Correlation between intraoperative and postoperative vaulting of the EVO implantable Collamer lens: a retrospective study of real-time observations of vaulting using the RESCAN 700 system

Background Implantable Collamer lens (ICL) vaulting is one of the most important parameters for the safety, aqueous humor circulation, and lens transparency after ICL implantation. This study aimed to investigate the factors associated with the actual vaulting after refractive EVO-ICL surgery. Methods This retrospective study included patients who underwent EVO-ICL surgery at a tertiary eye hospital between October and December 2019. A RESCAN 700 was used for the intraoperative and CIRRUS HD-OCT was used for postoperative observation of vaulting. Subjective and objective refractions, anterior ocular segment, corneal morphology, intraocular pressure (IOP), anterior chamber volume (ACV), crystalline lens rise (CLR), white-to-white distance (WTW), anterior chamber depth (ACD), axial length, corneal endothelial cell density (ECD), and fundoscopy were examined. A multivariable analysis was performed to determine the factors independently associated with 1-month postoperative vaulting. Results Fifty-one patients (102 eyes) were included. Compared with the eyes with normal vaulting, those with high vaulting had higher preoperative diopter values (P = 0.039), lower preoperative corrected visual acuity (P = 0.006), lower preoperative IOP (P = 0.029), higher preoperative ACD (P = 0.004), lower preoperative CLR (P = 0.046), higher ICL spherical equivalent (P = 0.030), higher intraoperative vaulting (P < 0.001), and lower IOP at 1 month (P = 0.045). The multivariable analysis showed that the only factor independently associated with high vaulting at 1 month after surgery was the intraoperative vaulting value (odds ratio = 1.005, 95% confidence interval: 1.002–1.007, P < 0.001). The intraoperative and 1-month postoperative vaulting values were positively correlated (R2 = 0.562). Conclusions The RESCAN700 system can be used to perform intraoperative optical coherence tomography to predict the vaulting value of ICL at 1 month.

Vitrectomy in Lens and Glaucoma Pathologies

Pars plana vitrectomy (PPV) is currently used as an effective method in many posterior segment pathologies. Although the most common indication is retina and vitreous pathologies, PPV is also preferred in some cases associated with lens and glaucoma. In case the crystalline lens or artificial intraocular lens, which is a product of industrial development, falls into the vitreous, it is essential to remove it mostly with the PPV approach. In some types of secondary glaucoma, especially malignant glaucoma, successful results are obtained in terms of visual prognosis and complications with vitreoretinal surgery techniques.

Os estudos de Thomas Young sobre a acomodação ocular: análise do episódio e tradução comentada do texto “Observations on vision” (1793)

Neste artigo, apresentamos uma tradução comentada para o português do texto “Observations on vision” (1793), de Thomas Young (1773-1829), seu primeiro trabalho publicado nas Philosophical Transactions da Royal Society. Nesse texto, Young discutiu algumas teorias e ideias sobre a acomodação visual existentes até sua época. Após apontar diversas falhas nessas teorias, ele propôs a sua, baseada na existência de uma musculatura no cristalino responsável especificamente por esse mecanismo. A tradução é precedida por três seções, em que aspectos da história da anatomia ocular e das teorias anteriores para a acomodação visual são abordados, a fim de contextualizar a leitura do material traduzido.Thomas Young’s studies on visual accommodation: an analysis of the episode and a commented Portuguese translation of his “Observations on vision”(1793)AbstractIn this paper, we present a commented Portuguese translation of Thomas Young’s (1773-1829) “Observations on vision” (1793), his first published paper in Royal Society’s Philosophical Transactions. In this article, Young discussed some previous theories and ideas on visual accommodation up to his days. After pointing out the flaws of these theories, he proposed his own: muscles in the crystalline lens were responsible for this mechanism. The translation is preceded by three sections in which we comment on aspects of the history of eye anatomy and of the previous theories for visual accommodation, in order to contextualize the reading of the translated material.Keywords: Visual accommodation; Optics; Vision; Thomas Young; Light.

Lens Biometry in Congenital Lens Deformities: A Swept-Source Anterior Segment OCT Analysis

Aims: To investigate the lens biometric parameters in congenital lens deformities, using a novel technique of swept-source anterior segment optical coherence tomography (SS-ASOCT).Methods: This prospective study included patients with microspherophakia (MSP), coloboma lentis (CL), and posterior lenticonus (PL). For this cohort, 360-degree high-resolution lens images were obtained using the latest SS-ASOCT (CASIA2, Tomey Corp, Nagoya, Japan). The lens biometric parameters were calculated by the CASIA2 built-in software for anterior lens radius (ALR), posterior lens radius (PLR), anteroposterior distance (APD), anterior chamber depth (ACD), equatorial diameter (Eq Dia), rear projection length (RPL), and maximum diameter of the lesion (MDL).Results: This study included two eyes each with MSP and CL and one eye with PL. The lens of MSP was spherical and posteriorly dislocated, with decreased ALR and PLR, Eq Dia, but increased APD. In patients with CL, the coloboma was isolated, bilateral, inferior, and located toward the maldeveloped ciliary body. High astigmatism was mainly lenticular, and this was calculated by the ALR and PLR. Regarding the site of coloboma, a significant decrease in ALR was observed, while the PLR and APD were not affected. The PL eyes had a cone-shaped protrusion of the posterior lens surface with a subtle cataractous region around the apex. An extremely high posterior surface curvature was observed with a mean PLR of 1.67 mm. The RPL and MDL were about 1.80 and 0.4 mm, respectively, which were homogenous at different sections.Conclusions: The CASIA2 is a valuable option for in vivo crystalline lens measurement for congenital lens deformities, enabling the accurate diagnosis and providing illuminating insights into the pathogenesis of MSP, CL, and PL

Analysis of Ocular Biometric Parameters in Patients with Cystoid Macular Edema

Relevance. Cataract surgeries are among the most frequently performed ophthalmic surgeries in the world. Despite the fact that they become less traumatic every year, such interventions are still accompanied by post-surgery complications, one of which is cystic macular edema (CME) or Irwin–Gass syndrome. Purpose. To analyze ocular biometric parameters in patients with CME. Material and Methods. The study included 40 patients (40 eyes) with post-surgery CME. All patients underwent ultrasound biometry, axial length measurement, crystalline lens thickness measurement with Bio&Pachy Meter AL-4000 (Tomey, Japan) and optical coherence tomography (OCT) with Cirrus HD-OCT 5000 (Carl Zeiss, Germany) to assess central foveal thickness. Depending on the axial length, all eyes were divided into “long” and “short” relative to the average axial length of 23.3 mm. The data was analyzed with STATISTICA 10 software (StatSoft Inc., USA). Results. The incidence of CME after uncomplicated cataract surgery in Cheboksary branch of the S. Fyodorov Eye Microsurgery Federal State Institution amounted to 0.002%. Axial length among patients with CME ranged from 20.53 mm to 25.4 mm; the average value amounted to 22.67 ± 1.05 mm. The majority of eyes were “short” – 31 eyes (77.5%), whereas 9 eyes (22.5%) were “long”. “Short” eyes exhibited a greater crystalline lens thickness (4.81 ± 0.53 mm) compared to “long” eyes (4.42 ± 0.42 mm) (рM-U = 0.014). Conclusion. The development of CME after uncomplicated cataract surgery is more often observed in eyes with axial length smaller than 23.3 mm.

Seeing the future: predictive control in neural models of ocular accommodation

Ocular accommodation is the process of adjusting the eye's crystalline lens so as to bring the retinal image into sharp focus. The major stimulus to accommodation is therefore retinal defocus, and in essence, the job of accommodative control is to send a signal to the ciliary muscle which will minimise the magnitude of defocus. In this paper, we first provide a tutorial introduction to control theory to aid vision scientists without this background. We then present a unified model of accommodative control that explains properties of the accommodative response for a wide range of accommodative stimuli. Following previous work, we conclude that most aspects of accommodation are well explained by dual integral control, with a "fast" or "phasic" integrator enabling response to rapid changes in demand, which hands over control to a "slow" or "tonic" integrator which maintains the response to steady demand. Control is complicated by the sensorimotor latencies within the system, which delay both information about defocus and the accommodation changes made in response, and by the sluggish response of the motor plant. These can be overcome by incorporating a Smith predictor, whereby the system predicts the delayed sensory consequences of its own motor actions. For the first time, we show that critically-damped dual integral control with a Smith predictor accounts for adaptation effects as well as for the gain and phase for sinusoidal oscillations in demand. In addition, we propose a novel proportional-control signal to account for the power spectrum of accommodative microfluctuations during steady fixation, which may be important in hunting for optimal focus, and for the nonlinear resonance observed for low-amplitude, high-frequency input. Complete Matlab/Simulink code implementing the model is provided at https://doi.org/10.25405/data.ncl.14945550

Keratometry, biometry, and prediction of intraocular lens power in adult tigers (Panthera tigris)

OBJECTIVE To calculate the necessary pseudophakic intraocular lens (IOL) power to approximate emmetropia in adult tigers. ANIMALS 17 clinically normal adult tigers. PROCEDURES 33 eyes of 17 clinically normal adult tigers underwent routine ophthalmic examination and B-scan ultrasonography while anesthetized for unrelated procedures. Specific ultrasound data (globe measurements and corneal curvature) and estimated postoperative IOL positions were utilized to calculate predicted IOL power by use of Retzlaff and Binkhorst theoretical formulas. Applanation tonometry and refraction were also performed. RESULTS Mean ± SD axial globe length was 29.36 ± 0.82 mm, preoperative anterior chamber depth was 7.00 ± 0.74 mm, and crystalline lens thickness was 8.72 ± 0.56 mm. Mean net refractive error (n = 33 eyes) was +0.27 ± 0.30 diopters (D). By use of the Retzlaff formula, mean predicted IOL power for the postoperative anterior chamber depth (PACD), PACD – 2 mm, and PACD + 2 mm was 43.72 ± 4.84 D, 37.62 ± 4.19 D, and 51.57 ± 5.72 D, respectively. By use of the Binkhorst equation, these values were 45.11 ± 4.91 D, 38.84 ± 4.25 D, and 53.18 ± 5.81 D, respectively. Mean intraocular pressure for all eyes was 14.7 ± 2.69 mm Hg. CLINICAL RELEVANCE The calculated tiger IOL was lower than reported values for adult domestic felids. Further studies evaluating actual PACD and pseudophakic refraction would help determine the appropriate IOL power to achieve emmetropia in this species.

The Complications of Cataract Surgery in Patients with Pseudoexfoliation

The senile cataract represents the blurring of the crystalline lens after the age of 65. It occurs due to metabolic changes in the crystalline lens which occur over the years. The only effective way to treat cataract is the surgical one. Pseudoexfoliation is an age related systemic disorder. PEX represents the accumulation fibrillar material in the extracellular matrix of the tissue. The most known ocular manifestation of the PEX are the collection at iris pupillary margin and anterior lens capsule. This accumulation is associated with many intraoperative and postoperative complications in patients scheduled for cataract surgery. The aim of the study was to investigate the prevalence of the surgical complications during phacoemulsfication in patients with PEX. The study included 91 patients scheduled for cataract surgery divided into two groups (PEX group 46, control group 45 patients). Poor intraoperative midryasis, zonular dehiscence, postoperative corneal edema, anterior chamber inflammation, elevated intraocular pressure and tear film instability had particularly higher rate of occurring in PEX group comparing to the control group (p<0.001). The highest mean value of intraocular pressure was observed in PEX group on the first postoperative day 25.6 ± 1.1 mmHg, while the best corrected visual acuity was measured in control group 0.71 ± 1.2 one month after phacoemulsification. Cataract surgery in patients with PEX carries great risk, but with adequate preoperative planning, the awareness of the potential complications, can provide safe and routine phacoemulification in these patients.

Phacoemulsification: Proposals for Improvement in Its Application

A cataract is defined as opacity of the crystalline lens. It is currently one of the most prevalent ocular pathologies and is generally associated with aging. The most common treatment for cataracts is surgery. Cataract surgery is a quick and painless process, is very effective, and has few risks. The operation consists of removing the opacified lens and replacing it with an intraocular lens. The most common intraocular lens removal procedure that is currently used is phacoemulsification. The energy applied in this process is generated by ultrasonic waves, which are mechanical waves with a frequency higher than 20 kHz. A great deal of research on the different ways to perform the stages of this surgical procedure and the analysis of the possible side effects of the operation has been published, but there is little information on the technical characteristics, the intensities applied, and the use of ultrasound-emitting (U/S) equipment for cataract removal. More studies on the method and depth of absorption of ultrasonic waves in our visual system when performing the phacoemulsification procedure are needed. It would be advisable for health authorities and medical professionals to develop guidelines for the handling and use of ultrasonic wave-emitting equipment, such as those that exist for ultrasound and physiotherapy. This could help us to reduce undesirable effects after the operation.