Effect of corneal light scatter on vision: a review of the literature

The cornea is the transparent connective tissue window at the front of the eye. The physiological role of the cornea is to conduct external light into the eye, focus it, together with the lens, onto the retina, and to provide rigidity to the entire eyeball. Therefore, good vision requires maintenance of the transparency and proper refractive shape of the cornea. The surface structures irregularities can be associated with wavefront aberrations and scattering errors. Light scattering in the human cornea causes a reduction of visual quality. In fact, the cornea must be transparent and maintain a smooth and stable curvature since it contributes to the major part of the focusing power of the eye. In most cases, a simple examination of visual acuity cannot demonstrate the reduction of visual quality secondary light scattering. In fact, clinical techniques for examining the human cornea in vivo have greatly expanded over the last few decades. The measurement of corneal back scattering qualifies the degree of corneal transparency. The measurement of corneal forward-scattering quantifies the amount of visual impairment that is produced by the alteration of transparency. The aim of this study was to review scattering in the human cornea and methods of measuring it

Subretinal recombinant tissue plasminogen activator and pneumatic displacement for the management of subretinal hemorrhage occurring after anti-VEGF injections for wet AMD

We describe three cases of submacular hemorrhage that occurred two to four days after anti-VEGF intravitreal injection for occult choroidal neovascularisation in age-related macular degeneration and their management with 25 gauge pars plana vitrectomy with injection of subretinal recombinant tissue plasminogen activator (rTPA) followed by fluid-air exchange and postoperative prone position. Vitrectomy, subretinal rTPA injection and fluid-gas exchange apply as a safe and effective treatment in these cases. Functional results seem to be positive especially if surgical treatment is promptly performed

Rapidly progressing subperiosteal orbital abscess: an unexpected complication of a group-A streptococcal pharyngitis in a healthy young patient

INTRODUCTION: Complications associated to group-A streptococcal pharyingitis include non-suppurative complications such as acute rheumatic fever and glomerulonephritis and suppurative complications such as peritonsillar or retropharyngeal abscess, sinusitis, mastoiditis, otitis media, meningitis, brain abscess, or thrombosis of the intracranial venous sinuses. CASE PRESENTATION: We described a case of a 15-year-old patient with a history of acute pharyngodinia early followed by improvise fever and a progressive formation of a diffuse orbital edema, corneal hyperaemia, diplopia and severe decrease of visual acuity. The patient was surgically treated with functional endoscopic sinus surgery (FESS) after the response of a maxillofacial computed tomography scans that showed a pansinusitis complicated by a left orbital cellulites. Numerous colonies of Streptococcus pyogenes were found in the samples of pus and an antibiotic therapy with meropenem was initiated on the basis of the sensitivity test to antibiotics. The patient was finally discharged with diagnosis of left orbital cellulites with periorbital abscess, endophtalmitis and acute pansinusitis as a consequence of streptococcal pharyngitis. CONCLUSION: The case highlights the possible unusual complication of a group-A streptococcal pharyingitis in a immunocompetent child and the needing of a prompt surgical and medical approach toward the maxillofacial complications associated to the infection

LONG-TERM INTRAOCULAR PRESSURE AFTER UNCOMPLICATED PARS PLANA VITRECTOMY FOR IDIOPATHIC EPIRETINAL MEMBRANE

\u2019Purrpose: To investigate long-term intraocular pressure trends after uncomplicated pars plana vitrectomy for idiopathic epiretinal membrane. Methods: Three hundred and sixty-eight eyes of 368 consecutive patients were enrolled. Changes in intraocular pressure 1, 3, 6, and 12 months after surgery and during the fi nal follow-up visit were evaluated in vitrectomized eyes and nonvitrectomized fellow eyes. Results: The median follow-up period was 36 months (range 12 \u2013 92 months). Longitudinal data analysis evidenced a 2.5-mmHg (2.2 mmHg; 2.7 mmHg, 95% con fi dence interval) statis- tically signi fi cant difference in intraocular pressure 30 days after surgery between treated and fellow untreated eyes, gradually recovering to a not signi fi cant 0.2-mmHg ( 2 0.1 mmHg; 0.4 mmHg, 95% con fi dence interval) difference within 26 months. The incidence of late-onset ocular hypertension was 5.7% (21 over 347, 2%; 12%, 95% con fi dence interval) without difference between the treated eyes and the group control. No signi fi cant difference in the incidence of late-onset ocular hypertension and sex, lens status, or gauge of vitrectomy instru- ments was detected. Only patient \u2019 sagewassigni fi cantly higher (mean difference 4.2 years; 0.1 \u2013 8.0 years, Monte Carlo, 95% con fi dence interval) in those who de veloped late-onset ocular hypertension in the vitrectomized eye. Conclusion: Uncomplicated pars plana vitrectomy for idiopathic epiretinal membrane seems not to increase the risk of late-onset ocular hypertension or open-angle glaucoma development.

Analysis of the optical quality of intraocular lenses.

PURPOSE. To evaluate the optical quality of different intraocular lenses (IOLs). METHODS. An optical test bench and suitable software were used to assist in analysis of the optical Fourier transform (OFT) of a test image and to determine the quality of the lens in terms of spatial frequency response. The OFT was automatically converted, by means of an optical– electronic calibration procedure, into a modulation transfer function (MTF) for each lens. The passband value calculated by computer analysis of the MTF is an objective index of the lens quality. Three randomly acquired samples of 24 different models of foldable IOLs were compared. Statistical analysis was performed with twoway and one-way ANOVA for repeated measurements and with the Ryan-Einot-Gabriel-Welsch multiple F test. RESULTS. The method was demonstrated to be precise and accurate. A large range of passband values was found. Statistically significant differences between the mean passband values for different lenses were found. The lowest passband value (125.60 line pairs [lp]/mm) was measured for the IOL (Lenstec LH3000; Lenstec, Inc., St. Petersburg, FL) and the highest (191.48 lp/mm) for the Acrysof SA30AL (Alcon, Fort Worth, TX). CONCLUSIONS. Different IOLs can transmit different spectra of spatial frequencies. The best frequency response was provided by acrylic IOLs, particularly those with an asymmetrically biconvex profile. This could be due to a reduction of optical degradation provided by this type of profile. A lens with a higher frequency response should determine a better quality of vision once implanted and the frequency response should therefore be considered when choosing the intraocular lens model. (Invest Ophthalmol Vis Sci. 2004;45:2682–2690) DOI: 10.1167/iovs.03-102

Profile of a new extended range-of-vision IOL: a laboratory study

Purpose To evaluate the surface profile of a new-generation extended range-of-vision intraocular lens (IOL) and to compare it with that obtained for a monofocal IOL based on the same platform. Methods Prospective, experimental, laboratory study comparing the surface profile of the DFT015 (AcrySof IQ Vivity; Alcon Laboratories, Inc.), a new-generation presbyopia-correcting IOL, with the profile of the SN60WF (AcrySof IQ; Alcon Laboratories, Inc.), an aspheric monofocal IOL based on the same platform. Raw profiles were obtained using contact profilometry. The best-fit form was then subtracted from each raw profile to highlight potential differences. Results No significant differences were appreciated in raw profiles. On the contrary, after form removal, the new extended range-of-vision IOL showed a peculiar profile characterized by the presence of two altitudinal symmetrical changes in the order of 1 µm, localized in the central portion of the optic. Conclusions The new-generation extended range-of-vision IOL evaluated showed a smooth change of its surface compared to the same platform monofocal IOL. The altitudinal changes blended in the central design of the new presbyopia-correcting IOL, although micrometric, might play a crucial role in creating a continuous focal range while minimizing visual disturbances.Open access funding provided by Università degli Studi di Trieste within the CRUI-CARE Agreement

In vivo antimicrobial activity of 0.6% povidone-iodine eye drops in patients undergoing intravitreal injections: a prospective study

To investigate the antimicrobial activity of a preservative-free 0.6% povidone-iodine eye drop as an antiseptic procedure in decreasing the conjunctival bacterial load in eyes scheduled for intravitreal treatment and to compare its efficacy to the untreated fellow eye used as the control group. Prospective cohort analysis in which 208 patients received preservative-free 0.6% povidone-iodine eye drops three times a day for three days before intravitreal injection. Before and after the prophylactic treatment, a conjunctival swab was collected from both the study eye and the untreated contralateral eye, used as control. The swab was inoculated on different culture media and the colony-forming units were counted. Bacteria and fungi were identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Treatment with 0.6% povidone-iodine eye drops significantly reduced the conjunctival bacterial load from baseline (p < 0.001 for blood agar and p < 0.001 for chocolate agar) with an eradication rate of 80%. The most commonly isolated pathogen at each time-point and in both groups was coagulase-negative Staphylococci, isolated in 84% of the positive cultures. The study provides evidence about the effectiveness of 0.6% povidone-iodine eye drops treatment in reducing the conjunctival bacterial load in eyes scheduled for intravitreal treatment

Qualitative and Quantitative Assessment of Vascular Changes in Diabetic Macular Edema after Dexamethasone Implant Using Optical Coherence Tomography Angiography

The aim of this study was to investigate retinal and choriocapillaris vessel changes in diabetic macular edema (DME) after the intravitreal dexamethasone implant (IDI) using optical coherence tomography angiography (OCTA). Moreover, a comparison between morphological and functional parameters of DME and healthy patients was performed. Twenty-five eyes of 25 type 2 diabetic retinopathy patients complicated by macular edema (DME group) and 25 healthy subjects (control group) were enrolled. Superficial capillary plexus density (SCPD) and deep capillary plexus density (DCPD) in the foveal and parafoveal areas, choricapillary density (CCD) and optic disc vessel density (ODVD) were detected using OCTA at baseline and after 7, 30, 60, 90 and 120 days post injection. Best corrected visual acuity (BCVA), retinal sensitivity, and central retinal thickness (CMT) were also evaluated in both groups of patients. A statistically significant difference between the two groups (DME and controls) was found in terms of functional (MP, p < 0.001 and BCVA, p < 0.001) and morphological (CMT, p < 0.001; SCPD in the parafoveal area, p < 0.001; DCPD in the foveal area, p < 0.05 and parafoveal area, p < 0.001; CCD, p < 0.001) parameters. After the treatment, SCPD and DCPD in the foveal and parafoveal areas did not modify significantly during the follow up

Quality of images with toric intraocular lenses

Purpose: To objectively evaluate the image quality obtained with toric intraocular lenses (IOLs) when misaligned from the intended axis. Setting: University Eye Clinic and the Department of Industrial and Information Engineering, University of Trieste, Trieste, Italy. Design: Experimental study. Methods: An experimental optoelectronic test bench was created. It consisted of a high-resolution monitor to project target images and an artificial eye. The system simulates the optical and geometric characteristics of the human eye with an implanted toric IOL. A 3.00 diopters corneal astigmatism was simulated. Images reproduced by the optical system were captured according to different IOL axis positions. The quality of each image was analyzed using the visual information fidelity (VIF) criterion. The VIF reduction was calculated at each IOL rotational step. Results: A 5-degree IOL axis rotation from the intended position determined a decay in the image quality of 7.03%. Ten degrees of IOL rotation caused an 11.09% decay of relative VIF value. For a 30-degree rotation, the VIF decay value was 45.85%. Finally, the image decay with no toric correction was 56.70%. Conclusions: The more the objective quality of the image decays progressively, the further the axis of the IOL is rotated from its intended position. The reduction in image quality obtained after 30 degrees of toric IOL rotation was less than 50% and after 45 degrees, the image quality was the same as that of no toric correction

Impact of Epiretinal Membrane on Optical Coherence Tomography Tools Used for Monitoring Glaucoma

Background: Retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) measurements can be influenced by many factors including the presence of concomitant retinal diseases. The aim of this study it to assess the impact of epiretinal membrane (ERM) on RNFL and GCL assessment using optical coherence tomography (OCT). Methods: GCL, peripapillary RNFL (pRNFL), and Bruch's Membrane Opening Minimum Rim Width (BMO-MRW) thicknesses were analysed using an SD-OCT (Spectralis OCT) in eyes with idiopathic ERM and compared with a control group. Results: 161 eyes were included, 73 eyes in the control group and 88 eyes with idiopathic ERM. The pRNFL analysis revealed a statistically significant difference between the two groups in overall and temporal sector thicknesses. For GCL thickness report, the percentage of scans in which the GCL was erroneously segmented by automatic segmentation was assessed for each eye. A statistically significant difference was found in all sectors (p &lt; 0.001), with the exception of external nasal sector. A statistically significant difference (p &lt; 0.001) in the GCL total volume report was found in ERM group compared to the control group. For MRW at BMO analysis, there was no statistically significant difference in MRW thickness in any sector. Conclusion: In eyes with ERM, the GCL and pRNFL analysis seemed affected by the morphological retinal layers' modification. MRW-BMO did not appear to be directly affected by the presence of ERM