S A Vernon

Peripapillary retinal nerve fibre layer thickness in highly myopic Caucasians as measured by Stratus optical coherence tomography

Aims: To assess peripapillary retinal nerve fibre layer (RNFL) thickness distribution in a group of non-glaucomatous Caucasian subjects with a high degree of myopia and to evaluate the relationship between RNFL thickness, both global and sectoral, and other variables including axial length and optic disc size. Method: 31 eyes of 31 healthy Caucasian subjects with spherical equivalent ⩾−6 dioptres (D) were recruited from a community optometric practice. RNFL thickness was measured using the Stratus optical coherence tomography (OCT) Fast RNFL 3.4 mm scan protocol. Optic disc area was measured using the Heidelberg Retinal Tomograph II and axial length using the IOL Master. Associations between RNFL measurements and axial length, spherical equivalent and optic disc area were evaluated by linear regression analysis. Results: The sample had a mean age of 48.1 years, mean spherical equivalent of −7.7 D, and mean axial length of 26.5 mm. The mean (SD) RNFL thickness was 81.4 (13.7) µm. In comparison with the Status OCT normative database, the distribution of RNFL thickness was substantially lower in the study group. The greatest disparity was around 7 clock hours centred on the nasal meridian in which 26/31 (83.9%) had one or more clock hours in which RNFL thickness was below normal at the 5% probability level in comparison with the Stratus normative database. No statistically significant associations between mean RNFL thickness and age (p = 0.12), gender (p = 0.76), spherical equivalent (p = 0.80), cup:disc area ratio (p = 0.88), optic disc area (p = 0.14) or axial length (p = 0.18) were identified in this group. However, RNFL thickness from vertical quadrants and in particular the superior sector correlated strongly with axial length, age and optic disc area. Conclusions: The Stratus OCT normative database may be misleading in highly myopic eyes from Caucasians resulting in a substantial proportion of false positive errors. Particular caution is needed when the RNFL appears to be below the normative database normal limit at the upper or lower poles or on the nasal side of the disc. Stratified normal databases are required for accurate diagnosis of conditions resulting in nerve fibre loss such as chronic glaucoma.

Screening for glaucoma in the community by non-ophthalmologically trained staff using semi automated equipment

Eighty-nine and a half per cent of the population of a general practice over the age of 49 years were screened for glaucoma and high risk ocular hypertension requiring treatment. Screening took place using semi-automated intraocular pressure and visual field equipment operated by non-ophthalmologically trained staff. An experienced ophthalmologist examined all patients in a single blind manner to reduce false negatives to a minimum. Patients suspected of requiring treatment on the grounds of raised intraocular pressure, abnormal visual fields or suspicious optic discs were subsequently examined in a hospital clinic. Treatment criteria, as commonly practiced, were carefully defined and the sensitivities and specificities of the methods of screening used were calculated. One and three tenths per cent of the practice population were known to be receiving treatment prior to the study and a further 1.4% were found to require treatment after screening.The sensitivity and specificity of the non-contact tonometer were 91.7% and 95.6% respectively with a predictive power of 22.5% for a positive result. The mean time taken to perform the test in both eyes was two minutes.Seventy per cent of the patients with pressures over 22 mmHg in both eyes on screening were found to require treatment. The routine use of the field screener did not increase either the sensitivity or specificity of the screening process but its use in cases with raised intraocular pressure is advised to indicate the degree of urgency of the referral.An algorithm based on the results of the study is suggested when planning the use of semi-automated equipment to screen for ocular disease related to raised intraocular pressure.

Diode laser cycloablation in adult glaucoma: long-term results of a standard protocol and review of current literature

Background:  To study the long‐term efficacy and safety of diode laser cycloablation under a standard protocol in refractory glaucoma.

Passing the DVLC field regulations following bilateral pan-retinal photocoagulation in diabetics

Twenty-one diabetics who had had bilateral retinal pan-photocoagulation preserving a visual acuity sufficient to pass the Driver and Vehicle Licensing Centre (DVLC) requirements were assessed with regard to their ability to satisfy the DVLC visual field requirements. Of the 19 patients treated with the laser alone, 17 met the requirements for a licence to drive a private vehicle.The use of the Xenon photocoagulator and large total burn area following laser was found to be associated with an increased risk of DVLC field test failure.Adequate PRP with 200 micron burns appeared to induce neovascular regression and be compatible with passing the DVLC field regulations in many patients.Panphotocoagulation of patients with early proliferative retinopathy using 200 micron burns does not appear to jeopardise a driving licence.Guidelines for laser treatment in diabetic retinopathy aimed at preserving the driving field are presented.

Incidence of ocular motility problems following scleral buckling surgery

The incidence and severity of extraocular muscle imbalance after conventional scleral buckling surgery was determined for 70 eyes of 68 patients with primary rheg-matogenous retinal detachment. Fifty-eight eyes had circumferential silicone explants, 10 eyes had radial sponges and 2 had both. Sixty-five per cent of eyes showed some restriction of ocular motility and 72% of patients had diplopia within their field of binocular single vision (BSV). The more extraocular muscles the explant was placed under, the more directions of gaze were likely to be restricted (p = 0.032). In 84% of eyes the restrictions could be related to the position of the explant. In 87% of patients their diplopia could also be related to the position of the explant. A second retinal detachment operation is more likely to cause restricted motility and more likely to cause diplopia within the expected field of BSV (p = 0.0297).

Reproducibility with the Keeler Pulsair 2000 non-contact tonometer.

AIMS--The IOP variation on repeated testing with the recently introduced Keeler Pulsair 2000 instrument was investigated. METHODS--One hundred normal individuals (50 male and 50 female) new to the instrument had three sets of IOP recordings within a 15 minute time period. RESULTS--The mean of the first set of IOPs from both right and left eyes was significantly higher than those from subsequent sets (p < 0.0001 for right eyes and p = 0.01 and < 0.0002 for left eyes). This tendency increased significantly with increasing IOP. Second and third IOP sets were, however, similar indicating stabilisation of IOP measurements. The coefficient of repeatability of the instrument between second and third sets was 4.2 mm Hg for right eyes and 3.6 mm Hg for left eyes. CONCLUSION--The Pulsair 2000 passes the British standard for reproducibility of a standard test method.

Longitudinal glaucoma screening for siblings of patients with primary open angle glaucoma: the Nottingham Family Glaucoma Screening Study

Aims: To assess the prevalence and cumulative incidence of open angle glaucoma (OAG) in a cohort group of siblings of OAG probands. Methods: Between 1994 and 2003, a group of siblings of OAG probands underwent both initial and follow up standardised ophthalmic examinations. Siblings were classified as “definite glaucoma” (primary OAG (POAG) and normal tension glaucoma (NTG)), “glaucoma suspects” (NTG suspects or ocular hypertension (OHT)), and normal. The prevalence and cumulative incidence of OAG over the follow up interval were calculated. Results: At the initial study, 271 siblings (mean age 63.6 years; female to male ratio 1.2) from 156 probands were examined. 32 (11.8%) were classified as definite glaucoma and 15 (5.5%) as suspects. In the follow up study, 157 of the 224 “normal” siblings from the initial study were examined (mean interval from initial study 7.0 (SD 1.0) years). 11 (7%) were classified as definite glaucoma and 30 (19.1%) as suspects. There were significant trends of increasing prevalence and incidence of OAG with age and a lifetime risk estimated at approximately 20% by age 70. Conclusion: Siblings of glaucoma patients have an increased risk of developing glaucoma and the risk increases with age. An effective and repeated screening programme should be considered for this high risk group.

Intraocular pressure control following microtrabeculectomy.

The use of the Kelly Descemets membrane punch enables the glaucoma surgeon to perform smaller trabeculectomies. The outcome of ‘microtrabeculectomy’ employing a 2 × 2 mm superficial scleral flap and a 0.75 mm internal osteum was evaluated on 65 eyes of 50 patients (mean age 70 years). The operation site was nasal in left eyes and temporal in right eyes. In the 56 eyes where 5-fluorouracil was not used, the mean intraocular pressure (IOP) on diagnosis was 33.4 mmHg, the mean pre-operative IOP being 25.1 mmHg. After a mean follow-up of 13.4 months (minimum 3 months) following surgery, the mean IOP was 13.4 mmHg with 88% of eyes controlled at <21 mmHg on no medications. Nasally sited microtrabeculectomies resulted in lower IOPs than temporally sited procedures (11.8 vs 14.9 mmHg, p = 0.003) at last follow-up visit.

INTRA-EYE PRESSURE RANGE AND PULSE PROFILES IN NORMALS WITH THE PULSAIR NON-CONTACT TONOMETER

The difference in intraocular pressure (IOP) between the highest and lowest measurements on an eye with non-contact tonometry (the range) has been reported to be less than 4 mmHg in most normals. The range of IOP to be expected with the Keeler Pulsair in normals over the age of 50 years was determined by analysing the results of IOP recordings on 741 normal individuals. Between 56% and 62% of eyes recorded a range >4 mmHg and between 4% and 8% a range >10 mmHg when four pulses per eye were used. Population pulse profile analysis indicated that this was not due to an erroneously high first pulse in a set of four, and that IOP asymmetry previously reported when screening females is due to a generalised tendency for IOPs in right eyes to measure higher than those recorded in the left. The occurrence of a range of IOP recordings up to 10 mmHg in an eye is relatively common with the Pulsair and individuals undergoing glaucoma screening with this instrument should not be referred purely on the basis of a large IOP range.

Trabeculectomy in diabetic patients with glaucoma

Forty-one eyes of 41 patients with diabetes mellitus who underwent trabeculectomy over a 4-year period were compared with 41 age- and sex-matched controls, who were also matched for date of operation and surgical technique. The two groups were comparable for glaucoma diagnoses, duration of glaucoma before admission and number of ocular hypotensive medications. The intraocular pressures at diagnosis and on admission were similar. Post-operative complications were equally frequent. The mean intraocular pressure at 6 months was significantly lower in the control group, and fewer diabetic patients achieved either an intraocular pressure <21 mmHg or successful drainage (defined as an intraocular pressure <21 mmHg on no treatment) at 6 months and at the final visit, after similar periods of follow-up. Trabeculectomy in diabetic patients with pre-existing retinopathy resulted in a significantly higher intraocular pressure at 6 months than when no retinopathy was present.