Distribution de l’épaisseur cornéenne centrale dans une population mélanoderme

[Central corneal thickness in black children examined under general anesthesia at the Yalgado Ouédraogo University Medical Center]

INTRODUCTION

Central corneal thickness measurement permits an evaluation of physiological and pathological corneal changes. It allows for an intra-ocular pressure correction factor. Our purpose was to determine the mean central corneal thickness in children aged 0 to 72 months and to examine factors that might affect it.

PATIENTS AND METHODS

This was a cross-sectional hospital study which took place from February to December 2019 in the ophthalmology service of YO University Medical Center. It included healthy eyes of children 0-72 months of age examined under general anesthesia. Ultrasonic pachymetry was used to measure the central corneal thickness. The studied variables were age, sex, CCT, corneal diameter, intraocular pressure, and cup/disc ratio.

RESULTS

One hundred and twenty-seven healthy eyes of 78 children 0-72 months of age were included. The mean age was 22 months. The overall mean CCT was 554.01±34.21μm. It was 556.58μm for children from 0 to 36 months of age and 536.12μm for subjects over 36 months. The mean CCT was 555.96±32.96μm in boys and 551.80±36.16μm in girls. In patients who underwent bilateral CCT measurement, the mean CCT was 554.74±35.67μm in the right eye and 549.76±24.08μm in the left eye. Lower IOP's were found in patients with thicker corneas (p=0.00).

CONCLUSION

The CCT values for black children over 36 months of age was similar to the CCT in black adults.

[Accuracy of Optical Coherence Tomography versus Ultrasound in pachymetry]

PURPOSE

Measuring the central corneal thickness is an important step in the diagnosis and monitoring of glaucoma. Ultrasound pachymetry was the gold standard before the advent of OCT. The purpose of this study is to assess the reliability of OCT pachymetry compared to ultrasound pachymetry in black patients.

PATIENTS AND METHODS

Pachymetry was performed as part of a glaucoma work-up. Ultrasonic pachymetry was measured using the Alcon Ocuscan by the same operator and OCT pachymetry using the Topcon 2000 OCT. The Student's t-test was used to compare means with statistical significance of 5%. The Pearson's correlation coefficient (r²) was used to measure correlations.

RESULTS

One-hundred thirty-five right eyes and 135 left eyes, corresponding to 270 eyes of 135 patients, were examined. There was a female predominance (59 men/76 women), with a gender ratio of 0.78. The mean age was 42.3±17.3 [8-86] years. In the right eye, the mean OCT pachymetry was 522.4±36.8μ versus 528.2±37.9μ for ultrasonic pachymetry (P=1.00). In the left eye, the mean OCT pachymetry was 522.0±33.8μ versus 524.9±42.5μ for ultrasonic pachymetry (P=1.00). The overall mean OCT pachymetry was 522.2±35.2μ versus 526.5±40.2μ, with a non-significant difference (P=1.00). There was a strong correlation between ultrasonic pachymetry and OCT pachymetry (r²=0.83; P<0.05). On the other hand, there was a very low correlation between pachymetry and age (r²=0.09; P<0.05). Pachymetry decreased by 5μ per 10 years, corresponding to corneal thinning of 0.5μ per year.

CONCLUSION

OCT pachymetry can be a reliable alternative to ultrasound pachymetry and could be performed at the same time as the OCT for glaucoma assessment.

[Optic disc features on OCT in glaucomatous and normal black Africans]

PURPOSE

To determine the correlations between the size of the optic disc and glaucomatous defects in black Africans.

DESIGN

Retrospective observational study.

METHODS

The study was conducted over a two-year period from November 2014 to October 2016, based on records of black Togolese patients who had undergone optic nerve head (ONH) OCT or ganglion cell complex OCT for assessment of glaucoma. The population was divided into 3 groups (I, II and III) depending on the size of the ONH. The ONH was considered small (Group I) if its size was less than the mean -1 SD, medium (Group II) if its size was within 1 SD of the mean, and large (Group III) if its size was greater than the mean+1 SD. Glaucomatous lesions were qualitatively identified on RNFL and or GCC. The ONH parameters were compared in the 3 groups. The Chi-square test was used to compare the percentages, and the t test to compare the means with statistical significance of 5%. The Pearson correlation coefficient (r²) was used to measure correlations.

RESULTS

A total of 586 eyes of 298 patients were examined, 314 glaucomatous eyes and 272 healthy eyes. The mean age was 41.0±15.7 [6; 86] years. There were 159 men vs. 137 women, with a sex ratio of 1.2. The mean surface area of the ONH was 2.80±0.55mm². Small ONH's (Group I) were defined as a surface area of less than 2.25mm², medium-sized ONH's (Group II) as an area between 2.25 and 3.35mm² and large ONH's (Group III) as an area greater than 3.35mm². Small ONH's represented 14.7%, (86 eyes), medium-sized 68.6% (408 eyes) and large ONH's 16.8% (98 eyes). The mean surface area of the neuroretinal rim, cup, the cup-disc ratio and the RNFL thickness were statistically significant in the 3 groups. Similarly, all these parameters were significant in groups of glaucomatous or non-glaucomatous eyes, except for the surface area of the cup. The RNFL thickness was weakly correlated with the surface area of the ONH (r²=0.39), moderately correlated with the surface area of the neuroretinal rim (r²=0.57). The surface area of the ONH was strongly correlated with the surface area of the cup (r²=0.7). The neuroretinal rim surface area was strongly correlated with the cup-disc ratio (r²=0.66).

CONCLUSION

The size of the ONH was correlated with the size of the cup, but it was not correlated to the surface area of the neuroretinal rim or the thickness of the nerve fibers. Analysis of the RNFL and GCC is essential for the diagnosis, especially in the case of large ONH's.