N. Harizman

Detection of glaucoma using operator-dependent versus operator-independent classification in the Heidelberg retinal tomograph-III

Objective: To compare the abilities of a new Glaucoma Probability Scoring (GPS) system and Moorfields regression analysis (MRA) to differentiate between glaucomatous and normal eyes using Heidelberg retinal tomograph (HRT)-III software and race-specific databases. Methods: In this prospective study, one eye (refractive error ⩽5 D) each of consecutive normal patients and those with glaucoma was enrolled. All patients underwent a full eye examination, standard achromatic perimetry (Swedish Interactive Threshold Algorithm-standard automated perimetry (SITA-SAP), program 24-2) and confocal scanning laser ophthalmoscopy (HRT-II) within 1 month. Normal patients had two normal visual fields in both eyes (pattern standard deviation (PSD) >5% and Glaucoma Hemifield Test within 97% normal limits) and a normal clinical examination. Glaucoma was defined on the basis of SITA-SAP visual field loss (PSD<5% or Glaucoma Hemifield Test outside normal limits) on two consecutive visual fields. HRT-II examinations were exported to the HRT-III software (V.3.0), which uses an enlarged race-specific database, consisting of 733 eyes of white people and 215 eyes of black people. Race-adjusted MRA for the most abnormal sector (operator-dependent contour line placement) was compared with the global race-adjusted GPS (operator independent). MRA sectors outside the 99.9% confidence interval limits (outside normal limits) and GPS ⩾0.64 were considered abnormal. Results: 136 normal patients (72 black and 64 white patients) and 84 patients with glaucoma (52 black and 32 white patients) were enrolled (mean age 50.4 (SD 14.4) years). The average visual field mean deviation was −0.4 (SD 1.1) db for the normal group and −7.3 (SD 6.7) db for the glaucoma group (p<0.001). Mean GPS values were 0.21 (SD 0.23) and 0.73 (SD 0.27) for normal and glaucomatous eyes, respectively (p<0.001). Sensitivity and specificity values were 77.1% and 90.3% for GPS, and 71.4% and 91.9% for MRA, respectively. Conclusions: In this cohort, GPS software sensitivity and specificity values are similar to those of MRA, which requires placement of an operator-dependent contour line. The development of software to detect glaucoma without a contour line is critical to improving the potential use of HRT as a tool for glaucoma detection and screening.

Axial length and optic disc size in normal eyes

Aim: To investigate the relationship between optic disc area and axial length in normal eyes of white and black people. Methods: Consecutive eligible normal subjects were enrolled. Ocular biometry was obtained using A-scan ultrasonography, and reliable images of the optic disc were obtained using a confocal scanning laser ophthalmoscope. The relationship between optic disc area and axial length was assessed using univariate and multivariate models. Results: 281 eyes of 281 subjects were enrolled. Black subjects (n = 157) had significantly larger discs (mean (SD) disc area, 2.12 (0.5) mm2) than white subjects (n = 124; 1.97 (0.6) mm2; t test, p = 0.02). Optic disc area increased with axial length (Pearson’s correlation coefficient, r = 0.13, p<0.035) for the entire study population. Multivariate regression models including race, disc area and axial length showed that a significant but weak linear relationship exists between axial length and disc area (partial correlation coefficient 0.14; p<0.024), and with race and disc area (partial correlation coefficient 0.19; p<0.017) when adjusted for the effects of other terms in the model. Conclusion: Increased disc area is associated with longer axial length measurements and African ancestry. This may have implications for pathophysiology and risk assessment of glaucoma.

Structural and functional assessment of the macular region in patients with glaucoma

Purpose: To investigate the correlation of a structural measure of the macular area (optical coherence tomography (OCT)) with two functional measures (10-2 Humphrey visual field (HVF) and multifocal visual evoked potential (mfVEP)) of macular function. Methods: 55 eyes with open-angle glaucoma were enrolled. The 10-2 HVF was defined as abnormal if clusters of ⩾3 points with p<5%, one of which had p<1%, were present. The mfVEP was abnormal if probability plots had ⩾2 adjacent points with p<1%, or ⩾3 adjacent points with p<5% and at least one of these points with p<1%. Two criteria were used for the macular OCT: (I) ⩾2 sectors with p<5% or 1 sector with p<1% and (II) 1 sector with p<5%. Results: 54 of the 55 eyes showed an abnormal 10-2 HVF and 50 had central mfVEP defects. The two OCT criteria resulted in sensitivities of 85% and 91%. When both functional tests showed a defect (in 49 eyes), the OCT was abnormal in 45. For the OCT the outer and inner inferior regions were the most likely to be abnormal, and both functional techniques were most abnormal in the superior hemifield. Conclusions: Good agreement exists between macular thickness and functional defects in patients with glaucoma. Study of the macular region may provide a quantitative measure for disease staging and monitoring.

Retinal nerve fibre thickness measured with optical coherence tomography accurately detects confirmed glaucomatous damage

Aim: To assess the accuracy of optical coherence tomography (OCT) in detecting damage to a hemifield, patients with hemifield defects confirmed on both static automated perimetry (SAP) and multifocal visual evoked potentials (mfVEP) were studied. Methods: Eyes of 40 patients with concomitant SAP and mfVEP glaucomatous loss and 25 controls underwent OCT retinal nerve fibre layer (RNFL), mfVEP and 24-2 SAP tests. For the mfVEP and 24-2 SAP, a hemifield was defined as abnormal based upon cluster criteria. On OCT, a hemifield was considered abnormal if one of the five clock hour sectors (3 and 9 o’clock excluded) was at <1% (red) or two were at <5% (yellow). Results: Seventy seven (43%) of the hemifields were abnormal on both mfVEP and SAP tests. The OCT was abnormal for 73 (95%) of these. Only 1 (1%) of the 100 hemifields of the controls was abnormal on OCT. Sensitivity/specificity (one eye per person) was 95/98%. Conclusions: The OCT RNFL test accurately detects abnormal hemifields confirmed on both subjective and objective functional tests. Identifying abnormal hemifields with a criterion of 1 red (1%) or 2 yellow (5%) clock hours may prove useful in clinical practice.

The Use of Postoperative Slit-Lamp Optical Coherence Tomography to Predict Primary Failure in Descemet Stripping Automated Endothelial Keratoplasty

PURPOSE To determine if central donor lenticle thickness as measured by slit-lamp optical coherence tomography (SL OCT; Heidelberg Engineering, Heidelberg, Germany) is predictive of primary donor failure in patients undergoing Descemet stripping automated endothelial keratoplasty (DSAEK). DESIGN Retrospective cross-sectional study. METHODS Eighty-four patients who underwent DSAEK surgery by 2 surgeons (D.C.R. and J.A.S.) were enrolled. At each postoperative visit (postoperative day 1, week 1, month 1, and month 2), an SL OCT scan was obtained. Statistical differences in SL OCT measurements of successful and failed DSAEK procedures were measured using the Student t test. A successful DSAEK surgery was defined as having an anatomically attached, clear recipient corneal stroma and donor lenticle compatible with good vision 2 months after surgery. A failed DSAEK surgery was defined as an attached donor lenticle with SL evidence of corneal edema and thickening visible at 2 months or more. RESULTS Ninety-three eyes of 84 consecutive patients who underwent DSAEK surgery also underwent postoperative SL OCT. After 2 months of follow-up, 82 (88%) procedures were successful and 11 (12%) procedures were failures. The average donor lenticle thickness in successful DSAEK eyes was 314 +/- 128 microm on postoperative day 1 as compared with failed DSAEK eyes, which averaged 532 +/- 259 microm (P = .0013). This was independent regardless of whether the lenticle was attached on the first postoperative visit. Seventy-nine (98%) successful DSAEK eyes had a lenticle thickness of < or = 350 microm at the 1-week visit. All of the failed DSAEK eyes (11 eyes) had a lenticle thickness > or = 350 microm at the 1-week postoperative visit. Statistically significant differences in SL OCT thickness measurements were seen between successful and failed DSAEK cases at all examinations after postoperative week 1. CONCLUSIONS Corneal thickness measurements made with SL OCT are an important predictor of DSAEK failure in both attached and detached lenticles within the first week of surgery. DSAEK lenticle thickness of 350 microm or less at 1 week had a predictability of success of more than 98%.

Correlation of Tono-Pen and Pneumatonometer Measurements from Four Scleral Quadrants with Intraocular Pressure Measurements from the Cornea

Objective: To assess whether Tono-Pen and pneumatonometer measurements obtained from the sclera correlate to intraocular pressure measurements obtained from the cornea. Methods: This is a prospective, cross-sectional study, conducted at the New York Eye and Ear Infirmary of Mount Sinai. Patients were randomized to have their left or right eye included in the study. Exclusion criteria included prior intraocular surgery (except uncomplicated cataract extraction), uveitis, corneal or scleral thinning, central corneal thickness 575 μm, and hyperopia greater than +2 diopters or myopia greater than -4 diopters. Goldmann applanation tonometry, Tono-Pen and pneumatonometer measurements were obtained from the cornea. Tono-Pen and pneumatonometer measurements were obtained from the sclera in the superonasal, superotemporal, inferonasal, and inferotemporal quadrants. Product moment correlation and linear regression were used to examine correlations between the measurements. Results: 50 eyes of 50 patients were enrolled. The scleral intraocular pressure measurements (S-IOP) differed significantly from the corneal intraocular pressure (C-IOP) readings. Moderate correlation was found between the pneumatonometer readings from the superotemporal (r=0.64, P 30 mmHg and an inferotemporal pneumatonometer S-IOP of >39 mmHg was 92.3% (95% Confidence Interval [CI] 63.9%, 98.7%) sensitive and 94.6% (CI 81.8%, 99.2%) specific for a C-IOP ≥ 20 mmHg with positive likelihood ratio of 17.1 (CI 4.4-66.3). Conclusion: S-IOP measurements, especially from the superotemporal and inferotemporal quadrants, can provide useful information about intraocular pressure in eyes in which accurate C-IOP measurements cannot be obtained.