Challenges in the management of ocular snake-bite injuries.

Ocular snake-bite injuries are quite rare away from natural habitats. However, when exotic animals are kept in captivity, the injuries sustained and their management can pose challenges when they present to their local eye department. This report describes an atypical eye injury inflicted by a python and its successful management involving surgical, laser and medical interventions. The case highlights the possible pitfalls resulting from the unusual mechanism of injury and the steps to avoid them. The article goes on to discuss the background of the injuries that can be caused by venomous and non-venomous snakes.

Advances in cataract surgery.

Cataract surgery is a technique described since recorded history, yet it has greatly evolved only in the latter half of the past century. The development of the intraocular lens and phacoemulsification as a technique for cataract removal could be considered as the two most significant strides that have been made in this surgical field. This review takes a comprehensive look at all aspects of cataract surgery, starting from patient selection through the process of consent, anaesthesia, biometry, lens power calculation, refractive targeting, phacoemulsification, choice of intraocular lens and management of complications, such as posterior capsular opacification, as well as future developments. As the most common ophthalmic surgery and with the expanding range of intraocular lens options, optometrists have an important and growing role in managing patients with cataract.

Refractive effect of reversed implantation of angled-haptic lens implants.

BACKGROUND: To study the refractive effect of reversed implantation of intraocular lenses. METHODS: Trigonometric calculations were used to calculate the extent of forward displacement of the optic for various lens designs available commercially. The SRK formula was used to estimate the relationship of axial length to the refractive power of the eye, with other variables remaining constant. RESULTS: The theoretical effect of a displaced posterior-chamber implant due to flipped insertion can vary from 1.46 dpt for a 12.5-mm diameter lens with an optic diameter of 6 mm (or a 13-mm diameter lens with an optic diameter of 6.5 mm) and a haptic angle of 5 degrees to 3.15 dpt for a 12.5-mm diameter lens with an optic diameter of 5.5 mm (or a 13-mm lens with an optic diameter of 6 mm) and a haptic angle of 10 degrees. CONCLUSIONS: There has been no study on the refractive effect of axial lens displacement due to a reversed implantation of a lens with a hinged haptic. This study identifies the major determinants (namely the haptic length and haptic angle) and gives an estimate of the effect on final refraction for each lens type commonly used when they are implanted on the reverse.

The relationship of Central Corneal Thickness (CCT) to Thinnest Central Cornea (TCC) in healthy adults.

PURPOSE: The aim of the study was to precisely quantify the relationship between the central corneal points, namely the pupillary centre and the thinnest point in the central cornea, in terms of their thickness and location in healthy adults. METHODS: 120 eyes of 60 healthy adult volunteers underwent pachymetry with a Scheimpflug imaging system (Pentacam). The thickness at the pupillary centre (Central Corneal Thickness, CCT) and the thickness at the Thinnest Central Corneal (TCC) point were measured. One eye of each patient was used to analyse the mean difference between CCT and TCC. Unpaired t-test (one tailed) was used to test significance and 95% confidence limits were used. The precise location of the TCC in relation to the corneal apex was measured using vector algebraic and trigonometric calculations. RESULTS: The mean CCT was 520+/-33microm and the TCC was 515+/-36microm. The difference between CCT and TCC was found to be 5.57microm (0-15.9microm, 95% CI; P=0.1909). The TCC location was inferotemporal to the corneal apex in 58/60 (96.7%) of the right eyes and in 49/60 (81.7%) of the left eyes. The average vector location of TCC of both eyes was inferotemporal. This coordinate was found to lie 0.62mm (right eye) and 0.79mm (left eye) from the corneal apex subtending and angle of 45.5 degrees (right eye) and -10.9 degrees (left eye) from the horizontal. CONCLUSION: The study has identified the parameters of TCC and its relationship to CCT in terms of the location and thickness. For clinical usage, they can be interchangeable as there is no significant difference between the two. The consistency in the (inferotemporal) location of the TCC merits further research in this regard to the development of corneal ectasia.

Complex visual hallucinations (Charles Bonnet syndrome) in the hemianopic visual field following occipital infarction.

Charles Bonnet syndrome is characterised by the occurrence of complex visual hallucinations in the presence of normal cognition in elderly individuals. It commonly happens following conditions where there has been a profound loss of vision or interruption of visual input into the occipital cortex. It is important to distinguish this largely innocuous condition from psychiatric conditions that exist in the same age group. This article describes a rare variant of this condition where such hallucinations occur in the hemianopic visual field of a patient with an occipital infarct whose visual acuity is largely unimpaired. The article details the various conditions where this phenomenon has been experienced; the theories that have been postulated for its aetiology and the treatment options. The variations of this case from the commonly observed scenarios are highlighted questioning previously held convictions as well as providing an insight into the widening spectrum of the phenomenon as more cases are described. The article hopes to raise awareness of this condition, which is much commoner than perceived by healthcare practitioners, as most patients in that age group are reluctant to be forthcoming with their symptoms for fear of being diagnosed with a psychiatric disorder.

Unusual presentation of Amsler's sign in Fuchs' heterochromic uveitis.

Hyphema occurring after ocular paracentesis has been described as a classic feature of Fuchs' heterochromic uveitis (FHU) (Amsler's sign). We describe a case of hyphema occurring after peribulbar anesthesia in a patient with FHU. The bleeding occurred before the surgery began. Although the occurrence of this phenomenon does not preclude successful surgical outcomes, topical anesthesia may lower the risk preoperatively.

Interpreting binasal hemianopia: the importance of ocular examination.

Binasal hemianopia is a rare neurological finding. Interpreting this can be challenging, especially in the absence of pathology on neuroimaging. As with other types of neurological visual field defects, there can be ocular causes. We report an incidentally discovered case of binasal hemianopia that was caused by keratoconus. There has been no published report of keratoconus giving rise to this kind of field defect to date. We also discuss published reports of binasal hemianopia to emphasise that this type of field defect has more to do with the 'eye' than the 'brain', and we recommend an ophthalmological opinion for such patients, especially in the absence of corresponding neurological signs.