Pupil to Limbus Diameter Ratio (Pld Ratio), Olfactory Sensitivity and Cognition in Females with Type 2 Diabetes Mellitus: A Case Control Study

 

Riya Regi¹, Kumar Sai Sailesh,¹ Mukkadan J K^2*

¹Department of Physiology, Little Flower Institute of Medical Sciences and Research, Angamaly, Kerala. India.

²Department of Research, Little Flower Medical Research Centre, Angamaly, Kerala, India.

 

ABSTRACT:

The present study was undertaken to observe the Pupil to Limbus Diameter Ratio (PLD Ratio), Olfactory Sensitivity and Cognition in females with type 2 Diabetes Mellitus. Thirty females with controlled type 2 diabetes mellitus and thirty age matched healthy females (controls) were included in the study after obtaining written , informed consent.PLD Ratio was measured by two-box method. Blast injection method was used to measure the olfactory sensitivity. Digit Symbol Substitution Test , Letter Cancellation Test , Immediate Word Recall , Immediate Object Recall , Mini Mental State Examination were used to assess the cognition. Height and weight of the diabetic patients is higher than control group participants (P<0.05). No significant difference was observed in olfactory sensitivity, Digit Symbol Substitution Test (DSS), Letter Cancellation Test (LCT), and Immediate Word Recall (IWR) scores Immediate Object Recall (IOR), Mini mental state examination (MMSE), pupil to limbus diameter (PLD) ratio of right and left eye of diabetic patients and healthy controls. We have not observed significant difference in PLD ratio, olfactory sensitivity and cognitive functions among diabetic females and healthy age matched females.              

 

 

 

 

INTRODUCTION:

Diabetes is a chronic metabolic disease, that occurs when the pancreas does not produce enough insulin or when the body cannot use the insulin effectively. This leads to a condition with high concentration of glucose in the blood called hyperglycemia¹. India leads the world with the largest number of diabetics and termed as “diabetes capital of the world”.

 

India has diabetes prevalence rate of 60 million in 2011 which is projected to increase by 63%, reaching about 98 million by 2030². The pupil is an aperture located in the center of the iris of the eye and it regulates the entry of light into the retina. The limbus constitutes the border between the white opaque sclera and transparent cornea³. Changes in the diameter of pupil increases during sympathetic stimulation⁴.

 

Olfaction is the function by which odours are perceived. Olfactory sensitivity is the response of the olfactory system of body to certain chemical substances⁵. Recent literature reported a relation between diabetes mellitus and an early or accelerated decline in cognition, including two fold increases in the risk of dementia⁶. Hence the present study was undertaken to observe the PLD Ratio, olfactory sensitivity and cognitive functions in females with type2 diabetes mellitus.

MATERIALS AND METHODS:

Participants:

The study was conducted at Little Flower Institute of Medical Sciences And Research from August 2016 to March 2017. Thirty females with controlled type2 diabetes mellitus and thirty age matched healthy females (controls) were included in the study after obtaining written, informed consent. The present study was approved by institutional human ethical committee (EC-27/1/2016). The following criteria were followed while recruiting the cases.

 

1.      Controlled diabetic patients (fasting blood sugar levels </=126 mg/dl and post prandial blood sugar level </=180 mg/dl), attending our diabetic clinic for regular check up.

2.      Having diabetes at least one year duration and those on diabetic diet and oral hypoglycemic agents.

3.      Age between 30-60 years.

4.      Willing participants.

5.      Not suffering with any other diseases or complications.

 

Outcome measures:

Assessment of pupil to limbus diameter PLD Ratio:

PLD Ratio was measured by two-box method as specified in the literature ³.

 

Assessment of Olfactory Sensitivity:

Blast injection method:

Blast injection method was used to measure the olfactory sensitivity. The olfactometer , manufactured by Anand Agencies, Pune was used in the study as standardized earlier [8].Presenting odor is 3 drops of jasmine oil mixed with 30 ml of water was used to present jasmine odor. Therapeutic essential jasmine oil was by Karmakara Company⁷.

 

Assessment of Cognition

Digit Symbol Substitution Test:

This is the test to check sustained attention and response speed. To substitute the symbols accurately and quickly, quick processing of information is needed. A hundred numbers were randomly printed out on a paper. The subject was asked to draw a triangle over odd numbers and a circle over even numbers. Then the time taken by the subject for substituting a symbol for all of the 100 digits was recorded ⁹.

Letter Cancellation Test:

On a white sheet of paper, the 26 letters of the English alphabet were jumbled and printed in black colour. All the letters were evenly spaced out. As soon as 10 letters were called out in random order, the subject was instructed to cancel out the appropriate letter as soon as he heard it being called. The time taken from calling to cancellation of all 10 letters was recorded ¹⁰.

 

Immediate Word Recall:

About 20 words were read at a constant rate of one word every 2 seconds. The subjects were asked to recall immediately and write down as many possible words from memory in 60 seconds ^{9, 11}.

 

Immediate Object Recall:

Subjects were exposed to 20 objects placed on a table. The objects include animal picture cards to households. The subjects were given 15 seconds to view these objects and then they were taken away. The subjects were instructed to write down as many possible objects from memory in 60 seconds^9,11.

 

Mini Mental State Examination (MMSE):

The MMSE is a tool used to assess mental status thoroughly and systematically. It is an 11- question measure which tests five areas of cognitive functions such as orientation, registration, attention and calculation, recall and language. Its maximum score is 30.A score of 23 or lower indicates cognitive impairment ¹².

 

Data Analysis:

Data was analyzed by SPSS 20.0 version using unpaired t test. P value <0.05 was considered as significant.

 

RESULTS:

Figure 1 presents demographic data of the participants. Height and weight of the diabetic patients is higher than control group participants (P<0.05). no significant difference was observed in olfactory sensitivity, Digit Symbol Substitution Test (DSS), Letter Cancellation Test (LCT), and Immediate Word Recall (IWR) scores Immediate Object Recall (IOR), Mini mental state examination (MMSE), pupil to limbus diameter (PLD) ratio of right and left eye of diabetic patients and healthy controls (figure 2,3).

 

Figure 1: Demographic data of the participants

Data was expressed as mean ± SD. *P<0.05 is significant, **P<0.01 is significant, ***P<0.001 is significant.

 

Figure 2: Olfactory sensitivity, Digit Symbol Substitution Test (DSS), Letter Cancellation Test (LCT), and Immediate Word Recall (IWR) scores of participant.

Data was expressed as mean ± SD. *P<0.05 is significant, **P<0.01 is significant, ***P<0.001 is significant.

 

Figure 3: Immediate Object Recall (IOR), Mini mental state examination (MMSE), pupil to limbus diameter (PLD) ratio of right and left eye of the participants.

Data was expressed as mean ± SD. *P<0.05 is significant, **P<0.01 is significant, ***P<0.001 is significant

 

DISCUSSION:

The present study was aimed to observe the olfactory sensitivity, PLD ratio and cognitive functions among females with type2 diabetes mellitus and healthy controls. We have not observed significant difference in the outcome measures among diabetic females and healthy controls. Changes in the pupil size were reported as an indicator for autonomic activity¹³. Pupillary diameter was not dependent with age but significantly related to diabetes duration systolic blood pressure, diastolic blood pressure and mean albumin/creatinine ratio¹⁴. Long-term diabetics when exposed to continuous light was reported to have a smaller pupil size than the controls¹⁵ and suggested to measure the pupillary responses in darkness. In the current study, we have assessed the PLD ratio in light and we have not observed significant difference in PLD ratio of right and left eye among diabetics and healthy controls. Earlier studies reported that Participants with diabetes had decreased olfactory sensitivity, impaired olfactory discrimination abilities, and reduced odor identification skills when compared with controls¹⁶. However, in the current study we have not observed significant difference in olfactory sensitivity among diabetics and healthy controls. Earlier studies reported that diabetes has significant association with impairment of cognitive functions¹⁷. In the current study, we have not observed significant difference in cognitive functions among diabetics and healthy controls. It may be because of two reasons; first one is all our cases are with controlled diabetic patients. Second reason is less sample size.

 

CONCLUSION:

We have not observed significant difference in PLD ratio, olfactory sensitivity and cognitive functions among diabetic females and healthy age matched females.

 

CONFLICTS OF INTEREST:

Nil.

 

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Accepted on 27.04.2017        © RJPT All right reserved