Journal of Ophthalmic and Vision Research
Year:2012 | Volume:7 | Issue:1|Papers Count:21

Over the past decade, a new discipline in biomedical research has emerged. Translational science, as it has been termed, is concerned with the application of laboratory or “bench” science to the diagnosis and treatment of human diseases. The importance and potential impact of this new discipline for collaboration, education, funding and public interest have been widely discussed.Moreover; the role of well-informed clinicians, invested in promoting as well as utilizing new research, is clearly recognized as crucial for the communal advancement of medicine and continued support of basic science.To meet these emergent objectives for vision scientists, Journal of Ophthalmic and Vision Research is establishing a new section entitled Translational Eye Research, to stimulate communication between basic scientists and clinicians.

The current issue of JOVR includes an article entitled “Is Noncycloplegic Photorefraction Applicable for Screening Refractive Amblyopia risk Factors?”.This is a well-constructed study comparing noncycloplegic photorefraction utilizing the plusoptiX SO4 screener to cycloplegic autorefraction (or cycloplegic retinoscopy in those few children in whom cycloplegic autorefraction could not be performed) in detecting AAPOS defined amblyopia risk factors. The authors compared refractive readings of the right eye from 185 children.

Purpose: To compare the accuracy of noncycloplegic photorefraction (NCP) with that of cycloplegic refraction (CR) for detecting refractive amblyopia risk factors (RARFs) and to determine cutoff points.Methods: In this diagnostic test study, right eyes of 185 children (aged 1 to 14 years) first underwent NCP using the PlusoptiX SO4 photoscreener followed by CR. Based on CR results, hyperopia (≥+3.5 D), myopia (≥ -3 D), astigmatism (≥ 1.5 D), and anisometropia (≥ 1.5 D) were set as diagnostic criteria based on AAPOS guidelines.The difference in the detection of RARFs by the two methods was the main outcome measure.Results: RARFs were present in 57 (30.8%) and 52 (28.1%) of cases by CR and NCP, respectively, with an 89.7% agreement. In contrast to myopia and astigmatism, mean spherical power in hyperopic eyes was significantly different based on the two methods (P<0.001), being higher with CR (+5.96 ± 2.13 D) as compared to NCP (+2.37 ± 1.36 D). Considering CR as the gold standard, specificities for NCP exceeded 93% and sensitivities were also acceptable (≥83%) for myopia and astigmatism.Nevertheless, sensitivity of NCP for detecting hyperopia was only 45.4%. Using a cutoff point of+1.87 D, instead of+3.5 D, for hyperopia, sensitivity of NCP was increased to 81.8% with specificity of 84%.Conclusion: NCP is a relatively accurate method for detecting RARFs in myopia and astigmatism. Using an alternative cutoff point in this study, NCP may be considered an acceptable device for detecting hyperopia as well.

Purpose: To report refractive outcomes following phacoemulsification (PE) and posterior chamber intraocular lens (PCIOL) implantation in eyes with previous corneal refractive surgery.Methods: In this retrospective comparative study, 18 consecutive eyes of 14 patients with previous keratorefractive surgery for myopia including photorefractive keratectomy (PRK, 6 eyes; 33.3%) and laser in situ keratomileusis (LASIK, 12 eyes; 66.7%) underwent PE+PCIOL. Computerized corneal topography was employed to determine the flattest keratometric reading within the 3-mm central zone. This value was inserted into the Sanders-Retzlaff-Kraff/T (SRK/T) formula to calculate IOL power. IOL power selected for implantation was 1 D greater than the calculated value described above.Results: Mean age and follow-up period were 54.1±11.5 years and 29.9±26.3 months, respectively. Mean implanted lens power was 18.56±3.86 D which was not significantly different from mean back-calculated IOL power for target refraction (19.04±4.16 D) (P=0.28). There was no significant difference between mean target refraction (-0.94±0.52 D) and achieved postoperative spherical equivalent refractive error (-0.62±1.06) at final follow-up (P=0.28). The achieved spherical equivalent refractive error was within ±0.50 D of intended refraction in 8 (44.4%) eyes, within ±1.0 D in 11 (61.1%) eyes, and within ±2.0 D in 16 (88.9%) eyes. In a subgroup of patients (5 eyes) with complete pre-refractive surgery data, the difference between post-refractive surgery keratometry method and all other methods (P=0.02) and between the current method and the Feiz-Mannis method (P=0.01) was statistically significant.Conclusion: The method suggested herein is simple and independent of pre-refractive surgery data with results comparable to other commonly used methods.

Purpose: To evaluate the long-term outcomes of two-step versus single application of mitomycin-C (MMC) during photorefractive keratectomy (PRK) for high myopia.Methods: This randomized clinical trial included consecutive patients with high myopia (exceeding 7 D). Patients underwent PRK and were randomized to two methods of MMC 0.02% application as follows: in the single application group, MMC was applied for 45 seconds followed by irrigation; in the two-step group MMC was used identically followed by repeat application for another 15 seconds and corneal surface irrigation. Visual acuity, refractive error, pachymetry, topography, corneal haze and complications were compared between the two groups 18 months after surgery.Results: One hundred and forty patients (70 subjects in either study arm) underwent PRK according to the study protocol. Mean spherical equivalent refractive error was significantly reduced from baseline to -1.16±0.39 D in the single application group and to -1.07±0.39 D in the two-step group. Sixteen (11.5%) versus 8 (5.7%) eyes lost one or more line (s) of best corrected visual acuity in the single application group as compared to the two-step group (P=0.05). Corneal haze was observed in 18 (12.9%) and 8 (5.7%) eyes in the single application versus two-step group, respectively (P=0.04).Grade 3 corneal haze was not observed in the two-step group but occurred in five eyes (3.6%) in the single application group (P=0.03). No eyes developed corneal ectasia during the follow-up period.Conclusion: Two-step intraoperative application of MMC 0.02% in highly myopic eyes undergoing PRK can reduce the frequency and severity of haze formation.

Purpose: To assess the prevalence of allergic conjunctivitis in Gambia and to determine its epidemiologic features, seasonal variations and associated ocular and systemic conditions.Methods: Records of patients clinically diagnosed with allergic conjunctivitis between April 2007 and March 2008 were reviewed. Variables including age, sex, date of presentation, and systemic and ocular findings were recorded.Results: A total of 7, 912 patients were visited within the study period, out of which 624 (7.9%) were diagnosed with allergic conjunctivitis. The disease was equally distributed in male and female subjects, with high preponderance in children (54.5%).Most patients (60.7%) presented during the dry season as compared to the rainy season. Refractive error was the most common ocular condition associated with the condition present in 7.4% of patients while the most common systemic association was asthma, reported in 1.4% of cases.Conclusion: Allergic conjunctivitis in Gambia is more common in children than in adults and has seasonal variation with more patients presenting during dry seasons.Refractive errors are the most common ocular problem associated with the disease and asthma is a systemic association.

Purpose: To evaluate the effect of tetracaine on intraocular pressure (IOP) in normal and hypertensive rabbit eyes.Methods: The study was conducted on 12 healthy rabbits as controls and 6 healthy rabbits in which an experimental model of ocular hypertension (OHT) was induced by administration of 70 mL/kg of tap water through an orogastric tube. One drop of tetracaine was instilled in the left eye while a drop of normal saline (placebo) was applied to the right eye of the control group. IOP was measured before and 0, 5, 10, 15, 20, 25, 30, 35 and 40 minutes after drop administration in this group. The OHT group also received one drop of tetracaine and normal saline in the left eyes and right eyes respectively, immediately after water loading; the instillation of drops was repeated after 55 minutes. IOP was measured before and 0, 5, 10, 15, 20, 25, 30, 35, 40, 55, 70, 85, 100 and 115 minutes after water loading in this group.Results: Tetracaine treated eyes in both groups (ocular hypertensive and normal controls) demonstrated significant IOP reduction at time zero (immediately after drop instillation) which was sustained up to 20 minutes, as compared to placebo treated eyes (P<0.05). In ocular hypertensive rabbits, repeat instillation of tetracaine significantly reduced IOP at 55 minutes up to 30 minutes thereafter.Conclusion: Topical tetracaine can reduce IOP; this fact should be considered in experiments evaluating IOP reducing agents.

Purpose: To compare electroretinogram (ERG) characteristics in patients with retinitis pigmentosa (RP) and normal subjects using frequency domain analysis.Methods: Five basic ERG recordings were performed in normal subjects and patients with a clinical diagnosis of RP according to the ISCEV (International Society of Clinical Electrophysiology of Vision) protocol. Frequency domain analysis was performed by MATLAB software. Different frequency domain parameters were compared between the study groups.Results: Peak frequency (Fmod) of flicker and oscillatory responses in RP patients showed significant (P<0.0001) high pass response as compared to normal controls.Peak frequency (Fmod) of the other responses was not significantly different between the two groups.Conclusion: In addition to conventional ERG using time domain methods, frequency domain analysis may be useful for diagnosis of RP. Oscillatory and flicker responses may be analyzed in frequency domain. Fast Fourier transform may reveal two distinct high pass responses (shift to higher frequencies) in Fmod. Time and frequency domain analyses may be performed simultaneously with many modern ERG machines and may therefore be recommended in RP patients.

Tumor necrosis factor alpha (TNF-a) is a pro-inflammatory cytokine produced by macrophages and T-cells. It plays an important role both in inflammation and apoptosis. In the eye, TNF-a appears to have a role in the pathogenesis of inflammatory, edematous, neovascular and neurodegenerative disorders. Several TNF-blocking drugs have been developed and approved, and are in clinical use for inflammatory diseases such as rheumatoid arthritis, psoriasis and ankylosing spondylitis. TNF-a blockers are widely used in ophthalmology as an off-label alternative to “traditional”immunosuppressive and immune-modulatory treatments in noninfectious uveitis.Preliminary studies suggest a positive effect of intravenously administered TNF-a blockers, mainly infliximab, for treating refractory diabetic macular edema and neovascular age-related macular degeneration. Unfortunately, much of the current data raises considerable safety concerns for intravitreal use of TNF-a inhibitors, in particular, intraocular inflammatory responses have been reported after intravitreal injection of infliximab. Results of dose-finding studies and humanized antibody or antibody fragments (e.g. adalimumab) are anticipated in the coming years; these will shed light on potential benefits and risks of local and systemic TNF-a blockers used for treatment of diseases of the retina and choroid.

Accumulation of misfolded proteins in the endoplasmic reticulum (ER) and their aggregation impair normal cellular function and can be toxic, leading to cell death.Prolonged expression of misfolded proteins triggers ER stress, which initiates a cascade of reactions called the unfolded protein response (UPR). Protein misfolding is the basis for a variety of disorders known as ER storage or conformational diseases.There are an increasing number of eye disorders associated with misfolded proteins and pathologic ER responses, including retinitis pigmentosa (RP). Herein we review the basic cellular and molecular biology of UPR with focus on pathways that could be potential targets for treating retinal degenerative diseases.

Purpose: To report an interesting case of concomitant bilateral Terrien’s marginal degeneration-like corneal ectasia and posterior polymorphous corneal dystrophy in a young man with quiescent rheumatoid arthritis.Case Report: A 24-year-old man with history of rheumatoid arthritis presented with bilateral decreased vision since four years ago. Slit lamp examination revealed bilateral circumferential peripheral corneal thinning and bulging with vascularization and lipid deposition in addition to band-like lesions in descemet’s membrane. Previous records revealed no gross corneal abnormalities up to 4 years ago. Corneal lesions were compatible with bilateral circumferential Terrien’s marginal degeneration concomitant with posterior polymorphous dystrophy.Conclusion: To our knowledge, this is the first report of concomitant bilateral Terrien’s marginal degeneration with peripheral corneal ectasia and posterior polymorphous dystrophy in a patient with rheumatoid arthritis. Bilateral circumferential involvement, younger age at presentation and total peripheral corneal ectasia as observed in this case are not typical for classic Terrien’s marginal degeneration.

Purpose: To report a case of early decomposition of retained heavy silicone oil droplets.Case Report: The single highly myopic eye of a 16-year-old boy with history of scleral buckling and buckle revision developed redetachment due to inferior retinal dialysis.The patient underwent pars plana vitrectomy and injection of heavy silicone oil.Early emulsification of the silicone oil was observed following surgery, which was removed 4 weeks later in another operation. Retained heavy silicone droplets lost their heavier- than-water specific gravity within 2 months together with extensive iris depigmentation, and release of pigment granules into the anterior chamber and vitreous cavity.Conclusion: This case report demonstrates that heavy silicone oil droplets canundergoin vivo chemical decomposition with possible toxic effects on ocular tissues.

Purpose: To present a patient with overlapping choriocapillaritis syndromes who first presented as a typical case of multiple evanescent white dot syndrome (MEWDS) and later with characteristic findings compatible with multifocal choroiditis (MFC).Case Report: A 40-year-old myopic woman presented with a paracentral scotoma OS.Fundus examination revealed pale discolored areas around the optic disc corresponding to faintly hyperfluorescent areas on fluorescein angiography (FA). On indocyanine green angiography (ICGA) there was extensive peripapillary hypofluorescence and confluent hypofluorescent dots superiorly. According to the clinical picture, a diagnosis of MEWDS was made. In 4 weeks, the visual field reverted to normal together with almost complete regression of hypofluorescence on ICGA. However, 4 months later fundus examination revealed some scars, a finding not typical for MEWDS. Besides, she developed another scotoma 12 months later accompanied by photopsia and the fundus illustrated more numerous scars than one year earlier.ICGA showed hypofluorescent areas corresponding to the scotoma delineated by visual field testing. The pattern of this recurrence clearly corresponded to MFC.Conclusion: This case illustrates an overlap between two entities, MEWDS and MFC in two sequential episodes. FA and fundus autofluorescence accounted for the lesions and optical coherence tomography showed damage to the photoreceptor outer segments, but only ICGA correlated well with functional evolution.

In May 2008, a 21-year-old single, non-obese, diabetic lady was referred to our clinic for routine eye examinations. The patient had been diagnosed with diabetes mellitus three months earlier and was receiving 100 milligrams of metformin daily and 80 milligrams of gliclazide twice daily orally, consistently maintaining her blood glucose levels between 72-90 mg/dl. She had a positive family history of diabetes mellitus.No related comorbidities were reported in her nephrology and rheumatology consultations and she had no visual complaints such as floaters, blurred vision, metamorphopsia or photophobia.

Herein we introduce a simple approach for clearing an edematous cornea during vitreoretinal surgery in eyes with decompensated corneal endothelium, allowing the surgeon to postpone penetrating keratoplasty. This technique was performed in 3 eyes by filling the anterior chambers with air or silicone oil, and sufficiently cleared the media for completion of vitrectomy. This simple technique enables completion of the vitrectomy without a temporary keratoprosthesis and penetrating keratoplasty in eyes with corneal edema due to endothelial decompensation.

Glaucoma is a neurodegenerative disorder in which a variety of complicated mechanisms lead to retinal ganglion cell (RGC) apoptosis and death. According to various theories, factors including elevated intraocular pressure (IOP) and vascular dysregulation primarily contribute to the initial insult during glaucomatous atrophy in the form of obstruction of axoplasmic flow within RGC axons, alteration in optic nerve microcirculation at the level of lamina and changes in the laminar glial and connective tissues. Deprivation of neurotrophic factors, such as the brain-derived neurotrophic factor, and release of a large number of neurotoxic agents within the retina, including glutamate, nitric oxide and free radicals, are the consequences of the above-mentioned events.

Ophthalmic research has developed into a multidisciplinary enterprise that requires the collaboration of basic and clinical scientists to understand and treat diseases that affect virtually every step in vision: from the entrance of light into the eye, through transduction in the retina, to higher processing in the visual cortex. It is a challenge to create and support a critical mass of diverse researchers together in one location.

Zebrafish have a marvellous visual system for study. Their retinas have abundant cones of four spectral types, i.e. red-, green-, blueand ultraviolet–sensitive cones. The animals are exceptionally responsive behaviourally; robust visual responses can be measured just four to five days after egg fertilization1. My group has been carrying out forward genetic studies on zebrafish for about fifteen years, seeking mutants with altered retinal neurons and/or circuitry such that we can advance our understanding of visual mechanisms. In addition, we study the functional organization of the retina in normal zebrafish. Herein, I describe two studies, one on a mutant that is providing new information on photoreceptor synapses and how certain visual responses may be mediated by the animal, and the other on an interesting phenomenon that occurs in young, larval zebrafish.

Although it is the major soluble protein component of the extracellular matrix bathing the photoreceptors, little is known about the structure and function of interphotoreceptor retinoid-binding protein (IRBP). The critical anatomic compartment it occupies cannot be overemphasized as through the involution of the optic vesicle, the retinal pigmented epithelium (RPE) comes in contact with the neural retina.1 The zonula occludens and adherens of the RPE and external limiting membrane respectively restrict the interphotoreceptor matrix (IPM) to the “subretinal space”.

After fixating on a colored pattern, observers see a similar pattern in complementary colors when the stimulus is removed. Afterimages were important in disproving the theory that visual rays emanate from the eye, in demonstrating interocular interactions, and in revealing the independence of binocular vision from eye movements. Afterimages also proved invaluable in exploring selective attention, filling-in and consciousness.

Gap junctions are responsible for the direct coupling of cells that enables intercellular exchange of ions, small metabolites and second messengers. Lens epithelial cells are well coupled (Fig.1a) by connexin (Cx) channels that constitute the structural subunits of gap junctions.Surprisingly, epithelial cell proliferation during the early postnatal period (Fig.1b) was found to be profoundly influenced by the type of connexin subunit present in the gap junction channels between cells. The loss, or functional replacement, of Cx50 caused a significant decrease in the number of dividing cells during the first postnatal week, suggesting that Cx50-mediated communication was essential for peak mitosis to occur.