Multifocal blue nevus of the conjunctiva

Blue nevus is a congenital benign melanocytic tumor that classically occurs in the skin and carries low potential for malignant transformation. We report an unusual case of widely dispersed multifocal common blue nevus of the conjunctiva simulating conjunctival melanoma. A 55-year-old Hispanic woman was found to have multiple darkly pigmented lesions on her left eye. Excisional biopsy and adjuvant cryotherapy were performed. Histopathology revealed six pigmented foci within the substantia propria composed of spindle-shaped cells with a wavy dendritiform configuration consistent with common blue nevus. One lesion had associated racial melanosis and no lesion showed junctional activity or melanoma. In conclusion, conjunctival blue nevus can be multifocal and masquerade as melanoma.     

Pattern electroretinogram of the blue cones

In man the electroretinogram to pattern reversal stimuli (P-ERG) represents a cone response of the proximal retina, dominated by the cone mechanisms sensitive to red (R) and green (G). Additionally there is a cone mechanism sensitive to blue (B) which can be studied with and without steady exposure to yellow light. During exposure to a super-imposed uniform yellow background (576 nm) the transient P-ERG of the B cones is represented by potentials of small amplitude (< 1 V). The latency (peak time) of the response is about 30 ms longer than that of the midspectral (R and G) cones. Furthermore, the P-ERG of the B cones saturates at low luminances and exhibits a maximum amplitude at about 460 nm. Without yellow adaptation, the P-ERG of the B cones can be studied only with low-intensity stimuli of short wavelengths. Near threshold, both the long-latency response of the B cones and the short-latency response of the R and G cones are recorded simultaneously, forming a double-peaked wave shape. At suprathreshold luminances, even of short wavelength (435 nm) the P-ERG of the B cones is concealed by the larger short latency response of the midspectral cone mechanism.     

Brilliant blue G selectively stains the internal limiting membrane/brilliant blue G-assisted membrane peeling

PURPOSE: To report the use of the dye brilliant blue G (BBG) for staining of the internal limiting membrane (ILM) during macular hole (MH) and epiretinal membrane (ERM) surgery. METHODS: This study was designed as an interventional, noncomparative, prospective, clinical case series. Twenty eyes from 20 consecutive patients with MH or ERM underwent BBG-assisted ILM and ERM removal. In MH cases, a posterior vitreous detachment was created, followed by the injection of 0.25 mg/mL BBG solution into the vitreous cavity and immediate washout of the BBG. This technique improved visualization of the ILM, enabling peeling and surgery to be performed successfully. However, in ERM cases, staining of the ERM could not be confirmed at this concentration. Finally, the ILM including the ERM was removed in all cases. Preoperative and postoperative ophthalmic examinations were performed. RESULTS: Postoperatively, 17 patients (85%) had visual acuity improved by at least 2 Snellen lines. No adverse effects were observed postoperatively during the observation period (mean follow-up +/- SD, 7.3 +/- 1.0 months). CONCLUSIONS: BBG selectively stains the ILM. This technique can facilitate the management of MH and ERM surgery without any adverse effects, as was shown in this short-term study.     

Filling-in of the foveal blue scotoma.

The blue-blindness (tritanopia) of the human foveola normally goes unnoticed but can be directly visualized by having observers view a flickering, monochromatic, short-wavelength field. The blue scotoma appears as a tiny dark spot in central vision, the visibility of which depends upon the wavelength of the field and the temporal frequency of modulation. Comparisons of fading times as a function of flicker frequency for the blue scotoma, foveal afterimages and optically stabilized images indicate a common time course, consistent with the hypothesis that perceptual filling-in of the foveal blue scotoma reflects the operation of neural processes similar to those involved in fading and regeneration of stabilized images.     

Cellular blue nevus of the conjunctiva.

BACKGROUND: Cellular blue nevi of the conjunctiva are extremely rare, and their natural history and malignant potential have not been fully ascertained. METHODS: A report of an unusually well-documented case of growth of a cellular blue nevus is presented, along with a review of current knowledge of this lesion. RESULTS: A 71-year-old woman presented with a darkly pigmented raised lesion of the conjunctiva, which had slowly enlarged over 47 years. There were nonconfluent areas of involvement of the upper and lower lids. Results of biopsy showed the lesion to be a cellular blue nevus, with no evidence of malignancy. CONCLUSION: This well-documented case of slow growth and spread without malignant transformation adds to the knowledge of this rare lesion.     

Permanent blue discoloration of a hydrogel intraocular lens by intraoperative trypan blue

A 79-year-old white man had cataract surgery in the right eye with implantation of an Acqua intraocular lens (IOL) (Mediphacos). Trypan blue 0.1% was used during surgery to stain the anterior capsule and enhance the contrast during capsulorhexis. Seven days after surgery, the patient presented with "dark and double" vision (monocular diplopia). The IOL was decentered superiorly and appeared dark blue. The lens was explanted 2 months after surgery and sent for gross and microscopic analyses in a dry state and after hydration. The same analyses were performed on 2 unused lenses of the same design that had been immersed in diluted trypan blue solutions (0.01% and 0.001%). On the explanted lens, the dark blue staining was denser in the optic, especially in its periphery. The blue discoloration could not be removed after 24 hours of lens immersion in a balanced salt solution at 37 degrees C. Permanent staining of the unused lenses was also obtained after immersion in the trypan blue solutions.     

Effects of subretinal injection of patent blue and trypan blue in rabbits

PURPOSE: To investigate the histologic and clinical effects of subretinal injection of patent blue (PB) and trypan blue (TB) in rabbits. METHODS: Dutch-belted rabbits (n=8) were vitrectomized followed by subretinal injection of 2.4 mg/ml PB (285 mOsm) and 1.5 mg/ml TB (312 mOsm); balanced salt solution (BSS) (300 mOsm) served as the control. Animals were examined 6, 12, and 24 hr and 14 days after the procedure by fluorescein angiography (FA) and indirect ophthalmoscopy; for retinal toxicity, histologic evaluation studies were performed by light and transmission electron microscopy. RESULTS: FA examination demonstrated window defects suggestive of retinal pigment epithelium (RPE) atrophy in positions of subretinal TB injection, but this was not observed after subretinal injection of PB or BSS. Histologic evaluation disclosed only minimal abnormalities on the photoreceptor outer segment (POS) after subretinal injection of BSS during all follow-up. Subretinal injection of PB caused POS and photoreceptor inner segment (PIS) abnormalities 12 and 24 hr after surgery as well as outer nuclear layer (ONL) damage 14 days after surgery. Subretinal TB injection resulted in POS and PIS damage at 12 hr follow-up. The ONL damage was observed 24 hr after surgery; additionally, POS, PIS, ONL, and RPE abnormalities were observed 14 days after surgery after TB injection. CONCLUSIONS: Subretinal injection of TB induced more significant clinical and histologic damage of neurosensory retina/RPE than did PB or BSS. Future human studies are necessary to access the clinical relevance of these in vivo experiments.     

Role of the blue mechanism in wavelength discrimination

The role of blue cones as well as the pathways they supply (collectively called the "blue mechanism") is evaluated by comparing ordinary wavelength discrimination functions with those obtained using two methods designed to inhibit the blue mechanism selectively. These methods use a just-noticeable-border criterion (JNB), instead of the usual one of just-noticeable-difference, and a yellow preadapting field to induce transient tritanopia. Without transient tritanopia, the data obtained using the just-noticeable-border criterion reveal a small contribution of the blue mechanism to wavelength discrimination. Transient tritanopia, with JNB, produces an additional selective loss of wavelength discrimination in a spectral region flanking 460 nm, which yields a function resembling those for tritanopes previously examined.     

Unveiling the foveal blue scotoma through an afterimage

The absence of short-wave-sensitive (S-) cones in the human foveola normally goes unnoticed, but the resulting foveal S-cone, or blue, scotoma can be visualized as the negative afterimage of a short-wavelength adapting field on a larger white background. The afterimage has an annular shape with a lighter inner region that corresponds to Maxwell's spot, and a small bright spot in the center corresponding to the foveal blue scotoma. We have shown that the visibility of the center spot in the afterimage approximately follows the spectral sensitivity curve of the S-cones. We further demonstrate that the central bright spot subtends a retinal area that is coincident with the tritanopic region of the foveola. The macular pigment distribution measured for the same observers also peaks in the central fovea, but has a relatively high density over a broader retinal region than the bright spot in the negative afterimage, and more closely corresponds to the lighter annular region of the afterimage. The results support the hypothesis of an active post-receptoral process for filling-in of chromatic scotomas.     

Nonlinear codes for the yellow/blue mechanism

The opponent yellow/blue mechanism is studied by means of an iso-cancellation technique. A qualitative and quantitative analysis of different photopigment models for the yellow/blue code is presented. On the basis of this analysis we provide a new model which ascribes the nonlinear character of the code to a power transformation of the short wave cone activity. This new model leads to predictions concerning the wavelength shift of the short wave component of a unique red. Tests of these predictions support the new model.     

Tracking blue cone signals in the primate brain

In this paper, we review the path taken by signals originating from the short wavelength sensitive cones (S‐cones) in Old World and New World primates. Two types of retinal ganglion cells (RGCs) carrying S‐cone signals (blue‐On and blue‐Off cells) project to the dorsal lateral geniculate nucleus (dLGN) in the thalamus. In all primates, these S‐cone signals are relayed through the ‘dust‐like’ (konis in classical Greek) dLGN cells. In New World primates such as common marmoset, these very small cells are known to form distinct and spatially extensive, koniocellular layers. Although in Old World primates, such as macaques, koniocellular layers tend to be very thin, the adjacent parvocellular layers contain distinct koniocellular extensions. It appears that all S‐cone signals are relayed through such konio cells, whether they are in the main koniocellular layers or in their colonies within the parvocellular layers of the dLGN. In the primary visual cortex, these signals begin to merge with the signals carried by the other two principal parallel channels, namely the magnocellular and parvocellular channels. This article will also review the possible routes taken by the S‐cone signals to reach one of the topographically organised extrastriate visual cortical areas, the middle temporal area (area MT). This area is the major conduit for signals reaching the parietal cortex. Alternative visual inputs to area MT not relayed via the primary visual cortex area (V1) may provide the neurological basis for the phenomenon of ‘blindsight’ observed in human and non‐human primates, who have partial or complete damage to the primary visual cortex. Short wavelength sensitive cone (S‐cone) signals to area MT may also play a role in directing visual attention with possible implications for understanding the pathology in dyslexia and some of its treatment options.