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BMC Ophthalmology Jun 2024To comparatively analyze the surgically induced astigmatism (SIA) of the anterior, posterior, and total corneas of eyes undertaking implantable collamer lens (ICL)... (Comparative Study)
Comparative Study
Analysis of surgically induced astigmatism of the anterior, posterior, and total cornea after implantable collamer lens implantation: a comparative study between temporal and superior clear corneal incisions.
BACKGROUND
To comparatively analyze the surgically induced astigmatism (SIA) of the anterior, posterior, and total corneas of eyes undertaking implantable collamer lens (ICL) implantation with temporal or superior corneal incisions.
METHODS
One hundred and nine eyes of 109 patients who received ICL implantation were recruited: 40 eyes had temporal incisions and 69 eyes had superior incisions. Total corneal refractive power (TCRP); simulated keratometry of the anterior (Sim-K) and posterior (Sim-K) corneal curvature; and astigmatism of the anterior (CA), posterior (CA), and total (CA) cornea were recorded through a Pentacam preoperatively and 3 months postoperatively. The SIA of the anterior, posterior, and total cornea were also compared between the two groups.
RESULTS
There were no significant intergroup differences for TCRP, Sim-K, Sim-K, CA, CA, or CA, preoperatively. However, values of CA, CA, and CA with temporal incision were significantly higher than those parameters with superior incision postoperatively. All of the SIA of the anterior, posterior, and total cornea were significantly lower for temporal incision than those with a superior incision (p < 0.001, p = 0.006 and p = 0.001 respectively). Meanwhile, the superior incisions created against-the-rule (ATR) astigmatism, and temporal incisions always induce with-the-rule (WTR) astigmatism in total cornea.
CONCLUSIONS
A superior incision may be suitable for correcting WTR astigmatism, while a temporal incision for correcting ATR astigmatism when using a non-toric ICL. Meanwhile, temporal incision could be a better choice with little preoperative astigmatism or that preoperative astigmatism would be corrected with toric ICLs.
TRIAL REGISTRATION
Registration number: ChiCTR2100051739. Prospectively registered: 01 October 2021.
Topics: Humans; Astigmatism; Female; Male; Adult; Cornea; Lens Implantation, Intraocular; Visual Acuity; Refraction, Ocular; Young Adult; Phakic Intraocular Lenses; Myopia; Middle Aged; Corneal Topography; Retrospective Studies; Postoperative Complications; Prospective Studies
PubMed: 38867207
DOI: 10.1186/s12886-024-03501-x -
BMC Ophthalmology Jun 2024Refractive errors, amblyopia, strabismus, and low vision are more common among children with hearing impairments in comparison with their hearing peers. Neglecting...
BACKGROUND AND AIM
Refractive errors, amblyopia, strabismus, and low vision are more common among children with hearing impairments in comparison with their hearing peers. Neglecting visual disorders can pose educational and social problems for these children. The present study aimed to assess the prevalence of refractive errors, amblyopia, strabismus, and low vision among hearing-impaired and deaf students in Kermanshah.
MATERIALS AND METHODS
A total of 79 deaf and hearing impaired students within the age range of 7-20 years (mean age of 15.01 ± 2.72) underwent optometric examinations, including autorefractometry, retinoscopy, ophthalmoscopy, slit lamp, visual acuity measurement, and cover-uncover test. Those who needed further evaluation were referred to the Ophthalmology Clinic of Imam Khomeini Hospital.
RESULTS
Regarding the prevalence of refractive errors, 32 (40.5%) subjects had one or a combination of refractive errors, the most common of which was astigmatism (36.7%), followed by amblyopia (15.1%). The most common type of strabismus was latent strabismus (heterophoria) (88.6%), followed by exophoria (81%). Moreover, 3 (3.7%) cases had nystagmus. A significant difference was observed between the prevalence of amblyopia and the degree of hearing loss (P = 0.026), and no significant difference was detected in other cases.
CONCLUSION
As evidenced by the obtained results, refractive errors, amblyopia, strabismus, and low vision are more prevalent among deaf and hearing-impaired children compared to normal children because deaf and hearing-impaired children are not able to convey their vision problems and need to compensate for their poor hearing with an enhanced sense of sight, inattention to these disorders can present these children with serious educational and social problems. Therefore, eye screening examinations are of paramount importance in deaf and hearing-impaired children.
Topics: Humans; Strabismus; Child; Adolescent; Male; Female; Refractive Errors; Vision, Low; Amblyopia; Prevalence; Young Adult; Visual Acuity; Iran; Cross-Sectional Studies; Persons With Hearing Impairments; Deafness; Students
PubMed: 38867144
DOI: 10.1186/s12886-024-03515-5 -
Clinical Ophthalmology (Auckland, N.Z.) 2024To evaluate and compare the effect of femtosecond laser-assisted cataract surgery on corneal astigmatism in post-LASIK eyes and virgin eyes.
PURPOSE
To evaluate and compare the effect of femtosecond laser-assisted cataract surgery on corneal astigmatism in post-LASIK eyes and virgin eyes.
PATIENTS AND METHODS
Patients who underwent femtosecond laser-assisted cataract surgery were included in the study and categorized into two groups: Group A, consisting of patients with post-LASIK eyes, and Group B, consisting of patients with virgin eyes. Visual acuity, corneal astigmatism, and surgically induced astigmatism (SIA) were evaluated. Additionally, the correlation between SIA and preoperative corneal astigmatism, mean corneal curvature, and central corneal thickness was also analyzed.
RESULTS
A total of 168 eyes were enrolled in this study, with 62 eyes in Group A and 106 eyes in Group B. Significant differences in corneal astigmatism and SIA were observed between the two groups in the early postoperative period following cataract surgery (P<0.05). However, there was no significant difference at 6 months postoperatively (P>0.05). Corneal astigmatism demonstrated an against-The-rule shift in both groups postoperatively. No significant correlation was identified between SIA and preoperative corneal astigmatism, corneal curvature or corneal thickness. Additionally, there was no significant difference observed between the two groups in terms of uncorrected distance visual acuity (UDVA) at 6 months postoperatively.
CONCLUSION
The effect of femtosecond laser-assisted cataract surgery on corneal astigmatism in post-LASIK eyes and virgin eyes was different in the early postoperative period. However, there was no significant difference at 6 months postoperatively. The post-LASIK eyes exhibited a delayed recovery compared to the virgin eyes.
PubMed: 38863679
DOI: 10.2147/OPTH.S466201 -
Clinical Ophthalmology (Auckland, N.Z.) 2024Uncorrected refractive errors (REs) and amblyopia can lead to visual impairment with deleterious effects on quality of life and academic performance. Early detection and...
PURPOSE
Uncorrected refractive errors (REs) and amblyopia can lead to visual impairment with deleterious effects on quality of life and academic performance. Early detection and treatment by community vision care programs, such as the UCI EyeMobile for Children, can aid in addressing preventable vision loss.
METHODS
A total of 5074 children between the ages of 3 and 10 years were screened at 153 locations, including preschools, head start programs, and elementary schools within Orange County (OC), California (CA). Subsequently, 1024 children presented for comprehensive eye examinations. A retrospective analysis of all examined children was conducted, determining the frequency and severity of REs and amblyopia and the spectacle prescription rate by age. Propensity score matching analysis evaluated the effect of median household income on RE and amblyopia frequency.
RESULTS
Among those who failed initial screening and were subsequently examined, significant rates of REs and amblyopia were detected: myopia (24.4%), hyperopia (35.4%), astigmatism (71.8%), anisometropia (8.9%), amblyopia (7.0%), and amblyopia risk (14.4%). A majority (65.0%) of those examined received prescription spectacles from UCI EyeMobile, with around a third requiring a new or updated prescription. The frequency of REs and amblyopia and the spectacle prescription rate were uniform across OC congressional districts. Myopia and amblyopia risk was positively and negatively associated with household income, respectively.
CONCLUSION
The UCI EyeMobile for Children serves as a vital vision care program, providing free vision screening, comprehensive eye examinations, and spectacles. A significant number of children required examination, and a high frequency of REs and amblyopia were detected in examined children, with subsequent provision of prescription spectacles to most children.
PubMed: 38860118
DOI: 10.2147/OPTH.S460879 -
Optics Express Apr 2024Focus stabilisation is vital for long-term fluorescence imaging, particularly in the case of high-resolution imaging techniques. Current stabilisation solutions either...
Focus stabilisation is vital for long-term fluorescence imaging, particularly in the case of high-resolution imaging techniques. Current stabilisation solutions either rely on fiducial markers that can be perturbative, or on beam reflection monitoring that is limited to high-numerical aperture objective lenses, making multimodal and large-scale imaging challenging. We introduce a beam-based method that relies on astigmatism, which offers advantages in terms of precision and the range over which focus stabilisation is effective. This approach is shown to be compatible with a wide range of objective lenses (10x-100x), typically achieving <10 nm precision with >10 μm operating range. Notably, our technique is largely unaffected by pointing stability errors, which in combination with implementation through a standalone Raspberry Pi architecture, offers a versatile focus stabilisation unit that can be added onto most existing microscope setups.
PubMed: 38859306
DOI: 10.1364/OE.520845 -
Journal of the Optical Society of... May 2024As a missile flies at high speed, the index and surface shape of the conformal dome will vary under the influence of the aero-optical effect, which will degenerate the...
As a missile flies at high speed, the index and surface shape of the conformal dome will vary under the influence of the aero-optical effect, which will degenerate the performance of the seeker's imaging detection system. However, many previous studies on aero-optical imaging deterioration of optical domes were usually carried out under fixed operating conditions, which are not in line with the real flight scene of the missile. In addition, the aero-optical imaging degeneration of the dome is diverse as the flight time increases. Therefore, it is of great significance to study the time characteristics of aero-optical imaging degradation of optical domes under variable work conditions. In this study, taking an air-to-air missile as an example, the Zernike polynomials, wavefront aberration, Strehl ratio, and image simulation are applied to evaluate the aero-optical imaging deterioration of an ellipsoidal dome in the flight time range of 0-10 s under variable working conditions. The simulation results show that, as the flight time increases, (1) the dynamic range of tilt, defocus, astigmatism, coma, and wavefront aberration increase; and (2) the Strehl ratio and the peak signal-to-noise ratio (PSNR) of the simulated images decrease. Therefore, the influence of flight time on the aero-optical image degradation of the ellipsoidal dome gradually becomes more serious.
PubMed: 38856583
DOI: 10.1364/JOSAA.515243 -
Journal of the Optical Society of... May 2024Using the flux tracing algorithm developed in the previous two parts, we examine the nonlinear rays that pass through the focus of a lens containing monochromatic...
Using the flux tracing algorithm developed in the previous two parts, we examine the nonlinear rays that pass through the focus of a lens containing monochromatic aberrations. Lens aberration is modeled differently in the numerical propagation algorithms relating to the thin lens and the ideal lens cases. For the former, an additive phase term is applied to the transmission function of the thin lens, which describes a distortion in the thickness function of the lens, and for the latter an additive phase term is added to the pupil function of the lens (the Fourier transform of the image plane). In both cases, the Zernike polynomials are applied to model various aberrations including spherical, defocus, comatic, astigmatism, trefoil, and quadrafoil. Despite the different methods of modeling aberration for the two types of lenses, remarkably similar results are obtained for both cases. A discussion is also provided on the relationship between classical wavefront aberration theory and nonlinear tracing. This paper demonstrates the extraordinary potential of nonlinear ray tracing to gain insights into complex optical phenomena.
PubMed: 38856578
DOI: 10.1364/JOSAA.503924 -
Applied Optics Apr 2024We have recently reported the dynamic adjustment of the focal length in an electrically tunable liquid crystal "foveal" lens, the center of which can be shifted over a...
We have recently reported the dynamic adjustment of the focal length in an electrically tunable liquid crystal "foveal" lens, the center of which can be shifted over a large working area. In the present work, we show that this design allows also the independent generation of astigmatism with arbitrary axis and tilt of the light wavefront by simply changing the phase and the voltage differences between 4 control electrodes. Furthermore, we also demonstrate the capability of generating highly localized negative (defocusing) lenses with the same device by using a dual frequency liquid crystal.
PubMed: 38856374
DOI: 10.1364/AO.517797 -
Clinical Ophthalmology (Auckland, N.Z.) 2024To determine if factors pertaining to corneal thickness and elevation were linked to the prescribed back optic zone radius and overall diameter in keratoconus (group I),...
PURPOSE
To determine if factors pertaining to corneal thickness and elevation were linked to the prescribed back optic zone radius and overall diameter in keratoconus (group I), and cross-linked keratoconus (group II), cases successfully fitted with rigid contact lenses.
PATIENTS AND METHODS
A review of cases adapted to contact lens wear (Rose K™) and assessed using Pentacam™ (for corneal anterior surface topography, astigmatism, elevation, and topographic thickness variation) was undertaken to determine the significance of any correlation with comfort, lens usage, grading of keratoconus, corrected distance visual acuity (with glasses and contacts), refractive error, prescribed lens powers, back optic zone radius and overall diameter values were assessed.
RESULTS
Chief findings were, comfort was rated highly, lenses were worn for more than 10 hours/day in 75% of cases. RCL corrected distance logMAR acuities (median, mode, inter-quartile ranges) were 0.11, 0.12 (0.08-0.13) and 0.08, 0.08 (0.06-0.11) in groups I and II, respectively. Multiple linear regression revealed significant correlations (p<0.01) between the [A] back optic zone radius, the thinnest value of corneal thickness (x1) and anterior corneal surface elevation (x2). The respective r values were 0.471 in group I and 0.512 in group II. [B] overall diameter, x1 and x2. The respective r values were 0.282 in group I and 0.505 in group II.
CONCLUSION
RCLs were well-tolerated in both groups. The r values imply there is a 50% chance of correctly predicting the suitable back optic zone radius in both groups, a 50% chance of correctly predicting the overall diameter in group II and 28% in group I cases using just x1 and x2. The thinnest value of corneal thickness and anterior corneal surface elevation could be used to quickly select the BOZR and OD during RCL fitting. This has the potential to reduce chair-time, waste and improve efficiency.
PubMed: 38855010
DOI: 10.2147/OPTH.S463305