The accuracy of continued clinical use of goldmann applanation tonometers with known calibration errors.

OBJECTIVES: With normal clinical use, Goldmann applanation tonometers frequently develop calibration errors. Only the manufacturer can perform recalibration. This study aimed to assess whether intraocular pressure (IOP) measured by Goldmann applanation tonometers with known small calibration errors could be adjusted to reflect true IOP to allow continued clinical use. DESIGN: Evaluation of diagnostic test. PARTICIPANTS: Patients under regular review who had undergone previous applanation tonometry. METHODS: Patients with a range of IOPs underwent IOP measurement using a gold standard 0-error tonometer and tonometers with known calibration errors in a randomized blind fashion. The calibration errors of the tonometers ranged 0 to +5 mmHg. MAIN OUTCOME MEASURES: Intraocular pressure. RESULTS: For the first part of the study, 125 eyes of 125 patients with a mean IOP of 18.5 mmHg (range, 8-43 mmHg) were tested. Mean IOP measured by the tonometer with an error of +1 mmHg was +1.0 (95% confidence interval [CI], 0.3-1.7 mmHg; P = 0.0076, compared with gold standard 0-error), with the +2 mmHg error was +1.2 (95% CI, 0.8-1.7 mmHg; P<0.0001), with the +3 mmHg error was +1.6 (95% CI, 1.2-1.9 mmHg; P<0.0001), with the +4 mmHg error was +3.6 (95% CI, 2.9-4.2 mmHg; P<0.0001), and with the +5 mmHg error was +3.3 (95% CI, 2.9-3.8 mmHg; P<0.0001). In the second part of the study, IOP measured by each of the tonometers with +2 mmHg error was +0.6 mmHg (95% CI, 0.1-1.1 mmHg; P = 0.0241), +1.5 mmHg (95% CI, 1.0-2.0 mmHg; P<0.0001), and +1.5 mmHg (95% CI, 1.9-2.1 mmHg; P<0.0001). CONCLUSIONS: There is a relationship between calibration error and clinical error in IOP measured, but it is not a one-to-one relationship. The error overestimates IOP and is consistent over a clinical range of IOPs. In certain circumstances where resources are limited, it may be clinically acceptable to use tonometers with calibration errors of less than +3 mmHg, because they do not overestimate IOP by more than 2 mmHg. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Cataract surgery in patients with late-onset retinal degeneration.

PURPOSE: To review the outcomes in a series of patients with long anterior lens zonular fibers associated with late-onset retinal degeneration who had phacoemulsification cataract surgery. SETTING: Newcastle Eye Centre, Newcastle upon Tyne, United Kingdom. DESIGN: Retrospective case series. METHODS: Inclusion criteria were patients with genetically confirmed late-onset retinal degeneration requiring cataract surgery. Perioperative data relating to surgery were collected. In addition, the corrected distance visual acuity (CDVA) and retinal imaging data were recorded. Selected lens capsules were examined using immunohistochemistry or scanning electron microscopy (SEM). RESULTS: Eleven eyes of 7 patients were included. The long anterior lens zonular fibers made capsulorhexis challenging; however, it was completed safely in all cases. There were no intraoperative or postoperative issues with lens stability. The CDVA improved postoperatively in those cases with intact foveal photoreceptors and retinal pigment epithelium. Over the longer term, the CDVA slowly declined because of progressive atrophy of the macula. Most patients noticed a subjective improvement in vision, even those with advanced disease at baseline. Immunohistochemistry showed that the C1QTNF5 protein was expressed within the lens capsule epithelial cells, although SEM of the long anterior lens zonular fibers showed them to be smaller in diameter than normal anterior lens zonular fibers and to be composed of a helix of fibers. CONCLUSIONS: In this small series of patients with late-onset retinal degeneration, cataract surgery was successfully performed without long-term complications involving intraocular lens stability. The objective improvement in CDVA seemed to be limited to patients with good foveal photoreceptor architecture.

Frequency of goldmann applanation tonometer calibration error checks.

PURPOSE: To investigate how quickly Goldmann applanation tonometers used in clinical practice develop calibration errors, and to determine the frequency of checks required to detect these errors. MATERIALS AND METHODS: Prospective check of the calibration error of all Haag-Streit Goldmann applanation tonometers in the department at month zero, month one, and month four. The tonometers were checked according to the Haag-Streit method using a standard calibration check weight bar by two independent observers. Calibration errors were classed as +/-0.5 to 2.5 mm Hg, +/-3 to 4 mm Hg, or >+/-4 mm Hg. Tonometers with a calibration error greater than +/-2.5 mm Hg were returned to the manufacturer for re-calibration. RESULTS: At month zero 2 of 34 (5.9%), at month one 3 of 29 (10.3%), and at month four 0 of 33 (0.0%) tonometers fell within the manufacturer's recommended calibration range of +/-0.5 mm Hg. A total of 14 of 34 (41.2%) tonometers at month zero, 10 of 29 (34.5%) tonometers at month one, and 17 of 33 (51.5%) tonometers at month four were identified to have calibration errors greater than +/-2.5 mm Hg. CONCLUSIONS: Goldmann applanation tonometers are not as accurate as the manufacturer's recommended calibration error tolerance of +/-0.5 mm Hg would suggest. Calibration error of less than +/-2.5 mm Hg is clinically acceptable. Calibration error checks should be carried out once monthly and tonometers with calibration error greater than +/-2.5 mm Hg returned to the manufacturer for re-calibration. Additional checks should be made if tonometers suffer specific damage. Ideally individual ophthalmologists should check calibration before each session.

Efficacy of transscleral diode laser cyclophotocoagulation in patients with good visual acuity.

PURPOSE: To study the effect on central vision of transscleral diode laser cyclophotocoagulation (TSDLC) for the reduction of intraocular pressure (IOP) in patients with visual acuity (VA) better than 6/18. METHODS: Retrospective chart review was conducted of patients undergoing cyclophotocoagulation between 2000 and 2008. Patients who underwent TSDLC with VA of 6/18 or better and at least 24 months follow-up were included. Primary outcome was decrease of 2 or more lines at 24 months. Secondary outcome was IOP control with or without treatment. RESULTS: A total of 46 eyes of 44 patients were included with VA ranging from 6/18 to 6/5 (median VA 6/12). Mean IOP was 24 mm Hg (range 12-35). A mean of 1.3 treatments were given per eye, with 12 eyes (26%) requiring retreatment. At 24 months, the median VA was 6/18 (range light perception-6/5). Eighteen eyes (39.1%) retained the same VA, 35 eyes (76.1%) retained VA of 6/18 or better, in 7 eyes (19.4%) VA was <6/60. Loss of ≥2 lines was recorded in 11 eyes (23.9%), and loss of 1 line in 13 eyes (28.3%). Mean IOP at 24 months was 17.2 mm Hg (range 12-28). Thirty-nine (84.8%) patients had IOP ≤21 mm Hg. CONCLUSIONS: This study suggests a role of TSDLC as an effective, safe, and rapid method of treatment in patients with good vision over a 24-month period. The loss of VA in some patients is similar to previously reported studies in patients having cyclodiode, trabeculectomy, or tube surgery.