[A case of fundus albipunctatus with a retinol dehydrogenase 5 gene mutation in a child]

BACKGROUND

We examined a family with fundus albipunctatus in which mutation of the retinol dehydrogenase 5(RDH 5) gene was suspected to be the cause of this disease.

CASE

An 8-year-old girl had diffuse multiple white dots in her fundus except for the macula. She had good central vision. The amplitude of her electroretinogram wave was low, but it recovered after three hours of dark adaptation. Dark adaptometry showed an elevated threshold for rod adaptation. No visual field loss was observed. A homozygous missense mutation was found in exon 5 of the RDH 5 gene that substituted histidine for arginine at codon 280(Arg 280 His). Her mother had a normal fundus but was heterozygous for the same mutation.

CONCLUSION

A missense mutation of RDH 5(Arg 280 His) was found in a Japanese family with fundus albipunctatus.

Analysis of Second-order Kernel Response Components of Multifocal Electroretinograms Elicited from Normal Subjects

PURPOSE

It has been reported that the second-order kernel response components of multifocal electroretinograms (mERGs) reflect the electrical activity of the inner retinal layers. In this study, we have investigated whether the amplitudes of the second-order kernel response components correlate with the spatial distribution of human retinal ganglion cells.

METHODS

Multifocal electroretinograms were recorded using the Veris III system from 5 healthy subjects with different stimulus and recording parameters. The mERGs were analyzed using the Veris Science software programs. The stimuli consisted of densely arranged arrays of 103, 61, 37 or 19 hexagonal elements. Four minutes were required to record one set of mERG responses using 8 sessions, and 8 minutes using 16 sessions. The second-order kernel response components were extracted and analyzed using the Veris Science program.

RESULTS

The signal-to-noise ratio of the first-order kernel response components was improved considerably by the summation of the nine reproducible responses from the same subject but the second-order kernel response components were not. The summation of the nine reproducible responses was insufficient to identify an array of the second-order kernel response components. Both the first- and second-order kernel response components were larger when fewer hexagonal elements were used. There was no significant difference in the individual responses between the 4-minute and the 8-minute recordings. A response density analysis revealed a weak correlation between the amplitude distribution of the second-order kernel response components and the spatial distribution of human retinal ganglion cells.

CONCLUSIONS

The distribution of the amplitudes of the second-order kernel response components of the mERGs elicited from normal subjects did not correlate with the distribution of human ganglion cells. This suggests that the theory that second-order kernel response components arise from the activity of retinal ganglion cells should be reconsidered.

Apoptosis after butyrate-induced differentiation in retinoblastoma cell line Y-79

PURPOSE

To study the fate of Y-79 human retinoblastoma cells after induction of differentiation.

METHODS

Y-79 cells were cultured in a synthetic medium and were induced to neuronal differentiation by butyrate treatment. Neurofilaments, p53, and DNA-synthesizing nuclei labeled with 5-bromodeoxyuridine were immunostained, and apoptotic cells were labeled by in situ DNA nick end labeling (TUNEL). We combined these immunostaining and labeling methods to determine whether the cells expressed these markers at the same time. DNA fragmentation and p53 levels were also determined by electrophoresis.

RESULTS

Y-79 cells proliferated in the synthetic medium. After butyrate treatment, they extended protrusions and increased neurofilament immunoreactivity. The differentiated features were striking on day 7. Thereafter, differentiated cells decreased and apoptotic cells increased. DNA synthesis was detected in the cells expressing immunoreactivity for neurofilaments or p53. At day 7, most of the cells with p53-positive nuclei were alive and neurofilament-positive. However at day 10, the p53-positive cells were apoptotic and neurofilament-positive apoptotic cells accumulated.

CONCLUSIONS

We conclude that the Y-79 cells express p53 and undergo apoptosis after neuronal differentiation. There could be a p53-dependent apoptotic pathway in butyrate-induced differentiated Y-79 cells due to the inability to regulate cell cycling.

Progression of visual field loss in patients with retinitis pigmentosa of sporadic and autosomal recessive types

PURPOSE

We examined the natural course of patients with retinitis pigmentosa of the eight sporadic and five autosomal recessive forms over 5 years.

METHODS

We measured the areas of the visual fields by Goldmann perimetry using a digitizer and a computer software.

RESULTS

The visual field of V-4 isopters in 4 sporadic cases was approximately 200 cm2 during 30 years after the initial examination, but decreased down to 40 cm2 in the next 10 years. The visual field was reduced to half the normal field in 3 autosomal recessive cases early below the age of 25 years. In 4 sporadic and 2 autosomal recessive cases, the inferior temporal visual field was the widest at the onset of the disease, but exhibited the most severe loss. The superior nasal area was the narrowest initially, and showed the mildest progression.

CONCLUSIONS

The visual field in retinitis pigmentosa is constricted age-dependently with severe loss of the inferior temporal visual area and mild damage to the superior nasal area.

Pattern electroretinogram elicited by a dartboard pattern

The receptive field size of retinal ganglion cells is closely related to their eccentricity from the fovea. To elicit larger pattern-reversal electroretinograms (P-ERGs), it may be useful to stimulate the retina with patterns having elements that parallel this change in receptive field size. We describe a dartboard pattern consisting of reversal elements that enlarge gradually from the central to the peripheral stimulus field. The utility of the dartboard pattern for eliciting P-ERG was investigated by comparing it with the conventional uniform checkerboard pattern, but with the other stimulus parameters remaining unchanged (96% contrast, 35.9 cd/m2 mean luminance, 3.3 rev/s temporal frequency, 15 degrees circular field). The dartboard pattern produced a significantly larger P50 amplitude than did the checkerboard pattern, while no difference in peak latency was found when 54 min of arc was used as a standard check size for the checkerboard pattern. The dartboard pattern for eliciting P-ERG should prove clinically useful.

Visual function in retinitis pigmentosa related to a codon 15 rhodopsin gene mutation

To determine the phenotype of a Japanese family in which retinitis pigmentosa cosegregates with a rhodopsin gene mutation, i.e. an asparagine-to-serine change at codon 15 (Asn-15-Ser), 5 affected and 5 unaffected members of one pedigree underwent several ophthalmic examinations as well as Ganzfeld electroretinography (ERG) and multifocal ERG. Genomic DNA samples were analyzed by PCR amplification, sequencing and restriction enzyme digestion. A codon 15 rhodopsin gene mutation (Asn-15-Ser) was found in all affected members. The region of pigmentary degeneration was localized in the lower hemiretina, and visual field defects corresponded to the retinal pigmentary changes. Scotopic ERG amplitudes, rather than photopic ERG amplitudes, were reduced. Multifocal ERG revealed a low magnitude of response density, even for the upper hemiretina, which showed no bony corpuscle pigmentation. Visual function in sectorial retinitis pigmentosa associated with rhodopsin gene codon 15 mutation is on the basis of the rod-cone dystrophy, regardless of differences in phenotypic expression.

Automatic static threshold perimetry is useful for estimating the effects of laser photocoagulation on diabetic maculopathy

Focal photocoagulation was performed on 18 eyes in 18 diabetes patients; a visual acuity test, fluorescein angiography and automated static threshold perimetry by Octopus automated static perimetry (program 31) were conducted before and 1, 3 and 6 months after krypton laser photocoagulation. Central field sensitivity and total loss were measured by automated static threshold perimetry. Group A (13 eyes) had a total loss of less than 150 dB. In these subjects, mild fluorescein leakage was detected within the area of the vascular arcade. In group B (5 eyes) with a total loss of greater than 150 dB, diffuse fluorescein leakage was also detected outside the vascular arcade. The central field sensitivity was reduced in 2 eyes of group B. The total loss worsened in 8 eyes of group A (61.5%) and 5 eyes of group B (100%). Inspection of photographs gave the impression that the degree of fluorescein leakage and the area of the avascular zone on fluorescein angiography accorded with total loss, thus suggesting that total loss reflects visual functions better than visual acuity or central field sensitivity. Therefore, automated static threshold perimetry appears to be a useful method for estimating visual functions after photocoagulation in diabetic maculopathy patients.

The Contribution of Inflammatory Cell Infiltration to Conjunctival Inclusion Cyst Formation

Purpose: The incidence of inclusion cysts was examined histopathologically in conjunctival disorders where inflammatory cell infiltration was seen in the subepithelial connective tissue.Method: The incidence of inclusion cysts was examined histopathologically in pterygium, vernal conjunctivitis, pyogenic granuloma and pingueculitis. The specimens of pinguecula were used as control.Results: Inclusion cysts were recognized in 5/(55) cases of pterygium, 2/(12) cases of vernal conjunctivitis, 1/(4) cases of pyogenic granuloma, and 1/(2) cases of pingueculitis. On the other hand no inclusion cyst was recognized in 20 cases of pinguecula in which no inflammatory cell infiltration was seen.Conclusions: Inflammatory cell infiltration may contribute to the formation of conjunctival inclusion cysts in pterygium, pingueculitis, vernal conjunctivitis and pyogenic granuloma.

Visual function and gene analysis in a family with Oguchi's disease

A family with 1 case of retinitis pigmentosa (III-1) and 2 cases of Oguchi's disease (III-2, 3) was examined in terms of electrophysiology as well as molecular biology. The proband (III-3), a 42-year-old female, and 2 older brothers (III-1, 2, aged 52 and 45 years) and 2 unaffected members in the same family participated in this study. Corrected visual acuities of the individuals with Oguchi's disease (III-2, 3) were 1.2. On funduscopy, blood vessels stood out in relief against a metallic-appearing background and a Mizuo-Nakamura phenomenon was evident. Full-field electroretinograms (ERGs) recorded from the proband were indicative of rod dystrophy, but results of other electrophysiological examinations (multifocal ERG, pattern ERG and visual-evoked cortical potential recordings) were within normal limits. Patient III-1 had corrected visual acuities of RE 20 cm/m.m. and LE 30 cm/n.d., severe chorioretinal atrophy in both fundi, and full-field ERG revealed rod-cone dystrophy. Mutation of the arrestin gene (1147de1A) was detected in all 3 patients. Visual function in each patient coincides with that of retinitis pigmentosa or Oguchi's disease, respectively.

Artifact removal procedure distorts multifocal electroretinogram

PURPOSE

To study whether the Artifact Removal procedure available for eliminating artifacts in multifocal electroretinograms (mERG) works correctly or not.

METHODS

A test response was made using a photo-diode circuit. mERGs were recorded from 3 well-trained normal subjects using the Veris III system, and were then analyzed by the procedure that is included in the Veris Science (Artifact Removal) software program. The stimuli consisted of densely arranged arrays of 103 or 37 hexagonal elements. It took a total of 8 minutes to obtain one mERG record, and 16 sessions were required to complete this record. The first-order as well as the second-order kernel response components were extracted by Veris Science software, and the Artifact Removal procedure was used for both components.

RESULTS

The Artifact Removal procedure influenced both the test response on the center element as well as the neighboring traces just around the test response. After the repetitions of the Artifact Removal procedure, the shape of the test response changed considerably. Some of the traces of the second-order kernel response components elicited from a normal subject changed irregularly when the Artifact Removal procedure was repeatedly used. The noise increased at the first iteration of the Artifact Removal procedure.

CONCLUSION

This procedure has been considered useful for eliminating artifact distortion in mERG, but should be carefully checked by well-established testing methods before clinical use.

Expression of stem cell factor in pterygium

PURPOSE

To investigate the possible role of stem cell factor (SCF) in the pathogenesis of pterygium.

METHODS

The localization of SCF was examined immunohistochemically in excised tissue from 4 primary pterygia and 5 normal conjunctival specimens.

RESULTS

Three of the four pterygia showed strong immunoreactivity of SCF in the subepithelial connective tissue at the cap area. This immunoreactivity was completely blocked by using a primary antibody preincubated with recombinant SCF. The SCF-positive cells were identified as a population of fibroblasts by immunostaining for vimentin and prolyl 4-hydroxylase in adjacent sections. No apparent immunoreactivity of SCF was observed in the subepithelial connective tissues in the head and body of the pterygia and in the normal conjunctiva.

CONCLUSION

Stem cell factor is overexpressed in fibroblasts at the cap area of most pterygia.

Purification and characterization of bovine cone arrestin (cArr)

To elucidate the quenching mechanism of phototransduction in vertebrate cone photoreceptors, a cDNA clone encoding cone specific arrestin (cArr) was isolated from a bovine retinal cDNA library using a human cArr cDNA probe. Affinity-purified anti-peptide antibody specific to cArr was prepared. Immunohistochemical staining displayed specific labeling of cArr in cone photoreceptors and immunoblotting identified a 46 kDa protein band. We purified cArr from bovine retinas by sequential column chromatography using DEAE-cellulose, gel filtration and mono Q columns. Binding studies revealed no binding of cArr to rhodopsin regardless of whether it was bleached and/or phosphorylated. cArr also failed to bind to heparin-Sepharose under conditions which rod arrestin (rArr) bound to the column. The present data suggest that cArr may play a role in the quenching of phototransduction in cone photoreceptors and that its activity therein is different to that of rArr.

[The contribution of inflammatory cell infiltration to conjunctival inclusion cyst formation]

PURPOSE

The incidence of inclusion cysts was examined histopathologically in conjunctival disorders where inflammatory cell infiltration was seen in the subepithelial connective tissue.

METHOD

The incidence of inclusion cysts was examined histopathologically in pterygium, vernal conjunctivitis, pyogenic granuloma and pingueculitis. The specimens of pinguecula were used as control.

RESULTS

Inclusion cysts were recognized in 5/55 cases of pterygium, 2/12 cases of vernal conjunctivitis, 1/4 cases of pyogenic granuloma, and 1/2 cases of pingueculitis. On the other hand no inclusion cyst was recognized in 20 cases of pinguecula in which no inflammatory cell infiltration was seen.

CONCLUSIONS

Inflammatory cell infiltration may contribute to the formation of conjunctival inclusion cysts in pterygium, pingueculitis, vernal conjunctivitis and pyogenic granuloma.

A basic investigation of multifocal electroretinogram: reproducibility and effect of luminance

PURPOSE

To investigate the reproducibility as well as the effect of luminance in multifocal electroretinogram (mERG).

METHODS

Multifocal electroretinogram recordings were repeated on different days in 6 normal subjects using the Veris III system. The mean luminance of the monitor displaying the stimuli was randomly varied by five kinds of neutral density (ND) filters.

RESULTS

The standard deviation of mERG amplitude from the macular region was approximately 10% of the mean value for each normal subject. Reproducibility largely depended on the condition of the subject and placement of the contact lens electrode. With decreases in the mean luminance of the monitor, the amplitude of mERG decreased exponentially, whereas the peak latency increased linearly. mERGs elicited from a patient with mild cortical cataract resembled the mERGs obtained from the control group using an ND filter between -0.30 and -0.52 log, whereas two patients with typical retinitis pigmentosa showed much lower response densities in mERGs.

CONCLUSIONS

It is necessary to pay attention to the reproducibility and the luminance effect to obtain reliable mERGs.

[Kerato-epithelin mutation (R 555 Q) in a case of Reis-Bücklers corneal dystrophy]

BACKGROUND

Mutations in the kerato-epithelin gene on chromosome 5 q 31 are known to cause four distinct autosomal dominant diseases of the human cornea: Reis-Bücklers, granular, lattice, and Avellino corneal dystrophy. Mutation of arginin to glutamine in codon 555 (R 555 Q) in kerato-epithelin was recently reported in four blood-related patients with Reis-Bücklers corneal dystrophy.

CASE

A 42 year-old female has had photophobia with decreasing vision since the age of 20 years. Her corrected visual acuity was 0.5 in both eyes. She showed subepithelial opacities in both corneas characteristic of Reis-Bücklers corneal dystrophy.

METHOD

The DNA was extracted from leukocytes according to standard protocols. The keratoepithelin gene was examined for a mutation by the polymerase chain reaction (PCR) and direct sequencing.

FINDINGS

We identified kerato-epithelin mutation R 555 Q. The patient's two children and 50 controls did not show missense mutation.

CONCLUSION

Kerato-epithelin mutation R 555 Q was present in a Japanese patient with Reis-Bücklers corneal dystrophy.

Effects of fluorescent light on growth of bovine retinal pigment epithelial cells in vitro incubated with linoleic acid or linoleic acid hydroperoxide

Light-induced peroxidation of polyunsaturated fatty acids (PUFA) may generate lipid hydroperoxides, which may have toxic effects on retinal pigment epithelial (RPE) cells in vitro. We investigated the effects of cool-white fluorescent light on the RPE cells incubated with linoleic acids (LA) or linoleic acid hydroperoxides (LHP) and the influence of antioxidative enzymes. We measured the bovine RPE cell number after exposure to fluorescent light (610 and 1,200 lux) in the presence of LA or LHP. Furthermore, the effects of superoxide dismutase (SOD) and catalase on LA- or LHP-treated RPE cells were also examined. Both LA and LHP treatment increased RPE cell number under weak illumination (610 lux), but dose-dependently decreased the number of cells exposed to strong illumination (1,200 lux). With exposure to strong illumination, LA caused a greater reduction in RPE cell number than LHP. Multiple linear regression analysis showed that the number of RPE cells was significantly decreased in a manner dependent on the interactions of the illuminance of light and the concentrations of LA or LHP. The antioxidative enzymes significantly ameliorated the damage to RPE cells from LA or LHP and exposure to light. Therefore, the exposure to fluorescent light augmented the cytotoxic effects of LA and LHP on RPE cells, and this effect is likely to be mediated by reactive oxygen species.

The localization of glutathione peroxidase in the photoreceptor cells and the retinal pigment epithelial cells of Wistar and Royal College of Surgeons dystrophic rats

INTRODUCTION

If degenerating photoreceptor outer segments not phagocytized by RPE cells in the retina of Royal College Surgeons (RCS) rats were to undergo peroxidation, the distribution of glutathione peroxidase (GSH-PO) in the mitochondria or cytoplasm of the retina might be altered. We evaluated the immunocytochemical localization of GSH-PO to identify subcellular organelles in sections of the retinas of RCS rats.

METHODS

Immunoblot analysis confirmed the presence of GSH-PO molecules in the retinas of RCS and Wistar rats aged 3 weeks. Sections were reacted with the F(ab) fragment of anti-rat alphaGSH-PO and then examined by laser scanning microscopy (LSM) and transmission electron microscopy (TEM).

RESULTS

The size of the GSH-PO molecule in the retina was about 21 KD in the mitochondria and 23 KD in the cytosol in both strains of rats. LSM revealed fluorescent granules in the photoreceptor inner segments of the Wistar rats, and immunohistochemical TEM revealed GSH-PO in the mitochondria of their photoreceptor inner segments and retinal pigment epithelial (RPE) cells. In the RCS rats, the degenerating photoreceptor outer segments were clearly seen to be positive for anti-GSH-PO by conventional light microscopy (CLM). However, the photoreceptor inner segments of the RCS rats were negative for staining with anti-GSH-PO by LSM, and no GSH-PO could be detected in the mitochondria of the photoreceptor inner segments or RPE cells by immuno-TEM.

CONCLUSION

Degeneration of the photoreceptor outer segments induced mitochondrial damage in the photoreceptor inner segments, and as a result GSH-PO shifted from the photoreceptor inner segments to the degenerating outer segments.

Mast cells in pterygium: number and phenotype

PURPOSE

To investigate the pathogenesis of pterygium.

METHODS

The number and phenotype of mast cells were examined in excised tissue from 35 pterygia patients and compared with those in normal conjunctival specimens obtained during cataract or other intraocular surgery.

RESULTS

Toluidine blue staining showed that the mean number of mast cells in the pterygia specimens was twice as high as that in the normal conjunctival tissues. Immunohistochemistry with a primary antibody to tryptase, specific for mast cells, also revealed a twofold increase in the mast cell number in the pterygia specimens compared with the normal conjunctival tissues. In the pterygia, more than 94% of the tryptase-positive mast cells were found to express chymase and c-kit. Almost all mast cells in the pterygia were tryptase-positive, chymase-positive mast cells (MC(TC)S). There was no phenotypic difference between the mast cells in the pterygia and those in the normal conjunctival tissues.

CONCLUSIONS

The MC(TC)S appear not to be immune system-related and to have functions in angiogenesis and tissue remodeling. The increase in the number of mast cells caused by nonallergic stimulation may contribute to the pathogenesis of pterygium.

[Histopathological observations on bullous keratopathy after argon-laser iridotomy]

PURPOSE

To elucidate histopathological mechanism of bullous keratopathy after argon-laser iridotomy (ALI).

CASE AND METHOD

The patient was a 60-year-old female who underwent penetrating keratoplasty because of bullous keratopathy after 2 years and 2 months of ALI. The corneal specimen was fixed with a mixture of 2.5% formalin and 1.0% glutaraldehyde, and examined under light and electron microscopes.

FINDING AND CONCLUSION

Laser-damaged endothelium produced a large amount of basement membrane-like material beneath Descemet's membrane. At the next stage, the severely damaged endothelium lost its organellae and cell membranes, and fell off. The surrounding healthy endothelium migrated into the damaged area and produced a small amount of material like basement membrane which covered Descemet's membrane. After that, stromal swelling, decrease of keratocytes, breaking and disappearance of Bowman's membrane, epithelial edema, connective tissue accumulation beneath basal cells, and epithelial detachment occurred in the laser-damaged area.

[Neuronal cell death mechanism in glaucomatous optic neuropathy]

Apoptosis of retinal ganglion cells has been observed in experimental glaucomatous models and human glaucomatous eyes in recent pathological studies. It seems that retinal ganglion cells in glaucomatous optic neuropathy die by a process similar to programmed cell death. Deprivation of neurotrophic factors, ischemia, chronic elevation of glutamate, and disorganized NO metabolism are suspected to be factors affecting neuronal loss in glaucoma, and most of these factors are known to activate the mechanism of cellular suicidal death. One of the common switches for the death mechanism seems to be in the mitochondria and to be controlled by Bcl-2 family proteins. A major goal of neuronal cell death research in glaucomatous neuropathy is to identify its molecular components and mechanisms of regulation. This information will lead to therapeutic agents that can modulate the cell death process in the treatment of glaucomatous neuropathy.

[Detection of parafoveal scotoma by multifocal electroretinograms]

We investigated the relation between multifocal electroretinograms (M-ERGs) and artificial parafoveal scotoma. M-ERGs were recorded from normal subjects using a circular piece of black paper attached to a monitor. Lower response density around the 10 to 15 degree parafovea region was not observed up to 3 degree scotoma (visual angle), but was detected above 5 degree scotoma in field topography of M-ERGs. The shape of the scotoma in field topography was not circular but somewhat oval. The results from two cases of parafoveal retinal degeneration were in good accordance with this basic study in normal subjects. We proved that detection of parafoveal scotoma by M-ERG is limited in comparison with the results obtained by automated static perimetry.

[Pterygium and mast cells--expression of basic fibroblast growth factor increase in mast cells of the pterygium]

We examined the expression of basic fibroblast growth factor (bFGF) protein immunohistochemically, and bFGF specific messenger RNA (bFGF-mRNA) by in situ hybridization in the excised tissue of 5 cases of pterygium and 4 cases of normal conjunctiva. Immunohistochemical staining for bFGF showed strong positive staining in metachromatic mast cells stained with toluidine blue in the pterygium and in normal conjunctival specimens. The mean metachromatic mast cell count in pterygium specimens was increased significantly when compared with normal conjunctiva. In mast cells, bFGF positive rate was 84% in pterygium specimens, and 69% in normal conjunctival specimens. In situ hybridization indicated that the bFGFmRNA is located in most mast cells in pterygium specimens, but in only a few mast cells in normal conjunctival specimens. These results suggest that increased bFGF protein produced and stored by mast cells in the pterygium may contribute to its progression.

[Effect of ultraviolet-filtering contact lens on rabbit eyes after exposure to ultraviolet light]

We evaluated the protective effect of a newly designed soft contact lens (SCL) on rabbit eyes. This SCL absorbs the ultraviolet B light of wavelengths between 280 nm and 320 nm. Three weeks after resecting the nictitating membrane, the rabbit corneas were covered either by the new SCL or a conventional SCL. The eyes were exposed to ultraviolet light from two 15 W lamps placed 20 cm anteriorly for 3 hours. Another three hours after the exposure, the cornea was examined first with a slitlamp biomicroscope after staining with fluorescein and then by histopathological means after enucleation. Six eyes wearing the new SCL showed moderate superficial punctate keratopathy. Six eyes wearing conventional SCL showed severe superficial keratopathy or corneal erosion. These findings were in good agreement with the histopathological findings. The new ultraviolet-filtering SCL was thus effective in protecting the rabbit cornea under our experimental conditions.

Relationship between visual field defect and multifocal electroretinogram

We investigated the effect of artificial parafoveal scotomata on the multifocal electroretinogram (M-ERG). M-ERGs were recorded from normal subjects using a monitor with several different sizes of black paper attached. A lower response density area around the 10 to 15 degree parafoveal region was not recognized for scotomata up to 3 degrees but was observed in scotomata above 5 degrees (visual angle) in the field topography of M-ERG. The shape of the scotomata was not circular but somewhat oval. The results from two cases of parafoveal retinal degeneration accorded well with this basic study.

X-ray microanalysis and phagocytotic activity of cultured retinal pigment epithelial cells in hypoxia

PURPOSE

To investigate the influence of the functional and morphological changes induced in retinal pigment epithelial (RPE) cells by retinal ischemia, we evaluated the phagocytotic activity, the concentration of various elements, and ultrastructure in cultured RPE cells in hypoxia.

METHODS

The concentrations of oxygen in incubators were adjusted to 20, 10, and 1% by the addition of nitrogen for 72 hr. To observe phagocytotic activity and its relationship to actin filaments, the filaments of RPE cells incubated with fluoresbrite carboxylate YG microspheres were stained with rhodamine phalloidin. Some of the specimens were subjected to X-ray microanalysis by scanning electron microscope after being fixed, freeze-dried, and coated with carbon to investigate the cytoplasmic concentration of elements. A part of the latter specimens was also observed by transmission electron microscope after being embedded in epon and cut into ultrathin sections to see the ultrastructural changes inside cell.

RESULTS

Lowering oxygen concentrations from 20% to 1% swelled RPE cells and decreased the number of fluoresbrite carboxylate YG microspheres phagocytized by RPE cells. Phagocytosis of a large amount of latex beads (30 microl) for 24 hr in 1% oxygen caused a disruption of RPE cells. Na, S, and P were detected in RPE cells cultured in 20% oxygen. Reducing the oxygen concentration from 20 to 10 or 1% significantly decreased Na and increased S. Mitochondria were observed in RPE cells in 20 and 10% oxygen, but many vacuoles were observed in the cytoplasm in 1% oxygen.

CONCLUSION

Hypoxia as low as 1% oxygen induced malfunction of phagocytosis and the fragility of RPE cells. We could speculate the imbalance of the electrolytes such as Na or a decrease of antioxidants such as glutathione containing S as a reason of disturbance of cell viability.

[Pterygium and mast cells--mast cell number, phenotype, and localization of stem cell factor]

We examined the number and phenotype of mast cells, and the localization of stem cell factor (SCF) as a growth factor of mast cells in the excised tissue of 38 cases of pterygium. In histopathology with toluidine blue stain and immunohistochemistry with a monoclonal antibody to tryptase, the mean mast cell count in pterygium specimens was twice as high as in normal conjunctiva. In pterygium specimens more than 94% of tryptase-positive mast cells were found to express chymase and c-kit. There was no phenotypic difference between mast cells in pterygium and normal conjunctiva. In all immunohistochemical specimens in which we could examine the head of the pterygium, SCF was expressed in subepithelial fibroblasts at the central edge of pterygium. The results suggest that overexpression of SCF was accompanied with the augmentation of mast cells in the pterygium.

[A case of dermatomyositis with severe retinopathy in a patient who died of acute interstitial pneumonia]

Sight threatening ocular complications are rare in adult patients with dermatomyositis. We encountered a 52-year-old female with dermatomyositis who had severe visual disturbance and rapidly progressive intersitial pneumonia. She was admitted to our hospital because of skin erythema, general fatigue, mild fever, and severe bilateral visual disturbance. Rentinal hemorrhages, cotton wool spots, and macular edema were observed in her fundus at the first ophthalmic examination. A diagnosis of dermatomyositis was made because of the myogenic pattern of her electromyogram, elevation of serum creatine kinase, and skin lesions. Oral prednisolone treatment was started and the retinopathy was improved, but was complicated by acute interstitial pneumonia. The interstitial pneumonia was not respond to steroid pulse therapy with methylprednisolone, and the patient died of respiratory failure on the 47th day after the onset of visual symptoms. In adult dermatomyositis patients, the complication of severe retinopathy should be considered as a risk factor for rapid progress of interstitial pneumonia.

Apoptosis in retinal ganglion cell decrease in human glaucomatous eyes

Hematoxylin-eosin staining, the TUNEL method for in situ detection of the intranuclear DNA fragmentation, which indicates apoptosis, and electron microscopy were used to study the morphologic changes in specimens from the eyes of 8 patients with secondary glaucoma and 2 normal control eyes to evaluate our hypothesis that apoptosis causes a decrease in retinal ganglion cells in human glaucomatous eyes. The TUNEL method permits identification of intranuclear DNA fragmentation. Apoptosis was found in the ganglion cells of 2 glaucomatous eyes with recent sight loss, and in the ganglion cells of a control eye from a 95-year-old subject, taken at autopsy. Results of our study indicate that a decrease in retinal ganglion cells in glaucomatous eyes is caused by apoptosis. In addition, apoptosis resulting from aging must be considered in order to understand the reduction of retinal ganglion cells in the glaucomatous eyes of elderly patients.

[A case of primary orbital chondrosarcoma]

The case of a twenty-year-old male with orbital chondrosarcoma is reported. He visited National Defense Medical College Hospital because of reduced vision in the right eye since two months previously. His corrected visual acuity was 8/20 in the right eye and 20/20 in the left eye. Fifteen degrees lateral displacement of the right globe and limitation of right ocular movement were recognized. Right fundus examination revealed optic disc edema and protuberant nasal fundus. Orbital computed tomography (CT) demonstrated a high density area between the inner part of the right orbit and the ethmoid sinus. Magnetic resonance imaging (MRI) showed a smoothly outlined and low intensity (T1) space occupying lesion. This lesion was irregularly enhanced by gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA). This orbital tumor was removed by an anterior approach. Histopathological examination revealed well-differentiated chondrosarcoma (grade 1) as determined by small prominent chondromatous cell projection into the collagen fibrous stroma, and existence of binucleate cells in the hypercellular region. After the operation the disc edema disappeared and his corrected right visual acuity improved to 20/20.

[Comparative study on diode laser (680 nm) and krypton laser mild photocoagulation--histological findings and therapeutic outcome for diabetic maculopathy]

A histopathological study of macaca monkey retina-choroid was carried out for one month after mild photocoagulation with a diode laser (680 nm) and a krypton laser (647 nm). Both lasers produced the same damage to the outer layer of retina and to the melanocytes of 1/3 of the inner choroid. Mild focal photocoagulation was done for 6 patients (12 eyes) with diabetic maculopathy. The patients were 41 to 67 years old, suffering from diabetes mellitus for 5 to 25 years. The grade of their retinopathy was Fukuda's classification AI, AII, and BI. AII eyes were tested before and 3-6 months after photocoagulation for corrected visual acuity, fluorescein angiography, and visual field sensitivity by Octopus automated static perimetry. Visual acuity was stable in all cases. Central sensitivity was better in 2 eyes and unchanged in 4 eyes in both types of laser photocoagulation. In cases of total loss, one eye was improved, 4 eyes were unchanged and one eye was worsened by diode laser photocoagulation and one eye was improved, 2 eyes were unchanged and 3 eyes were worsened by krypton laser photocoagulation. The diode laser (680 nm) might be as useful for ophthalmic laser treatment as the krypton laser.

[Immunohistochemical localization of acidic and basic fibroblast growth factor through corneal neovascularization in vivo and in vitro]

Neovascularization on the center of rabbit cornea was induced by 5N.NaOH alkali burns. We studied the change in localization of acidic fibroblast growth factor (a-FGF) and basic fibroblast growth factor (b-FGF) through corneal neovascularization with immunohistochemistry, using eyes which we enucleated on the 3rd, 7th, and 14th day. Moreover, by co-cultivation of rabbit corneal stromal cells and adrenal cortical vascular endothelium of bovine, a capillary-like code was induced, in which we also studied the localization of a-FGF and b-FGF on the 3rd, 7th, and 14th day. On the 14th day after the alkali burn we recognized intrastromal neovascularization and positive staining of a-FGF and b-FGF around it. Strong staining of a-FGF was observed in goblet cells through the experimental period. In control eyes we recognized positive reaction of a-FGF in corneal and conjunctival epithelium. In co-cultured cells, we recognized positive staining of both a-FGF and b-FGF around the capillary-like code which was induced among the corneal stromal cells.

[Natural process of wound healing of photocoagulated retinal pigment epithelium in culture--observation of DNA synthesis by BrDu incorporation]

We examined the proliferation of retinal pigment epithelial (RPE) cells after krypton laser photocoagulation in culture. A pigmented monolayer of chick embryonic RPE cells was cultured on a collagen membrane placed on collagen gel. RPE cells were labeled with bromodeoxyuridine (BrDu) every 12 hours until 7 1/2 days after the photocoagulation and stained immunocytochemically with anti BrDu antibody. Immediately after the photocoagulation, RPE cells became detached at the burned lesion and the collagen membrane beneath the RPE layer was exposed. Some cells adjacent to the burned lesion showed DNA synthesis and subsequent mitosis between 12 to 24 hours after the photocoagulation. Cells with labeled nuclei migrated into the denuded burned area after 24 hours and covered the whole burned area within three days after the photocoagulation. DNA synthesis continued in these on the burned lesion after complete coverage of the lesion but stopped temporarily 3 1/2 to 4 1/2 days after the photocoagulation. Thereafter DNA synthesis increased again and continued until the end of the experiment. Such use of the cultured RPE cells might be useful in studying cellular reaction after photocoagulation.

Histology of fetal eyes with oculocutaneous albinism

The diagnosis of tyrosinase-negative oculocutaneous albinism (OCA) was made in a 19-week-old fetus by skin biopsy. Because the parents had an 11-year-old son with tyrosinase-negative OCA, they requested that the fetus be aborted at the 20th week of gestation. A histological analysis of the eyes was performed. Throughout the retina, the ganglion cell layer was separated from the inner neuroblastic layer by the inner plexiform layer. However, the number of ganglion cells was decreased and the nerve fiber layer was immature. Bipolar and horizontal cells had begun to segregate into the inner nuclear layer. Rods and cones were identifiable in the posterior, but not peripheral, retina. Cones were more numerous in the center of the retina, and no rod-free area was identifiable. In addition, the ciliary body (epithelial folds, blood vessels in the mesodermal connective tissue core, and ciliary muscle) was less developed than in a normal fetus. Melanosomes in the retinal pigment epithelium only contained filaments without melanization and were therefore classified as stage I or II melanosomes. However, the ciliary epithelium also contained some stage III melanosomes with melanin adherent to the filaments.

Comparative effects of linoleic acid and linoleic acid hydroperoxide on growth and morphology of bovine retinal pigment epithelial cells in vitro

PURPOSE

Outer segments of the photoreceptor rods that are phagocytized by the retinal pigment epithelial (RPE) cells contain a high proportion of polyunsaturated fatty acids (PUFA). PUFA are susceptible to lipid peroxidation. We hypothesized that the resulting peroxides could injure RPE cells leading to retinal degeneration. Accordingly, we compared the effects of linoleic acid (LA) and its hydroperoxide (LHP) on the growth and morphology of RPE cells using laser scanning microscopy and transmission microscopy.

METHODS

We counted the number of RPE cells after incubation for 24 and 48 hrs with concentrations of LA or LHP of 0.035, 0.175, and 0.35 mM. To observe the actin filaments, cultured RPE cells were stained with rhodamine phalloidin. The cells were prefixed with 2% glutaraldehyde and postfixed in 1% osmium tetroxide. Specimens were embedded in Epon 812 after dehydration, and the ultrathin sections were doubly stained with 2% uranyl acetate and 2% lead acetate for examination by transmission electron microscopy.

RESULTS

Exposure to LA or LHP produced dose-dependent damage to RPE cells with a significantly greater effects of LHP than LA. After incubation for 24 hrs with 0.35 mM LA, the number of vacuoles in RPE cells exceeded that observed in control RPE cells by 365 nm laser microscopy. Exposure to 0.35 mM LHP for 24 hrs produced a pycnotic nucleus, with diffuse and granular autofluorescences observed in and around it. Exposure of RPE cells to 0.35 mM LA for 24 hrs showed that the LA incorporated into the lysosomes was digested and released extracellularly from lysosomes via exocytotic vesicles. However, such exposure to LHP damaged the RPE cells, including the membranes in the pinocytotic vesicles. The packed membranes resembled myelin.

CONCLUSIONS

While the LA incorporated into the lysosomes was released extracellularly, LHP persisted in the RPE cells, being observed as autofluorescent lipofuscin-like materials. LHP was cytotoxic, and caused damage to the membranes of pinocytotic vesicles and lysosomes.

[Aging changes in conjunctiva visualized by fluorescein angiography and histopathology]

In order to investigate the aging changes of the conjunctiva, we examined fluorescein-positive areas by fluorescein angiography. The deposition of melanin in basal cells, the degranulation of mast cells, and the lumens of capillaries were examined by light microscopy in 35 cataractous eyes without diabetes or hypertension. The fluorescein leakage increased with aging. The number of basal cells with deposition of melanin granules and mast cells with degranulation correlated significantly with aging. On the other hand, the narrowing of capillary lumens in conjunctival stroma was not observed with aging. Based on the above results, we conclude that the weakness of the conjunctival vessels without the narrowing of capillary lumens might be caused by functional disorder of the endothelium and pericytes. The increase of deposition of melanin granules in basal cells may be caused by the breakdown of the metabolic pathway of melanin. Long-time mechanical stimuli and metabolic disorders of active substances may increase the degranulation of mast cells.

Effects of superoxide dismutase and catalase on growth of retinal pigment epithelial cells in vitro following addition of linoleic acid or linoleic acid hydroperoxide

The rod outer segments of the retina that are phagocytized by retinal pigment epithelial (RPE) cells are susceptible to lipid peroxidation because of their high content of polyunsaturated fatty acids. Linoleic hydroperoxides (LHP), synthesized by peroxidation of linoleic acids (LA), produce greater damage to retinal function than does LA. We compared the effects of LHP and LA on the growth of cultured chick embryonic RPE cells and analyzed a model of data sets using multiple linear regression for the number of cells as a function of time. The spectrum of LA had a sharp peak at 205 nm and a broad spectrum at 235 nm, while LHP had only a broad spectrum at 235 nm. Exposure to LA and LHP caused dose-dependent damage of chick embryonic RPE cells: they were significantly more affected by the addition of LHP than LA. The antioxidative enzymes catalase and superoxide dismutase minimized damage to the RPE cells caused by LHP in proportion to the enzyme concentration. However, RPE cells incubated with LA were more affected by the enzymes than when no enzymes were added.

[The effects of dopa and oxygen on RNA concentrations in cultured chick embryonal retinal pigment epithelial cells]

We measured RNA and DNA concentrations in cultured chick embryonal retinal pigment epithelial cells to investigate the effects of dopa and oxygen on DNA and RNA synthesis. RNA/DNA ratios were decreased by addition of 250 microM dopa. Decrease of RNA/DNA ratios was suppressed when the oxygen concentrations were reduced from 20% to 10%. Incubation with medium containing 100 microM dopa increased RNA/DNA ratios in 10% oxygen. Exposure of retinal pigment epithelial cells to 250 microM dopa caused the decrease of RNA concentrations in the retinal pigment epithelial cells, which was ameliorated by lowering oxygen concentrations. However, the addition of 100 microM dopa in 10% oxygen stimulated retinal pigment epithelial cells and seemed to increase RNA concentrations.

Missense mutation of rhodopsin gene codon 15 found in Japanese autosomal dominant retinitis pigmentosa

Heterozygous missense mutation in codon 15 of the rhodopsin gene was detected in a patient with autosomal dominant retinitis pigmentosa (ADRP), where a transition of adenine to guanine at the second nucleotide in codon 15 (AAT-->AGT), corresponding to a substitution of serine residue for asparagine residue (Asn-15-Ser) was detected. None of the remaining unrelated 42 ADRP, 24 autosomal recessive RP (ARRP) and 34 normal individuals had this alteration. Her funduscopic findings were sectorial in type similar to that of the patients with the same mutation found in an Australian pedigree (Sullivan et al., 1993). This study shows phenotypic similarities in patients with the same mutation of a different ancestry.

[Effects of anticoagulant therapy on retinal vein occlusion]

The combined effect of prostaglandin E1, stellate ganglion block, warfarin potassium and photocoagulation on 66 cases (eyes) of retinal vein occlusion was investigated immediately after, and 3 months and 6 months after final treatment. The time between onset and treatment was 2 months or less. Macular hemorrhage and edema were observed in all cases. The effectiveness rate 6 months after treatment was 35% in hemorrhagic central retinal vein occlusion and 63% in branch retinal vein occlusion. Visual acuity increased gradually with time from immediately after to 6 months after treatment. The effectiveness of treatment including warfarin potassium was lower than that of treatment without warfarin potassium in branch retinal vein occlusion, and many cases showed a marked decrease of visual acuity which might be related to the prolonged hemorrhage. These results suggest that combining prostaglandin E1, stellate ganglion block and photocoagulation in retinal vein occlusion produces better effects on visual acuity than ordinary treatment or spontaneous regression.

[A case of radiation optic neuropathy after resection of a pituitary adenoma]

A case of optic neuropathy after postoperative radiation therapy is reported. A 69-year-old woman had a partial resection of a pituitary adenoma in 1990 and was treated with 45Gy of irradiation to the postoperative pituitary lesion for one month. Seven months later she had sudden right visual field loss. Goldmann perimetry examination revealed remarked visual field defect in her right eye with visual acuity of 1.0. The right relative afferent pupillary defect was positive. The value of critical flicker fusion for her right eye was reduced and the amplitude of steady-state pattern-reversal visually evoked cortical potential was significantly less for the right monocular stimulation than that for the fellow eye stimulation, but Ganzfeld electroretinograms were normal for both eyes. Magnetic resonance imaging using Gadolinium-diethylene triaminepenta-acetic acid revealed enhancement on the right optic nerve, which had not been recognized immediately after the radiation therapy, without any suggestion of right optic nerve compression by the residual pituitary adenoma.

Clinical and histopathologic features of corneal dystrophies in Japan

PURPOSE

To examine retrospectively the frequency of various corneal dystrophies among Japanese patients who underwent keratoplasty or keratectomy at the authors' institution over a 34-year period, and to compare the histopathologic features of these disorders in the Japanese population with those reported in the Western literature.

METHODS

Corneal specimens obtained during keratectomy or keratoplasty (lamellar and penetrating) performed at the authors' institution from 1959 through 1992 were reviewed. Immunohistochemical studies were performed using monoclonal antibodies to keratan sulfate and gelsolin, as well as two lectins (concanavalin A and wheat germ agglutinin).

RESULTS

Of 1259 corneal specimens, 159 (12.6%) specimens from a total of 80 patients showed corneal dystrophy. Virtually all were non-Fuchs dystrophies; only one case of primary Fuchs dystrophy was identified histologically. Granular dystrophy and gelatinous drop-like dystrophy were the most common dystrophies identified in the specimens, largely because of multiple specimens from individual patients with recurrent disease. These two disorders accounted for 86 of the 159 specimens. In terms of numbers of patients, lattice dystrophy was the most common (26 patients, 32.5%), followed by macular dystrophy (16 patients, 20%), gelatinous drop-like dystrophy (15 patients, 18.8%), granular dystrophy (14 patients, 17.5%), and Avellino dystrophy (3 patients, 3.75%). Dystrophies represented by only one or two patients included congenital hereditary endothelial dystrophy, primary spheroidal keratopathy, posterior polymorphous dystrophy, Schnyder crystalline dystrophy, and Fuchs dystrophy.

CONCLUSIONS

This histopathologic study showed a very low incidence of Fuchs dystrophy in the authors' Japanese patient population, compared with the incidences seen in studies of populations in Western countries. Of the non-Fuchs dystrophies, lattice dystrophy was the most common among the patients, although there were large numbers of specimens with granular dystrophy and gelatinous drop-like dystrophy due to their recurrent character. The causes of clinical and histopathologic differences and similarities among the Japanese patients and the patients described in the Western literature are likely related to genetic factors, but a complete understanding of their specific mechanisms awaits future molecular biologic and genetic elucidation.

[Incidence of tumors and tumor-like lesions in the conjunctiva and the cornea]

Incidence of tumors and tumor-like lesions in conjunctiva and cornea seen at Juntendo University during the 13-year period from 1980 to 1992 was analysed histopathologically. There were 126 cases including 116 benign (92.1%) and 10 malignant lesions (7.9%). Pigmented nevi (32 cases) were most frequently found, accounting for 27.6% of the benign tumors and tumor-like lesions, half of which were compound nevi (16 cases). Nevi were closely followed by cysts (24 cases, 20.7%) and dermoids (15 cases, 12.9%). Carcinoma in situ (3 cases) was most frequently found, accounting for 30% of the malignant tumors (10 cases), closely followed by malignant lymphoma (2 cases), squamous cell carcinoma (2 cases), mucinous carcinoma (1 case), sebaceous gland carcinoma (1 case) and metastatic tumor (1 case). The ratio of males to females was 4:6. Age distribution of the patients was 47-92 years.

[Clinical importance of inclusion cysts of nevi in bulbar conjunctiva]

We investigated 30 cases of nevi in bulbar conjunctiva histopathologically from 1980 to 1992. The patients' ages were between 5 and 85 years old (mean, 21 years). Investigated parameters of the tumors were the location, growth pattern, and the presence of inclusion cysts, melanin granules, goblet cells, and feeding vessels. Of 30 cases, 26 cases (87%) had inclusion cysts which were characteristic findings of conjunctival nevi. The mucous secretion from goblet cells may play an important role in the synthesis of inclusion cysts, but goblet cells were not found in 9 cases. This finding suggests that other secretory cells may be present. Four cases without inclusion cysts consisted of flat tumors. From this finding, the presence of inclusion cysts may be related to the growth of tumors. We conclude that the growth of the pigmented conjunctival tumors with inclusion cysts suggests a benign growth pattern. A periodical follow-up study or biopsy should be performed, if inclusion cysts are not found.

[Comparative study on frequency-doubled Nd: YAG laser, krypton laser and diode laser photocoagulation for diabetic maculopathy]

Twenty six eyes of thirteen patients with diabetic maculopathy (Fukuda's classification AI, AII, BI) were treated with frequency-doubled Nd:YAG laser (6 eyes) or krypton laser (7 eyes) in one eye and diode laser (13 eyes) in the other eye. Group A was treated with frequency-doubled Nd: YAG laser and diode laser, and group B was treated with krypton laser and diode laser. The visual acuity, visual field (Octopus program 31) and fundus were examined at one month, 3 months, and 6 months after photocoagulation. Visual acuity was stable in all eyes. The central 30 degree visual sensitivity decreased more after diode laser treatment than after that of the other lasers. Krypton laser photocoagulation maintained the better visual function and was easy to use followed by frequency-doubled Nd: YAG laser. Because the appearance immediately after diode laser lesion was weaker than one hour after coagulation, it was difficult to get the proper power setting.

A comparison between melanotic and amelanotic retinal pigment epithelial cells in vitro concerning the effects of L-dopa and oxygen on cell cycle

Melanin precursors and free radicals, cytotoxic substances, are produced during melanin synthesis by tyrosinase. We compared these cytotoxic effects of L-dopa and oxygen on the cell cycle of melanotic retinal pigment epithelial (RPE) cells with amelanotic RPE cells because of the differences of tyrosinase activities between melanotic and amelanotic RPE cells. Flow cytometric DNA analysis of RPE cells exposed to L-dopa (100 microM and 250 microM) were conducted at several oxygen concentrations (20%, 10%, and 5%). The dose-dependent effect of L-dopa to arrest the cell cycle (the S phase) was more pronounced in melanotic than in amelanotic RPE cells, and oxygen caused arrest in the G1 phase.

[Influence of the yellow-tinted intraocular lens on spectral sensitivity]

One of the complaints of patients with aphakic eyes or pseudophakic eyes implanted with UV or non-UV intraocular lenses (IOLs) is chromatopsia. To determine the extent of color distortion, we measured the spectral sensitivity curve of normal subjects with visual acuity above 1.0 with correction, if any, including subjects implanted with the yellow-tinted IOL (UVCY IOL: HOYA Co.). We found that color sensitivity in the blue range (400-440 nm) declined rapidly with subjects age. We drew a regression line plotting age against sensitivity for 66 normal subjects. Sensitivity for pseudophakic eyes implanted with UVCY and UV IOLs at 400 nm corresponds to that of subjects in their early 20's. That of pseudophakic eyes implanted with non-UV IOLs and aphakic eyes corresponded to that of infants. In summary, compared to UV IOL and non-UV IOLs, the UVCY IOL was found to best approximate the color sensitivity of healthy eyes.

Mechanism of intraocular pressure decrease after contact transscleral continuous-wave Nd:YAG laser cyclophotocoagulation

Twenty-two eyes of 11 cynomolgus monkeys were subjected to contact transscleral cyclophotocoagulation with a continuous-wave Nd:YAG laser. The right eye of each monkey was coagulated at the pars plicata region by the contact probe placed 1.0 mm from the limbus, while the left eye of each monkey was coagulated at the pars plana region by the contact probe placed 3.0 mm from the limbus. Physiological and morphological studies were carried out up to 6 months after the treatment. The postoperative intraocular pressure showed a significant decrease within 1 week, corresponding to the inflammation of the anterior chamber. A gradual increase of the intraocular pressure occurred from the 2nd week on and returned to the preoperative value 8 weeks after pars plicata coagulation. The pars plana coagulation group maintained the intraocular pressure lower than the preoperative value until the end of the observation period. Histopathological examinations were carried out by the use of tracer particle perfusion into the anterior chamber. The pathologic features of pars plicata coagulation were necrosis, followed by atrophy of the ciliary process. The tracer particles accumulated at the anterior portion of the space between the bundles of ciliary muscle. The pathologic features of pars plana coagulation were necrosis followed by extension of proliferative tissue into the vitreous. The surrounding extracellular space of the stroma was enlarged, and the ciliary muscles were separated from the sclera. The tracer particles accumulated at the enlarged extracellular space of the stroma and the opened suprachoroidal space. These results suggest that the decrease of the intraocular pressure after pars plicata cyclocoagulation resulted from the reduction of aqueous secretion, whereas that after pars plana cyclocoagulation resulted from enhancement of the uveoscleral outflow through the enlarged extracellular space from the anterior chamber into the suprachoroidal space.