FP919 : Altered Tear Dopamine – Biomarker for Pediatric Myopia

Dr. Jyoti Matalia, M10661, Dr. Pratibha Panmand, Dr. Pooja Ghalla, Dr. Rohit Shetty

Introduction: Literature review has shown that local dopamine levels play a role in propensity to development of deprivation myopia and lens induced myopia but most of the studies done about dopamine and refractive errors were mainly in animal models. However, there has been no study comparing the levels of tear dopamine in normal and myopic eyes. We are investigating the role of dopamine in development of refractive errors by measuring the levels of dopamine in tears. This study was done to see if this non-invasive method of tear collection and tear dopamine level evaluation could provide us any actual correlation in human eyes with reference to myopic refractive errors.

Purpose: To study the dopamine levels in the tear fluid (non- invasive) in myopic children and correlation of thedopamine levels between emmetropes and different grades of myopia.

Material and Methods: The study was conducted at a tertiary care centre after obtaining ethic committee approval.

Inclusion Criteria:Patient less than 18 years reporting at the pediatric OPD having signs and symptoms pertaining to refractive error. Children with myopia were included in the study.  Myopia was classified into low (-1.5 Ds to -2.5Ds), moderate (-4.0Ds to -5.0Ds) and high myopia (-6.5Ds to -8.0DS).Healthy volunteers with no ocular conditions were recruited for the relevant control groups.

Exclusion Criteria:The following subjects/patients were excluded from the study.

1. Those with recent (last three months) history of eye allergy or infection
2. Those with any underlying systemic autoimmune or other inflammatory conditions
3. Those wearing contact lenses
4. Those who have recent history of surgical or medical treatment for an ocular condition
5. Those with known general malnutrition
6. Those on any systemic medications.

On the basis of the above, 30 children with different grades of myopia and 10 emmetropes were included in this study. All children underwent detailed ophthalmic evaluation including cycloplegic refraction, anterior and dilated posterior segment evaluation. Axial length was measured using A-scan using IOL Master.

Tears were collected from all over Schirmers strips, stored at -80degC and analysed by flow cytometry.Total dopamine level in the tears was measured by competitive inhibition enzyme linked immunoassay.

Statistical analysis

All statistical analyses were performed with Graph Pad Prism 6.0 (Graph Pad Software, Inc., La Jolla, CA, USA). Shapiro-Wilk normality test was used to check distribution of the data set. Spearman correlations analysis, Kruskal-Wallis and Mann-Whitney test were used to analyze data sets that were not normally distributed. The mean value of the individual groups was reported as mean±SEM. P< 0.05 was considered to be statistically significant.

Results:

Ten emmetropes, 10 low, 7 moderate and 13 high myopes were included.

• Average age of children in emmetrope group was 11.8±1.1 years and myopia group was 11.4±0.6 years.
• There were 4 females and 6 males in the emmetrope group while there were 14 females and 16 males in the myopia group. No difference was observed in the tear dopamine levels between the male and female subjects.
• Mean axial length was 22.9±0.2mm in emmetropes and 25.3±0.3mm in myopes.

Grade / severity dependent increase (p <0.05; Mann Whitney Test) in the axial length across grades of myopia was observed but was not statistically significant.

Negative correlation (r = -0.8215; p < 0.0001) was observed between spherical equivalent and axial length measurements in the study subjects. These observations confirm that the subjects recruited for the study is appropriate.

• No correlation was observed between tear dopamine levels and axial length.
• Average dopamine tear levels in emmetropeswere 1158±650pg/ml while in myopes it was 165± 74pg/ml. The tear dopamine levels were observed to significantly (p < 0.05) lower in the myopic subjects compared to emmetropes
• The dopamine tear level amongst different grades of myopes:
  • Low myopia: 58±20pg/ml,
  • Moderate: 69±15pg/ml
  • High: 143±82pg/ml.

No significant difference in the tear dopamine levels between the grades/severity of myopia was observed.

Conclusion: This study suggests a possible role of tear dopamine as a biomarker for predicting progressive myopia in children.

1. Significantly low level of dopamine was observed in myopia compared to emmetropia
2. It was observed that there is very less difference in levels of dopamine within the subgroups except in the pathologic group which is relatively highbut the difference in tear dopamine levels within the myopic subgroups was not significantly different and to detect a trend a study with larger sample size in subgroups may be needed..
3. There is a negative correlation between axial length and spherical aberration.
4. Finally there is no correlation observed between dopamine and axial length and also between dopamine and spherical aberration.