Clinical applications of OCTA in ocular oncology: pearls and pitfalls

Background: Optical Coherence Tomography Angiography (OCTA) is a valuable imaging tool for the diagnosis of several retinal and choroidal diseases. Its role in ocular oncology is clinically promising but still controversial. In this review we report the main applications and limits of the use of OCTA for the study of intraocular tumors. Summary: OCTA allows a rapid, safe, low-cost and high-resolution visualization of the retinal and choroidal vasculature. Attempts have been made to use this technology in ocular oncology to differentiate benign and malignant lesions and to assist physicians in the evaluation and monitoring of post-treatment complications. Main limitations include failure in correct segmentation due to tumor inner profile or thickness, poor penetration of laser into the lesion, masking effect from overlying fluid and media opacities and poor fixation. Key messages: The main applications of OCTA in ocular oncology consist in the documentation of tumor-associated choroidal neovascularizations and the study of vascular changes following tumor treatments. In particular, the diffusion of wide-field protocols makes OCTA suitable for the diagnosis and follow-up of radiation chorio-retinopathy allowing a detailed visualoization of both macular and peripheral ischemic changes. Optimistically, future innovations in OCTA technology may offer new perspectives in the diagnosis and follow-up of intraocular tumors.

The Clinical Use of Vernier Acuity: Resolution of the Visual Cortex Is More Than Meets the Eye

Vernier acuity measures the ability to detect a misalignment or positional offset between visual stimuli, for example between two vertical lines when reading a vernier scale. It is considered a form of visual hyperacuity due to its detectable thresholds being considerably smaller than the diameter of a foveal cone receptor, which limits the spatial resolution of classical visual acuity. Vernier acuity relies heavily on cortical processing and is minimally affected by optical media factors, making it a useful indicator of cortical visual function. Vernier acuity can be measured, usually in seconds of arc, by freely available automated online tools as well as via analysis of steady state visual-evoked potentials, which allows measurement in non- or pre-verbal subjects such as infants. Although not routinely measured in clinical practice, vernier acuity is known to be reduced in amblyopia, glaucoma and retinitis pigmentosa, and has been explored as a measure of retinal or neural visual function in the presence of optical media opacities. Current clinical utility includes a home-based vernier acuity tool, preferential hyperacuity perimetry, which is used for screening for choroidal neovascularisation in age-related macular degeneration. This review will discuss the measurement of vernier acuity, provide a current understanding of its neuro-ophthalmic mechanisms, and finally explore its utility through a clinical lens, along with our recommendations for best practice.

Endoscopic Vitreoretinal Surgery; Basic Principles, Indications and New Directions

In this review, we aimed to give information about the historical development, basic features, and major indications of microendoscopy in vitreoretinal surgery. Microendoscopy permits vitreoretinal surgery for tissues that are not visible using operating microscopy ophthalmoscopy. Evolving technology may overcome the technical limitations of current endoscopic technology. Endoscopic vitreoretinal surgery is particularly useful when tissue details blurred by ocular media opacities or anterior chamber aberrations in contemporary surgical microscopic ophthalmoscopy. Microendoscopy is a robust platform for vitreoretinal surgery. Ophthalmic microendoscopy as a complementary method to modern vitreoretinal surgical techniques is very useful for safe surgery when an operating a microscope becomes insufficient.

Photostress Recovery Time Among Welders in Owerri Municipal Council, Southeast, Nigeria

Purpose: The photostress recovery time (PSRT) scores of welders were measured based on age, workexperience and welding-method.Methods: A quasi-experimental study was conducted among 50 purposively sampled welders, who had clear ocular media, healthy fundi and visual acuities of 6/6 or better in the tested eyes. The pre-bleach distant visual acuity of the right eye was determined with the Snellen’s visual acuity chart, while direct ophthalmoscopy was done to rule out media opacities, retinopathies and maculopathies. The right eye was dazzled for 10 seconds with the light of a direct ophthalmoscope held at 2cm from the eye. The time required in seconds to read at least, three optotypes on the line directly above the baseline acuity was recorded as the PSRT.Results: The 22-31 years age group recorded the least mean PSRT (16±8.8seconds), followed by the 32-41 age group (19.9±6.8 seconds), while the 42-51 years category had the highest mean PSRT (31.4±10.5seconds). Age associated significantly (p˂0.05) with mean PSRT. Welders within the 1-12 years’ work experience had the least mean PSRT (15.9±8.1seconds) while those within the 25-36 years recorded the highest mean PSRT (33.4±9.3seconds). The observed difference in mean PSRT with years of work experience was statistically significant (p˂0.05). Gas welders had significantly (p˂0.05) higher mean PSRT (26.6±9.9secs) than electric arc welders (16.6±9.2secs).Conclusion: Gas welding, increasing age and work-experience were found to be predictive markers of elevated photostress recovery time (PSRT) among welders. This underscores the need for eye-care practitioners to routinize PSRT tests in the ocular assessment of welders. Keywords: Photostress recovery time (PSRT); electric-arc; gas welding; welders; age.

Seeing Invisible Light: 2-photon Microperimetry to Measure Visual Function

Purpose: The accuracy of conventional visual function tests, which emit visible light, decreases in patients with corneal scars, cataracts, and vitreous hemorrhages. In contrast, infrared (IR) light exhibits greater tissue penetrance than visible light and is less susceptible to optical opacities. We therefore compared visual function results obtained using conventional visual function tests and infrared 2-photon microperimetry (2PM-IR) in a subject with a brunescent nuclear sclerotic and posterior subcapsular cataract before and after cataract surgery. Methods: Visual function testing using the cone contrast threshold (CCT) test, conventional microperimetry (cMP), visible light microperimetry from a novel device (2PM-Vis), and 2PM-IR were performed before and after cataract surgery. Results: Cone contrast threshold testing improved for the S-cone, M-cone, and L-cone by 111, 14, and 30. Retinal sensitivity assessed using cMP, 2PM-Vis, and 2PM-IR improved by 18 dB, 17.4 dB, and 3.4 dB, respectively. Conclusions and Importance: 2PM-IR, unlike conventional visual function tests, showed minimal variability in retinal sensitivity before and after surgery. Thus, IR visual stimulation introduces a paradigm shift for measuring visual function in the retina and posterior visual pathways by circumventing optical media opacities.

Two-Photon Microperimetry: A media opacity-independent retinal function assay

Humans perceive light in the visible portion of electromagnetic radiation. However, visible light is scattered and attenuated by optical media opacities. Because all conventional visual function tests rely on visible light, test results are reduced in patients with optical media opacities like corneal scars, cataracts, and vitreous hemorrhages. Infrared (IR) light has greater penetrance through tissue than visible light. Two-photon IR visual stimulation, a recently pioneered technology, should enable testing of retinal visual function and produce results that are less susceptible to media opacities. The effects of simulated media opacities on visual performance in young healthy volunteers and the change in visual function in healthy phakic patients of two age ranges (20-40 and 60-80-year-old) were studied using conventional testing and 2-photon infrared visual stimulation. All subjects completed visual function testing using cone contrast threshold (CCT) testing, conventional microperimetry, visible light microperimetry from a novel device (2PM-Vis), and infrared 2-photon microperimetry (2PM-IR). Retinal sensitivity measured by 2PM-IR demonstrated lower variability than all other devices relying on visible spectrum stimuli. Retinal sensitivity decreased proportionally with the transmittance of light through each filter. CCT scores and retinal sensitivity decreased with age in all testing modalities. Visible spectrum testing modalities demonstrated larger test result differences between young and old patient cohorts; this difference was inversely proportional to the wavelength of the visual function test. 2PM-IR mitigates media opacities which may mask small differences in retinal sensitivity when tested with conventional visual function testing devices.One Sentence SummaryTwo photon infrared visual function testing produces results that are less susceptible to media opacities than conventional tests.

Amblyopia

Amblyopia is a reduction of vision in one or both eyes due to a failure of normal neural development in the immature visual system.Amblyopia occurs due to two basic conditions – abnormal binocular interaction (e.g., strabismus) and blurring or distortion of visual image due to uncorrected refractive errors or media opacities. Best-corrected visual acuities in amblyopic eyes range from mild deficits to severe vision loss.The principle of treating amblyopia involves clearing any image blur and encouraging use of the amblyopic eye with occlusion of the better-seeing eye. Paediatric Eye Disease Investigator Group (PEDIG) studies show that both part-time and full-time occlusions can produce similar results in the eye with severe amblyopia and occlusion can be prescribed initially at 2 hours per day for the moderate amblyope. Studies show that daily atropine and patching for 6 hours/day can be equivalent treatment options and that if pharmacologic blurring is used for treatment, initial treatment can begin with just weekend use of atropine for moderate amblyopia.Amblyopia can lead to permanent loss of vision; therefore vision screening is strongly recommended over the course of childhood to detect amblyopia early enough to allow successful treatment.