Is axial length a risk factor for idiopathic macular hole formation?

Current theories for macular hole formation implicate antero-posterior and tractional forces at the vitreofoveal interface. It is thought that localized perifoveal defects enlarge from centrifugal forces acting about the axis of ocular rotation. If this is true, eyes with longer axial lengths should have an increased incidence of macular holes. The aim of this study was to determine if axial length is a risk factor for macular hole development. The study group comprised 40 patients with refractive errors from hyperopia to myopia with stage 3 and 4 idiopathic macular holes. Controls matched for age, gender and spherical equivalent (SE) were used for statistical comparison. Axial length (AL) was analyzed using SPSS 13.0 statistical software and compared using Student's t test. P < 0.05 was considered significant. SE ranged from -8.88 to +3.63 dioptres in the macular hole group and -8.50 to +3.63 in controls. In the macular hole group, mean AL ± standard deviation was 23.62 ± 1.20 mm (21.81-27.51); in controls, 23.09 ± 1.16 mm (21.31-26.58). Univariate analysis showed that higher AL is associated with macular hole formation. The mean difference in AL was 0.531 mm (95 % confidence interval -0.1596 to -0.9024). Two-tailed t test: P < 0.006. This study showed that increasing ocular AL is significantly associated with macular holes. Dynamic forces at the macula would be greater in these eyes suggesting this may play a causative role in macular hole formation.

The management of "coats' response" in a patient with x-linked retinitis pigmentosa-a case report.

The management of exudative retinal detachment in Coats disease can be very difficult with variable results. A case is presented of a 12 year old boy who was diagnosed with X-linked retinitis pigmentosa with an associated "Coat's Response". The patient had a marked reduction in his left visual acuity due to intragel and subhyaloid haemorrhage as well as exudative retinal detachment. This was managed successfully with vitrectomy and endolaser, resulting in clearance of the haemorrhage and flattening of the retina. In our experience endolaser should be considered as viable therapeutic option in the management of this condition.

Evidence for the aqueous absorption of gas from the eye following vitreoretinal surgery.

A standard part of vitrectomy surgery is to inject a bubble of gas into the eye, and an important question for the surgeon and patient alike is to know the volume of the bubble and how long it is likely to last. A related question of considerable importance is the mechanism by which it is absorbed. In this paper, we show how to use patients' measurements of the daily variation of their far points to calculate the changing volume of the bubble and hence the rate of gas absorption throughout the post-operative period. The results show that the rate of absorption contains a term in time squared, indicative of absorption through the exposed surface area of the aqueous fluid rather than via the exposed retina.

Comparison of pars plana vitrectomy and scleral buckling for uncomplicated rhegmatogenous retinal detachment.

Retinal detachment surgery can now achieve a final reattachment rate in over 90% of cases. The operation of choice in most cases is that of external scleral buckling with or without drainage of subretinal fluid. However, in a minority of cases these techniques are difficult to apply either when the breaks are unseen due to media opacities or when the breaks are complex, eg, posterior, large, or multiple breaks at different distances from the ora. Improvements in the technique of pars plana vitrectomy for retinal detachment now offers us an alternative method for treating these difficult cases. Pars plana vitrectomy for retinal detachments with unseen or complex breaks has a final attachment rate of over 90%, is technically easier to perform than conventional surgery, and avoids the refractive and ocular motility problems associated with complicated buckles. For these reasons and despite the high risk of nuclear sclerosis in phakic eyes, a pars plana vitrectomy may be the preferred option in selected cases of primary retinal detachment.

Severe idiopathic posterior scleritis in children.

Posterior scleritis is an uncommon condition that usually occurs in adults and the diagnosis is often missed. It is even more rare in children. We report five cases of the disease in children. The patients presented with severe pain in an inflamed eye and usually had orbital signs with lid swelling and limitation of extraocular movements; four of the five had optic disc swelling and two had exudative retinal detachments. The diagnosis was confirmed on B-scan ultrasonography and CT scanning and no child had clinical or laboratory evidence of associated systemic disease. The disease took a protracted course and all the children required long-term systemic immunosuppression (15-27 months), which was well tolerated. All children retained good vision and were either off treatment or on a small dose of immunosuppression at last follow-up. This condition, although rare, should be recognised in children as part of the differential diagnosis of acute orbital inflammation.

Confocal imaging of the fundus using a scanning laser ophthalmoscope.

A confocal scanning laser ophthalmoscope (cSLO) was used to examine the effects of confocal optics on the image of the human fundus in vivo. Patients from a retinal clinic and a glaucoma clinic were examined using the cSLO in the confocal mode. A degree of optical sectioning could be achieved, and the results agree with a best axial resolution of 300 microns measured in a model eye. The main advantage of using a confocal system was found to be the improved contrast of the images. This improved the resolution of structures such as the lamina cribrosa and optic disc drusen which are seen in low contrast in conventional images. The improved contrast of the confocal images is partly achieved by excluding light which has been scattered within the plane of focus. Structures which multiply scatter light will become less visible with confocal optics and hard exudates were found to be an example of such a structure. The cSLO and the fundus camera are seen as complementary instruments rather than as alternatives for imaging the fundus. It is envisaged that confocal imaging will enable details of the fundus to be revealed which are at present not seen in conventional images.

Iris clipping of a diode laser beam when performing retinal photocoagulation.

The Microlase infrared diode laser has recently become available for retinal photocoagulation. It uses a laser beam with a large convergence angle (23 degrees). This gives rise to a laser beam with a relatively large cross section at the subject's pupil. In this study the pupillary area required to view the fundus at the slit-lamp with a 90-dioptre lens is determined. It is found that the pupillary area required to view the fundus is smaller than the cross section of the Microlase laser beam at the pupil. Thus iris clipping of the laser beam can occur even though the surgeon has a clear and bright view of the fundus. Care should be taken to use the Microlase only in the presence of a widely dilated pupil.

A computerised diagnostic index for medical and neuro-ophthalmology.

We have developed a classification that meets the requirements of the Medical Eye Unit and computerised it. The classification uses three categories: anatomical site of lesion, pathological process, and clinical diagnosis. Each patient is identified by standard data and up to three entries in each of anatomical localisation, pathological diagnosis, and clinical diagnosis. This system allows the formation of groups of patients which can be either very specific or very broad by appropriate combination of selection criteria in the different categories. No codes are used but computer validation ensures consistent nomenclature. Computerisation allows rapid searching of records even with multiple selection criteria. The program is simple to use and validates data entries. An additional benefit is that it facilitates medical audit of the department's work.