Foveal densitometry in central serous choroidopathy

Delayed dark adaptation in central serous chorioretinopathy

Purpose

To evaluate the effect of central serous chorioretinopathy (CSCR) on retinal function using dark adaptation in a human subject, and to follow it through resolution of the disease.

Patients

Single patient, 50 years old male patient, with acute CSCR in one eye and resolved old CSCR in the other eye.

Observations

Observational study in patient with CSCR followed through resolution of the subretinal fluid (52 days). Dark adaptation was assessed using the AdaptDx® (Maculogix Inc.) measured by Rod Intercept time (RIT) in minutes. A normal retinal locus of the same eye on the opposite side of the fovea was used as control. Retinal separation (microns) was measured using Spectralis Optical Coherence Tomography (Spectralis®, HRA + OCT, Heidelberg engineering). Change in time to dark adapt, were correlated with retinal separation measured in microns, during the course of CSCR.

The Rod Intercept time was delayed in the area of detached retina compared to the normal region (control) on presentation with retinal separation (RS) of 104 μm. The Rod Intercept time returned to normal as the retinal separation from retinal pigment epithelium decreased and eventually resolved.

Conclusions

This case shows that delay in dark adaptation is proportional to the amount of separation of neurosensory retina from retinal pigment epithelium in CSCR, this may offer a potential of using DA to characterize visual function in CSCR. The association of dark adaptation response with the state of retinal pigment epithelial function and its ability to predict the recurrence of CSCR needs further evaluation.

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.

THE EFFECT OF PHOTOPIGMENT BLEACHING ON FUNDUS AUTOFLUORESCENCE IN ACUTE CENTRAL SEROUS CHORIORETINOPATHY

PURPOSE

To evaluate the effect of photobleaching on fundus autofluorescence (FAF) images in acute central serous chorioretinopathy.

METHODS

We obtained prephotobleaching and postphotobleaching images using an Optomap 200Tx, and photobleaching was induced with a Heidelberg Retina Angiograph 2. Degrees of photobleaching were assessed as grayscale values in Optomap images. Concordances among the three kinds of images were analyzed. Hyper-AF lesions in prephotobleaching images were classified as Type 1 (changed to normal-AF after photobleaching) and Type 2 (unchanged after photobleaching). The FAF composite patterns of central serous chorioretinopathy lesions were classified as diffuse or mottled. Initial and final best-corrected visual acuity, central retinal thickness, and disease duration were compared according to fovea FAF type.

RESULTS

Forty-one eyes of 41 patients were analyzed. The lesion brightness of postphotobleaching Optomap FAF showed greater concordance with Heidelberg Retina Angiograph 2 FAF (94.74%) than the prephotobleaching Optomap FAF (80.49%). Eyes with Type 1 fovea had greater initial and final best-corrected visual acuity (20/23 vs. 20/41, 20/21 vs. 20/32, P < 0.0001, P = 0.001, respectively) and shorter disease duration (19.68 ± 12.98 vs. 51.55 ± 44.98 days, P = 0.043) than those with Type 2 fovea. However, eyes with diffuse Type 2 fovea had only lower initial and final best-corrected visual acuity (20/23 vs. 20/45, 20/21 vs. 20/36, P < 0.0001, P < 0.0001, respectively) than those with Type 1 fovea.

CONCLUSION

Understanding the photobleaching effect is necessary for the accurate interpretation of FAF images. Furthermore, comparing prephotobleaching and postphotobleaching FAF images may be helpful for estimation of lesion status in central serous chorioretinopathy.

Photopigments in central serous chorioretinopathy

PURPOSE

To investigate functional abnormalities in eyes with central serous chorioretinopathy (CSC).

DESIGN

Observational case series.

METHODS

Sixteen eyes with CSC were enrolled. Autofluorescence densitometry was performed to measure the optical density of the photopigments. Serial fundus autofluorescence (FAF) images were obtained by Heidelberg Retina Angiogram 2. We calculated the autofluorescence optical density difference from the FAF images. To compare the distribution pattern of autofluorescence optical density difference to the findings of outer retina, spectral-domain optical coherence tomography (SD-OCT) was performed in the acute phase and after resolution of CSC.

RESULTS

The autofluorescence optical density difference decreased at the serous retinal detachment (SRD) in all 16 eyes. After resolution, the photoreceptor inner and outer segment junction (IS/OS) was irregular in 13 eyes and defective in 3 eyes on SD-OCT. The autofluorescence optical density difference did not improve in any eyes. Five eyes were reexamined 3 month after resolution. In 4 of the 5 eyes, SD-OCT showed that the IS/OS was well delineated and 1 eye defective. The autofluorescence optical density difference improved in 2 of the 4 eyes, but not in the other 2 eyes. In the 1 eye without well-delineated IS/OS, the autofluorescence optical density difference did not improve.

CONCLUSION

In eyes with CSC, the photopigment density decreased at the SRD. The density remained decreased immediately after resolution and showed delayed recovery. The photopigments decreased even in eyes with morphologic recovery of the outer retina.

Localized retinal dysfunction in central serous chorioretinopathy as measured using the multifocal electroretinogram

PURPOSE

To determine the extent of electrophysiologic dysfunction in patients with central serous chorioretinopathy (CSC).

DESIGN

Prospective observational case series.

PARTICIPANTS

Six patients with unilateral CSC (mean age, 40 years) were recruited into the study.

METHODS

Six patients with CSC underwent multifocal electroretinogram (mfERG) testing on both their clinically affected and opposite uninvolved eyes using the VERIS System, with a stimulus array of 103 scaled hexagons. The first positive peak responses were analyzed within six concentric ring annuli centered on the fovea. Amplitudes and implicit times were compared with those of an age-similar control group.

MAIN OUTCOME MEASURES

Local electroretinographic response amplitudes and implicit times within the central 40 degrees with the mfERG.

RESULTS

All the clinically uninvolved eyes showed mfERG amplitudes and implicit times within the normal range throughout the central 40 degrees of the retina. All six eyes with CSC showed reduced amplitudes and/or delayed implicit times that were limited to the regions of the macula in which clinical changes associated with CSC were apparent.

CONCLUSIONS

We observed electroretinographic changes only in the clinically affected eyes, and these were limited to regions with ophthalmoscopically apparent fundus changes. Our findings do not support the conclusion that functional impairment, as measured by the mfERG, in eyes with CSC extends beyond clinically observed fundus changes. We did not observe abnormal mfERG responses in the clinically normal eyes of such patients.

Extrafoveal photostress recovery test in glaucoma and idiopathic central serous chorioretinopathy

BACKGROUND/AIMS

A photostress recovery test was designed to differentiate macular diseases from optic nerve disorders, but recently an abnormal recovery time was reported in glaucoma. The purpose of this study was to search for the difference in abnormality of the photostress recovery test between glaucoma and idiopathic central serous chorioretinopathy (ICSC).

METHODS

This study involved 21 normal subjects, 14 patients, with ICSC and 10 patients with primary open angle glaucoma (POAG). A scanning laser ophthalmoscope (SLO) was used with microperimetry for bleaching the test point and measuring the recovery of sensitivity. Photostress recovery time (SLO-PSRT) could be measured at extrafoveal points outside and inside the affected area. The initial sensitivity change and the time constant of recovery after bleaching were calculated by fitting an exponential equation to the data.

RESULTS

In normal subjects, neither the initial sensitivity change nor the time constant were correlated with the location of the test point. In 14 patients with ICSC, the initial sensitivity change in the detached area was significantly smaller than that in the unaffected area which was not significantly different from that in the age matched normal subjects. The time constant in the detached area was significantly longer than that in the unaffected area, which was not significantly different from that in the normal subjects. In 10 patients with POAG, the initial sensitivity change inside and outside the scotoma was not significantly different from that of age matched normal subjects. The time constant inside the scotoma was significantly longer than that outside the scotoma, which was not significantly different from that of the age matched normal subjects.

CONCLUSION

Both ICSC and POAG showed a prolonged time constant of recovery, but the initial sensitivity change was reduced only in ICSC. The difference in our results between ICSC and POAG may be caused by the difference of the retinal pathology. Further, the SLO-PSRT is very useful when the lesion is located outside the fovea.

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.

Colour vision in retinitis pigmentosa. Influence of cystoid macular edema

In retinitis pigmentosa patients the effect of cystoid macular edema on colour vision was studied. The occurrence of cystoid macular edema decreases with increasing colour vision defect. The mutual proportion of the main types of colour vision defects remains stable until visual acuity has dropped to 0.5; at lower VA levels the number of red-green defects increases. Neither the finding of a blue-yellow colour vision defect in FM100 Hue testing nor the appearance of anomaloscopic pseudoprotanomaly is influenced by cystoid macular edema. The authors conclude that cystoid macular edema in retinitis pigmentosa patients mainly affects visual acuity and not colour vision. They also noted a familial occurrence of cystoid macular edema.

Interphotoreceptor retinoid-binding protein (IRBP). Molecular biology and physiological role in the visual cycle of rhodopsin

The regeneration of visual pigment in rod photoreceptors of the vertebrate retina requires an exchange of retinoids between the neural retina and the retina pigment epithelium (RPE). It has been hypothesized that interphotoreceptor retinoid-binding protein (IRBP) functions as a two-way carrier of retinoid through the aqueous compartment (interphotoreceptor matrix) that separates the RPE and the photoreceptors. The first part of this review summarizes the cellular and molecular biology of IRBP. Work on the IRBP gene indicates that the protein contains a four-fold repeat structure that may be involved in binding multiple retinoid and fatty acid ligands. These repeats and other aspects of the gene structure indicate that the gene has had an active and complex evolutionary history. IRBP mRNA is detected only in retinal photoreceptors and in the pineal gland; expression is thus restricted to the two photosensitive tissues of vertebrate organisms. In the second part of this review, we consider the results obtained in experiments that have examined the activity of IRBP in the process of visual pigment regeneration. We also consider the results obtained on the bleaching and regeneration of rhodopsin in the acutely detached retina, as well as in experiments testing the ability of IRBP to protect its retinoid ligand from isomerization and oxidation. Taken together, the findings provide evidence that, in vivo, IRBP facilitates both the delivery of all-trans retinol to the RPE and the transfer of 11-cis retinal from the RPE to bleached rod photoreceptors, and thereby directly supports the regeneration of rhodopsin in the visual cycle.

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.

Reflectometry with a scanning laser ophthalmoscope

We describe noninvasive techniques to optimize reflectometry measurements, particularly retinal densitometry, which measures the photopigment density difference. With these techniques unwanted scattered light is greatly reduced, and the retina is visualized during measurements. Thus results may be compared for each retinal location, and visible artifacts are minimized. The density difference measurements of the cone photopigment depend on the optical configuration of the apparatus. The cone photopigment density difference is greatest near the fovea and for most observers decreases rapidly with eccentricity. A research version for reflectometry and psychophysics of the scanning laser ophthalmoscope is described.

Local macular electroretinographic responses in idiopathic central serous chorioretinopathy

Using focal stimuli to human macular regions, we recorded electroretinograms in 24 patients with central serous chorioretinopathy of recent onset (mean visual acuity, 20/20). The stimulus spot was 10 degrees in diameter. Intact fellow eyes served as controls. The local macular electroretinograms of the affected eyes were significantly reduced and the implicit time in each component was significantly prolonged. The mean (+/- S.D.) amplitudes, expressed as percentages of mean amplitudes recorded in fellow eyes, were 64.6% +/- 22.7% (a-wave), 49.6% +/- 21.0% (b-wave), and 15.0% +/- 21.6% (oscillatory potentials). Two to five months after the macular detachment resolved, recordings in 18 patients showed remarkable recovery of a- and b-waves and shortened implicit times. However, the oscillatory potentials showed significantly small recovery in amplitude. Since oscillatory potentials and b-waves were significantly more deteriorated than a-waves in the presence of macular detachment, and oscillatory potentials showed selective delay of recovery in the convalescent stage, central serous chorioretinopathy may involve functional disturbances in the inner retinal layer as well as the photoreceptors.

Foveal cone photopigment bleaching in central serous retinopathy

Color-matching techniques were used to follow the course of central serous retinopathy in thirteen patients. During periods of neurosensory detachment?, cone optical densities were low. In some patients optical densities remained low following clinical resolution of the disease. In addition, abnormalities of bleaching were observed for one patient in one eye that appeared clinically unaffected during a period of detachment of the fellow eye. Analysis of the data indicates that for longitudinal measurements of optical density, standard Nagel anomaloscope matches can provide an accurate estimate of changes in foveal optical density, although they cannot provide a measure of the absolute optical density.

Foveal cone pigments and sensitivity in young patients with Usher's syndrome

Psychophysical and reflection retinal densitometric techniques were used to investigate foveal function of three patients (ages 14, 16, and 19 years) with Usher's syndrome who had good central visual acuity and, by ophthalmoscopic examination, normal foveal areas. During dark adaptation foveal sensitivity and its relation to proportion of cone pigment present were normal, but the kinetics of regeneration of the pigments were markedly abnormal. Measurements were made to consider the possibilities that the disorders of regeneration were associated with altered light-catching capacities of the patients' cone pigments, deranged transport of visual cycle substances between the retinal pigment epithelium and photoreceptors, or lingering photoproducts. None of the mechanisms fully accounted for the observed kinetics. The results suggested that abnormal kinetics of regeneration are among the earliest signs of malfunction of the foveal photoreceptor-pigment epithelial complex in some of the retinal degenerative disorders.

Retinal dysfunction in central serous retinopathy

Patients with acute and chronic central serous retinopathy (CSR) were studied by psychophysical and photochemical means to establish the extent of visual depression and to investigate the basis of rod dysfunction in this disorder. In acute disease with serous detachment of the retina, the loss of sensitivity attains 3 log units and parallels the height of retinal elevation as does its recovery with resolution of the episode. Immediately after resolution, there is a residual 0.5 log unit threshold elevation. In chronic disease, marked loss of function exists over areas of abnormal retinal pigment epithelium in the absence of clinically detectable serous detachment. Although rhodopsin levels are low in both acute and chronic CSR, this relative lack of visual pigment does not totally account for the functional deficits in either situation.

Foveal densitometry as a diagnostic technique in Stargardt's disease

Foveal densitometry was performed in eight patients with Stargardt's disease. Their visual acuities were between 20/200 and 20/16. All eight had low two-way densities, ranging from 0.07 to less than or equal to 0.01 (mean value for a control group, 0.32 +/- 0.03). Two patients had poor visual acuities combined with ophthalmoscopically normal maculas. Because two-way densities were very low in these patients, ranging between 0.04 and less than or equal to 0.01, foveal densitometry may be a useful diagnostic technique in the diagnosis of Stargardt's disease. Foveal densitometry was also performed in two patients with fundus flavimaculatus and good visual acuities for the sake of comparison. Two-way densities were between 0.09 and 0.24. One patient with cone dystrophy and poor visual acuity had low two-way densities (0.02 bilaterally). Three patients with vitelliform dystrophy and vitelliform cysts on ophthalmoscopy had two-way densities between 0.07 and 0.14 and increased half-times of regeneration (between 90 and 126 seconds). One patient with a vitelliform cyst in one eye showed only fine pigmentations in the other eye, which had a normal two-way density (0.32).