Visual function in acute posterior multifocal placoid pigment epitheliopathy

Resilience of the Photoreceptors in Posterior Multifocal Placoid Pigment Epitheliopathy Observed by Microperimetry over Time

AIMS

To analyze the morphological and functional findings using microperimetry and optical coherence tomography angiography (OCTA) in patients with acute posterior multifocal placoid pigment epitheliopathy (APMPPE).

METHODS

This retrospective observational case series included four eyes of two patients with APMPPE. Best-corrected visual acuity range was from 20/20 to 20/250. Microperimetry and OCTA evaluation were obtained in the acute and healed phase. The OCTA images of the choriocapillaris were superimposed on the microperimetry map at the last visit.

RESULTS

The retinal sensitivity improved between the baseline and the last visit in three out of the four eyes. At resolution phase, OCTA revealed zones with choriocapillaris flow deficit, which were associated with points of reduced retinal sensitivity.

CONCLUSIONS

Microperimetry allows for a better evaluation of the extent of the unhealed functional defect in eyes with AMPPE. The multimodal imaging showed that structural and functional findings were associated in the resolution phase.

Fifty Years Exploring the Visual System

We as a couple spent 50 years working in visual psychophysics of color vision, temporal vision, and luminance adaptation. We sought collaborations with ophthalmologists, anatomists, physiologists, physicists, and psychologists, aiming to relate visual psychophysics to the underlying physiology of the primate retina. This review describes our journey and reflections in exploring the visual system.

Measurement of the photoreceptor pointing in the living chick eye

The chick eye is used in the study of ocular growth and emmetropization; however optical aberrations in the lens and cornea limit the ability to visualize fine retinal structure in living eyes. These aberrations can be corrected using adaptive optics (AO) allowing for cellular level imaging in vivo. Here, this capability is extended to measure the angular tuning properties of individual photoreceptors. The left eyes from two White Leghorn chicks (Gallus gallus domesticus) labeled chick A and chick B, were imaged using an AO flood illuminated fundus camera. By translating the entrance pupil position, the same retinal location was illuminated with light of varying angles allowing for the measurement of individual photoreceptor pointing. At 30° nasal from the pecten tip, the pointing direction for both chicks was towards the pupil center with a narrow distribution. These particular chicks were found to have a temporal (T) and inferior (I) bias in the alignment with peak positions of (0.81 T, 0.23 I) and (0.57 T, 0.18 I) mm from the pupil center for chicks A and B respectively. The rho, ρ, values for the major, ρL, and minor, ρs, axes were 0.14 and 0.17mm(-2) for chick A and 0.09 and 0.20mm(-2) for chick B. The small disarray in the alignment of the chick photoreceptors implies that the photoreceptors are aligned to optimize the light entering the eye through the central portion of the pupil aperture. The ability to measure pointing properties of individual photoreceptors will have application in the study of eye growth and various retinal disorders.

Persistent Placoid Maculopathy

PURPOSE

To describe a previously unreported clinical entity superficially resembling macular serpiginous choroiditis but with a distinct presentation and clinical course.

DESIGN

Retrospective observational case series.

PARTICIPANTS

Six patients, 50 to 68 years old, exhibiting this entity who were seen at 5 different centers from 1984 to 2006.

METHODS

Review of medical records.

MAIN OUTCOME MEASURES

Best-corrected visual acuity (VA) and clinical and angiographic findings.

RESULTS

The lesions in our patients are similar to those of acute macular serpiginous choroiditis. Our patients had well-delineated whitish plaquelike lesions involving the macula and sparing the peripapillary areas of both eyes. In contrast to serpiginous choroiditis, VA remained good despite early involvement of the fovea until complications related to choroidal neovascularization or pigmentary mottling developed. Angiographic characteristics and the clinical course were also atypical. Fluorescein angiography revealed well-defined early hypofluorescent areas that partially filled in in the late phase. Indocyanine green angiography showed the hypofluorescence to be persistent. Unlike serpiginous choroiditis, the white macular lesions faded over a period of months to years, whereas the characteristic angiographic findings often persisted longer. Choroidal neovascularization developed in 11 of 12 eyes, with subsequent conversion to disciform macular scars in 9 of 12 eyes. Unlike serpiginous choroiditis, none of the eyes showed chorioretinal scar formation unless related to choroidal neovascularization.

CONCLUSION

Persistent placoid maculopathy has features resembling macular serpiginous choroiditis but differs in its clinical course and effect on VA. It appears to be a new entity. The majority of eyes develop choroidal neovascularization that results in loss of central vision.

On the symmetry between eyes of wavefront aberration and cone directionality

There are two optical processes that control the retinal image sampled by the photoreceptor array: aberrations of the ocular optics and cone directionality (Stiles-Crawford effect). The shape of wavefront aberration and Stiles-Crawford functions are known to vary markedly across subjects. In this study we investigate in twelve subjects the symmetry between right and left eyes of wavefront aberration (measured using a spatially resolved refractometer) and cone directionality (measured using an imaging reflectometric technique). The pattern of aberrations is in general non-symmetric, suggesting that the development of aberrations follow independent paths in many right and left eye pairs. Cone directionality is in most cases mirror-symmetric (with one case of direct symmetry), suggesting some systematic process underlying cone orientation. Except in two subjects, symmetry in these two functions seems to be unrelated. Cone directionality apodization improves optical quality, but not optimally in all eyes, and it does not tend to increase symmetry in the optical performance of left and right eyes.

Clinical applications of fundus reflection densitometry

Fundus reflection densitometry or retinal densitometry is a non-invasive technique to examine the visual photopigment kinetics in living eyes. The technique is based on the comparison of the reflected light from the fundus in a fully light adapted eye (when all visual photopigment has been bleached) with the reflected light following complete dark adaptation (when the retina contains its maximum amount of visual photopigment). The technique provides a measure of the density of visual photopigment, its time constant of regeneration, its distribution and spectral characteristics if measured at a series of wavelengths. Fundus reflection densitometry in the human eye was introduced 40 years ago. Presently, it is the only available technique from which direct and objective insight can be obtained into visual photopigment. This knowledge is particularly relevant in eyes where abnormalities of photoreceptor function are suspected. This paper summarizes the current knowledge of fundus reflection densitometry in the diseased and in the aging human retina, gathered over the last 30 years. Considerable improvements of the instrument for clinical purposes have been obtained, and are also discussed.

Acute posterior multifocal placoid pigment epitheliopathy

Images

Parametric representation of Stiles-Crawford functions: normal variation of peak location and directionality

Evidence suggests that the psychophysically determined Stiles-Crawford effect of the first kind (SCE) reflects waveguide properties of human photoreceptors. The peak of the SCE data set is assumed to reflect the principal alignment tendencies, and the spread (e.g., rho value, the curvature or width at half-height) is assumed to reflect the directionality (i.e., interreceptor differences in alignment) of the population of photoreceptors being tested. As such, disruption of the normal SCE can be used and/or has been used (1) to document early natural history of retinal pathology involving the photoreceptors, (2) to provide a firm rationale for therapeutic intervention, and (3) to provide a method for monitoring therapies designed to alter the natural course of retinal-disease processes. We report large-sample norms for foveal SCE peak location and spread (horizontal peak location, nasal 0.51 +/- 0.72, horizontal rho value 0.047 +/- 0.013, vertical peak location, superior 0.20 +/- 0.64, vertical rho value 0.053 +/- 0.012), compare these norms with values determined in other laboratories, and discuss the various mathematical forms used for the empirical description of SCE data sets.

Scotopization and pseudoprotanomaly in blue-yellow/colour vision defects

With a routine clinical colour vision test battery we found scotopization in 32% of retinal diseases presenting with pseudoprotanomaly as sign of an acquired type III blue-yellow colour vision defect. In blue-yellow colour vision defects of retinal origin scotopization is a transient phenomenon, present in early stages of the disease, but it is not an obligatory finding. There is no evident relationship between visual acuity and scotopization.

Foveal densitometry in adult-onset diffuse drusen

We compared the results of foveal densitometry with results of other retinal function tests in five asymptomatic subjects with adult-onset diffuse drusen. All results of routine retinal function tests, including visual acuity, Rayleigh equation color matches, multiple static perimetry, electroretinography, and electro-oculography, were normal. All five subjects had decreased foveal cone photopigment density with densitometry, indicating an early dysfunction at the level of the foveal cone photoreceptors. Several functional defects may be responsible for the densitometric results in adult-onset diffuse drusen, including retinal pigment epithelium dysfunction, foveal cone photoreceptor misalignment, and a reduction of the in situ foveal cone photopigment.

Long-term follow-up of acute multifocal posterior placoid pigment epitheliopathy

Eleven patients with acute multifocal posterior placoid pigment epitheliopathy were followed up for 47 to 175 months (mean 106 months). Seven of 18 affected eyes (39%) developed progressive mild alterations in the retinal pigment epithelium. Seventeen eyes (94%) had a final visual acuity of 20/30 or better. One eye with progressive retinal pigment atrophy involving the fovea lost visual acuity from 20/25 to 20/60.

Acquired dyschromatopsias

Theories of color vision have been founded on behavioral observations of how the human eye distinguishes colors and mixtures of colors. Studies of congenital dyschromatopsias (inherited disorders of color vision) have been important to the development of these theories. Subsequent studies of acquired dyschromatopsias (disorders of color vision caused by disease) were understandably influenced by these concepts. Theories to explain the patterns of color vision impairment found in acquired diseases (for example, preferential hue discrimination defects) have stressed the likelihood of selective damage to specific components of the afferent visual system (photoreceptors, ganglion cells, synaptic elements, axons etc.). More recent evidence suggests, however, that impairment of color vision by diseases of the retina and optic nerve is commonly nonspecific, and not the result of selective impairment of individual neural mechanisms responsible for mediating color vision. Rather, the patterns of acquired dyschromatopsias often appear to be related to a physiologically heterogeneous distribution of color vision in the foveal and perifoveal visual field, coupled with a tendency for the visual field defects caused by acquired diseases to be unevenly distributed in these same areas.

Foveal densitometry in central serous choroidopathy

We evaluated foveal cone photopigment kinetics by retinal densitometry in 14 patients (12 men and two women, ranging in age from 30 to 54 years) with central serous choroidopathy. At the initial examinations when 12 of the 14 patients showed active leaks, the measured two-way density of pigment was low and the time-course of regeneration was slow. At later examinations, we found low two-way densities with normal regeneration times in five patients without active leakage. Near normal two-way densities occurred only in three patients who had complete clinical recoveries.

Basic phenomena in acquired colour vision deficiency

Acquired colour vision defects are directly related to the fixation mode: blue-yellow defects in foveolar fixation, blue-yellow or red-green defects in eccentric fixation. The primary localization of a disease can be retraced from the degree of cone damage. Optic nerve diseases essentially lack signs of cone damage. Processes at the level of the choriocapillaris/retinal pigment epithelium induce a non-selective receptor impairment. There are minor signs of cone damage. In cone dystrophies there is selective cone damage. Scotopization indicates a relatively well-preserved rod function.

Carotid artery aneurysm simulating pituitary adenoma

We describe a case of a giant carotid artery aneurysm presenting as an intrasellar mass with suprasellar extension, with radiographic and endocrinologic findings suggestive of pituitary tumor. This case emphasizes that elevated prolactin is not specific for prolactinoma. This case also supports consideration of angiography before proceeding with transsphenoidal surgery for presumed pituitary adenoma.

Colour vision as a diagnostic aid

The minimum requirements for a reliable study of (acquired) defects of colour vision have been formulated by Verriest. Taking these minimum requirements as a guide, about 200 patients were selected. For the differential diagnosis of disorders of the retina and the optic nerve the determination of the neutral zone and examination with the anomaloscope are important. This is true for both red-green and blue-yellow defects.

Visual function abnormalities in macular heterotopia caused by proliferative diabetic retinopathy

In seven patients with displacement of the macula in one eye caused by vitreoretinal traction from proliferative diabetic retinopathy, the macula was displaced toward the optic disk in all but one eye. The eyes with macular heterotopia showed (1) reduced visual acuity (ranging from 6/6 (20/20) to 6/24 (20/80), (2) reduced static perimetry sensitivity (particularly in the temporal field) with displacement of the peak sensitivity toward the blind spot, (3) loss of hue discrimination, and (4) metamorphopsia. In two eyes with macular heterotopia, Stiles-Crawford data provided evidence for photoreceptor disorientation; one eye had mixed orientation, and the other a displaced peak suggesting regular photoreceptor tilting. The proposed mechanisms of visual loss in eyes with macular heterotopia secondary to traction from proliferative diabetic retinopathy include detachment of the macula, disorientation of photoreceptors in the macula, and disturbance of normal neural connections within the retina caused by stretching of the retina.

Cone pigments in acute posterior multifocal placoid pigment epitheliopathy

We measured cone pigment density and kinetics with a reflection retinal densitometer during the evolution and resolution of posterior pole lesions in a 17-year-old patient with acute posterior multifocal placoid pigment epitheliopathy. Three weeks after onset, density was markedly reduced and regeneration complex and nonexponential. Pigment density increased, and kinetics returned to normal as the disease resolved.

Fundus flavimaculatus with cystoid macular changes and abnormal Stiles-Crawford effect

A 13-year-old boy with fundus flavimaculatus had a macular disease consisting of many transparent cystoid spaces which were not hyperfluorescent on fluorescein angiography. The Stiles-Crawford effect was abnormal, suggesting that the cystoid changes in the maculas created a disorientation of the patient's foveal retinal photoreceptors.