Automated segmentation of retinal blood vessels and identification of proliferative diabetic retinopathy.

Proliferative diabetic retinopathy can lead to blindness. However, early recognition allows appropriate, timely intervention. Fluorescein-labeled retinal blood vessels of 27 digital images were automatically segmented using the Gabor wavelet transform and classified using traditional features such as area, perimeter, and an additional five morphological features based on the derivatives-of-Gaussian wavelet-derived data. Discriminant analysis indicated that traditional features do not detect early proliferative retinopathy. The best single feature for discrimination was the wavelet curvature with an area under the curve (AUC) of 0.76. Linear discriminant analysis with a selection of six features achieved an AUC of 0.90 (0.73-0.97, 95% confidence interval). The wavelet method was able to segment retinal blood vessels and classify the images according to the presence or absence of proliferative retinopathy.

Effect of isovolaemic haemodilution on visual outcome in branch retinal vein occlusion.

AIMS: To assess the efficacy of isovolaemic haemodilution therapy (IHT) in the treatment of patients with branch retinal vein occlusion (BRVO). METHODS: Patients presenting with BRVO between 1 July 1991 and 31 August 1993 were eligible for inclusion and randomised into treatment and control groups. Patients randomised to receive IHT were treated for 6 weeks with venesection and volume replacement using hydroxyethylstarch, a plasma expander. The target haematocrit was 35%. Follow up was for 1 year. RESULTS: The baseline visual acuity of the two groups was similar at 0.74 and 0.75 logMAR units (Snellen 6/36), for the IHT and control groups, respectively. At 6 weeks, visual acuity in the IHT group had improved by 0.20 logMAR units (2 lines on the Bailey-Lovie chart) (p = 0.0001). Vision was unchanged in the control group. At 1 year, the IHT group exhibited an improvement of 0.43 logMAR units. By comparison, the improvement in the control group at 1 year was significantly less at 0.17 logMAR units (p = 0.03). The final visual acuity in the IHT and control groups was 0.30 (Snellen 6/12) and 0.60 (Snellen 6/24) logMAR units, respectively. CONCLUSIONS: The results support the theory that IHT has a positive effect on the visual outcome in patients with BRVO.

A randomised prospective study of outpatient haemodilution for central retinal vein obstruction.

PURPOSE: Central retinal vein obstruction (CRVO) has significant visual morbidity. We prospectively evaluated an outpatient haemodilution (HD) regimen for CRVO. METHODS: We recruited 59 patients with CRVO of less than three months' duration and visual acuity (VA) worse than or equal to 6/9.5. Thirty patients underwent HD (packed cell volume of <0.35, 12 weeks); there were 29 controls and follow-up was for six months. RESULTS: Incidence rates for VA improvement (P = 0.708) and rubeosis iridis (P = 0.619) between the two groups were not different. The incidence rate of VA deterioration was 5.315 times higher with HD (P = 0.035, Cox Proportional analysis). CONCLUSION: This data does not support the previous studies on haemodilution.

The venous closing pressure in central retinal vein obstruction.

OBJECTIVE: To assess the rate of change in the central retinal venous closing pressure in central retinal vein obstruction over time, and its relationship to visual acuity improvement and the development of rubeosis iridis. METHODS: Fifty patients presenting with central retinal vein obstruction of less than three months' duration, between the ages of 40 and 80 years, were reviewed prospectively. The central retinal venous closing pressure was measured by digital ocular compression. Patients were discharged from the study after the six-month visit. RESULTS: All patients had elevated venous closing pressure at presentation, whereas at six months only 24 patients had persistent elevation. Of 16 patients with lowering of the venous closing pressure within four months of onset of central retinal vein obstruction, 11 (69%) had two or more lines of visual acuity improvement. Only two of 10 patients (20%) developing lowering of the venous closing pressure thereafter had visual improvement. No patient developed rubeosis iridis after the venous closing pressure lowered. CONCLUSION: The central retinal venous closing pressure is raised in central retinal vein obstruction to about central retinal arterial diastolic pressure, and is its pathognomonic sign. This sign is easily elicited via digital pressure on the eyelid, and has prognostic significance for visual acuity improvement and the development of rubeosis iridis.

A foveal-sparing pattern of cytomegalovirus retinitis in the acquired immunodeficiency syndrome.

PURPOSE: We describe the clinical course of 12 eyes of 10 patients in whom recurrent cytomegalovirus (CMV) retinitis exhibited a foveal-sparing pattern. METHODS: We retrospectively reviewed the case records and photographic charts of 10 patients (12 eyes) with the acquired immunodeficiency syndrome (AIDS), in whom recurrent CMV retinitis exhibited a foveal-sparing pattern within 1500 mm of the foveola. RESULTS: The site of primary retinitis was temporal in 10 eyes of nine patients in whom it was known. The median number of recurrences up to the observation of foveal-sparing retinitis was two (range one to eight), and five patients had active CMV retinitis despite treatment for at least two continuous months. Once established, the median rate of progression in a non-foveal vector was 2.3 times faster than toward the fovea, and the median time to reduction in acuity to < 6/30 (or death) was 11 to 14 weeks. Three eyes of three patients retained 6/30 or better acuity up to death. Foveal CMV retinitis ultimately reduced acuity to < 6/30 in five eyes. Six eyes suffered retinal detachment, involving the fovea in five, and being the primary reason for acuity of < 6/30 in four. Four patients suffered dose-limiting toxicity. CONCLUSION: Foveal-sparing CMV retinitis arises in patients with recurrent CMV retinitis resistant to treatment ('clinically resistant'), particularly that which has arisen temporally. Despite its foveolar proximity, and ultimate significant loss of function, the pattern of progression allows for preservation of useful foveal vision for longer periods than would have been expected.

Cytomegalovirus retinitis in patients with AIDS: current status.

About 20%-30% of patients with AIDS will develop cytomegalovirus (CMV) retinitis when they are severely immunodeficient (CD4 cell count below 40 cells/microL). It causes extensive retinal damage with visual deficits, and relapses are frequent. Intravenous ganciclovir and foscarnet are standard therapy, but their high toxicity and long term intravenous access mean that advances in treatment, including oral prophylactic agents, intravitreal injections and surgical implants, may provide a better quality of life for patients. Prophylactic ophthalmological screening of patients with CD4 cell counts below 100 cells/microL to detect asymptomatic retinitis is needed.

A sensitive and specific polymerase chain reaction-based assay for the diagnosis of cytomegalovirus retinitis.

PURPOSE: To develop a sensitive and specific laboratory assay for the diagnosis of cytomegalovirus retinitis. METHOD: We used a polymerase chain reaction-based assay for detection of cytomegalovirus DNA in vitreous samples. We attempted to detect cytomegalovirus DNA in 19 vitreous samples from patients with the acquired immunodeficiency syndrome (AIDS) who had untreated cytomegalovirus retinitis and in 40 vitreous samples from patients with AIDS who had been treated with systemic ganciclovir or foscarnet, or both. We also attempted to detect cytomegalovirus DNA in vitreous samples from 54 immunocompetent patients, including 32 with retinal detachment or macular hole, 11 with vitreous inflammation, and 11 with vitreous hemorrhage. Additionally, we attempted to detect cytomegalovirus DNA in 15 vitreous samples from patients with AIDS who had vitreoretinal inflammation not caused by cytomegalovirus. RESULTS: Cytomegalovirus DNA was detected in 18 of 19 eyes with untreated cytomegalovirus retinitis. We detected cytomegalovirus DNA in 19 of 40 vitreous samples from patients with previously treated cytomegalovirus retinitis. Cytomegalovirus DNA was not detected in any of 69 patients who did not have a clinical diagnosis of cytomegalovirus retinitis. Thus, the assay had an estimated sensitivity of 95% in detecting untreated cytomegalovirus retinitis and a sensitivity of 48% in detecting cytomegalovirus retinitis that had been treated with systemic ganciclovir or foscarnet, or both. The assay did not give false-positive results in patients with vitreous hemorrhage or vitreous inflammation. Most important, the assay did not give false-positive results in AIDS patients with vitreous inflammation from causes other than cytomegalovirus retinitis. CONCLUSION: We have developed a sensitive and specific diagnostic assay that will assist in the diagnosis of cytomegalovirus retinitis.

Macular holes. Pathogenesis, natural history and surgical outcomes.

Idiopathic full-thickness macular holes (FTMH) are a common cause of usually uniocular reduced visual acuity. The accepted pathogenesis has macular hole formation proceeding in stages from an impending hole to a FTMH, with visual acuity deteriorating to less than 6/60 in 85% of cases. Recent surgical advances in the treatment of FTMH, with excellent anatomic and visual results, have changed the surgical indications for both impending and established full-thickness macular holes.

Progressive zonal outer retinitis.

We examined an immunocompetent patient with uniocular acute progressive outer retinitis. The retinitis was curvilinear in shape, showed progressive enlargement, and appeared to be altered by treatment with intravenous acyclovir. When regressed, the affected area of retina appeared atrophic and, at one-year follow-up, demonstrated intraretinal pigment migration with retinal pigment epithelial atrophy and atrophy of the choriocapillaris. Although visual acuity was unaffected, a dense scotoma was recorded on field testing. The response to acyclovir implicates the herpesvirus family, and acyclovir or another antiherpetic agent should be considered for such cases.

Adult Coats' disease in branch retinal vein occlusion.

We report a case of adult Coats disease secondary to a branch retinal vein occlusion. Angiograms show the relationship of the peripheral telangiectasis, aneurysm formation and vascular incompetence to the peripheral retinal ischaemia. The possible role of vascular remodelling in the pathogenesis of this uncommon complication of a common condition is discussed.