Effect of Demographic Variables on the Regional Corneal Pachymetry

Normative corneal biometric parameters in sub-Saharan African populations: A systematic review and meta-analysis

BACKGROUND

Despite the importance of corneal biometric parameters in ophthalmology, there is limited comprehensive data on these measurements in Sub-Saharan African (SSA) populations. This study systematically reviewed the evidence on corneal biometric parameters of Sub-Saharan African populations, focusing on their variability, influencing factors, and implications for clinical practice and public health interventions.

METHODS

A systematic review and meta-analysis were conducted following PRISMA guidelines. Eligible studies published between January 2003 and December 2023 were identified through comprehensive searches in PubMed, Scopus, and Web of Science, with a specific focus on African populations. Inclusion criteria comprised non-interventional studies reporting central corneal thickness (CCT), corneal curvature, radius of curvature, or horizontal corneal diameter (HCD) of eyes of continental Africans. Data were synthesized using random-effects meta-analyses, with heterogeneity assessed using the I2 statistic. Subgroup analyses examined variations by geographic region, measurement instrument, and sex.

RESULTS

Twenty-eight studies with a total of 14,009 participants were included. The pooled mean CCT was 553.35 µm (95 % CI: 548.52-558.18 µm), with regional variations ranging from 555.66 µm in West Africa to 510.17 µm in Southern Africa. Males exhibited slightly higher CCT values compared to females (539.11 µm vs. 533.78 µm). Additional parameters assessed included mean corneal curvature (43.07 D), radius of curvature (7.70 mm), and HCD (11.59 mm). Variability in the measurements was attributed to demographic, geographic, and methodological factors.

CONCLUSIONS

Corneal biometric parameters exhibit substantial regional and demographic variability in SSA. These findings underscore the importance of population-specific data in enhancing diagnostic precision and guiding the development of regionally tailored clinical protocols. Further research is needed to address current knowledge gaps and improve eye care outcomes across the African continent.

FUNDING

This research received no specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Differences in Ocular Biometry Between Short-Axial and Normal-Axial Eyes in the Elderly Japanese

Purpose

Among patients with angle-closure glaucoma, it is common to have a short-axial eye, which also makes it difficult to select an appropriate intraocular lens. Previous studies have focused on the ocular biometry of the long-axial eye, whereas only a few reports have focused on the short-axial eye. This study aimed to clarify the characteristics of the short-axial eye on ocular biometry among the elderly Japanese.

Patients and Methods

This retrospective cross-sectional study included 142 patients who consulted at our hospital. The ocular axial length (AL), central corneal thickness (CCT), average anterior corneal radius of curvature (CR), white-to-white (WTW), anterior chamber depth (ACD), and lens thickness (LT) were measured using OA-2000. The short-axial and normal-axial groups (short-axial [SA] and normal-axial [NA] groups) included those with an AL less than 22.5 mm and ranging from 22.5-26.5 mm, respectively. Comparisons between groups were analyzed using the Wilcoxon rank sum test. Spearman's rank correlation coefficient tests and multiple regression analyses were performed for all parameters overall and per group.

Results

The parameters that were significantly different between the SA and NA groups were CR, WTW, and ACD (all P < 0.0001). In the SA group (42 patients), only ACD was significantly correlated with AL (r = 0.33, P = 0.031). On multiple regression analysis for the SA group, none of the parameters had a significant effect on AL (all P > 0.05).

Conclusion

In the SA group, ACD was the only factor that positively correlated with AL; it was significantly shallower than in the NA group. Thus, in the SA eye, it is clinically important to be aware of ACD.

Associations of ocular anterior segment structures with sex and age: the Yamagata study (Funagata)

PURPOSE

To investigate the associations of tomographic parameters in anterior segment optical coherence tomography (AS-OCT) with sex and age in a cohort study.

STUDY DESIGN

A cohort design.

MATERIALS AND METHODS

AS-OCT data from 391 Japanese participants aged ≥ 35 years were obtained using swept-source OCT. In the cornea, the keratometric power at the flat (Kf) and steep (Ks) meridians, maximum keratometric power (Kmax), keratometric cylinder, spherical power, regular astigmatism, asymmetry, higher-order irregularity (HOI) from the anterior and posterior surfaces, and the central and thinnest corneal thicknesses were evaluated. Also, anterior chamber depth (ACD), lens thickness, crystalline lens rise (CLR), and nasal and temporal angle opening distances at 500 μm from the scleral spur (AOD500) were assessed. Sex differences and age-related changes were analyzed.

RESULTS

Women exhibited higher anterior Kf, Ks, and Kmax and lower posterior Kf, Ks, and Kmax than men. The ACD and nasal/temporal AOD500 were shorter in women than in men. The CLR was higher in women, whereas the lens thickness did not differ between the sexes, indicating a more anteriorly positioned lens in women. Age-related changes included increased anterior/posterior HOI, increased lens thickness and CLR resulting in decreased ACD and AOD500.

CONCLUSION

This study reveals sex-related differences in corneal shape, anterior chamber conformation, and lens position, as well as age-related changes in tomographic parameters. ACD, CLR, nasal and temporal AOD500 showed significant sex differences in the 50-70 s, whereas lens thickness showed no difference.

Correlation of Ocular Biometry with Axial Length in Elderly Japanese

Purpose

Ocular parameters are not only useful for diagnosing diseases but also for guiding treatment approaches. A lot of previous studies have reported ocular parameters and its relations before cataract surgery. However, despite ethnic differences in ocular biometry, few reports have dealt with Japanese. Hence, this retrospective cross-sectional study aimed to measure parameters of preoperative cataract patients and examines the correlations between each parameter in Japanese elderly people.

Patients and Methods

The 210 subjects had their ocular axial lengths measured with OA-2000. The endpoints were ocular axial length (AL), central corneal thickness (CCT), average anterior corneal radius of curvature (CR), white-to-white (WTW), anterior chamber depth (ACD), and lens thickness (LT). Our analyses utilized the eye with the longer AL in each person. Each parameter was analyzed for correlations in a round-robin manner. Regression analyses were performed on parameters correlated with AL.

Results

The parameters correlated with AL were CR (r = 0.33, P < 0.0001), WTW (r = 0.29, P < 0.0001), ACD (r = 0.59, P < 0.0001), and LT (r = -0.30, P < 0.0001). These parameters related to AL in all simple regression equations (CR (P < 0.0001), WTW (P = 0.0002), ACD (P < 0.0001), LT (P = 0.0001)). In multiple regression analyses, CR, ACD, and LT might relate to AL (CR (P = 0.0002), ACD (P < 0.0001), LT (P = 0.018)). LT tended to be thinner as AL increased, while CR, WTW, and ACD tended to increase.

Conclusion

This information may be useful in developing strategies for ophthalmic surgery, as it provides information on the location of intraocular tissues. Various parameters have been used in intraocular lens (IOL) power calculations in recent years and knowledge of the interrelationship among parameters may be useful in determining IOL power according to ethnicity in the future.

Schematic sectioning approaches for corneal and retinal surfaces used in ophthalmology and vision-related clinical practice and research

Schematically, the corneal surface area and other similar surfaces such as the retinal surface and the visual field area have been represented by a circle. While there are different types of schematic sectioning patterns in use, not all patterns are recognized or referred to with their respective appropriate terminology. In scientific communications, as well as in clinical practice, when dealing with corneal or retinal surfaces, it is imperative to have the ability to refer to specific areas with an as high degree of accuracy as possible. The necessity arises in many situations, either when performing tests such as corneal surface staining, corneal sensitivity test, scanning the corneal surface, reporting of the findings related to any specific corneal surface area, or using a sectioning pattern for parts of the retinal surface when locating retinal lesions, or when referring to loci with changes in the visual field. Applying the appropriate geometric terms when any pattern is used for sectioning of surfaces such as cornea or retina, for precise localization and description of the findings or changes with a high degree of accuracy using the correct terminology is a sine qua non. Hence, the idea for this work is to gain an overview of the sectioning methods that are available and in use as methodological guidance in different sectioning patterns related to the corneal, retinal, and visual field.

Investigation of the Sectorized Corneal Thickness of Eyes With Corneal Endothelial Dysfunction Using Anterior-Segment Optical Coherence Tomography

PURPOSE

The aim of this study was to investigate the sectorized corneal thickness of eyes with corneal endothelial dysfunction using anterior-segment optical coherence tomography.

METHODS

We retrospectively collected anterior-segment optical coherence tomography data conducted before endothelial keratoplasty on 53 eyes of 53 patients with corneal endothelial dysfunctions including Fuchs endothelial corneal dystrophy, bullous keratopathy (BK) after trabeculectomy, and BK after laser iridotomy and from 18 normal eyes of 18 subjects. The imaging points were divided into 17 sectors. The mean for each sector was calculated and compared with the corresponding superior/inferior and temporal/nasal sectors.

RESULTS

In the normal eyes, the superior sectors were thicker than the inferior and the temporal sectors thinner than the nasal. In the diseased eyes, the superior sectors were thicker than the inferior in all subgroups; however, this tendency was no longer observed after the values were divided by the mean for the normal eyes. No significant differences were found on horizontal comparisons; however, after the values were divided by the mean for the normal eyes, the temporal sectors were thicker than the nasal. When comparing the values between the with-hole and the without-hole sides in the BK after laser iridotomy eyes, the sectors on the with-hole side were thicker than the other side.

CONCLUSIONS

Corneal thickness of endothelial dysfunction was thicker in the superior sectors than the inferior but at a similar level to normal eyes. No significant differences were found for horizontal comparisons but, based on comparison with the normal eyes, the temporal sectors were thicker than the nasal.

Corneal Donation: Current Guidelines and Future Direction

PURPOSE

This review aims to outline current practices and guidelines of corneal donation and eye banking, describes the implications of COVID-19 and emerging diseases on the corneal donor pool, and discusses future trends to improve and increase the efficiency of the processes involved in corneal donation and eye banking.

SUMMARY

Corneal screening, preservation, corneal storage, and prevention of systemic disease transmission from donor to recipient have been crucial in shaping the policies of the FDA and eye banks across the world. Eye banks globally have developed varying guidelines and criteria for evaluating the viability of donor corneas. Variables such as the age of the donor, medical history, and potential disease transmission are important screening parameters. While known infectious diseases may be transmissible through the cornea, emerging infectious diseases that are not well studied may be more transmissible than other infections. In particular, coronavirus has impacted corneal transplantation as SARS-CoV-2 expression has been detected in corneal tissue and conjunctiva. In recent years, partial-thickness corneal transplantations have been introduced. Lamellar grafts and other corneal layers are now utilized for transplantation of the specific areas that are damaged.