Retinal nerve fibre layer thickness of natives of high altitude versus low altitude (topcon 3d oct-1maestro based study)

Purpose: To study Retinal nerve fibre layer thickness of natives of high altitude versus low altitudeat Indira Gandhi Medical College Shimla in the hilly terrain of Himachal Pradesh.
Methods: A hospitalbased prospective observational study was conducted from July2017 to June2018 in the ophthalmology department at Indira Gandhi Medical College Shimla. Total of 200 healthy subjects underwent retinal nerve fibre layer thickness analysis by Spectral domain OCT. Of the 200 subjects, 100 subjects residing at a height, greater than 2000m above the sea level were included in the study group (cases), 100 subjects residing at a height of less than 2000m above the sea level were included in the control group.
Results:The study population consisted of 200 healthy subjects from 30 to 69 years of age. There were 49 males and 51 females were in the both the groups. Average RNFL thickness in high altitude was 97.66 ± 7.04µm and 125.79 ± 10.91µm in inferior, 116.20 ± 10.49µm in superior, 82.49 ± 10.13µm in nasal and 66.26 ± 7.63µm in temporal quadrant. Average RNFL thickness in low altitude was 102.59 ± 7.10µm and 129.69 ± 11.12µm in inferior, 122.21 ± 10.64µm in superior, 88.02 ± 9.50µm in nasal and 70.56 ± 7.12µm in temporal quadrant.The high altitude group had thinner RNFL parameter than low altitude group, in data adjusted for age and gender (all P <0.05). Normal RNFL thickness values follow the ISNT rule with decreasing RNFL thickness values starting from the thickest quadrant inferiorly to the thinnest quadrant temporally. Thinner RNFL measurements were associated with older age.
Conclusion: This study concluded that natives of high altitude have thinner RNFL values as compared to low altitude. Thinner RNFL measurements observed in older age group. There was no relationship between RNFL thickness and gender.