Analysis of macular thickness by spectral domain OCT in normal healthy population of Gujrat, India

Study was conducted to analyse the average macular thickness globally from different age group from the healthy Indian population. Study will help to quantify any difference in thickness between gender and right and left eye too. Data can be compared with different ethnic groups.

In total 147 patients have been enrolled in study attending daily ophthalmology out patient department. Age distribution of patients are 11 to 75 years. After patient fits inclusion criteria, single handed macular thickness measurement by spectral Domain OCT was carried out after consent. Measurement area is automatically identified by placing rim of 1mm, 3mm and 6mm diameter evenly around the centre of macula. Here we have encountered only central subfoveal values. Then macular thickness is calculated itself by algorithm. Protocol also displays binocular symmetry. To make sure for the accuracy of the results only the signal strength of 6 or higher and binocular symmetry more then 85% will be accepted in our study. Each patient was scanned single time with accuracy. Change in macular thickness was calculated by using paired sample t test, independent sample t test and T-test assuming equal variences.

Mean central subfoveal thickness for our population is 238.7278±14.2460 μ. However for different age group A, B, C and D the values for central subfoveal thickness are 241.9038±14.6972μ, 241.6428±8.2017μ, 235.5681±14.3381μ and 236.8428±18.1032μ respectively. There is weak negative corelation between left eye macular thickness and age which is statistically significant (r=-0.22)(p=0.005) (95% CI for r=-0.37 to 0.06). There is no correlation between right eye macular thickness and age (r=-0.07)(p=0.35) (95% CI for r=-0.23 to 0.08). The mean±SD values for Right and Left eye are 237.5986±13.7804 and 239.8571±14.6568μ respectively. In paired t test for right and left eye macular thickness difference is statistically significant (p=0.0043)(95% CI-3.7967 to-0.7203). Mean values for different age group A, B, C and D for right eye are 239.1923±13.7579μ, 240.2380±7.9994μ, 233.4318±14.5496μ and 238.4857±17.2496μ respectively. While for the left eye 244.6153±15.3650μ, 243.0476±8.2549μ, 237.7045±13.9610μ and 235.2000±19.0259μ respectively. Normative values we found for male and female are 238.5735±13.4868μ and 238.9556±14.9075μ respectively. Difference in right and left macular thickness in male and female is not statistically significant as (p=0.5867, p=0.9221)(95%CI-5.6616 to 3.2148, -4.5699 to 5.0468). Mean±SD for different age group A, B, C and D for male are 242.8076±12.7059μ, 240.8157±8.0868μ, 236.6052±14.1240μ and 234.5882μ respectively. While for left eye central subfoveal thickness for different age group A, B, C and D are 241.00±16.6589μ, 242.3260±8.3214μ, 234.7800± 14.5914μ and 238.9722±19.1989μ respectively.

Study has provided normative data of central subfoveal thickness for normal west Indian population. Normative values derived from this study can be used for different macular diseases in which macular thickness either increases or decreases. However studies from different ethnic group shows different mean values for macular thickness. This should be considered while diagnosing any macular pathology involving thickness. In our study difference between gender is not statistically significant while difference between right and left eye shows significant difference.