Measurement of anterior segment parameters in Saudi adults with myopia

Measurements of white-to-white corneal diameter and anterior chamber parameters using the Pentacam AXL wave and their correlations in the adult Saudi population

Background

Assessment of eye parameters such as the white-to-white (WTW) corneal diameter, anterior chamber depth (ACD), and anterior chamber angle (ACA) are essential for preoperative evaluation of refractive surgery and diagnosing and managing some ocular diseases.

Objective

To report the distribution and association between white-to-white corneal diameter and anterior chamber parameters in the Saudi adult population.

Methods

Cross-sectional prospective study consisting of 82 Saudi adults. White-to-white corneal diameter, anterior chamber angle, anterior chamber depth, and axial length were collected from healthy subjects using the Pentacam AXL Wave in a tertiary eye care setting.

Results

Mean white-to-white corneal diameter, anterior chamber angle, anterior chamber depth, and axial length were 11.95 ± 0.39 mm, 37.94 ± 5.01°, 2.97 ± 0.31 mm and 23.93 ± 0.97 mm, respectively. A significant moderate correlation was found between white-to-white corneal diameter and anterior chamber angle (r = 0.31, p ≤ 0.01), anterior chamber depth (r = 0.49, p ≤ 0.01), and axial length (r = 0.50, p ≤ 0.01) and between anterior chamber angle and anterior chamber depth (r = 0.71, p ≤ 0.01). Furthermore, age was moderately correlated with anterior chamber angle (r = 0.44, p 0.01) and anterior chamber depth (r = 0.39, p 0.01) and weakly correlated with white-to-white corneal diameter (r =0.17, p = 0.12). Males had a significantly (p < 0.01) higher white-to-white corneal diameter (12.12 ± 0.38 mm) than females (11.84 ± 0.36.mm).

Conclusion

Reference values for white-to-white corneal diameter and anterior chamber parameters would help eye care professionals choose the right lenses for cataract and refractive surgeries as well as in diagnosing glaucoma and corneal disorders.

Intracameral phenylephrine for surgical mydriasis and intraoperative floppy-iris syndrome: systemic adverse effects and optimal dose

Phenylephrine, a potent sympathomimetic, induces mydriasis via iris dilator muscle contraction. Intracameral (IC) phenylephrine has been successfully used in cataract surgery for initial mydriasis, maintaining mydriasis, and management of intraoperative floppy-iris syndrome. Serious systemic adverse events (mainly cardiovascular) have been described with topical phenylephrine drops, but we found very little evidence of such adverse events associated with IC phenylephrine use. However, we suspect under-reporting of such adverse events, as they may instead be ascribed to anxiety, positioning, anesthesia, etc. Optimal dosage/concentrations for IC phenylephrine use in different purposes have not been fully studied. In the absence of robust evidence, we suggest that lower but effective IC phenylephrine concentrations are used: a lower concentration (0.31%), in conjunction with an anticholinergic and lidocaine, may be used for initial mydriasis. For management of intraoperative floppy-iris syndrome, 0.31% may be effective, though a higher concentration (1% to 1.25%) may be required.

Assessment of refractive outcomes in eyes that underwent intraocular lens implantation in the posterior chamber but not "in-the-capsular bag:" A comparative retrospective study

PURPOSE

The purpose of this study was to report visual and refractive outcomes in eyes that underwent intraocular lens (IOL) fixation in the absence of capsular support.

METHODS

This was a retrospective chart review of cases undergoing posterior chamber iris-fixated IOL (IFIOL) and scleral-fixated IOL (SFIOL) implants from June 2014 to March 2020 with more than 3 months of follow-up and having a preoperative best-corrected visual acuity of 20/80 and more.

RESULTS

Records of 120 eyes of 112 patients were reviewed. The mean age of the patients was 46.9 ± 22.3 (14.4-98.0) years, and 62% (n = 70) of participants were male. Most of the eyes (102: 85%) were aphakic at the time of surgery. The mean follow-up was 22.95 ± 17.1 months. The efficacy index of sutured IFIOL and glued SFIOL outperformed sutured SFIOL at 3 months and final visits postoperatively (P < 0.001). All techniques studied here resulted in a similar safety index at 3 months (P = 0.4). The mean predictive error (postoperative spherical equivalent refraction minus intended target refraction) was +0.07 ± 1.5 D and -0.12 ± 1.4 D at 3 months and the final postoperative visit, respectively.

CONCLUSION

The studied techniques have relatively good visual and refractive outcomes in this series. In addition, techniques involving a small corneal incision with foldable IOL fixation to the iris or scleral tissue have superior efficacy and safety indices compared to creating large corneoscleral wounds for rigid IOL fixation techniques.

Comparison of anterior segment parameters in myopia with and without primary open-angle glaucoma

PURPOSE

To compare anterior segment parameters between myopes with and without primary open-angle glaucoma using Pentacam scheimpflug tomography.

METHODS

This was a single-center retrospective cross-sectional study. Records of patients examined with a Pentacam scheimpflug tomographer (Wavelight-Allegro Oculyzer, GmbH, Erlangen, Germany) were reviewed. Variables studied were recorded from the topographic map and included anterior chamber angle, anterior chamber volume, anterior chamber depth, keratometric readings, and corneal thickness. A general linear model for age-and spherical equivalent refraction-adjusted intergroup comparisons of the anterior segment parameters was conducted.

RESULTS

The study included myopes previously diagnosed with primary open-angle glaucoma (POAG) [Mild defect, n = 81; Moderate-severe defect, n = 50] and non-glaucomatous myopes (n = 247). The results revealed a smaller anterior chamber angle, shallower anterior chamber depth, and flatter cornea curvature in the mildly glaucomatous group compared to the non-glaucomatous group (p < 0.05). Smaller anterior chamber angle, shallower anterior chamber depth, and thinner cornea thickness were also observed in the moderate-severely glaucomatous group compared to the non-glaucomatous group (p < 0.05).

CONCLUSION

Glaucomatous damage in myopic patients with POAG was associated with comparatively small anterior chamber angle, shallow anterior chamber depth, flat cornea curvature, and thin cornea.

A comparative study of Pentacam indices in various types and severities of refractive error in candidates for photorefractive keratectomy (PRK) surgery

This study aimed to specify Pentacam indices in patients who suffered from different types of refractive error and underwent photorefractive keratectomy (PRK) surgery. It is a descriptive cross-sectional study carried out on 1125 patients (2215 eye samples) who underwent PRK surgery in the Noor Surgical Center of Ardabil, Iran, over a 5 year period (2014-2018). A particular checklist was provided to patients, which consisted of demographic data, pachymetry test, keratometry, refractive error, corneal-thickness indices, and corneal surface area indices. The data were analysed using the statistical analysis package of IBM^® V25. The mean age of the participants in this study was 28.48±6.82 years, and the ratio of women to men was 66.4%. It was observed that the differences between angle, volume, the depth of the anterior chamber, IVA, and ISV were significant (P=0.00) when compared to each other in all types of refractive errors. High myopes had significantly higher K_max front than low myopes (P=0.00). In astigmatism patients, the K_max in front of the cornea in extreme type was significantly higher than in moderate (P=0.00) and high (P=0.01) types. High myopes had significantly lower R_min than mild myopes (P=0.02), and extreme astigmatism had significantly lower R_min than high (P=0.014) and moderate types (P=0.013). The data from this study revealed that in patients undergoing PRK surgery, some Pentacam indices could be related to some types of refractive error, and in some of these indices, there are statistically significant differences between different severities of refractive errors. Therefore, their preoperative evaluation is very important.

Age- and sex-related differences in the measures of anterior segment parameters in a myopic clinical sample using Pentacam Scheimpflug tomography

PURPOSE

To assess age-and sex-related differences of anterior segment parameters in a myopic clinical sample.

METHODS

This clinic-based retrospective study involved eligible subjects grouped into myopia (i.e., low-to-moderate) and high myopia. Demographics and anterior segment parameters measures were recorded and analyzed.

RESULTS

Some 153 eligible eyes were analyzed-98 myopia and 55 high myopia-comprising 87 males and 66 females. The mean ages and ranges were 28.47 years (SD = 9.59 years), 8-50 years, and 27.82 years (SD = 9.69 years), 10-51 years, for the myopia and the high myopia groups, respectively. The means of the spherical equivalents were - 3.02 D (SD = 1.46 D, range: - 0.50 to - 5.85 D), for the myopia group and - 10.42 D (SD = 5.50 D, range: - 6.00 to - 21.86 D) for the high myopia group. No significant difference was found between degree of myopia and anterior segment measures. Males had larger anterior chamber volume (mean 175.71 ± 26.27, range: 124-225 mm³); (P = 0.007) and deeper anterior chamber depth (3.73 ± 0.27, range: 3.06-4.41 mm) (P = 0.017) than females in the myopia group. Females also had significantly steeper anterior corneal curvature, Km (ant.) but flatter posterior corneal curvature, Km (post.), (- 6.31 ± 0.25, range - 7.00 to - 5.90 D) in both the myopia group [Km (ant.): 44.06 D ± 1.33 D, range: 41.30-47.10; Km (post.): - 6.31 D ± 0.25 D, range: - 7.00 to - 5.90; P = 0.008, P = 0.002, respectively] and the high myopia group [Km (ant.): 43.79 D ± 0.33 D, range: 41.00-47.10; Km (post.): - 6.22 D ± 0.30 D, range: - 6.80 to - 5.60; P = 0.034, P = 0.049, respectively]. Age was not correlated with the anterior segment parameters in both degrees of myopia.

CONCLUSION

Sex has significant influence on the corneal curvature, anterior chamber volume and anterior chamber depth regardless of the degree of myopia.

Pentacam Indices in Photorefractive Keratectomy Surgery

Refractive eye surgeries are one of the most non-emergent ophthalmic surgeries due to the effect on the reduction of refractive errors, increasing visual acuity, enhancing the quality of vision, and indirectly increasing the quality of life of patients. The aim of this study was to determine Pentacam indices in the patients who underwent photorefractive keratectomy (PRK) during 2014-2018, as well as to show their correlation with the type of refractive error. This descriptive cross-sectional study was performed on 2215 eyes of 1125 patients undergoing PRK surgery. The patients’ checklist, including demographic information, refractive index, keratometry, pachymetry, corneal surface zone indices, and progressive corneal thickness indices, was provided. All data were analyzed using the IBM SPSS software, version 25. The findings showed that there was a significant association between posterior corneal astigmatism (PCA) and anterior corneal astigmatism (ACA) (p=0.00). The mean Kmax front was recorded as 44.844 ± 1.58 D, which was significantly correlated with the type of refractive errors (p=0.00). According to the findings, there was a significant relationship between anterior chamber indices and refractive error types and their severity (p=0.00). There was also a significant correlation between the surface zone and keratoconus indices (i.e., index of surface variance - ISV, index of vertical asymmetry - IVA, index of height asymmetry - IHA, and minimum radius of curvature - Rmin) with refractive errors (p=0.00). The findings showed that some of the Pentacam indices could be related to the types of refractive errors in patients undergoing PRK surgery. Therefore, their evaluation is of great importance in this regard.

Correlations among peripapillary vasculature, macular superficial capillaries, and eye structure in healthy and myopic eyes of Chinese young adults (STROBE)

The correlations between retinal vessel distribution, anterior chamber depth (ACD) and other myopic eye structural parameters remains elusive. This study aims to investigate retinal vasculature and eye structure correlations in healthy and myopic eyes of Chinese young adults.In this cross-sectional study, 181 eyes (97 adults) were recruited. Macular and peripapillary vasculature was quantified by optical coherence tomography angiography. Correlations between retinal vasculature and eye structure were analyzed using multivariable linear regression.There were significant differences in ACD, spherical equivalent, axial length (AL), superficial macular vascular density (MVD), peripapillary vascular density (PVD) and circumference of foveal avascular zone (FAZ) among emmetropia, low-myopia, moderate-myopia, and high-myopia groups (both P < 0.05). Furthermore, ACD had significant positive correlation with AL and FAZ, but negative correlation with PVD. MVD also had a negative correlation with AL (beta = -0.247, P < .001). In addition, there was a significant negative correlation between circumference of the FAZ and spherical equivalent as well as central subfield thickness (beta = -0.20, P = .005; beta = -0.334, P < .001, respectively).The degree of myopia affected ACD, MVD, PVD, and circumference of the FAZ in eyes of young healthy adults. Meanwhile, ACD has a positive, while retinal vascular system measurements have a negative correlation with increasing severity of myopia.