a group of metabolic diseases, characterised by high BGL resulting from deficient insulin secretion, insulin action or both.[4] Currently, it is classified on the basis of the pathogenic process that leads to hyperglycaemia. Under this classification, the terms type 1 diabetes mellitus (T1 DM) and type 2 diabetes mellitus (T2 DM) have replaced insulin-dependent DM, juvenile-onset diabetes and non-insulin-dependent DM, respectively, for adult-onset diabetes.[4] Common symptoms of DM are polyuria, polydipsia, polyphagia, weight loss and blurred vision.[4]. A point to note is that the crystalline lens is metabolically active and requires nourishment in order to maintain its growth and transparency, whilst the IOL is not metabolically inert.[9]
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