Anurag Shrivastava

The effect of cataract extraction on intraocular pressure.

Purpose of review To review the current ophthalmic literature regarding the impact of modern cataract surgery on intraocular pressure (IOP). Recent findings Many articles in the literature demonstrate a modest, long-lasting decrease in IOP following phacoemulsification and posterior chamber intraocular lens implantation in patients with primary open-angle glaucoma and ocular hypertension. The mechanism of this average pressure-lowering effect has yet to be elucidated. The IOP reductions obtained in patients with angle closure glaucoma are often more pronounced than those seen in patients with open angles. Patients with higher levels of preoperative IOP obtain greater average reductions in IOP, although this phenomenon may partially be explained by a statistical effect known as regression to the mean. Summary Although it is well recognized that phacoemulsification may result in a modest sustained reduction in IOP, there are several limitations in the studies that have assessed the magnitude of this effect. The implications of such IOP reduction with cataract surgery on the medical and surgical algorithms for care in patients with open-angle glaucoma and coexistent cataract remain unclear. In contrast, the substantial benefits of cataract surgery in patients with acute and chronic angle-closure glaucoma have been well studied and are generally widely accepted. An improved understanding of the pathophysiological mechanisms of IOP lowering after cataract extraction may help us better predict which patients are most likely to benefit from simple cataract extraction, obviating the need for combined cataract and glaucoma surgical procedures in such circumstances.

Intraocular pressure fluctuations: how much do they matter?

Purpose of review To review the current literature with regard to the importance of IOP fluctuation/variation as independent risk factors for glaucoma progression. Recent findings There are conflicting reports in the literature assessing the relative importance of ‘intraocular pressure (IOP) fluctuation’ and ‘mean IOP’ as risk factors for glaucoma progression. There has been a trend toward more studies concluding that IOP fluctuation is an important independent risk factor for such progression but there is considerable variability in the quality of such studies. In particular, assumptions regarding causality have created doubt regarding some conclusions. Recent studies have also suggested that we should not abandon mean IOP as the important predictor of glaucoma progression. It should be noted that several analyses pertaining to this subject have emerged from large prospective randomized clinical trials primarily designed to answer other questions. Summary A review of the literature reveals that there is no conclusive evidence that IOP fluctuation/variation are independent risk factors for glaucoma progression. One should not discount the importance of mean IOP as a predictor of such progression. A major factor limiting all analyses pertaining to this issue is the inability to continuously measure IOP and thus optimally assess mean and variability.

Medical management of glaucoma: Principles and practice

Glaucoma care is more an art than science. The introduction of several new classes of glaucoma medications and the completion of many large randomized clinical trials have not changed this fact. While we now have better choices when initiating glaucoma therapy relative to our predecessors, the principles of glaucoma therapy have not changed much during this period. Debates continue regarding the utility of concepts such as “the monocular therapeutic trial,” “target intraocular pressure (IOP),” and “maximal medical therapy.” Our tools for detecting and following glaucomatous disease have improved but are not precise enough for us to prospectively predict which patients will do better or worse than others. Much attention has been given to disease stage, rate of progression, and compliance with medications but regular patient follow-up, an area that has received little attention, may be among the most important predictors of patient outcomes.

Refractive surgery and the glaucoma patient.

Purpose of review Patients considering corneal refractive surgery undergo extensive preoperative testing, but current protocols may not address the management of glaucoma appropriately. This review outlines the current body of literature on the diagnostic and management challenges that exist in the treatment of glaucoma patients undergoing laser ablative surgery, and makes recommendations to improve current perioperative protocols. Recent findings As permanent structural alterations to the cornea after laser-assisted in-situ keratomileusis surgery make Goldmann applanation tonometry inaccurate, the advent of new diagnostic modalities and recommendations to accurately measure postoperative intraocular pressure (IOP) and subtle damage to the optic nerve have been further analyzed and tested. Summary As IOP is the only modifiable risk factor in the treatment of glaucoma to date, traditional diagnostic and treatment algorithms may not be appropriate for refractive surgery patients. Glaucoma remains a relative contraindication to refractive procedures, but as new diagnostic modalities emerge, our ability to diagnose and manage these patients may improve. More uniform recommendations need to be implemented to improve our long-term management of these patients.

The impact of cataract surgery on glaucoma care

Purpose of review To summarize the effects of cataract surgery on the management of glaucoma, in terms of the effect on both the intraocular pressure (IOP) and postoperative diagnostic as well as therapeutic considerations. Recent findings Recent evidence corroborates prior data demonstrating significant and sustained IOP reduction after cataract extraction, particularly in closed-angle variants of glaucoma, but also in individuals with open-angle glaucoma or ocular hypertension. Performing cataract surgery after trabeculectomy increases the odds of filtration failure with the likelihood of this adverse effect being inversely proportional to the duration between the glaucoma and cataract procedures. Although cataract has a significant effect on the results of visual field testing, the Visual Field Index may be less influenced than other parameters such as the mean and pattern deviation. The accuracy of time-domain ocular coherence tomography and spectral-domain ocular coherence tomography are also negatively impacted by cataract. Summary Considering cataract surgery as an IOP-lowering procedure may be appropriate in select patients. Performing cataract extraction prior to glaucoma surgery has numerous benefits. The sequence of the procedures performed has implications in terms of complications, surgical success, and diagnostics. Reestablishing perimetric and structural baselines with imaging modalities is appropriate after cataract surgery is performed in glaucoma patients.

Axial length does not correlate with degree of visual field loss in myopic chinese individuals with glaucomatous appearing optic nerves

PurposeWe previously described a group of patients of Chinese ancestry who presented with optic nerve appearance and visual field loss suggestive of glaucoma but did not show progression characteristic of this disease for up to 7 years. The purpose of this study was to assess whether axial length is a risk factor for visual field loss in patients presenting with this cluster of findings. Patients and MethodsTwenty patients of Chinese ancestry with characteristics of this previously described condition including myopia, tilted discs, and glaucomatous visual field abnormalities who also had asymmetric visual field loss were enrolled in this study. Patients underwent axial length measurement of both eyes and a fellow eye analysis was performed to determine the relationship between axial length and visual field loss. ResultsTilted discs were found in 30 out of 40 eyes, with cup/disc ratios ranging from 0.5 to 0.9. Myopia >6.00 diopters was also found in 30 out of 40 eyes. In these subjects with disease that was discordant between the 2 eyes, longer axial length was not found to be associated with greater visual field loss (P>0.99, Freeman-Halton extension of the Fisher exact test). No correlation was found between axial length and mean deviation on visual field testing (r=−0.06). ConclusionsWe did not find axial length to be a risk factor for visual field loss in eyes with asymmetric disease in this patient population. These findings suggest that factors other than progressive lengthening of the eye play an important role in the etiology of glaucomatous appearing optic nerve damage and visual field loss in this specific subset of patients.

Effect of partial posterior vitreous detachment on retinal nerve fiber layer thickness as measured by optical coherence tomography

OBJECTIVE To evaluate the effect of partially attached posterior vitreous detachments (pPVDs) at the optic disc on retinal nerve fiber layer (RNFL) thickness as measured by optical coherence tomography. METHODS A retrospective study was conducted using stored Stratus optical coherence tomography III scans of patients with suspected glaucoma from January 2003 to September 2006 at the Montefiore Medical Center, Bronx, New York. All scans were evaluated for vitreous attachments at the disc and were divided into control (without pPVD) and pPVD groups. The RNFL thickness was compared using the fast RNFL protocol. Patients were defined as glaucoma suspects based on clinical findings of either glaucomatous-appearing optic discs or elevated intraocular pressure. All study patients had normal Humphrey visual fields. RESULTS A total of 110 eyes from 110 patients were included; 59 were in the pPVD group and 51 were controls. Partial PVD was found in 40% of the glaucoma suspects. The mean RNFL thickness of eyes with pPVD was significantly broader than that of controls (101.6 microm vs 95.6 microm, respectively; P < .001). The average RNFL thickness of each quadrant was greater in the pPVD group than in the control group, with statistically significant differences in superior and inferior quadrants (P < .001 and P = .001, respectively). CONCLUSIONS More than one-third of this population of glaucoma suspects had a pPVD, indicating that this is a common phenomenon. The results suggest that RNFL thicknesses are greater in patients with pPVD than in controls. This may indicate a limitation of using RNFL thickness as a criterion for evaluating glaucomatous damage in patients with pPVD.

Early Aggressive Intraocular Pressure Lowering, Target Intraocular Pressure, and a Novel Concept for Glaucoma Care

Early diagnosis of glaucomatous optic nerve damage offers the potential for early treatment which may prevent vision loss from this neurodegenerative disease. Even in patients who do not begin early treatment, early diagnosis allows for better monitoring of disease at a stage where the stakes are lower relative to later stages of the disease. For these reasons, early diagnosis of glaucomatous optic nerve disease is desirable and opens the door for appropriately aggressive therapy. The target intraocular pressure (IOP) concept is widely employed by glaucoma practitioners. Although there have been no randomized clinical trials or other high-quality studies showing the benefits of setting a target IOP versus not using this approach, there is ample evidence that lowering IOP slows glaucoma progression and, in general, lower is better, regardless of disease stage and baseline IOP level. We propose an alternative approach to managing glaucoma without the use of the target IOP concept and suggest that this market IOP concept should be compared with the target IOP approach in an appropriately powered comparative clinical trial.

Update on the Medical Treatment of Primary Open-Angle Glaucoma.

AbstractGlaucoma comprises a group of progressive, neurodegenerative disorders characterized by retinal ganglion cell death and nerve fiber layer atrophy. Several randomized controlled trials have consistently demonstrated the efficacy of intraocular pressure lowering to slow or halt the measurable progression of the disease. Medical therapy, in places where it is easily accessible, is often the primary method to lower intraocular pressure. We review the medical options currently available and possible future options currently in development. The 5 contemporary classes of topical agents in use include prostaglandin analogs, beta blockers, carbonic anhydrase inhibitors, alpha agonists, and cholinergics. In addition, several fixed combination agents are commercially available. Agents from each of these classes have unique mechanisms of action, adverse effects, and other characteristics that impact how they are used in clinical practice. Despite the plethora of medical options available, there are limitations to topical ophthalmic therapy such as the high rate of noncompliance and local and systemic adverse effects. Alternate and sustained drug delivery models, such as injectable agents and punctal plug delivery systems, may in the future alleviate some such concerns and lead to increased efficacy of treatment while minimizing adverse effects.

Pupillary Dynamics of Patients on Tamsulosin Exhibiting Intraoperative Floppy Iris Syndrome During Cataract Surgery

Purpose: To examine the pupillary dynamics of patients on tamsulosin who exhibited intraoperative floppy iris syndrome during cataract surgery using the Neuroptics NPi-200 (Irvine, CA), a handheld, digital pupillometer Setting: Patients who underwent cataract surgery at a University-affiliated eye surgery center Design: Prospective cohort study Methods: Pupillary dynamics of patients on tamsulosin and control patients who underwent cataract surgery at an ambulatory surgery center at Montefiore Hospital in the Bronx NY were measured prior to and after dilation for surgery. Measured pupillary dynamics included: resting/maximum pupil diameter (mm), constricted/minimum pupil diameter (mm), constriction latency (ms), constriction velocity (m/s), and dilation velocity (m/s). The operating surgeon, masked to the groups, determined the presence of intraoperative floppy iris syndrome and rated severity based on a grading scale developed from criteria described in the literature. Exclusion criteria included age under 18, concurrent medications known to have autonomic effect, prior ophthalmic laser or incisional surgery, prior diagnosis of optic neuropathy, primary or secondary glaucoma. Two-tailed t-tests were used to compare differences between the two groups. A p-value of <0.05 was considered to be statistically significant. Results: 15 eyes of 15 tamsulosin patients and 22 eyes of 22 control patients were included. Mean pre-dilation minimum aperture (mm) for tamsulosin patients was significantly smaller than that of control patients (2.24 ± 0.40 vs. 2.64 ± 0.73; p=0.05). Similarly, results were approaching significance for the mean pre-dilation maximum diameter in which the tamsulosin group had smaller pupils than controls (3.09 ± 0.70 vs. 3.63 ± 0.93; p=0.07), as well as for mean post-dilation maximum diameter in which the tamsulosin group measured had smaller pupils than controls (6.59 ± 1.11 vs. 7.20 ± 0.56; p=0.07). All other pupillary dynamics were not significantly different between the two groups. 7 out of 15 (47%) tamsulosin patients experienced IFIS to varying degrees, and of the 7 tamsulosin patients that experienced IFIS, 29% were Grade 1 IFIS, 43% were Grade 2 IFIS, and 29% were Grade 3. Finally, a difference in mean post-dilation maximum diameter (mm) was significant, with IFIS patients being significantly smaller than non-IFIS (5.97 ± 1.12 vs. 7.14 ± 0.82; p=0.04). Conclusion: The pupillometer measured significant differences in pupillary dynamics between patients on tamsulosin and controls. It also identified a statistically significant difference in post dilated maximum pupil size between IFIS patients and non-IFIS patients. Therefore, pupillary dynamics of patients on tamsulosin may be measured prior to surgery to determine if IFIS is likely to occur informing surgeons to use special precautions.