Influence of fasting during Ramadan on intra-ocular pressure.

To the Editor: The month of Ramadan is a holy month for Muslims during which they fast from sunrise until sunset. The prolonged dietary restrictions during this month can lead to changes in hematocrit and electrolyte imbalance. The aim of this study was to evaluate the influence of fasting during the month of Ramadan on intraocular pressure (IOP). We performed a prospective cohort study on 144 eyes of 72 normal Muslim patients observing a period of fasting during the month of Ramadan. Patients with glaucoma or a family history of glaucoma, and systemic diseases were excluded. Eleven patients did not come back for follow-up and were also excluded.

A complete ophthalmological exam was done with IOP measured by applanation tonometry of Goldman. These measures were performed during the third week of Ramadan and 5 weeks later. The two measures were taken at the same moment of the day (at noon), by the same examiner and by the same tonometer that had been calibrated before.

The mean age of our patients was 49 years old and 52.8% were males. During the month of Ramadan, the mean value of IOP was 13.86 mm Hg for the right eye and 13.97 mm Hg for the left eye . After Ramadan, the mean value of IOP increased to 14.5 mm Hg for the right eye (P=.13) and 13.97 mm Hg for the left eye (P=.10) but remained statistically insignificant. The stratified analysis according to sex found no statistically significant difference between men and women during (P=.5) or after the month of Ramadan (P=.7).

Ramadan is the ninth month of the lunar year. Fasting during this month constitutes the fourth of the five fundamental bases on which Islam is built. The prolonged dietary restrictions can lead to changes in hematocrit and electrolytic imbalance1 and even to an increase in the incidence of central retinal vein occlusion2 and to changes in lachrymal secretion.3 Only three studies in the literature have addressed the relationship between fasting and IOP.4–6 One concluded that fasting in healthy adults does not modify diurnal IOP. We had the same results in our study even though lower values during Ramadan were recorded. The third study6 reported different results, with a mean that decreased significantly during fasting.

Several physiopathological hypotheses have been proposed to explain the reason for IOP alteration during fasting. The likeliest explanation is that the dehydration induced by fluid restriction causes an aqueous humor reduction and thereby a decrease in IOP. Secondly, depletion of fat stores during fasting causes a decrease in prostaglandin secretion and an IOP decrease.4 Another survey showed that conditions of dehydration and fasting produce a significant reduction of the blood flow velocity of retrobulbar vessels measured by color Doppler ultrasonography.5 Our study did not record any variation by sex. the inclusion of women in our study may have confounded the results since premenpausal women do not fast during menstruation. However, this confounding effect is unlikely since most of the women in this study were postmenpausal and were fasting. The absence of an influence of fasting on the IOP suggests that the practice of Ramadan can be allowed in glaucomatous patients without any modification of therapy.