Phillip H. House

Value of retinal vein pulsation characteristics in predicting increased optic disc excavation

Background: Retinal vein pulsation is often absent in glaucoma, but can be induced by applying a graded ophthalmodynamometric force (ODF) to the eye, which is elevated in glaucoma. Aim: To assess whether ODF has a predictive value in determining glaucoma progression. Methods: 75 patients with glaucoma and suspected glaucoma were examined prospectively in 1996, and then re-examined at a mean of 82 months later. All subjects had intraocular pressure, visual fields, stereo optic disc photography and ODF measured on their initial visit. When venous pulsation was spontaneous, the ODF was said to be 0 g. At re-examination, central corneal thickness and blood pressure were also measured. Initial and subsequent optic disc photographs were compared and graded into those that had increased excavation and those that had remained stable. The relationship between increased excavation (recorded as a binary response) and the measured variables was modelled using a multiple mixed effects logistic regression. Results: ODF at the initial visit was strongly predictive of increased excavation (p = 0.004, odds ratio 1.16/g, range 0–60 g), with greater predictive value in women than in men (p = 0.004). Visual field mean deviation was predictive of increased excavation (p = 0.044), as was optic nerve haemorrhage in association with older age (p = 0.038). Central corneal thickness was not significantly predictive of increased excavation (p = 0.074) after having adjusted for other variables. Conclusion: ODF measurement seems to be strongly predictive of the patient’s risk for increased optic disc excavation. This suggests that ODF measurement may have predictive value in assessing the likelihood of glaucoma progression.

The association between retinal vein ophthalmodynamometric force change and optic disc excavation

Aim: Retinal vein ophthalmodynamometric force (ODF) is predictive of future optic disc excavation in glaucoma, but it is not known if variation in ODF affects prognosis. We aimed to assess whether a change in ODF provides additional prognostic information. Methods: 135 eyes of 75 patients with glaucoma or being glaucoma suspects had intraocular pressure (IOP), visual fields, stereo optic disc photography and ODF measured on an initial visit and a subsequent visit at mean 82 (SD 7.3) months later. Corneal thickness and blood pressure were recorded on the latter visit. When venous pulsation was spontaneous, the ODF was recorded as 0 g. Change in ODF was calculated. Flicker stereochronoscopy was used to determine the occurrence of optic disc excavation, which was modelled against the measured variables using multiple mixed effects logistic regression. Results: Change in ODF (p = 0.046) was associated with increased excavation. Average IOP (p = 0.66) and other variables were not associated. Odds ratio for increased optic disc excavation of 1.045 per gram ODF change (95% CI 1.001 to 1.090) was calculated. Conclusion: Change in retinal vein ODF may provide additional information to assist with glaucoma prognostication and implies a significant relationship between venous change and glaucoma patho-physiology.

Software for 3-D visualization/analysis of optic-disc images

Discusses a software tool called the stereo optic disc analyzer (SODA) (patent pending ID:P09819, 1997), which has been developed for quantitative image processing of stereo optic-disc photographs to aid in the diagnosis and assessment of retinal disease. It is able to perform color matching and alignment of two images so that they are superimposed and viewed in 3-D sequential display by use of a pair of 3-D goggles. These 3-D images of the same patient are taken at different times, often over periods of several years. Measurements of optic-disc cupping, vertical and horizontal cup/disc ratio, cup and disc area, diameter, shape, and neuroretinal rim width can be determined using a predefined template placed over the image (one for the right eye and one for the left eye). Sequential display of stereo images (stereo flicker chronoscopy) and digital stereophotogrammetry provide sensitive methods for monitoring glaucomatous changes to the optic disc.

Comparison of optic disc image assessment methods when examining serial photographs for glaucomatous progression

AIM To assess serial, simultaneous stereo optic disc images by four methods for glaucomatous progression. METHODS Using varying techniques, two ophthalmologists assessed serial optic disc images of 52 eyes from 27 patients with a mean duration between images of 18 months. The neuroretinal rim width was qualitatively assessed by four assessment methods and compared with quantitative rim measurements made using PC based software. RESULTS The highest sensitivity of 83% was achieved using computerised stereo chronoscopy. CONCLUSION Stereo chronoscopy improved the detection of subtle optic disc changes when compared with simpler assessment techniques.

Color adjustment techniques to improve utility of stereo flicker chronoscopy and chronometry assessment of serial optic disk photographs in glaucoma patients

The aim of this study was to develop a computerized stereo- flicker chronoscopy and chronometry system to improve the technique of neuroretinal optic disc rim assessment. Digitized stereo photographs of 22 eyes of glaucoma patients were analyzed subjectively by computerized flickering of serial images, and objectively by measuring the width of the neuroretinal rim at 18 positions around the optic disc. A major source of error was identified as color changes in the images over time. Color adjustment algorithms were developed and the assessments and measurements were repeated. For chronometry after color adjustment there was improvement to most of the tests on the data: agreement (50% to 73%), specificity (45% to 84%), positive agreement (50% to 71%) and negative agreement (50% to 73%). Sensitivity remained constant at about 55%.

Postoperative deposits on the Acrysof intraocular lens

Purpose: To report a commonly occurring change on the anterior surface of the Acrysof intraocular lens which is presumed to be due to the proliferation of lens epithelial cells from the capsulo-rhexis margin. Method: Forty-one consecutive cases (31 patients) of Acrysof intraocular lens implantation were followed prospectively. Clinical charts were reviewed for changes on or within the lens and visual acuity and refractive changes recorded. All cases were dilated at 3–5 weeks postoperatively to facilitate observation of changes. Representative slit lamp photos were taken. Results: Deposits on the intraocular lens surface were noted on 18 of 41 lenses at 3–5 weeks post surgery. Deposits were not found on examinations conducted during the first postoperative week. All changes had fully resolved by 3 months. Conclusions: The changes recorded had no impact on visual acuity. The deposits noted do not represent clinically important pathology. They may be an unusual marker of biocompatibility with this lens. Surgeons using this lens should be aware of these changes.

Correspondence. Mitomycin C and Molteno tube implantation: reply

The recent clinical controversy discussion on endophthalmitis provided stimulating reading, and highlighted the incontrovertible need for prompt vitreous sampling together with injection of empirical intravitreal antibiotics. 1 The authors also provide good evidence for use of systemic oral antibiotics in settings when biofilms might be suspected (especially culture-negative cases), and highlight the debate that continues regarding the role of intravitreal steroids. Unfortunately both authors have misquoted the Endophthalmitis Vitrectomy Study (EVS) 2 with regard to the finding for when to intervene with vitrectomy, and there are a number of other errors through the discussion. The EVS found that only patients with perception of light or worse visual acuity benefited from formal vitrectomy, although it should be noted that a significant selection bias existed in the EVS patients. 2 Nonetheless the important message provided by the authors in the clinical controversy section remains: that urgent vitreous tap and intravitreal antibiotic injection is required. 1 Unfortunately the intravitreal antibiotic dose given for vancomycin by the two authors is different and it should be noted that the correct dose for vancomycin is 1 mg in 0.1 mL. Both authors highlight the good theoretical benefit of antiinflammatory agents, and although the EVS did not specifically address the value of anti-inflammatory treatment, both authors omitted from their discussion on steroids that all patients enrolled in the EVS were prescribed systemic steroid (30 mg prednisone b.i.d. for 5–10 days). All EVS patients also received intensive topical steroid and cycloplegia, and because significant anterior segment inflammation exists higher doses of topical steroids are needed than would normally be given after cataract surgery. In fact the EVS visual results were even better than the Moorfields results quoted, 3 with 53% of patients achieving 6/12 or better and 74% achieving 6/30 or better. 2 This reinforces the fact that with prompt and effective treatment endophthalmitis patients can achieve a reasonable result, and unless other contraindications exist then all patients should be given systemic steroids. In the absence of a ‘no steroids’ control then future studies require a systemic steroids arm as per EVS plus or minus a ‘no steroids’ control arm, before the intravitreal steroids debate can be adequately addressed. Contrary to the authors’ comment that there is no human evidence against use of steroids in endophthalmitis, 1 there has been one human paper that reported poorer visual outcomes following the use of intravitreal steroids (albeit a retrospective review). 4 If intravitreal steroids are contemplated then the dosage typically recommended for dexamethasone is 0.4 mg in 0.1 mL and not 1 mg as stated. 1