Refractive Objective Research Articles

Comparison of long-term visual quality after keratorefractive lenticule extraction and implantable collamer lens V4c for high myopia.

To compare the long-term refractive outcomes and visual quality after keratorefractive lenticule extraction (KLEx) and EVO-implantable collamer lens (ICL) implantation for high myopia. Eye & ENT Hospital of Fudan University, Shanghai, China. Retrospective study. This study included 31 KLEx-treated patients (31 eyes, spherical equivalent: -7.62 ± 1.22 diopters [D]) and 32 ICL-treated patients (32 eyes, spherical equivalent: -8.22 ± 1.18 D). Refractive outcomes and objective visual quality were examined. Subjective visual quality was evaluated by a customized questionnaire. Patients' satisfaction was graded. 5 years postoperatively, the efficacy (KLEx: 0.96 ± 0.20; ICL: 1.03 ± 0.20; P = .164) and safety indices (KLEx: 1.12 ± 0.20; ICL: 1.21 ± 0.19; P = .067) were comparable. Statistically higher proportions of ICL-treated eyes achieved a postoperative uncorrected distance visual acuity of 20/20 or better ( P = .035). Refractive predictability was similar between the 2 groups ( P = .947), whereas more KLEx-treated eyes had myopic refractive errors ( P < .001). Total coma was significantly higher after KLEx ( P = .020), and greater total trefoil was observed after ICL implantation ( P = .006). Haloes were the primary visual disturbance in both groups (KLEx: 64.5%; ICL: 93.8%). The incidences of haloes ( P < .001), glare ( P = .004), and starbursts ( P = .043) were notably higher after ICL implantation. The patient's satisfaction scores were similar (KLEx: 9.10 ± 1.27; ICL: 9.10 ± 1.27; P = .894). For high myopia, EVO-ICL yielded better long-term refractive outcomes than KLEx. Haloes were the chief concern in both groups, with a significantly higher incidence after ICL implantation.

Awareness and Knowledge About RefractiveSurgery Among Medical Students in Baghdad

Purpose: Refractive error represents a common eye disorder that can significantly impact an individual's visual function and overall well-being. There are several methods of correcting refractive errors and objective of this study was to assess the awareness of refractive surgery and the preferred methods of refractive error correction among medical students in Baghdad. Study Design: Cross sectional survey. Place and Duration of Study: University of Baghdad Al-Kindy College of Medicinefrom November 2022 to March 2023. Methods: Medical students from six Baghdad medical colleges with total sample size of 350 were included. Students who had undergone refractive surgeries and fifth and sixth year medical students were also excluded. Level of knowledge was categorized as; &lt;50% (0-5) poor knowledge, 50-70% (6-8) moderate knowledge and &gt;70% (9-12) good knowledge. Results: Among the students with refractive errors, 82% had knowledge about their refractive error. Forty percent had myopia, 12% had astigmatism, 15 % had myopia and astigmatism, 10% had hyperopia, 5% had hyperopia and astigmatism. Among them 57.8% were not willing to undergo refractive surgery due to fear of complications. Forty eight percent had poor knowledge,43.1% had moderate and only 8.26% had a good knowledge of refractive surgeries. The majority preferred eyeglasses (82.6%) followed by both eyeglasses and contact lenses. Conclusion: Students had good awareness about refractive surgery but their familiarity and knowledge about it remained poor because of complications. An overwhelming majority of students still preferred spectacles as the method for vision correction.

Optical characterization and through-focus performance of two advanced monofocal intraocular lenses

PurposeTo compare the refractive power profile, subjective depth-of-field and objective optical quality of two advanced monofocal intraocular lenses (IOLs) designed to improve intermediate vision.MethodsThis prospective study evaluated forty-six eyes of twenty-three patients, aged 54–68 years, binocularly implanted with two monofocal enhanced intraocular lenses (IOLs), the Tecnis Eyhance and the Physiol Isopure. Subjective through-focus visual acuity curves were obtained by placing trial lenses in front of the eye while wearing its best spherical-cylindrical correction for distance. Objective optical quality was defined as the area under the modulation transfer function, calculated from the wavefront maps measured with a high-resolution aberrometer. The optical design of both lenses was compared based on their refractive power profiles measured with the lenses immersed in saline solution.ResultsBoth lenses have progressive aspherical geometries, in which the sagittal power decreases rapidly from the center to the edge of the optical zone. Mean monocular through-focus curves show a best corrected distance visual acuity of − 0.02 logMAR with both lenses. Through-focus visual acuity was marginally higher for the Eyhance, with a difference of 1 letter at the defocus position of − 0.5D and 3 letters between − 1.0D and − 2.0D. Objective assessment of optical quality revealed only a difference of about 2 points in MTF area at distance.ConclusionBoth IOLs use a similar approach to improve intermediate vision. The Eyhance showed marginally better subjective performance than the Isopure at the target vergences between − 1.00D and − 2.00D, although these results did not reach statistical significance and were not replicated by the objective findings.

Change in Corneal Epithelial Thickness After Photo Refractive Keratectomy (PRK)

Purpose: The study of change of the epithelium of the cornea in two points after Photo Refractive Keratectomy (PRK): at the peak of the cornea (ETpeak) and in the middle of the cornea (ETcenter). The study of the change of Lower Order Aberrations (LOAs) and Higher Order Aberrations (HOAs), Contrast Sensitivity (CS) and Corrected Distance Visual Acuity (CDVA) and the relationship of these parameters with the change of ETpeak and ETcenter after PRK. Materials and Methods: Twenty-seven patients (5 women and 22 men) with an average age of 27 years (age range 23-36) underwent PRK. For two years all 27 patients had stable refraction. The refractive objective was emmetropia. Results: After PRK, a statistically significant difference was found between pre-surgery and post-surgery measurements of ETpeak and ETcenter with in relation to LOAs, HOAs, CS and CDVA. As well as between CS and HOA (Z33). Conclusion: In conclusion, after PRK, the change in ETcenter and ETpeak is associated with the change in CDVA and the changes in LOAs and HOAs. Also, the change in CDVA is related to SC, LOAs and HOAS. Finally, the change in the ETcenter appears to be related to the change in the CS.

Two-Dimensional Peripheral Refraction and Image Quality for Four Types of Refractive Surgeries.

To provide a comprehensive investigation of the optical quality across the visual field for current mainstream types of refractive surgeries. Sixty eyes from 60 adults who received refractive surgery of either femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK), Q-value guided customized laser in situ keratomileusis (Q-LASIK), small incision lenticule extraction (SMILE), or Implantable Collamer Lens (ICL) (STAAR Surgical) implantation were included in this study. Refraction and optical aberrations from a visual field of horizontal 60° (from temporal 30° to nasal 30°) and vertical 36° (from superior 20° to inferior 16°) were measured using a custom-made Hartmann-Shack wavefront peripheral sensor. Refractive error, higher order aberrations, point spread function (PSF), and Strehl ratio were compared among these groups prior to and after the surgical procedures, respectively. All types of surgical procedures achieved an almost plano refraction in the central retina. This was also the case in the peripheral retina for the three types of laser refractive surgeries. However, residual peripheral relative hyperopic defocus was observed after ICL implantation. In all groups prior to the surgery, PSFs showed increasing distortion with eccentricity and arrow-like shape pointing toward the central fovea in the periphery in diagonals. Degradation of the PSFs was diminished by all three types of laser refractive surgeries, whereas ICL implantation made the peripheral distortion more prominent. Although ICL implantation produced a similar impact on refractive correction and objective optical quality in the central vision compared with other laser refractive surgeries, its outcome on the peripheral optics is different. The impact of this difference on visual performance deserves notice and warrants further investigation. [J Refract Surg. 2023;39(1):40-47.].

Extended depth of focus for high-end machine vision lenses by annular achromatic add-on diffractive elements

In modern machine vision systems high-end lens objectives allow superior imaging on state-of-the-art sensor arrays due to highly corrected optical aberrations and large apertures. The resultant shallow depth of focus is a disadvantage, usually leading to programmatic attempts of extending it, with compromised image resolution. Here we present a simple optical system equipped with novel, annular peripheral add-on diffractive elements, allowing highly extended range of sharp imaging without any pre- or post-processing. The separation of main refractive focusing power from the proposed filters enables sparse kinoform zones leading to easy manufacturing and negligibly low chromaticity in polychromatic imaging. The undisturbed central region of the refractive objective sustains the full native imaging quality of the test Zeiss Otus lens. Convergent numerical and experimental results are presented, showing improved readability of alphanumerical symbols in a wide range of w20 defocus parameters up to 24 wavelengths. Robust neural network-based method of image quality assessment is also proposed based on statistical optical character recognition, allowing high dynamics and easy implementation in experimental use as compared to established methods.

Improved nondegenerate multiphoton microscopy and axial registration with a reflective objective.

Conventional, degenerate multiphoton microscopy (D-MPM) requires the use of a high-numerical-aperture (NA) objective. Nondegenerate MPM (ND-MPM) imposes the additional demand for precise spatiotemporal overlap of two distinct excitation sources. We demonstrate that the axial focal shift introduced by refractive objective chromatic aberration hinders the spatial requirement of ND-MPM, whereas the use of a reflective objective overcomes this challenge and allows for improved ND excitation efficiency in spite of a lower NA. Moreover, we demonstrate that reflective objective focusing eliminates the axial misregistration of volumetric stacks in traditional D-MPM experiments when multiple excitation wavelengths are used.

Corneal Cap Thickness and Its Effect on Visual Acuity and Corneal Biomechanics in Eyes Undergoing Small Incision Lenticule Extraction.

Purpose To evaluate the effect of corneal cap thickness on visual acuity and corneal biomechanics in small incision lenticule extraction (SMILE) for the treatment of myopia. Methods Forty eyes of 20 patients undergoing SMILE for the treatment of myopia were enrolled in this prospective controlled study. The patients with 510 μm–560 μm central corneal thickness (CCT) and a refractive spherical equivalent of −3.00 D to −8.00 D were included. It was designed randomly to undergo SMILE with a 110 μm cap thickness in one eye and 150 μm cap thickness in the other. Ophthalmic examinations included best-corrected and uncorrected visual acuity (UCVA); refractive status, contrast sensitivity, and objective visual quality were evaluated at 2 h, 4 h, and 24 h postoperatively; while at 3 months after the procedure, corrected intraocular pressure (IOP), higher order aberrations (HOAs), and morphologic modifications of corneal architecture of both eyes were assessed. Results Compared with the 150 μm group, the incidence of OBL was significantly higher in the 110 μm cap thickness group (P=0.004), and UCVA, Strehl ratio (SR), objective scatter index (OSI), modulation transfer function (MTF) cutoff frequency, and photopic and scotopic contrast sensitivity at medium spatial frequency were all significantly better in 110 μm group at 2 h and 24 h postoperatively (P < 0.05). Corneal spherical aberration and corrected IOP by Corvis ST were significantly higher in the 110 μm group at 3 months postoperatively (P < 0.05). No statistically significant differences were found in manifest refraction, UCVA, SR, OSI, MTF cutoff, and mesopic and photopic contrast sensitivity at low frequency, photopic contrast sensitivity at high frequency, endothelial density, corneal coma, and total HOAs at 3 months after the procedure. No visual decline was found in the patients in this study. Conclusions Both 110 μm and 150 μm cap thickness in SMILE were safe and effective for treatment of myopia. A 110 μm cap thickness demonstrated better visual outcomes during early and late postoperative periods with higher corneal spherical aberration and corrected IOP at 3 months postoperatively. This trial is registered with ChiCTR-IOR-17013369.

Phenotypes of orthostatic blood pressure behaviour and association with visual acuity.

Manifestations of neurocardiovascular instability (NCVI), including orthostatic hypotension (OH) orthostatic hypertension (OHTN) and impaired blood pressure variability (BPV), have been associated with cardiovascular (CV) events. The eye is highly vascular and we propose an ideal target end organ to investigate pathological implications of NCVI. To identify and define clinically applicable phenotypes of orthostatic blood pressure (BP) behaviour, analogous to OH, OHTN, and orthostatic BPV and to investigate their relationship to vision. Wave one data from the Irish Longitudinal Study on Ageing (TILDA) were used. Orthostatic BP (OBP) phenotypes were identified and defined from beat-to-beat BP data, measured by digital photoplethysmography during an active stand (AS) lasting 110 s (s). Visual acuity (VA) was assessed using the Early Treatment Diabetic Retinopathy Study (EDTRS) LogMAR chart. The relationship between OBP phenotypes and VA in 4355 adults aged ≥50 years was investigated through multivariate linear regression models. There was a wide fluctuation in the prevalence of OH and OHTN up to 20 s after standing. After 30 s, four distinct OBP phenotypes were identified: in 70 % BP stabilised to within 20/10 mmHg of baseline BP, 4 % had persistent OH, 2 % had persistent OHTN and 25 % had exaggerated orthostatic blood pressure variability BPV. Systolic BPV was associated with worse VA (P = 0.02) as was diastolic BPV (P = 0.03), following adjustment for demographics, health behaviours, self-report eye diseases and diabetes, uncorrected refractive error, objective hypertension and antihypertensives. The hypothesis that NCVI may independently modulate CV risk is supported the independent association of exaggerated BPV and worse VA.

Common path in-line holography using enhanced joint object reference digital interferometers

Joint object reference digital interferometer (JORDI) is a recently developed system capable of recording holograms of various types [Opt. Lett. 38(22), 4719 (2013)]. Presented here is a new enhanced system design that is based on the previous JORDI. While the previous JORDI has been based purely on diffractive optical elements, displayed on spatial light modulators, the present design incorporates an additional refractive objective lens, thus enabling hologram recording with improved resolution and increased system applicability. Experimental results demonstrate successful hologram recording for various types of objects, including transmissive, reflective, three-dimensional, phase and highly scattering objects. The resolution limit of the system is analyzed and experimentally validated. Finally, the suitability of JORDI for microscopic applications is verified as a microscope objective based configuration of the system is demonstrated.

Précision réfractive et qualité de vision objective après implantation torique pseudophaque

To study efficacy and predictability of toric IOL implantation for correction of preoperative corneal astigmatism by analysing spherocylindrical refractive precision and objective quality of vision. Prospective study of 13 eyes undergoing micro-incisional cataract surgery through a 1.8mm corneal incision with toric IOL implantation (Lentis L313T(®), Oculentis) to treat over one D of preoperative corneal astigmatism. Preoperative evaluation included keratometry, subjective refraction, and total and corneal aberrometry (KR-1(®), Topcon). Six months postoperatively, measurements included slit lamp photography, documenting IOL rotation, tilt or decentration, uncorrected visual acuity, best-corrected visual acuity and objective quality of vision measurement (OQAS(®) Visiometrics, Spain). Postoperatively, mean uncorrected distance visual acuity was 8.33/10 ± 1.91 (0.09 ± 0.11 LogMar). Mean postoperative refractive sphere was 0.13 ± 0.73 diopters. Mean refractive astigmatism was -0.66 ± 0.56 diopters with corneal astigmatism of 2.17 ± 0.68 diopters. Mean IOL rotation was 4.4° ± 3.6° (range 0° to 10°). Mean rotation of this IOL at 6 months was less than 5°, demonstrating stability of the optic within the capsular bag. Objective quality of vision measurements were consistent with subjective uncorrected visual acuity. Implantation of the L313T(®) IOL is safe and effective for correction of corneal astigmatism in 1.8mm micro-incisional cataract surgery.

Ultra-slim plastic endomicroscope objective for non-linear microscopy

Non-linear microscopy has the potential to provide clinically useful information on the structure of biological tissue in vivo via an endomicroscope. The ability to use plastic as the optical material in a multiphoton objective was evaluated based on several criteria including autofluorescence, injection molding induced birefringence, and pulse broadening due to group velocity dispersion. An all-plastic, refractive ultra-slim endoscope objective was built with design specifications of NA = 0.4, FOV = 250 μm, 1.27 mm outer diameter, and 0.8 mm clear aperture. Initial images of second-harmonic generation signal (illumination at 780 nm) in collagen fibers and two-photon excited fluorescence (illumination at 920 nm) of Convallaria rhizome are reported.

Common path Fourier domain optical coherence tomography based on multiple reflections within the sample arm

We present a common path Fourier domain optical coherence tomography (FDOCT) setup where the reference signal arises from multiple reflections within the sample arm. Two configurations are demonstrated. The first is based on a reflective microscope objective while the second is based on a normal (refractive) microscope objective. The second configuration is effectively a Mireau interferometer. We present a sensitivity analysis of these setups and images of in vivo skin. Advantages of both common path arrangements include: 1) the reference surface is not close to the sample surface while keeping the optical path lengths matched (so the additional interferometer is not needed) and 2) the user can independently control reference and sample arm power. Additionally, the configuration using the refractive objective ensures that the coherence gate and focus gate always match. A disadvantage is that the reference arm power in certain circumstances is not optimal (i.e. close to saturating the CCD). However, this issue can be removed by a light source of sufficient output power. We believe the idea is scalable and therefore of interest to endoscopy applications.

Laser epithelial keratomileusis: outcome of initial cases performed by an experienced surgeon.

To evaluate refractive outcome and objective clinical data, and determine efficacy, predictability, and safety of laser epithelial keratomileusis (LASEK) for myopic treatments. We performed a retrospective non-comparative single-surgeon case series on the first 20 LASEK procedures (Alcon LADARVision 4000 laser). Mean patient age was 41.2 years (range 21 to 60 yr): 13 men and 7 women. Mean preoperative spherical equivalent refraction was -6.47+/-2.78 D. Corneal haze, uncorrected and spectacle-corrected visual acuity and manifest refraction were evaluated. Of 20 eyes studied, 3 were corrected for monovision. In the non-monovision group, 20/40 or better visual acuity was achieved in 94% (16 eyes) at 1 month, 100% (13 eyes) at 3 months, and 91% (10 eyes) at 6 months after LASEK; 20/20 or better was achieved in 12% (2 eyes) at 1 month, 46% (6 eyes) at 3 months, and 45% (5 eyes) at 6 months. Corneal haze at 1 month was grade 0.5 in 35% (7 eyes), 1 in 20% (4 eyes) and 2 in 10% (2 eyes). At 3 months, 62% (12 eyes) had grade 0.5 and 31% (6 eyes) had grade 1. At 6 months, 58% (12 eyes) had grade 0.5, 25% (5 eyes) had grade 1, and 8% (2 eyes) had grade 2. LASEK is a challenging procedure. Creating the epithelial flap is not simple and may have contributed to the high haze incidence in our study.

Quasi-wavelength-independent broadband optical Fourier transformer

The chromatic behaviour associated with diffractive optical elements is exploited herein to design a hybrid (diffractive-refractive) lens triplet showing very great wavelength-compensation capabilities for the Fraunhofer diffraction pattern of any diffracting screen under broadband point-source illumination. Within the paraxial Fresnel diffraction theory, we show that perfect compensation for the axial position of the Fourier transform of the input can be accomplished if we neglect the secondary spectrum of the refractive objective. Simultaneously, an achromatic correction for the scale of the Fraunhofer pattern is achieved. In this way, even for white light, only a low residual transversal chromatic aberration remains.

Hybrid diffractive-refractive telescope

Telescopes, microscopes, and similar compound systems often require achromats for objectives, since the longitudinal chromatic aberration from a singlet objective is so large that eyepieces cannot easily correct it. Such achromats can limit large-aperture systems because the curvatures required of their components are much stronger than the curvatures of singlets with the same net optical power. The hybrid diffractive-refractive telescope formed by combining a diffractive eyepiece with an unachromatized refractive objective is shown to eliminate the need for such bulky objectives, since a diffractive eyepiece is capable of correcting the large longitudinal chromatic aberrations of singlet refractive objectives. By splitting the holographic eyepiece into two elements, paraxial lateral color may also be corrected. First-order design considerations in these hybrid telescopes are presented, and a practical hybrid telescope layout is developed in which 1) primary chromatic aberration is eliminated, 2) paraxial lateral color is corrected, and 3) a useful eye relief is obtained.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Adaptation of the Schupmann Medial Telescope to a Large Scale Astronomical Optical System

The classical Schupmann medial telescope is free of the secondary-spectrum residual associated with large refractors. The difficulties in obtaining large glass disks of the necessary optical quality and the problem associated with their mounting preclude the use of this unconventional lens in large scale astronomical systems. However, to circumvent these limitations, the Schupmann lens was modified by replacing the refractive objective with a spherical mirror producing a new catadioptric lens configuration adaptable to large-scale astronomy. The design parameters and performance data are given for an f/5.4, 5.5-m focal length design covering a 2 degrees full field.

RETROBULBAR NEURITIS IN DIABETES

Apart from the commonly recognized ocular manifestations of diabetes, such as refractive changes, premature presbyopia, cataract and objective fundus changes, there are amblyopias affecting the peripheral and particularly the central visual fields. It is our purpose in this paper to discuss the latter, and to record the clinical history of another case in point. Retrobulbar neuritis arising in the course of diabetes, the evident result of an endogenous toxin or toxins liberated during the disease, which exercises a selective action on the papillomacular bundle of the optic nerve, is undoubtedly a clinical entity. Leber 1 has reported fourteen cases among fifty diabetic patients. Foster Moore 2 saw six cases in sixty-one diabetic patients. Wendell Reber 3 reported a case with scotoma for red, which was persistent six years after the attack. Ronne 4 reported two cases studied clinically and at necropsy to which reference will be made later. One of