We appreciate Dr. Kadyan’s letter regarding our study “Non-arteritic anterior ischaemic optic neuropathy and presumed sleep apnoea syndrome screened by the Sleep Apnea scale of the Sleep Disorders Questionnaire (SA-SDQ)” . He requests clarification on several issues and, to the best of our ability we will attempt to respond to each in turn. Regarding the proportion of cases and controls diagnosed with glaucoma, this information appears in Table 1 of the published manuscript.
Regarding exclusion criteria for the control group, as stated in the published manuscript the controls were randomly selected from patients seen in the Department of Ophthalmology clinic for reasons other than NAION; there were no other exclusionary criteria. With respect to the other ocular diagnoses of the control group, we did not collect this information. We also do not have information on the results of any sleep studies the study participants may have obtained.
Finally, regarding which of the specific sleep apnea syndrome symptoms in the SA-SDQ were associated with NAION, it appears that the cases reported more frequent loud snoring (or bothering others), having nose block up when wanting to sleep, and snoring/breathing getting worse when sleeping on the back compared to controls. There were no statistically significant differences for the other SAS specific items nor for any of the non-SAS items (e.g., body mass index, smoking status). Furthering these analyses to create a weighted score is an interesting idea and something we may consider pursuing in the future.
Gerald McGwin, Jr., M.S., Ph.D. Cynthia Owsley, Ph.D., M.S.P.H. Departments of Epidemiology and Ophthalmology University of Alabama at Birmingham Birmingham, Alabama
1. Li J, McGwin G, Vaphiades, Owsley C. Non-arteritic anterior ischaemic optic neuropathy and presumed sleep apnoea syndrome screened by the Sleep Apnea scale of the Sleep Disorders Questionnaire (SA-SDQ). Br J Ophthalmol. 2007;91:1524-7.