A review was made of patients diagnosed with NAION, who were admitted to the Ophthalmology Clinic at Bozyaka Training and Research Hospital, Izmir, Turkey between 2011 and 2015. The study group included a total of 30 eyes of 30 patients who attended the clinic for a routine check-up between June 2014 and October 2015 and a control group included a total of 31 patients who attended the clinic for a refraction examination. The medical records of all patients were reviewed and a comparison was made of the study group and the control group. The study was conducted in accordance with the tenets of the Declaration of Helsinki, with approval from the Local Ethics Committee of this hospital. Informed consent for participation in this study was obtained from each participant.
The criteria required for diagnosis of NAION were as follows: (1) a history of sudden visual loss and an absence of other ocular, orbital, systemic, or neurological diseases that may influence or explain the patient’s visual symptoms; (2) presence of optic disc edema at the time the patient came to medical attention shortly after the onset of acute symptoms; (3) spontaneous resolution of optic disc edema was observed; and (4) the eye had optic disc-related visual field defects.
Patients were excluded if they had media opacities that would preclude fundus examination or visual field evaluation, glaucoma, coexistence of ophthalmic or neurological disease, or any other retinal pathology, or if they had undergone previous eye surgery other than uneventful cataract surgery. Patients with diabetes mellitus were included, but those who had vitreous hemorrhages, traction detachment, or other complications influencing visual acuity or visual fields were excluded. Eyes with unreliable visual fields were excluded. In addition, patients who were in the acute stage of NAION were excluded from the study, in order to minimise the effects of optic disc swelling.
The control group consisted of subjects with no history of chronic ocular or systemic disease or of ocular surgery other than uneventful cataract surgery. The inclusion criteria for this group were that they had a normal visual field test, IOP of less than 21 mmHg, a normal, symmetric optic disc head between left and right eyes, an open anterior chamber angle, no history of chronic, ocular or systemic corticosteroid use, spherical refraction of < ±5.00 dioptres and astigmatism of < ±3.00 dioptres.
A detailed medical history was taken from each participant including all previous or current systemic diseases, with particular focus on arterial hypertension, diabetes mellitus, ischaemic heart disease and hyperlipidemia. Blood pressure measurements were taken using a brachial sphygmomanometer (DS66, Welch Allyn, Skaneateles, NY, USA) and a Littmann Classic II stethoscope (3 M, St Paul, MN, USA) on the upper right-side arm after a rest period of at least 5 minutes. Patients were told to abstain from caffeine, exercise, and smoking for at least 30 minutes before the examination. The measurements were repeated after a 5-minute interval and the average of the two values was recorded. The height (in centimeters) and weight (kilograms) of the patients were measured using a standard scale, and in light clothing and bare feet, and noted. Body Mass Index (BMI) was calculated using the formula weight (kg)/height squared (m2).
A comprehensive ophthalmic evaluation was performed at that time, which included (1) recording of the best-corrected visual acuity (BCVA) using a Snellen chart, (2) the visual field measurement using a Humphrey Automated Field Analyzer (Carl Zeiss Meditec Inc, Dublin, CA, USA) program 30–2 and the standard Swedish interactive threshold algorithm (SITA) strategy, (3) slit-lamp examination of the anterior segment, lens, and vitreous, (4) IOP with Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT, PASCAL, Swiss Microtechnology AG, a Ziemer Ophthalmic Systems Group Company), (5) OPA with DCT, (6) The central corneal thickness (CCT) was measured three times using ultrasonic pachymetry with a Pacscan 300P USP device (Sonomed Inc., Lake Success, NY, USA) (6), direct and indirect ophthalmoscopy and (7) color fundus photography. OPA measurements were taken using a slit lamp-mounted DCT device at the same time of day (09:00–10:00) in all cases, thus avoiding diurnal fluctuations. All the measurement procedures were applied by the same two experienced ophthalmologists (DA and OK) according to the manufacturer’s recommendations. Only Quality index (‘Q’) readings of 1 or 2 (range: 1–5, with higher values indicating lower quality) were included in the analysis. The ‘OPA’ value of each eye was calculated as the mean of three consecutive readings. Both eyes were examined in the study and control groups but only the values of the right eyes of the control group were used for analyses.
Statistics were analyzed using SPSS software version 15.0 (SPSS, Inc, Chicago, Illinois, USA). The data were given as mean values ± SDs. The Gaussian distribution of the parameters was tested using the Kolmogorov–Smirnov test. Continuous variables were compared between the groups using the Student t-test and categorical variables were compared using the χ2 test. The Pearson Chi-square test with Yates continuity correction or the Fisher exact test, as appropriate, were used for frequency distribution comparisons. All tests were two tailed, and significance was set at 0.05.