|Year : 2014 | Volume
| Issue : 2 | Page : 62-65
The effect of fasting on intra ocular parameters
Salem Musa Alameen1, Ahmed Alsiddig A Albagi2
1 Department of Optometry, Sudan Eye Center, Alneelian University, Khartoum, Sudan
2 Assisted Professor at the Faculty of Optometry and Visual Science, Alneelian University, Khartoum, Sudan
|Date of Web Publication||6-Feb-2015|
Ahmed Alsiddig A Albagi
Assisted Professor at the Faculty of Optometry and Visual Science, Alneelian University, Khartoum
Objectives: The objective was to assess the effect of fasting on the intraocular parameters. Materials and Methods: A total of 114 subjects enrolled in this study. The method included was the measurements of the keratometry readings, axial length, anterior chamber depth, lens thickness, vitreous thickness, and calculation of intraocular lens (IOL) power. These measurements were done twice at first while the patient is in the fasting state and second while the patient is in the fed state. Result: No change occurred in keratometry readings, lens thickness or vitreous thickness. The axial length decreased by 0.251 mm in the fasting state while the anterior chamber depth was 0.165 mm shorter. Furthermore, the power of IOL calculated by Sanders, Retzlaff, and Kraft formula was found to be increased by 1 D in the fasting state which was found to be statistically significant. Conclusion: Measuring the intraocular parameters for a patient who is in the fasting state will result in a shorter axial length and higher IOL power so care should be taken when measuring the intraocular parameters for a patient who is in the fasting state.
Keywords: Fasting, fed, ocular parameters
|How to cite this article:|
Alameen SM, Albagi AA. The effect of fasting on intra ocular parameters. Sudanese J Ophthalmol 2014;6:62-5
| Introduction|| |
Fasting is among the most prevalent activities in the world; many people practice fasting regardless of nationality or religion. Islamic fasting is done by refraining from eating or drinking during daylight hours in the 9 month of Islamic calendar, the month of Ramadan, which can occur in any season. The pattern, type, and the amount of food consumed during Ramadan evidently differ from that consumed during other months. To endure the effects of hunger and dehydration, people intentionally eat a significant amount of food and drink plenty of fluid just before dawn.
Several studies showed that fasting influences a variety of physiological parameters that can impact the ocular system, triggering a fall in insulin secretion and a rise in glucagon and sympathetic activity, which can lead to free fatty acid release and elevated norepinephrine and cortisol concentration. 
Cataract is the leading cause of blindness. Worldwide, about 20 million persons are blind because of cataract.  The main cause of blindness in Sudan is also cataract with prevalence of about 60%. Cataract surgery increased, and intraocular lens (IOL) implantation rate also increased, in 2010 implantation rate in Sudan was 98% compared to <20% in 2003. 
With respect to these, one may anticipate a hypothetical (if proved to occur) distortion of ocular parameters during Ramadan. Parameters fluctuation during fasting may lead to a false prediction of the accurate power of the IOL.
| Materials and Methods|| |
All the procedures were taken place at Sudan Eye Center.
Two hundred and twenty-eight eyes of 114 subjects (42% were males and 58% were females) have enrolled in the study.
All the subjects in this study are older than 21 years. The subjects are emmetrope (the refraction between +0.25 D sph and −0.50 D sph) and free from any ocular or systemic diseases.
| Procedures|| |
All the subjects were seen twice: At first while they were in the fasting state and second while they were in the fed state.
The procedures begin by measuring the K readings using Shin Nippon Accuref-k 9001. The measurements have been taken by the automatic mode, and the degree of accuracy is ±0.12 D, and then followed by measuring the A-scan using Nidek Echoscan US-800. The axial length, anterior chamber depth, lens thickness, vitreous thickness, and IOL power calculation using Sanders, Retzlaff and Kraft equation are all recorded from the A-scan.
The procedures are the same in the fasting and the fed state. In the fasting state, all the measurements were taken during the month of Ramadan in 2013 after 2.00 p.m. while in the fed state measurements were taken after the month of Ramadan and within 2 hours from the last meal.
The differences in means of the measurements between the fasting state and the fed state were computed using the paired-samples t-test.
| Results|| |
A total of 114 volunteers participated in this study, 67 of them were females, and 47 were males, aged between 22 and 39 years old with a mean age of 27.2 years.
The following seven tables will give a comparison between the measurements of the ocular parameters in the fasting state and the fed state. The tables also show whether the changes in measurements between the fasting state and the fed state are statistically significant or not (calculated by the paired-sample t-test).
| Discussion|| |
K-readings showed no differences in the measurements between the fasting and the fed state as shown by [Table 1] and [Table 2]. This finding agrees with the finding of Nowroozzadeh et al. 
|Table 1: The difference in K1 reading between the fasting state and the fed state |
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|Table 2: The difference in K2 reading between the fasting state and the fed state |
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A 0.251 mm difference was recorded in axial length between the fasting state and the fed state as shown in [Table 3]. The axial length was longer in the fed state.
|Table 3: Axial length differences between the fasting state and the fed state |
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Statistically, the difference was not significant, but in terms of IOL power calculation this 0.251 mm difference will lead to about +0.6 D error in IOL power which may be considered a significant error by some cautious surgeons.
This finding also agrees with what Nowroozzadeh et al. have obtained with their study.
In the case of anterior chamber depth, the difference between the fasting state and the fed state was 0.165 mm as shown in [Table 4], and it is longer in the fed state than in the fasting state. Statistically, the 0.165 mm difference is considered to be a significant difference (P = 0.023) in comparison to the small depth of the anterior chamber which measures approximately 2.5 mm.  Also in term of IOL power calculation, this change will have a small effect on the final calculated power.
|Table 4: Comparison of the anterior chamber depth in the fasting state with the depth in fed state |
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This finding disagrees with that of Kerimoglu et al.  who considered the difference was not significant. This finding also conflicts with that of Nowroozzadeh et al. who stated the presence of a significant increase in anterior chamber depth in the fasting state and this study result showed that the anterior chamber depth has decreased due to fasting.
The crystalline lens and the vitreous thickness did not show a significant variation between the measurements of the fasting and the fed state. The crystalline lens was 0.177 mm thicker in the fasting state while the vitreous thickness decreased by 0.239 mm. These results are showed in [Table 5] and [Table 6] for the lens thickness and vitreous thickness, respectively.
|Table 5: The comparison in lens thickness between the fasting state and the fed state |
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|Table 6: The differences in vitreous thickness between the fasting state and the fed state |
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Intraocular lens power calculation while the volunteers were in the fasting state resulted in a lens power that is 1.06 D higher than the IOL power in the fed state as shown by [Table 7]. This change is statistically significant (P = 0.030).
|Table 7: The differences in IOL power between the fasting state and the fed state |
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The three important parameters in calculating the IOL power are the corneal power, axial length, and anterior chamber depth.  The corneal power was approximately the same and showed no significant variation between the measurements in the fed state and the fasting state. The axial length and the anterior chamber depth were showed reduction when measured in the fasting state, theoretically the decrease in axial length and anterior chamber depth should change the refractive state of the eye toward hypermetropia, , but in reality, the effect of the decreased axial length and the anterior chamber depth was compensated by the increase in the lens power. This explains why the refractive state of the volunteers showed no change between the fasting state and the fed state.
In the fed state, the axial length and the anterior chamber depth increased in their length, and this length increasing was accompanied by a reduction in lens power. The combination of these two will cause no change in the refractive state of the eye.
The existence of a change in IOL power between the fasting state and the fed state also has been confirmed in the study that has been conducted by Nowroozzadeh et al.
| Conclusion|| |
The study was conducted at Sudan Eye Center with the participation of 114 volunteers; most of them are females.
The result of the study indicated that some ocular parameters such as K-readings, lens thickness, and vitreous thickness showed no significant variation when shifting from the fed state to the fasting state. On the other hand, the axial length was 0.251 mm shorter in the fasting state, and the anterior chamber depth decreased by 0.165 mm. The reduction in axial length and anterior chamber depth was counterbalanced by about 1D increase in the lens power.
Care should be taken when measuring the intraocular parameters for a fasting patient.
| Recommendation|| |
For the purpose of accuracy, ocular biometry should be conducted while the patient is in the fed state.
| Acknowledgment|| |
My thanks and gratitude are extended to the administration and all my colleagues at Sudan Eye Center for their great assistance. Also, I want to thank all the volunteers who participated in the study.
| References|| |
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]