Central Corneal Thickness and Intraocular Pressure Changes in the Third Trimester of Pregnancy: A Comparative Study in a Cameroonian Population

Nyouma Paulette Jasmine^1,2*, Nomo Arlette Francine³, Ndongo Jean Audrey², Tenadjang Poundie Nelson Ange⁴, Aboubakar Hassan², Mangala Kwele Fulbert ², Mare Njoya Josiane¹, Akono Zoua Marie Evodie³, Tchente Nguefack Charlotte², Godefroy Koki³, Halle Ekane Gregory⁴

¹Ophthalmology Unit, Douala General Hospital, Douala, Cameroon
²Faculty of Medicine and Phamaceutical Sciences, University of Douala, Douala, Cameroon
³Faculty of Medicine and Biomedical Sciences, University of Yaounde I, Yaounde, Cameroon
⁴Faculty of Health Sciences, University of Buea, Buea, Cameroon

*Correspondence author: Nyouma Paulette Jasmine, Ophthalmology Unit, Douala General Hospital, Douala, Cameroon; Email: jasminenyouma@hotmail.com

Citation: Jasmine NP, et al. Central Corneal Thickness and Intraocular Pressure Changes in the Third Trimester of Pregnancy: A Comparative Study in a Cameroonian Population. J Ophthalmol Adv Res. 2025;6(3):1-6.

Copyright^© 2025 by Jasmine NP, et al. All rights reserved. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Table 1: Sociodemographic characteristics of participants.

Amongst the pregnant women, 5 complained of visual symptoms: blurred vision (n=4) and diplopia (n=1) Amongst pregnant participants, 29 (54.7%) had a reduction in far visual acuity compared to 12 (22.6%) amongst their non-pregnant counterparts. Far visual acuity amongst pregnant participants ranged from 1.58 to 0 LogMAR with median value been 0.05 LogMAR. Amongst non-pregnant participantit ranged from 1.58 to 0 LogMAR with median value been 0 LogMAR.

In our study, the values for CCT amongst pregnant women ranged between 427µm – 606µm. The mean CCT value for both eyes in our study was found to be 531,1 ± 32,4µm for the right eye and 530,2 ± 28.1µm for the left eye amongst pregnant women. The mean CCT amongst pregnant women for both eyes was 531,2 ± 35,2µm. CCT values amongst nonpregnant subjects ranged from 415 – 606µm, with mean CCT value been 514,6 ± 32,6µm for the right eye and 514,1 ± 26.4 for the left eye. The mean CCT amongst non-pregnant women for both eyes was 514.3 ± 29.3µm. There was therefore a 16,9µm difference amongst pregnant participants compared to non-pregnant participants. Hence, a 3,2% increase in CCT was observed during third trimester pregnancy. The mean CCT was significantly greater in pregnant women (531.2 ± 35.2 µm) compared to non-pregnant women (514.3 ± 29.3µm), a difference of 16.9 µm (3.2%, p<0.01). The mean IOP was significantly lower in the pregnant group (11.5 ± 2.5 mmHg) than in the control group (13.6 ± 2.3 mmHg), with a difference of 2.1 mmHg (15.5%, p=0.04) (Table 1). The Table 2 summarize the mean visual acuity, IOP and CCT for both eyes amongst the two groups of participants.

Table 2: Repartition of Far visual acuity, Intraocular pressure and Central corneal thickness amongst groups.

Awareness of ocular changes during pregnancy was very low among all participants. Only 8 out of 106 women (7.6%) were aware that such changes could occur. When asked which changes they were aware of, the most common responses were dry eyes (62,5%) and blurred vision (37,5%). The primary sources of information were the internet (75%) and healthcare providers (25%).

Discussion

In our study, participants were aged 15 to 46 years, which is comparable to the results reported in similar studies from Nigeria and Turkey [4-6]. This similarity can be attributed to the fact that these investigations, like ours, focused exclusively on women of reproductive age.

The mean Visual Acuity (VA) among third-trimester women was 0.1 LogMAR, compared to 0.05 LogMAR in non-pregnant women. This indicates a relative reduction in far visual acuity during pregnancy, whereas short-distance acuity showed only minimal variation between groups. Our findings are consistent with those of Nkiru, et al., who also reported no significant difference in near vision among pregnant women in the third trimester [4]. Blurred vision when viewing the smallest characters on the Snellen’s chart was the most common symptom, reported by 29 of 53 pregnant participants (54.7%) compared with 12 of 53 (22.6%) non-pregnant participants. This prevalence closely reflects the 40% reported by Nkiru, et al. [4]. The mechanism is likely related to corneal thickening during pregnancy, leading to subtle refractive changes that predominantly affect distance vision. Notably, only 9.4% of pregnant participants self-reported visual problems, despite more than half demonstrating reduced distance VA on testing. This discrepancy suggests that many women adapt to mild visual blurring or misattribute it to general fatigue. Clinicians should therefore be proactive in assessing visual function during pregnancy and providing appropriate reassurance.

Central Corneal Thickness (CCT) was increased by 3.2% in pregnant women compared to non-pregnant controls, with mean values of 531.2 µm and 514.3 µm, respectively. This degree of change is strikingly consistent with reports from diverse populations: 3.19% in Nigeria, 3.1% in Turkey and 3.0% in the United States [5,11,13]. The reproducibility of this finding across different ethnic backgrounds indicates that CCT elevation in pregnancy is a robust physiological response rather than an ethnic or environmental variation. Importantly, our data confirm that pregnancy-induced CCT changes are systematic, predictable and clinically relevant [1,3,7].

We observed an IOP decrease of 2.1 mmHg in the third trimester of pregnancy. This change is clinically meaningful in pregnant patients with glaucoma or ocular hypertension, where choices of treatment protocols are often reduced [14]. Such a decrease may mask disease progression, lead clinicians to underestimate glaucomatous risk or prompt unnecessary alterations in therapy if the physiological basis of the IOP decline is unknown. Conversely, in patients with borderline pressures, this pregnancy-related decrease may delay the need for medical or surgical intervention. Elsewhere in glaucoma with normal IOP, it can motivates interruption of treatment in the third trimester until delivery to ensure the safety of the fetus. Careful longitudinal monitoring, ideally supplemented with structural and functional assessments, is therefore critical when managing pregnant patients with pre-existing glaucoma [15].

These findings have several key implications. First, the increase in CCT must be carefully considered in Intraocular Pressure measurement and interpretation. Thicker corneas tend to overestimate IOP readings on applanation tonometry [16,17]. However, in our study, IOP decreased by 15.5%, consistent with hormonal influences such as progesterone-mediated enhancement of aqueous outflow and reduced episcleral venous pressure [1,3]. Thus, failure to account for pregnancy-related CCT changes may lead to underestimation of the true IOP decrease or to misclassification of glaucoma severity in pregnant patients. Second, the consistent magnitude of CCT highlights the need to delay the prescription of corrective glasses after delivery. Third, its emphasizes the importance of adjusting corneal biomechanics in refractive surgery planning. Elective refractive procedures should ideally be postponed until after delivery, when CCT values normalize, to avoid inaccurate surgical planning and unpredictable outcomes. These findings highlight the need for clinicians to maintain vigilance in conditions where corneal thickness plays a role in risk assessment and management particularly in glaucoma, keratoconus and refractive errors. The mean CCT among non-pregnant participants in our study was lower than values previously reported in Cameroon by Eballe, et al. [11]. It may be explained by the methodological differences, as Eballe , et al., used ultrasound pachymetry-a technique that can yield slightly different measurements and a wider age range (5-75 years) than our study (15-49 years) [14].

Knowledge of pregnancy-related ocular changes was markedly low, with only 7.5% of participants aware of potential visual disturbances, compared to 27.5% in the study by Nwachukwu, et al. [5]. This profound lack of awareness points to a gap in antenatal education. Incorporating information on expected ocular changes into routine antenatal counselling could both reassure patients and prevent unnecessary ophthalmological consultations.

Limitations

The study was conducted in a single urban center. We didn’t compare the intraocular pressure and central corneal thickness changes in other pregnancy trimesters and post-partum within the same individuals.

Conclusion

Our study confirms that third-trimester pregnancy in Cameroonian women is associated with a significant increase in central corneal thickness and a decrease in intraocular pressure, consistent with global findings. These are relevant datas that assess the importance of education about common ocular change into routine antenatal counselling and adjustment of anti-glaucomatous treatment for pregnant patients in  their third trimester. Future longitudinal studies are needed to measure CCT and IOP changes across all trimesters and postpartum in African populations.

 Conflict of Interest

The author declares no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Financial Disclosure

No financial support was received for the writing, editing, approval or publication of this manuscript.

Acknowledgments

Thanks to all the people who agreed to participate to this study.

Informed Consent Statement

Informed consent was obtained from the participant involved in this study.

Authors’ Contributions

All authors have contributed equally to this work and have reviewed and approved the final manuscript for publication.

Consent for Publication

Informed consent for publication was obtained from the patient involved in this case report, as documented in the manuscript.

Ethical Statement

This project was exempt from IRB review as it did not qualify as human subject research under federal regulations.

References

1. Agrawal N, Agarwal LT, Lavaju P, Chaudhary SK. Physiological ocular changes in the different trimesters of pregnancy. Nepal J Ophthalmol. 2018;10(1):16-22.
2. Soma-Pillay P, Catherine NP, Tolppanen H, Mebazaa A. Physiological changes in pregnancy. Cardiovasc J Afr. 2016;27(2):89-94.
3. Pei X, Li Z. Pregnancy and ocular health: physiological changes and pathological challenges. Curr Ophthalmol Rep. 2025;13(4).
4. Nkiru ZN, Obiekwe O, Lilian O, Daniel CN, Uchenna IN, Rich U. Visual acuity and ocular changes among pregnant women in Enugu, Southeast Nigeria. J Fam Med Prim Care. 2016;5(3):646-51.
5. Nwachukwu N, Okoye O, Okoye O, Eze C, Nwachukwu D, Nwagha U, et al. Relationship between intraocular pressure and corneal biomechanical properties among pregnant women in a tertiary hospital in Nigeria. Niger J Clin Pract. 2020;23(1):43-9.
6. Sen E, Onaran Y, Nalcacioglu-Yuksekkaya P, Elgin U, Ozturk F. Corneal biomechanical properties during pregnancy. Eur J Ophthalmol. 2014;24(3):314-9.
7. Wang C, Li AL, Pang Y, Lei YQ, Yu L. Changes in intraocular pressure and central corneal thickness during pregnancy: A systematic review and meta-analysis. Int J Ophthalmol. 2017;10(10):1573-9.
8. Yang Y, Ye J, Ng TK. Changes in corneal biomechanics during pregnancy in Chinese healthy females. Eur J Ophthalmol. 2020;31(2):361-6.
9. Muthu Krishnan V, Jayalatha K, Vijayakumar C. Correlation of central corneal thickness and keratometry with refraction and axial length: A prospective analytic study. Cureus. 2019;11(12):e3917.
10. La Rosa FA, Girard LJ, Knighton RW. Central corneal thickness of Caucasians and African Americans in glaucomatous and nonglaucomatous populations. Arch Ophthalmol. 2001;119(1):23-7.
11. Eballe AO, Epee E, Koki G, Bella AL, Leundji H, Mvogo CE. Central corneal thickness and intraocular pressure in the Cameroonian nonglaucomatous population. Clin Ophthalmol. 2010;4:717-24.
12. Bonnemaijer PWM, Cook C, Nag A, Hammond CJ, van Duijn CM, Lemij HG, et al. Genetic African ancestry is associated with central corneal thickness and intraocular pressure in primary open-angle glaucoma. Invest Ophthalmol Vis Sci. 2017;58(7):3172-80.
13. Efe YK, Ugurbas SC, Alpay A, Ugurbas SH. The course of corneal and intraocular pressure changes during pregnancy. Can J Ophthalmol. 2012;47(2):150-4.
14. Shakha, Gupta S, Panigrahi A, Singh A, Gupta V. Outcomes of pregnancy after exposure to antiglaucoma drugs. Indian J Ophthalmol. 2024;72(4):599-601.
15. Salvetat ML, Toro MD, Pellegrini F, Scollo P, Malaguarnera R, Musa M, et al. Advancing glaucoma treatment during pregnancy and breastfeeding: Contemporary management strategies and prospective therapeutic developments. Biomedicines. 2024;12(12):2685.
16. Clement CI, Parker DG, Goldberg I. Intraocular pressure measurement in a patient with a thin, thick or abnormal cornea. Open Ophthalmol J. 2016;10:35-43.
17. Babbar S, Martel M, Martel J. Comparison of central corneal thickness by ultrasound pachymetry, optical coherence tomography and specular microscopy. New Front Ophthalmol. 2017;3(3).