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

Lamellar macular defects: are degenerative lamellar macular holes truly degenerative?

PurposeTo investigate morpho-functional changes after surgical treatment for ERM foveoschisis or lamellar macular hole (LMH), and to evaluate whether the two entities are associated with different healing processes and long-term outcomes.DesignRetrospective interventional case series.MethodsA total of 56 eyes, treated for lamellar macular defects and followed up for 24 months, were enrolled. The eyes were divided into two groups: 34 with ERM foveoschisis and 22 with LMH. Changes in the following features were evaluated and compared between the two groups: best-corrected visual acuity (BCVA), external limiting membrane (ELM) and ellipsoid zone (EZ) defects, central foveal thickness (CFT), and autofluorescence (FAF) diameter and area.ResultsAfter surgery, progressive BCVA improvement was observed with no significant difference between the two groups (p-value: 0.06). An increased number of eyes with intact outer-retinal layers was found both in the ERM foveoschisis and LMH groups. FAF diameter and area decreased significantly throughout the FU with no significant difference between the two groups (p-value: 0.2).ConclusionIn the present study, significant functional and microstructural improvements were observed after surgery for both ERM foveoschisis and LMH, demonstrating considerable repair potential in both types of lamellar defects. These findings question the true “degenerative” nature of LMH

A case of unilateral circumscribed posterior keratoconus evaluated by three different imaging tools: optical coherence tomography, videokeratography, and Scheimpflug corneal tomography

Posterior keratoconus is a rare corneal anomaly which is part of the ectatic corneal disorders. We report a clinical presentation of a unilateral posterior keratoconus in a 42-year-old man. At the time of presentation, corrected distance visual acuity (CDVA) was 20/20 with a correction of +2.50 +2.50 × 90° in the right eye and 20/40 with +1 +3.00 × 105° in the left eye. Slit lamp microscopy showed in the left eye an evidence of corneal thinning with a mild anterior protrusion and a remarkable posterior excavation. The intraocular pressure was 19 mmHg in right eye and 16 mmHg in left eye. Ultrasound pachymetry showed a minimum corneal thickness of 556 μ in right eye and 289 μ in left eye. The anterior segment optical coherence tomography (AS-OCT) revealed central corneal thinning and showed a reduced epithelial thickness. Videokeratography showed an increase of the corneal curvature in a defined area with central steepening in the area of the posterior corneal depression with gradual paracentral flattening. The description of this case underlines the importance of this instruments such us AS-OCT and corneal topography in diagnosis of posterior keratoconus. It can also be observed that in the contralateral eye there are no signs of ectasia as in the rare condition of unilateral keratoconus

Sliding keratoplasty followed by transepithelial iontophoresis collagen cross-linking for pellucid marginal degeneration

PURPOSE: To describe the changes in visual acuity and topographic analysis in a patient affected by advanced pellucid marginal degeneration (PMD). METHODS: A 59-year-old woman with bilateral PMD who was contact lens intolerant was treated by sliding keratoplasty before and 3 months after transepithelial (epi-on) iontophoresis collagen cross-linking (I-CXL) in one eye. Corrected distance visual acuity (CDVA), spherical equivalent and cylinder refraction, corneal topography, ultrasound pachymetry, and endothelial cell count were assessed at baseline and up to 12 months postoperatively. RESULTS: After 1 year of follow-up, CDVA increased from 20/200 to 20/50 and the videokeratographic patterns significantly improved. Endothelial cell counts did not change significantly (P > .05). CONCLUSIONS: Sliding keratoplasty combined with I-CXL was safe and effective in the treatment of advanced PMD

Intravitreal Injection of Dexamethasone Implant in Serous Macular Detachment Associated with Waldenström's Disease

Purpose: To evaluate the efficacy of one intravitreal injection of dexamethasone (Ozurdex®; Allergan, Inc., Irvine, Calif., USA) in serous macular detachment (SMD) of one eye, associated with bilateral central retinal vein occlusion (CRVO) in a patient affected by Waldenström's macroglobulinemia (WM). Patients and Methods: A female patient, affected by WM, complained of a progressive decrease in visual acuity, mainly in the left eye (LE). SMD in the LE associated with bilateral CRVO was diagnosed. One intravitreal injection of dexamethasone was administered in the LE and the patient was tested 1, 2, and 6 months after the injection. Results: 1, 2, and 6 months after the injection, the spectral domain optical coherence tomography (SD-OCT) showed a progressive slight reduction of foveal thickness that was not related to any improvement of visual function. Conclusions: Treatment with dexamethasone (Ozurdex) induced a progressive slight reduction of SMD but no improvement of visual acuity, and it is possible that this is related to the condition of hematic hyperviscosity that is present in WM

Intravitreal Injections for Macular Edema Secondary to Retinal Vein Occlusion: Long-Term Functional and Anatomic Outcomes

Purpose. To report the long-term visual and anatomic outcomes of intravitreal injections for macular edema (ME) secondary to retinal vein occlusion (RVO) in a real-life clinical setting. Design. Retrospective interventional case series. Methods. A total of 223 consecutive eyes with ME secondary to RVO, treated with the first three intravitreal Ranibizumab or dexamethasone injections between August 2008 and September 2018, were enrolled in the study. Subsequent retreatment was guided by best-corrected visual acuity (BCVA) and central macular thickness (CMT) measurements, aimed at achieving macular fluid regression and BCVA stability. BCVA and CMT were recorded at baseline and at subsequent annual time points. The mean number of injections administered each year and the incidence of adverse events were recorded. Results. The mean BCVA and CMT at baseline were 0.79 logMar (SD 0.71) and 615.7 μm (SD 257.5), respectively. The mean follow-up (FU) period was 47.8 months (min 12–max 120). At 12 months, the mean BCVA and CMT had significantly improved to 0.62 logMar (SD 0.68; p<0.0001) and 401.04 μm (SD 183.8; p<0.0001). Improvements remained significant at the final FU visit. Eyes with BRVO and nonischemic RVO showed significantly better visual outcomes when compared to eyes with CRVO and ischemic RVO, over the entire FU period. An average of 4.08 (SD 2.1) Ranibizumab and 1.5 (SD 0.6) Ozurdex injections were administered over the first 12 months. The number of injections decreased thereafter progressively. One eye with CRVO developed endophthalmitis and one with BRVO developed an intraocular pressure increase that was refractory to topical medications and ultimately treated with trabeculectomy. Conclusion. Intravitreal Ranibizumab and/or dexamethasone injections were found to be effective at inducing a long-lasting improvement of BCVA and CMT in a real-life clinical setting. A safety profile similar to that already well-established in Ranibizumab and dexamethasone treatment was observed, as well as a steady decrease in the number of intraocular injections required. The results support intravitreal treatments for BRVO and CRVO in patient populations with similar characteristics in similar settings