A pinboard by
Nevin El-Nimri

PhD student , University of California, Berkeley


I aim to investigate the mechanisms underlying the increased risk of glaucoma in myopic patients

Title: The Interrelationship between Axial Length, Intraocular Pressure and Optic-Disc Dimensions and Influence of Myopia in young Guinea Pigs

Purpose: To evaluate the interrelationship between axial length (AL), intraocular pressure (IOP) and optic disc (OD) dimensions in myopic and normal eyes of young guinea pigs. Methods: Five guinea pigs underwent monocular form deprivation (FD; white plastic diffusers) to induce myopic changes from 14-days of age for 12-weeks. Ocular axial dimensions (high frequency A-scan ultrasonography) and IOP measurements (iCare tonometer) were monitored weekly and ODs imaged monthly (Bioptigen SD-OCT). Maximum horizontal dimensions (ODDs), were measured using a custom MATLAB program from cross-sectional, 200×200 pixel images, the termination of Bruch's membrane being used to define the OD boundary. Results: As expected, FD eyes elongated faster than their fellows over the treatment period while IOP increases were similar in both eyes. At week 12, mean interocular differences in AL and IOP were 0.16 ±0.08 mm (p=0.05) and -1.47 ± 2.2 mmHg (p=0.16) resp. Optic disc diameters also appeared to increase with AL for myopic eyes (R2 = 0.8651; p= 0.069), but ODDs were not correlated with ALs for fellow eyes (R2 = 0.73, p= 0.14). Conclusion: Optic discs tended to increase in size with increasing AL in the myopic eyes of young guinea pigs, paralleling the trends reported for human myopia. Although IOPs were similar in their two eyes, the scleras of the larger myopic eyes would have experienced more mechanical stress. Whether the lamina cribrosa ultrastructure is also altered with myopia in this guinea pig model is the subject of on-going investigations.


The Relationship between the 24-hour Fluctuations in Schlemm's Canal and Intraocular Pressure: An Observational Study using High-Frequency Ultrasound Biomicroscopy.

Abstract: To assess 24-hour fluctuations in Schlemm's canal (SC) parameters (cross-sectional area, perimeter) and intraocular pressure (IOP) and the relationship between these fluctuations in healthy individuals.SC and IOP were examined in 29 participants at 2:30, 5:30, 11:30, 17:30, and 23:30 within one day. The superior, inferior, nasal, and temporal SC quadrants were evaluated using 80-MHz ultrasound biomicroscopy.SC parameters and IOP fluctuated significantly within 24 hours (all P < 0.05). After age, gender, axial length, and central corneal thickness were adjusted, compared with the baseline (23:30) value, the change in SC cross-sectional area was negatively associated with the change in IOP at 2:30, 5:30, 11:30, and 17:30 (β = -0.072[-0.094, -0.049], -0.070[-0.102, -0.038], -0.046[-0.079, -0.013], and -0.033[-0.062, -0.004], respectively; P < 0.001, < 0.001, = 0.009, and = 0.028, respectively). The nasal (175.6 ± 36.0 pixels) and inferior (174.8 ± 36.0 pixels) SC cross-sectional areas were significantly larger than the superior area (156.2 ± 27.1 pixels) (P = 0.018 and 0.048, respectively) at 23:30. The observable SC proportion did not change among the quadrants or measurement time points (all P > 0.05).SC cross-sectional area fluctuated throughout the day and was negatively associated with changes in IOP.

Pub.: 18 Jun '17, Pinned: 30 Jun '17

Risk factors for Rapid Glaucoma Disease Progression.

Abstract: To determine the intraocular and systemic risk factor differences between a cohort of rapid glaucoma disease progressors and non-rapid disease progressors.Retrospective case control study Methods SETTING: Five private ophthalmology clinics STUDY POPULATION: 48 rapidly progressing eyes (progression ≥1dB mean deviation (MD)/year) and 486 non-rapidly progressing eyes (progression <1dB MD/year). Patients were eligible if they had a diagnosis of glaucoma from their ophthalmologist and if they had greater than or equal to 5 Humphrey visual fields (24-2) conducted. Patients were excluded if their sequential visual fields showed an improvement in MD or if they had greater than 5dB MD variation in between visits. Patients with obvious neurological fields were excluded.Clinical and demographic data (age, gender, CCT, IOP, refraction, medications) as well as medical, surgical and ocular histories were collected.Risk factor differences between the cohorts were measured using the independent t-test, Wald chi-squared and binomial regression analysis.Rapid progressors were older, had significantly lower CCT and baseline IOPs and were more likely to have pseudoexfoliation, disc haemorrhages, ocular medication changes and IOP lowering surgery. They also had significantly higher rates of cardiovascular disease and hypotension. Subjects with cardiovascular disease were 2.33 times more likely to develop rapidly progressive glaucoma disease despite significantly lower mean and baseline IOPs.Cardiovascular disease is an important risk factor for rapid glaucoma disease progression irrespective of IOP control.

Pub.: 19 Jun '17, Pinned: 30 Jun '17

Optic Nerve Tilt, Crescent, Ovality, and Torsion in a Multi-Ethnic Cohort of Young Adults With and Without Myopia.

Abstract: The purpose of this article is to evaluate optic nerve head (ONH) characteristics in an ethnically diverse cohort of young U.S. adults.In this study, 409 myopes and 206 nonmyopes (median age 22 years) completed measures including biometry and spectral domain optical coherence tomography from enface (ovality and torsion) and cross-sectional (tilt and crescent width) scans. Associated factors were evaluated using multivariable models.In myopic versus nonmyopic right eyes, median tilt (6.0° vs. 2.4°; P < 0.0001) and frequency of crescents (49% vs. 10%; P < 0.0001) were higher in myopes. Right eyes with crescents had higher median tilts (8.8° [myopic], 9.0° [nonmyopic]) than those without crescent (2.5° [myopic], 2.1° [nonmyopic]), irrespective of refractive group (both P < 0.0001). Torsion was similar between groups, with a slight difference in ovality (0.89 vs. 0.91; P < 0.03). Data in the left eyes were similar, and modeling was done only for the right myopic eyes. Multivariable models showed that an increased tilt was associated with ethnicity (P < 0.001), the presence of crescent (P < 0.001), and smaller ONH diameter (P < 0.0031), with interactions between ethnicity and crescent (P = 0.002). Specifically, ONH tilt was significantly higher in Asian eyes without crescent (P < 0.0001 for all comparisons), and crescent width was associated with increased tilt in non-Asian eyes (P < 0.02). Crescent width was associated with ethnicity (greatest in Asians) and disc tilt. Interactions were observed between tilt and ethnicity, whereby tilt had a greater effect on crescent width in non-Asian eyes, and crescent width was associated with increased tilt in non-Asian eyes.The data clarify the influence of ethnicity and myopia on ONH characteristics in young adults and may inform future studies of biomechanical properties or of retinal pathology of the myopic eye.

Pub.: 28 Jun '17, Pinned: 30 Jun '17

Follow-up of the retinal nerve fiber layer thickness of diabetic patients type 2, as a predisposing factor for glaucoma compared to normal subjects.

Abstract: To evaluate and follow-up the retinal nerve fiber layer (RNFL) thickness in patients with diabetes mellitus type 2 compared to a group of healthy individuals with similar demographic characteristics.This is a prospective, noninvasive, observational case series study. For the purposes of the study, 27 eyes of diabetic patients without diabetic retinopathy, 24 eyes of patients with mild retinopathy, and 25 normal age-matched subjects (control group [CG]) were examined. All participants underwent complete ophthalmological examination and imaging with GDx variable corneal compensation scanning laser polarimetry. Follow-up was 2 years for all three groups.The mean inferior average was statistically significantly lower in both diabetic groups compared to CG at baseline examination and during follow-up. The nerve fiber indicator (NFI) was higher in both diabetic groups compared to CG, both at baseline examination and during follow-up. The NFI was 21.7±11.9 and 22.0±11.8 for the diabetic group without retinopathy, 20.8±9.6 and 21.9±9.8 for the group with mild retinopathy, and 15.3±5.4 and 15.9±5.5 for the normal subjects, at baseline and 24 months, respectively. There was no statistically significant reduction of the RNFL thickness in all three groups compared to baseline examination.This is the first long-term study documenting the RNFL thickness in diabetic patients in comparison with normal controls. Although the lower RNFL was found thinner in diabetics, the 2-year follow-up showed no significant reduction of RNFL thickness in all groups, indicating that RNFL damage may occur early in diabetic patients.

Pub.: 28 Jun '17, Pinned: 30 Jun '17