Effects of single, short term exposures of human retinal pigment epithelial cells to thiotepa or 5-fluorouracil: implications for the treatment of proliferative vitreoretinopathy

AIM—To investigate the effects of single, short term (5 or 30 minutes) exposures to thiotepa or 5-fluorouracil (5-FU) on collagen lattice contraction and retinal pigment epithelial (RPE) cell proliferation.
METHODS—For collagen contraction studies, RPE cells seeded into free floating type I collagen lattices were exposed to single 5 or 30 minute treatments with thiotepa (0.06-4 mg/ml), or 5-FU (0.25-25 mg/ml), or phosphate buffered saline alone as a control. For proliferation studies, RPE cell monolayers were similarly exposed to these agents. The degree of contraction, effects on cell number, and viability were determined up to 14 days after treatment.
RESULTS—Contraction of collagen lattices containing RPE cells and proliferation of RPE cells were significantly inhibited (p<0.05) by thiotepa and 5-FU at concentrations above 0.06 mg/ml and 0.25 mg/ml respectively (for both 5 and 30 minute treatments), compared with controls. Cell death did not occur except for exposure of the RPE cells in collagen lattices to the highest concentration of thiotepa (4 mg/ml).
CONCLUSION—It was concluded that single 5 or 30 minute exposures to thiotepa or 5-FU significantly inhibited collagen contraction and the proliferation of RPE cells. These findings suggest that short, single, non-toxic exposures to thiotepa or 5-FU which can be reproduced clinically may be useful in the modulation of proliferative vitreoretinopathy.

Keywords: proliferative vitreoretinopathy; collagen matrix contraction; thiotepa; 5-fluorouracil     

Effect of mitomycin C on the optic nerve in rabbits

AIM—To prevent scarring after surgical optic nerve sheath decompression, it has been suggested that treating the area of fenestration with mitomycin C (MMC) might be effective. An animal model was used to test whether this toxic substance may cause optic neuropathy.
METHODS—The optic nerves of 15 rabbits were exposed to balanced salt solution (BSS) or mitomycin C (MMC) in a concentration of 0.2 or 0.5 mg/ml. The unoperated fellow eyes and the eyes that received BSS served as controls. Steady state visual evoked potentials (VEPs) at 40, 50, and 60 Hz were recorded before and 4 weeks after surgery. The nerves were examined by light and electron microscopy after 5 weeks.
RESULTS—VEPs in all non-operated eyes and eyes treated with BSS before and 4 weeks after surgery demonstrated responses at all three stimulus frequencies tested. Eyes operated with MMC had extinguished responses for one, two, or all the different temporal frequencies after 4 weeks with marked reduction in VEP amplitude. Eyes operated with MMC at a concentration of 0.5 mg/ml had significantly more reduced VEP responses than those where MMC 0.2 mg/ml was used. On histopathological examination, special stains for myelin and axons showed normal axons and myelin. On electron microscopy, no distinct abnormalities were seen among nerves operated with MMC and controls.
CONCLUSION—The data from this study suggest that in rabbits, the application of MMC to the optic nerve has a dose dependent toxic effect in the short term postsurgical follow up period. While a functional alteration could be demonstrated reproducibly by steady state VEPs, the extent was not obvious on histopathological examination of the nerves.

     

Transplanted and repopulated retinal pigment epithelial cells on damaged Bruch's membrane in rabbits

AIMS—The authors studied how artificially damaged Bruch's membrane influenced growth and differentiation of transplanted embryonic retinal pigment epithelial (RPE) cells and of host RPE cells in rabbits.
METHODS—Embryonic RPE cells obtained from pigmented rabbits were transplanted into the subretinal space of adult albino rabbits. The host RPE was removed with a silicone cannula, and Bruch's membrane was damaged by scratching with a microhooked 27 gauge needle under the detached retina in closed vitrectomy. The transplantation sites were examined 3, 7, and 14 days after surgery by light and electron microscopy.
RESULTS—Varying degrees of damage in Bruch's membrane were observed. Pigmented and hypopigmented RPE cells showed a normal polarity and tight junctions were seen at the sites of mild to moderate damage 3-7 days after the surgery. In contrast, fibroblast-like cells with no such features of RPE cells formed multiple layers at the sites of severe damage involving the full thickness of Bruch's membrane and the choriocapillaris even 14 days after the surgery. Without transplantation, host RPE cells repopulated the damaged areas in the same way as transplanted RPE cells.
CONCLUSIONS—Transplanted embryonic RPE cells as well as host RPE cells grew and differentiated on the moderately damaged Bruch's membrane, while the severely damaged Bruch's membrane did not allow differentiation of RPE cells although these cells could grow and cover the damaged areas.

Keywords: transplantation; repopulation; retinal pigment epithelial cells; Bruch's membrane; rabbit     

Endogenous cortisol profile in patients with central serous chorioretinopathy

AIM—To study the endogenous cortisol levels in patients with central serous chorioretinopathy (CSCR).
METHODS—Endogenous cortisol levels in urine and plasma were determined in 30 patients with acute CSCR and compared with 30 age and sex matched controls.
RESULTS—The mean values of the 8 am plasma cortisol (29.97 µg/dl v 18.76 µg/dl), 11 pm plasma cortisol (22.03 µg/dl v 13.06 µg/dl), and 24 hour urine cortisol (11.01 mg/24 h v 7.39 mg/24 h) revealed significantly higher values in the patient group (p<0.001).
CONCLUSIONS—Increased levels of endogenous cortisol are present in patients with CSCR.

     

Decreased choriocapillaris perfusion following surgical excision of choroidal neovascular membranes in age-related macular degeneration

AIMS/BACKGROUND—To evaluate macular changes following surgical excision of subfoveal choroidal neovascular membranes (CNVs) in age-related macular degeneration (AMD).
METHODS—The clinical records, fluorescein angiograms, and CNV histopathology of 12 patients with AMD who underwent surgical excision of subfoveal CNV were reviewed.
RESULTS—New areas of decreased choriocapillaris perfusion were noted by fluorescein angiography in the previous location of the CNV in 8/12 (75%) cases. Surgically excised tissue contained retinal pigment epithelium (RPE) in 11/11 specimens and choriocapillaris in 1/11 specimen studied.
CONCLUSIONS—Choriocapillaris atrophy may partly underlie the limited visual outcome following subfoveal surgery for AMD. Abnormal choriocapillaris perfusion following CNV excision may be due to pre-existing choriocapillaris atrophy, to choriocapillaris damage or removal at the time of surgery, or to RPE removal at surgery with abnormal RPE repopulation of the dissected area and subsequent choriocapillaris degeneration.

     

Local hypothermia protects the retina from ischaemic injury in vitrectomy

AIMS—Hypothermic irrigating solutions were used during vitrectomy in pressure induced ischaemic eyes so that their effects on retinal function and histological changes could be investigated.
METHODS—After anaesthetised albino rabbits underwent closed vitrectomy, their vitreous cavities were continuously irrigated for 30 minutes at a perfusion pressure of 140 mm Hg. The rabbits were divided into three groups according to their intraocular perfusion temperatures—8°C, 22°C, and 38°C. Electroretinograms were taken before and after irrigation. Glutamate levels in the vitreous were examined after irrigation. Eyes were enucleated on the seventh postoperative day and examined histologically.
RESULTS—On the seventh postoperative day, the recovery rate of a-wave amplitudes was significantly lower in the 38°C group than in the 8°C group, and that of b-wave amplitudes was significantly lower in the 38°C group than in either the 8°C or 22°C group. Retinal damage in the 38°C group revealed more severe histological impairment than in either the 8°C or 22°C group. Oedema of the inner retinal layer was significant in both the 22°C and 38°C groups. Glutamates reached peak values 30 minutes after the end of ischaemia in the 38°C group. However, no significant glutamate increases were detected 15 to 60 minutes after ischaemia in either the 8°C or 22°C group.
CONCLUSION—Local hypothermia during vitrectomy in acute ischaemic eyes appears to decrease retinal damage.

     

Ultrasound enhanced thrombolysis in experimental retinal vein occlusion in the rabbit

AIMS—To investigate if it was possible to lower the dose of streptokinase and maintain an effective thrombolysis by adding pulsed low energy ultrasound.
Methods—53 retinal veins in 27 rabbits were occluded by rose bengal enhanced laser treatment. Six rabbits were treated with streptokinase (50 000 IU/kg), 10 rabbits were treated with a low dose of streptokinase (25 000 IU/kg), and 11 rabbits were treated with a low dose of streptokinase (25 000 IU/kg) and pulsed ultrasound during 1 hour. Fluorescein angiography was performed immediately before the thrombolytic treatment and after 12 hours.
RESULTS—In the group treated with streptokinase (50 000 IU/kg) all vessels were open. In the group that was given streptokinase (25 000 IU/kg), 21% of the vessels were open. In the group that was treated with streptokinase (25 000 IU/kg) and ultrasound, 64% of the vessels were open. The difference between groups 2 and 3 is statistically significant (p= 0.011)
CONCLUSION—Adding pulsed low energy ultrasound makes it possible to lower the dose of streptokinase while maintaining a good thrombolytic effect.

Keywords: retinal vein occlusion; ultrasound; thrombolytic treatment; streptokinase     

Mitomycin C dissolved in a reversible thermosetting gel: target tissue concentrations in the rabbit eye

AIMS—To determine whether a new, reversible thermosetting gel enhances mitomycin C transfer to target ocular tissues in the rabbit eye.
METHODS—A 0.1 ml solution of mitomycin C containing 0.22 µg, 2.9 µg, or 28 µg of the agent dissolved in a reversible thermosetting gel consisting of methylcellulose, citric acid, and polyethylene glycol was injected subconjunctivally in 30 New Zealand albino rabbits. Scleral and conjunctival tissues were excised at 0.5, 1, 2, 4, or 24 hours after the injection and mitomycin C concentrations in these tissues were determined by high performance liquid chromatography. The concentration over time was approximated to a single exponential curve, and initial mitomycin C concentrations, time constants, and half life values were determined. Finally, the areas under the curves (AUCs) between 0.5 and 24 hours were calculated.
RESULTS—The mitomycin C concentrations in the target tissues were dose dependent and decreased rapidly over 24 hours. Both the initial mitomycin C concentrations as well as AUCs in these eyes treated with mitomycin C, dissolved in a reversible thermosetting gel, were higher than those in eyes treated similarly in a previous study in which the gel was not used.
CONCLUSION—Applied subconjunctivally in the rabbit eye, mitomycin C dissolved in the reversible thermosetting gel enhanced transfer of the agent to the sclera and the conjunctiva.

     

Comparison of the safety and efficacy of the fixed combination of dorzolamide/timolol and the concomitant administration of dorzolamide and timolol: a clinical equivalence study

AIMS—To compare the tolerability and efficacy of a fixed combination solution of dorzolamide/timolol (Cosopt), administered twice daily with the concomitant administration of its components, dorzolamide (Trusopt) twice daily and timolol (Timoptic) twice daily.
METHODS—After a 2 week timolol run in, patients with open angle glaucoma or ocular hypertension were randomised (1:1) to receive treatment with either the dorzolamide/timolol combination solution twice daily (combination) or the dorzolamide solution twice daily plus timolol maleate solution twice daily (concomitant) for 3 months.
RESULTS—299 patients were entered and 290 patients completed the study. Compared with the timolol baseline, additional IOP lowering of 16% was observed at trough (hour 0) and 22% at peak (hour 2) at month 3 in both the concomitant and combination groups. The IOP lowering effects of the two treatment groups were clinically and statistically equivalent as demonstrated by the extremely small point differences (concomitant − combination) observed in this study−0.01 mm Hg at trough and 0.08 mm Hg at peak. The safety variables of the concomitant and combination groups were very similar. Both combination and concomitant therapy were well tolerated and few patients discontinued due to adverse effects.
CONCLUSIONS—The dorzolamide/timolol combination solution administered twice daily is equivalent in efficacy and has a similar safety profile to the concomitant administration of the components administered twice daily.

Keywords: dorzolamide; timolol; intraocular pressure; glaucoma; ocular hypertension     

Anti-Acanthamoeba activity of contact lens solutions

AIMS—This study was undertaken to investigate the effects of contact lens disinfecting solutions on strains of Acanthamoeba from the United Kingdom and southern Africa and to compare the results with those of other researchers. No information was previously available for southern African isolates.
METHODS—11 contact lens solutions were tested on cysts of 10 strains of Acanthamoeba.
RESULTS—Not all solutions used in the study were effective, with some for hard and gas permeable contact lenses being more satisfactory than those for soft contact lenses. The most effective of the gas permeable and hard contact lens solutions tested was Transoak (0.01% (wt/vol) benzalkonium chloride), which killed cysts of all strains within 4 hours of exposure. Oxysept 1 (31 mg hydrogen peroxide/ml) was the best soft contact lens solution tested. It eliminated cysts of certain strains within 4 hours, whereas cysts of other strains were only inactivated within either 8 or 72 hours.
CONCLUSIONS—Manufacturers should be aware of the killing time for Acanthamoeba by contact lens solutions and should provide appropriate guidelines for the use thereof. The killing time for cysts of the African and UK isolates studied is, in general, similar. Therefore, it must in the present state of knowledge be assumed that usage guidelines suggested in the UK are also appropriate for travellers to South Africa and for local residents in South Africa.

Keywords: contact lenses; Acanthamoeba; keratitis     

Clinicopathological correlation of primary and recurrent choroidal neovascularisation following surgical excision in age related macular degeneration

AIMS/BACKGROUND—Fluorescein angiography and histopathological findings were correlated in two patients with recurrent choroidal neovascular membranes (CNVs) in an attempt to gain insight into the possible causes of recurrent CNVs and into the healing response after CNV excision.
METHODS—Two patients with recurrent CNVs underwent repeat excision, and the excised tissue was studied with light and electron microscopy.
RESULTS—Incomplete CNV excision probably led to the recurrences. The portion initially excised appears to have been anterior to the RPE in case 1. In both cases, recurrent CNVs contained RPE-like cells suggesting that native RPE can repopulate the dissection bed. The tissue excised at the second operation contained areas with hyperplastic RPE and fragments of Bruch's membrane (external to the RPE basement membrane) in a matrix of fibrillar collagen and fibrocytes, suggesting that initial removal of the CNV can be followed by an abnormal anatomical arrangement of RPE and scarring of Bruch's membrane.
CONCLUSIONS—Abnormal resurfacing of the dissection bed by RPE and fibroblasts may underlie, in part, the limited visual outcome often seen after surgical excision of CNVs in age related macular degeneration.

Keywords: age related macular degeneration; choriocapillaris atrophy; choroidal neovascularisation; fluorescein angiography     

Influence of topical human epidermal growth factor on postkeratoplasty re-epithelialisation

AIM—To test the efficacy and safety of recombinant human epidermal growth factor (hEGF) on corneal re-epithelialisation following penetrating keratoplasty.
METHODS—A prospective, randomised, placebo controlled study was carried out in which patients were matched for diagnosis and received either hEGF ophthalmic solution (30 µg/ml or 100 µg/ml) or placebo in a double masked fashion. Matched pairs of patients received donor corneas from the same donor and were operated by the same surgeon on the same day. At the end of surgery all donor epithelium was removed mechanically. Patients were examined twice daily and fluorescein stained photographs were taken until the epithelium had closed. The area of the defect was measured by planimetry of the fluorescein stained defect on the photographs.
RESULTS—There were no significant differences in re-epithelialisation of the donor cornea between the placebo group and the group treated with 30 µg/ml hEGF. Time until complete closure was slightly longer with 100 µg/ml hEGF compared with 30 µg/ml hEGF and with placebo. Mean healing rate of the epithelial defect with 100 µg/ml hEGF was significantly slower than in the other groups.
CONCLUSION—No significant acceleration of corneal re-epithelialisation was demonstrated with the use of recombinant hEGF after penetrating keratoplasty in humans.

     

CA 19-9 ELISA test: a new method for studying mucus changes in tears

AIMS—This study investigated mucus changes in the tears in various eye conditions using impression cytology. The quantity of mucins was measured by enzyme linked immunosorbent assay (ELISA) using the tumour marker CA 19-9. This assay quantifies the sialylated Lewis^a structure mainly associated with ocular mucins.
METHODS—Impression cytology was performed using a cellulose nitrate membrane, on 53 healthy patients, 50 glaucoma patients treated with β blockers, 24 patients suffering from dry eye syndrome, and 45 contact lens wearers. The tear film glycoproteins were eluted and CA 19-9 was measured.
RESULTS—CA 19-9 content expressed as kilo units (kU) per µg of tears was significantly decreased in dry eye syndrome (25.8 kU (SD 17.3)/µg) (p<0.05), glaucoma patients over 60 years (28.9 (19.5) kU/µg) (p<0.05), and contact lens wearers (28.4 kU (18)/µg) (p<0.05), when compared with healthy individuals (39.4 kU (22.2)/µg).
CONCLUSION—Impression cytology can be regarded as a valuable method for obtaining samples of glycoconjugates of mucin. The decrease of sialylated chains observed with this method confirms the hypothesis that some quantitative changes in the tear film may be encountered in ocular surface disorders.

Keywords: impression cytology; tears; glycoconjugate; sialic acid     

Oxygen free radical damage in the cornea after excimer laser therapy

AIMS/BACKGROUND—To evaluate the extent of oxygen radical damage in the cornea after excimer laser ablation.
METHODS—The 193 nm argon fluoride excimer laser was programmed for an average fluence of 150 mJ/cm², with a firing rate of 5 Hz and an ablation zone diameter of 6 mm. Phototherapeutic keratectomy was performed to remove 30 µm of epithelium and 50 µm of stroma from the corneas of New Zealand white rabbits. Oxidative tissue damage after laser was determined by measuring oxidised lipids (conjugated dienes and ketodienes) in corneal lipid extracts, and by fast blue B staining to localise the lipid peroxide in the tissue.
RESULTS—Conjugated diene levels were 3.73 (SD 0.56) nmol per hemicornea in ablated corneas and 1.99 (0.33) nmol per hemicornea in normal corneas (p = 0.0044). Ketodiene levels were 2.72 (0.38) nmol per hemicornea in treated corneas and 0.91 (0.12) nmol per hemicornea in normal corneas (p < 0.001). Fast blue B staining disclosed that the tissue damage occurred primarily on the surface of the ablated cornea.
CONCLUSION—The presence of lipid peroxidation in the superficial corneal stroma in excimer laser treated corneas was demonstrated. This lipid peroxidation could be from oxygen free radicals generated by the infiltrating polymorphonuclear cells at the site of tissue damage.

     

Monocular optokinetic nystagmus in humans with age-related maculopathy

AIM—To investigate full field monocular optokinetic nystagmus (OKN) in patients with age-related maculopathy (ARM) and relative central scotoma.
METHODS—Six patients aged 59-88 years with bilateral ARM and an aged-matched control group of six patients aged 54-83 years were examined. Visual fields were assessed with a Humphrey field analyser using the threshold 30-1 routine. Monocular full field horizontal optokinetic stimuli were presented on a hemicylindrical screen subtending 172° horizontally and 50° vertically. The stimulus was a projected random dot pattern and three stimulus velocities were used, 30, 50, and 70°/s in both nasalward and temporalward directions. Each trial lasted between 30 and 40 seconds and eye movements were monitored using infrared oculography.
RESULTS—The ARM patients had relative central scotomas with an average depth of 10 dB. Neither the ARM nor the age-matched groups displayed any directional preponderance or a buildup of the slow phase eye velocity with time. No statistically significant difference in the gain was found between the two groups (p>0.05).
CONCLUSIONS—Marked central field loss in ARM does not significantly impair OKN gain. This supports the view that complete central retinal integrity is by no means essential and that the peripheral retina provides an important input to the generation of OKN.

     

Increased expression of angiogenic growth factors in age-related maculopathy

AIMS/BACKGROUND—The late stages of age-related maculopathy (ARM), especially neovascular macular degeneration (ARMD), can severely affect central vision and are the main cause of blindness in the elderly in the Western world. It has been shown that angiogenic growth factors are present in neovascular membranes in ARMD. However, it is not known if angiogenic growth factors play a role in the onset of neovascularisation.
METHODS—In order to elucidate the involvement of angiogenic growth factors in the initiation of neovascularisation in early stages of ARM, the expression patterns of VEGF, TGF-β, b-FGF, and PDGF-AA on 18 human maculae with ARM, and on 11 control specimens were investigated immunohistochemically.
RESULTS—A significantly increased expression of VEGF (p=0.00001) and TGF-β (p=0.019) was found in the retinal pigment epithelium (RPE) of maculae with ARM compared with control maculae. Furthermore, an increased expression of VEGF and PDGF was found in the outer nuclear layer of maculae with ARM.
CONCLUSION—These results demonstrate an increased expression of VEGF in the RPE, and in the outer nuclear layer in maculae with ARM, that could be involved in the pathogenesis of neovascular macular degeneration. Furthermore, enhanced TGF-β expression in the RPE cells of maculae with early stages of ARM was shown.

     

Treatment of ocular symptoms of Behçet's disease with interferon α2a: a pilot study

AIM—To study long term effects of interferon α_2a (IFNα_2a) on panuveitis in seven patients with Behçet's disease in a prospective, open clinical trial.
METHODS—Seven patients were treated with IFNα_2a for a mean of 23.6 months (14-37 months). They received an initial dose of IFNα_2a of 6×10⁶ IU/day, followed by 3×10⁶ IU/day after 1 month and 3×10⁶ IU every other day after 3 months. Two patients received low dose prednisolone (between 0.2 and 0.4 mg/kg/body weight) additionally at the beginning of the therapy. Complete cessation of IFNα_2a was possible in three patients (observation period 22, 6, and 4 months).
RESULTS—Marked improvement occurred in six patients who had ocular manifestations of Behçet's disease for the first time or with minor damage during their course of chronic relapsing panuveitis. In one patient with advanced ocular Behçet's disease, new relapses were prevented. Retinal infiltrates resolved within 2 weeks; vasculitis, macular oedema, infiltration of the anterior chamber and vitreous resolved within 4 weeks. Mean posterior uveitis score before treatment (nine affected eyes) was 6.6, 4 weeks after IFN it was reduced to 0.4. The mean observation period is 27.6 months, ranging from 14 to 42 months.
CONCLUSION—Treatment of ocular symptoms of Behçet's disease with IFNα_2a alone or in combination with low dose steroids led to complete remission of ocular vasculitis in all patients treated in this open, uncontrolled trial. Treatment with IFNα_2a may prevent permanent retinal or optic nerve damage due to vascular occlusion. No severe side effects occurred. Controlled randomised studies are warranted in order to prove the efficacy of IFNα_2a in ocular Behçet's disease and to compare it with other, established treatments such as azathioprine or cyclosporin A.

Keywords: Behçet's disease; uveitis; interferon α_2a     

Reliable keratometry with a new hand held surgical keratometer: calibration of the keratoscopic astigmatic ruler

AIM—Some surgeons consider hand held surgical keratometers unreliable. This may be due to incorrect use through not realising that the distance that the keratometer is held from the cornea influences the shape of the image. When a keratometer is held closer to the astigmatic cornea, the elliptical image will appear more circular, particularly for larger degrees of astigmatism. However, the keratoscopic astigmatic ruler (KAR) has design features that correct the hitherto unrecognised problems with the use of a hand held keratometer. This study assesses the reliability and accuracy of measurement of astigmatism using the KAR.
METHODS—The KAR and the Bausch & Lomb keratometer (B&L) were compared using six back surface toric cut contact lens blanks representing 1 to 6 dioptres of astigmatism. Two observers (one experienced in the use of the keratometers, the other a novice) took eight randomly repeated "masked" measurements of each lens blank with the KAR and four measurements with the B&L in a similar fashion.
RESULTS—There was no difference between the measurements with either instrument by each of the observers (p=0.95, ANOVA). The standard error of measurement for the KAR was 0.59 D, for the B&L, 0.31 D. The intraclass correlation coefficient of reliability for the KAR was 0.90 and for the B&L it was 0.97. The coefficient of repeatability for the KAR was plus or minus 0.83 D, and for the B&L plus or minus 0.77 D. The interobserver reliability for the KAR was 0.898, and for the B&L, 0.975.
CONCLUSION—These results suggest that the KAR has good reliability and reproducibility and compares favourably with the B&L keratometer. Inexperience with use does not affect reliability.

     

Pigmented uveal tumours in a transgenic mouse model

AIMS/BACKGROUND—The authors have developed transgenic mouse strains at the Arizona Cancer Center using a tyrosinase promoter to target expression of the mutated T24 Ha-ras gene in melanin producing cells. Histopathology and electron microscopy (EM) were performed to characterise the intraocular tumours observed phenotypically.
METHODS—Transgenic TPras mice (n=8) and normal, age matched control mice (n=6) were sacrificed at 3 weeks, 6 weeks, 7 weeks, 4 months, 5 months, 9 months, and 11 months. Six were processed in formalin for light microscopic examination and eight in a glutaraldehyde/formalin solution for electron microscopic examination.
RESULTS—Six of the TPras mice were found to have bilateral pigmented melanocytic/RPE proliferations of the uveal tract. The cytological characteristics of the tumours included low nuclear to cytoplasmic ratios (N:C ratios), bland nuclei, and abundant intracytoplasmic melanin. By EM two populations of cells were identified, including spindle-shaped cells with round to oval melanin granules and cuboidal cells with apically located, cigar-shaped, melanin granules, and basement membrane formation. A 3 week and an 11 month old TPras mouse had a higher grade, bilateral, melanocytic proliferation of the uveal tract which, although not metastatic, was morphologically melanoma. Cytological features included increased N:C ratios, nuclear pleomorphism, and prominent nucleoli. The uveal tract was normal in both eyes in all of the control animals.
CONCLUSION—Pigmented intraocular tumours developed in transgenic strains of mice that express a mutated Ha-ras gene in melanin producing cells. The morphology was most consistent with a melanoma in two of the mice and a benign melanocytic/RPE proliferation in the remaining mice.

Keywords: histopathology; melanoma model; transgenic mice; uveal melanoma     

Effects on IOP restoration and blood-aqueous barrier after long term treatment with latanoprost in open angle glaucoma and ocular hypertension

AIMS—To evaluate whether long term treatment with the prostaglandin analogue latanoprost has a deleterious effect on the blood-aqueous barrier (BAB) and to determine the duration of the effect on intraocular pressure (IOP) after withdrawal of treatment.
METHODS—Patients with ocular hypertension or glaucoma were topically treated with latanoprost 50 µg/ml once daily for 6-12 months. In 26 patients IOP was followed for 14 days after withdrawal of treatment. Aqueous flare was measured with a laser flare meter during 6-12 months' treatment in 16 patients.
RESULTS—On the last day of treatment IOP was 6.9 mm Hg (95% CI 5.3-8.5) lower than before treatment. It increased slowly during the follow up period but was still 1.3 mm Hg (95% CI 0.2-2.5) lower than pretreatment IOP 14 days after cessation of treatment. No change in aqueous flare was seen throughout the study.
CONCLUSION—Latanoprost has no clinically significant effect on the permeability of the BAB and IOP will return to pretreatment levels within a few weeks, indicating that latanoprost is safe for long term treatment.