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PURPOSE: Fundus reflection densitometry was used as an objective means for monitoring the recovery of foveal cone photopigments in nine patients who underwent anatomically successful surgery of a rhegmatogenous retinal detachment with macular involvement. METHODS: Postoperative assessment of foveal densitometry, visual acuity, color matching, and the Amsler grid were performed at repeated intervals for up to 14 months. RESULTS: Gradual recovery of foveal cone photopigments was found in all patients 1 to 14 months after surgery, with considerable interindividual variation. Maximal recovery to values equalling those in the fellow eye was found in only one patient with a macular detachment duration of 5 days. All other patients had final photopigment densities below those of the fellow eye. The length of the preoperative detachment period was inversely related to the recovery of photopigment. The recovery of photopigment seems to increase further in the second year after surgery. Visual acuity increased rapidly in all patients during the first 6 months after surgery, to levels ranging between 20/67 and 20/25; thereafter, visual acuity did not change. A return to normal color matching after an episode of pseudoprotanomaly was found in four of nine patients, whereas pseudoprotanomaly remained in five patients. Complete resolution of metamorphopsia after surgery was seen only in the patient who had the shortest detachment duration. Metamorphopsia was consistent with decreased foveal cone photopigment densities. CONCLUSION: Foveal densitometry shows a slow recovery of the cone photopigments after reattachment, probably because of regrowth and realignment of the cone photoreceptor outer segments and metabolic recovery of the retinal pigment epithelium-cone photoreceptor complex. Recovery of photopigment, color matching, and metamorphosia follow a slower time course than recovery of visual acuity.

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A 28-year-old man with multiple evanescent white dot syndrome (MEWDS) in the left eye was examined with a scanning laser densitometer. The first measurements were taken in the acute stage, and repeat examinations were performed during the process of recovery. Fundus pictures were obtained from a 20 degrees retinal field, in dark and light adapted stages. From these images visual pigment density maps were derived. In the acute stage of the disease, maps revealed small round areas of absent visual pigment, which did not always correspond with the visible white dots. The areas of absent visual pigment density were also larger than the white dots seen on funduscopic examination. Single spot densitometry at the fovea was also performed and showed no significant density difference of the foveal cones. Rod density difference measured at a locus 16 degrees in the temporal retina was much lower than normal with an increased time constant of rhodopsin regeneration. Ten weeks after the onset of the disease, no white dot lesions were visible on funduscopic examination. Rod density difference and regeneration time had become normal again, but with scanning laser densitometry the abnormal areas of no pigment were still faintly visible. It is concluded that these findings, completed with data of electroretinography, anomaloscopic testing, and perimetry, are in agreement with a metabolic disturbance at the level of the retinal pigment epithelium-photoreceptor complex.

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Twelve subjects with minimal expression of the myotonic dystrophy (MyD) gene were investigated by retinal densitometry, a technique which has been used to study the properties of photopigments in the living eye and to detect photoreceptor abnormalities. Other investigations included slit-lamp examination, funduscopy, raleigh matches with the anomaloscope, tonometry, and neurological examination, including electroretinography (ERG) and pattern visual evoked potentials recording. Foveal densitometry demonstrated reduced values of the macular photopigment density difference with normal photopigment kinetics in early phases of the disease, even in asymptomatic individuals. The densitometric values correlated with decreased amplitudes of the photopic ERG a-wave. These findings may be explained by loss or dysfunction of the outer segments of foveal receptors. It is yet unknown whether or not these changes are secondary to other observed neuroretinal abnormalities in MyD. The most likely explanation might be an abnormality of the Na, Ca:K exchanger at the level of the outer segments of the photoreceptors whether or not in combination with a dysfunction of voltage generation systems, involving both photoreceptors and retinal pigment epithelium.

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Four unrelated males with X-linked retinoschisis and a golden fundus reflex had Mizuo-Nakamura phenomenon, which, to our knowledge, has been described only in Oguchi's disease and X-linked cone dystrophy. These findings, together with experimental observations and data from the literature, led us to hypothesize that the Mizuo-Nakamura phenomenon is caused by an excess of extracellular potassium in the retina as a result of a decreased potassium scavenging capacity of retinal Müller cells.

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Cone photopigment kinetics were investigated by retinal densitometry in six patients with acute posterior multifocal placoid pigment epitheliopathy (APMPPE). Our goal was to document the course of cone impairment during a period of at least 12 months following the onset of the disease process. During the active stage, we found that the amount of pigment measurable by densitometry (the density difference) was reduced and that the time constant of pigment regeneration was unmeasurable. Following resolution of the fundus lesions, the densitometric parameters gradually improved in eight of ten eyes. In patients who maintained foveal fixation (five eyes), the density difference and the time constant of pigment regeneration improved simultaneously, though with individual differences in time course. Photopigment kinetics returned to normal in all these patients but the density difference remained lower than normal in four of the five eyes. In patients with parafoveal fixation (five eyes), photopigment kinetics were slow, possibly reflecting mixed cone and rod contributions. With time, the density difference improved to a level comparable to that measured in normal observers at a similar retinal location, but the photopigment regeneration time constant remained abnormal or unmeasurable. Recovery was variable, with one eye changing from parafoveal to foveal fixation, and no improvement noted in two eyes with extreme parafoveal fixation. Our findings demonstrate a large interpatient variation associated with APMPPE.

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Since the non-invasive technque of retinal densitometry became available in 1955, rhodopsin kinetics could be studied in vivo. It was obvious that with this new tool investigators focussed attention on the aetiology of night blindness in various diseases. A brief review about the clinical developments in the past two decades is given. Also three case-reports are presented, which suggest that in some cases of congenital stationary night blindness (CSNB) the night blindness might arise from the absence of rhodopsin. This is contrary to the standing opinion and present problems regarding the integrity of the retina.

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Rod densities were measured in ten patients with congenital stationary night blindness (CSNB) using the Utrecht densitometer. In five patients rod density was within the range observed in a group of control subjects. One of these patients reached a normal rod two-way density after a prolonged regeneration time. In five patients with different hereditary patterns of CSNB we found decreased amounts of rhodopsin. These observations deviate from the findings on four CSNB patients hitherto described in the literature, where normal concentrations and kinetics of rhodopsin were found. We observed no relationship between the age of CSNB patients and mode of rhodopsin kinetics. No inconsistencies between rod densitometry and electro-retinography were revealed. The different electroretinography patterns were not helpful in predicting the densitometric responses in CSNB. The present results included, five of fourteen CSNB patients ever studied with the technique of retinal densitometry show abnormal rhodopsin kinetics. We propose a schema of CSNB subtyping based on the different rhodopsin kinetics.

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We investigated foveal cone photopigment kinetics by retinal densitometry in 34 eyes of 29 healthy subjects with clear optical media and good visual acuity, ranging in age from 39 to 79 years. Our aim was to assess possible senile disturbances of foveal cones. To assess the effects of ocular straylight, we measured not only in subjects with a clear crystalline lens, but also in pseudophakia and aphakia. In a limited number of subjects color vision was assessed with a Nagel anomaloscope; no systematic changes with age were found. A significant decrease in two-way density and in time constant of regeneration was found to occur only after age 60, with large individual variations. There was no indication that results for subjects with their natural crystalline lens, in aphakia, or in pseudophakia were different. We argue that a reduction in the number of cones with age, rather than an increase in ocular stray light is the most likely explanation of our findings.

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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).

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The density difference between fully bleached and fully dark-adapted retinas was assessed for 77 eyes (47 subjects) in the age group 13-50 yr. No significant change in density was found as a function of age. The time constant of pigment regeneration was also found to show no age effects up to the age of 50 yr. These findings are at odds with another study on the density of foveal cones.

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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.

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Cone density and psychophysical thresholds were investigated in patients with retinitis pigmentosa. Our aim was to assess possible disturbances of foveal cones, especially in patients with good visual acuity. Using the continuously recording densitometer described by van Norren and van der Kraats, we examined ten patients (19 eyes). With the same apparatus it was possible to determine cone final threshold. In all patients double density values were lower than in an age-matched and sex-matched control group of an equal number, and the half time of regeneration was increased in eight eyes. In 12 eyes of eight patients the foveal final threshold was raised above normal. Pseudoprotanomaly was found in seven eyes in four males. Possible explanations for these findings are discussed. Since reduced double density was found in all patients with retinitis pigmentosa, we conclude that disturbed foveal cones are probably a common and rather early feature in this disease.

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This paper describes a family, the propositus of which suffers from dystrophia retinae pigmentosa combined with fundus flavimaculatus and Stargardt's disease. The patient's mother and a maternal uncle suffer from a dystrophia retinae pigmentosa, whereas a sister shows peripheral degenerations. A further sister has a scotopic b wave of the ERG of low amplitude.

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