Evaluation of Retinal Nerve Fibre Layer Thickness in Black Glaucoma Suspects

Background: There is a need to evaluate glaucoma suspects to ascertain those who actually have the disease and commence treatment to avoid progression to blindness and monitor closely those with a tendency to progress to glaucoma. It is also necessary to rule out those without glaucoma and save them from the psychological, emotional and financial burden of being labeled a glaucoma patient. Therefore, analyzing the retinal nerve fibre layer thickness will be of great importance in achieving this.

Aim: To evaluate the retinal nerve fiber layer thickness in black glaucoma suspects.

Method: This is a non-intervention observational hospital-based study using consecutive allocation of glaucoma suspects as they presented to the glaucoma clinic between October 2nd, 2012 and January 31st, 2013, Medical history was recorded, and comprehensive ocular examination done on each of the subjects. Ocular examination included visual acuity, visual field, tonometry and ophthalmoscopy. Instruments used during the research were Pen torch for examination of the external structures of the eyes, Keeler ophthalmoscopes for fundus examination, Snellen’s charts both literate and illiterate charts for visual acuity assessment, Reichert AT 555 Auto non-contact tonometer for measurement of the intra-ocular pressure. Observations were done using the Optical Coherence Tomography machine with minimum normal RNFL thickness value set at 93.46μm. Data was analyzed using the statistical package EPI info version 6.04d, a software package designed by the Centers for Disease Control and Prevention (CDC), USA in 2001.

Results: A total of 120 participants comprising 60males and 60 females were examined with a mean age of 42.8±13.79; the age range was 19 to 75 years. The retinal nerve fiber layer was noticed to be thickest in the inferior quadrant, followed by the superior, nasal and temporal quadrants. The RNFL thickness decreased with increasing age (p < 0.05; r = - 0.38). A total of 30.4% of the eyes (n = 73/240) had their average RNFL thickness lesser than 93.46μm.

Conclusion: The ISNT rule was obeyed in this study as the distribution of the peripapillary RNFL thickness in the various quadrants showed that the inferior quadrant had the thickest RNFL, followed by the superior, nasal and temporal quadrant. Increasing age was associated with a decrease of RNFL thickness which was statistically significant. Minority of the subjects had their average RNFL thickness lesser than the normal value.

Keywords:Retinal; Nerve; Fibre; Layer; Thickness; Glaucoma; Suspect