Derek G. Chan

Contact versus immersion biometry of axial length before cataract surgery.

Purpose: To compare the repeatability and agreement of contact and immersion ultrasound (US) biometry of axial length. Setting: Prince of Wales Hospital, Sydney, Australia. Methods: This prospective stratified randomized study comprised 36 patients with a preoperative refractive error less than 4.00 diopters (D) sphere or 2.00 D cylinder who were recruited before cataract surgery. Each of 3 operators measured both eyes of 12 patients by contact and immersion US techniques. A repeat measurement by both techniques was performed by the same operator in 6 cases and by a different operator in the other 6. Repeat and operator effects were examined. Results: The mean and standard deviation of the measurement sets were compared, and the differences between repeat measures were calculated. Axial length measurement was longer with the contact method than with immersion by 0.03 mm (P = .04). The repeatability of the 2 techniques was similar. Conclusions: When the measurement set was repeated, the precision of contact US biometry was comparable to that of immersion, with no clinically significant difference in mean axial length measurements.

Smokers’ veins: a useful clinical sign

We believe retinal venous calibre may demonstrate changes that can indicate whether a patient has been smoking. Over a 21-year period, we have consistently observed that the diameter of retinal veins around the optic disc closely correlates clinically with the approximate number of cigarettes smoked per day. Although there is a large differential diagnosis for retinal venous dilatation, the ophthalmologist as well as the general physician should keep in mind the possibility of the patient smoking when observing this physical sign. In 1983, one of us (ICF) observed that many patients who were Second World War or Vietnam War veterans were heavy smokers and they typically demonstrated varying degrees of retinal venous dilatation. In 1987, at a hospital Neurology Grand Rounds meeting, ICF was invited to examine a patient’s fundus in front of the neurological audience. The only abnormality was that of retinal venous dilatation. He asked the patient if he was a smoker, and suggested that the patient might have smoked 25–30 cigarettes per day. The patient was surprised but replied in the affirmative. The fundus of a 59-year-old man who presented for investigation of his watery eyes demonstrated moderately dilated retinal veins (Fig. 1). His haemoglobin, haematocrit, white cell count, lipids and proteins were all within normal limits. However, he smoked 18–25 cigarettes a day and we believe this degree of retinal venous dilatation is typically consistent with this degree of smoking. The differential diagnosis of retinal venous dilatation includes aetiologies highlighted in Table 1. Most of these diagnoses can be excluded by simple history and examination. Although it can be clearly seen that retinal venous dilatation is not a specific clinical sign, once it is recognized, it allows the examiner to question the patient about the ongoing consumption of cigarettes. Theoretically, if a linear relationship pertains, it may enable the examiner to form a reasonably objective estimation of how many cigarettes the patient smokes each day. This observation should be confirmed by comparing digital images of retinal venous diameters in a cohort study utilizing a smoking and non-smoking group. The underlying pathology causing retinal venous dilatation in smokers has not been elucidated. Possible hypotheses may include the relatively high haematocrit of secondary polycythaemia, alterations induced by nicotine in the autoregulation of retinal vessels, 1

Comparison of macular morphology between femtosecond laser–assisted and traditional cataract surgery

Comparison of macular morphology between femtosecond laser–assisted and traditional cataract surgery After reading the article by Nagy et al. on femtosecond laser–assisted cataract surgery technology, we have significant methodological concerns about the risk for postoperative cystoid macular edema (CME). These render the conclusions drawn by the authors difficult to support. The incidence of CME following cataract surgery is variable. Differing definitions of CME make it difficult to determine accurately its incidence; a recent review reported the incidence as 0.1% to 2.5%. It is essential to differentiate clinical CME, in which visual impairment is present, from angiographic or subclinical macular edema, in which visual acuity is not impaired. Flach identified 20 factors that could affect the reported incidence of postoperative CME. These factors relate to the patient (underlying vascular diseases such as diabetes mellitus, hypertension, and chronic kidney disease), research methodology, and surgical technique. The numerous shortcomings we find in the Nagy et al. study methodology are as follows. 1. Relevance of subclinical macular edema. The authors state that the incidence of subclinical macular edema after uneventful cataract surgery has become an issue of safety. This is in fact not the case. Subclinical macular edema is defined and diagnosed using fundus fluorescein angiography. It is considered a precursor process that might predispose to CME. The major objective outcome parameter after cataract surgery remains corrected distance visual acuity (CDVA). While macular edema is a critical determinant of surgical success, it is only so when it is clinically significant and results in an adverse effect on CDVA. The authors suggest that the mean CDVA was similar in the traditional phacoemulsification group and the femtosecond laser–assisted cataract surgery group, but no statistical analysis was performed. 2. Methodological bias. Specific patient factors such as age, sex, and refractive error were accounted for, but systemic illnesses (cited above) known to affect the risk for CME were not documented. Despite the study being documented as a prospective case-control series, the criteria for allocation to the traditional phacoemulsification cohort versus the femtosecond laser–assisted cataract surgery cohort were not addressed. There was no record of masking the observers during follow-up and optical coherence tomography (OCT). The mean follow-up was stated to be similar in the 2 cohorts, but there was no statistical

Comment on 'Medial canthal tendon repair for moderate to severe tendon laxity'.

A study of patients assessed for cataract extraction at Dunedin Hospital in 1998 found that 48 of 49 current drivers (98%) reported some difficulty associated with driving, particularly at night, and 20 (41%) current drivers had a visual acuity below the New Zealand requirements for a driver licence. The increasing proportion of ageing drivers in the population has been identified as an important public health issue in New Zealand and elsewhere. 1 Adequate vision is crucial to the task of driving. In New Zealand between 1997 and 1999, 25 motor vehicle accidents (resulting in three deaths, three seriously injured and 24 receiving minor injuries) were attributed to defective vision. 2

Comment on 'Glaucoma from topical corticosteroids to the eyelids'.

Draping technique is essential in any form of surgery to obtain and retain a sterile field. 1 The fact that drapes can move is a reflection of the tension on the drapes between two points on the skin where the drapes may be lifted off. This is particularly relevant with intraocular surgery. Ophthalmic draping techniques are underemphasized. Nevertheless, for use in ocular plastic surgery we described a draping technique that allowed the patient’s head drape to sit comfortably without moving down into the operative field or up into the hairline. 2

Correspondence. Effective draping for cataract surgery by using a relieving incision in the operative drape

Draping technique is essential in any form of surgery to obtain and retain a sterile field. 1 The fact that drapes can move is a reflection of the tension on the drapes between two points on the skin where the drapes may be lifted off. This is particularly relevant with intraocular surgery. Ophthalmic draping techniques are underemphasized. Nevertheless, for use in ocular plastic surgery we described a draping technique that allowed the patient’s head drape to sit comfortably without moving down into the operative field or up into the hairline. 2

Response to ‘Sodium bicarbonate in the treatment of blepharitis’

2. Tranos PG, Wickremasinghe SS, Stangos NTT, Topouzis F, Tsinopoulos I, Pavesio CE. Macular edema. Surv Ophthalmol 2004; 49 : 470–90. 3. Okhravi N, Lightman S. Cystoid macular edema in uveitis. Ocul Immunol Inflamm 2003; 1 : 29–38. 4. Williamson J, Jasani MK. Examination for posterior subcapsular cataracts in patients treated with topical steroids. Br J Ophthalmol 1967; 51 : 554–6. 5. Okada AA, Wakabayashi T, Morimura Y, Kawahara S, Kojima E, Asano Y, Hida T. Trans-Tenon’s retrobulbar triamcinolone infusion for the treatment of uveitis. Br J Ophthalmol 2003; 87 : 968–71. Efficacy of periocular corticosteroid injections in the management of posterior uveitis