Volume 7-1, 2005
Excerpts From: The International Glaucoma Review, Volume 7-1, 2005:
World Glaucoma Congress
(Second in a Series From This Publication)
From the American Glaucoma Society Meeting (March, 2005)
- Physician treatment of disease is not uniform for all ethnic groups and gender. In this study [OHTS], the authors demonstrate that women are not treated as frequently as men for a given level of disease. This information has ramifications for current treatment paradigms and glaucoma suspects.
- Jeffrey Liebmann and James Brandt
M & T Commentary:
We are not sure what to make of this, except to point out that since women generally outlive men, perhaps it is even more important to detect and treat OHT and/or POAG in women than men, since their optic nerves may have to be protected for a longer period of time.
From Glaucoma at ARVO (May 2005)
- The measurement of progressive change in field is complex and the ideal method has not yet been devised.
- Therapy for ocular hypertensives is complicated by inadequate compliance, side-effects, and failure to take effect of quality of life into account .
- A cost-benefit analysis suggested that treatment of ocular hypertensives with IOP greater than 24mmHg is within the cost range of therapies considered valuable in general medical treatment.
- The cost of saving one eye from blindness by treatment of ocular hypertension was estimated at $800,000.
- About 1.3 million ocular hypertensives are being treated in the United States at this time.
- Harry Quigley
- A population-based glaucoma survey in China found that POAG was slightly more common than PACG.
- Tin Aung
M & T Commentary:
Such knowledge probably applies to Chinese-Americans as well, so we need to be cognizant that narrow angles should be detected and gonioscopically quantified, particularly in this special subset of our population.
RE: 24-hours IOP
Comment by Tasos Kontas
The current day-to-day management of glaucoma often ignores the biological rhythm inherent in the only parameter we can currently treat, the intraocular pressure (IOP) and its clinical implications. Since glaucoma is a 24-hour disease, it is logical that we should aim to determine and control the IOP throughout the 24-hour cycle. Sadly though, we generally assess the IOP control by a single, daytime office measurement. Although the detection and follow-up of glaucoma patients with single IOP measurements is quick and convenient, this strategy may provide inadequate, or even misleading information and may not reflect the pattern of IOP characteristics before and during therapy. It is now well established that peak IOP is often missed, and of course IOP fluctuation cannot be determined with a single IOP measurement. It is thus important to investigate the correlation between office-hour IOP readings and 24-hour IOP parameters. In an interesting and clinically relevant paper Mosaed et al. employ a retrospective review of records from a sleep laboratory to determine the correlation between office-hour IOP (four readings between 9:30 and 15:30) and peak nocturnal IOP in untreated healthy and glaucomatous eyes. Overall Mosaed et al. find a strong correlation between supine IOP during office hours and peak nocturnal IOP. There was no correlation between office-hour IOP and peak nocturnal IOP in young healthy subjects, highlighting the greater unpredictability of 24-hour IOP characteristics in younger patients. On the other hand, the correlation between mean office-hour sitting IOP and peak nocturnal IOP was strong in older untreated glaucoma patients. In the same group, a strong correlation existed between mean supine IOP readings during office hours and peak nocturnal IOP. In these patients there was only a small mean difference (0.4mmHg) between supine IOP and peak nocturnal IOP. These data may help the clinician in estimating the nocturnal IOP in their untreated glaucoma patients. The study reiterates once again that the mean IOP from several readings during office hours is far superior to a single reading and suggests that employing an IOP reading in the supine position may be helpful. Similar to other studies in this field the question remains how relevant are these data to the day-to-day clinical practice and how accurately the sleep laboratory setting reflects real life glaucoma? Clearly, it will be important to determine in the future whether these correlations apply in other clinical settings and, as the authors point out, we need to determine whether these relationships are also applicable to glaucoma patients receiving medical or other forms of therapy.
The duration and homogeneity of 24-hour IOP lowering effect is a key characteristic of successful therapy. It may be important to develop (just like our medical colleagues have done in the management of arterial hypertension), suitable IOP indices such as the trough to peak ratio, the morning to evening IOP ratio and the smoothness index assessing the features of antiglaucoma therapy. Nevertheless, much remains to be elucidated in this important area.
M & T Commentary:
Interesting! It may be that one day, we will all be measuring IOP in both supine and sitting positions as a component of our glaucoma evaluations. Of course, this would require all of us to have either Kowa or Perkins hand-held Goldmann applanation tonometers in our offices.
Central corneal thickness and thickness of the lamina cribrosa in human eyes: JB Jonas and Holbach L. Investigative Ophthalmology and Visual Science 2005; 46: 1275-1279
Conclusion: In nonglaucomatous human globes, central corneal thickness may not correlate significantly with lamina cribrosa thickness, peripapillary scleral thickness, and shortest distance between intraocular space and cerebrospinal fluid space. Histologic artifact and sectioning methods could partially account for the lack of an association. The study results may suggest clinically than an assumed relationship between central corneal thickness and susceptibility to glaucoma cannot explained by an anatomic correspondence between corneal thickness and histomorphometry of the optic nerve head.
Comments by Peter Shah
Jonas and Holbach published an excellent and high recommended histomorphometric study evaluating the relationship between central corneal thickness and lamina cribrosa thickness in enucleated nonglaucomatous human eyes. All eyes had been removed because of malignant choroidal melanoma. Mean central corneal thickness (CCT) of 616.6 ± 108.3 micrometers and mean central lamina cribrosa thickness (LCT) 378.1 ± 117.8 micrometers were statistically independent of each other. The study showed that CCT did not correlate significantly with LCT, peripapillary scleral thickness or shortest distance between the intraocular space and cerebrospinal fluid space.
An observational retrospective cross-sectional study by Shimmyo and Orloff aimed to determine whether there is an association between central corneal thickness (CCT) and axial length (AL) in a clinical setting. There was no statistically significant relationship between central corneal thickness and axial length. In particular the authors found that thinner corneas are not associated with longer eyes.
This clinical observational cross-sectional study by Henderson et al. examined the relationship between retinal nerve fiber layer (RNFL) measurements obtained by scanning laser polarimetry with variable corneal compensation (using the GDx VCC) and corneal thickness (CCT) measurements in ocular hypertensive (OHT) patients. This well-conducted study compared 44 OHT patient with 48 healthy subjects.
Higher GDx VCC parameter nerve fiber indicator (NFI) scores, indicative of thinner RNFL, were correlated significantly with thinner CCT measurements in the OHT patient group. The NFI values were not significantly different between OHT patients with thicker corneas and healthy subjects. The authors comment that these findings support the notion that RNFL defects as assessed by the GDx VCC may represent early glaucomatous damage in OHT eyes. It is important to remember that the study was not designed to assess this possibility as a primary outcome measure.
Comment by Anders Heijl
The paper [the Erlangen Glaucoma Register, Jost Jonas et al.] addresses the relationship between corneal thickness and glaucoma damage at the time of referral and with perimetric progression. The authors find that low CCT was significantly associated with larger damage at baseline. [This finding] is in agreement with observations made by several other groups. I agree with the authors that the most plausible explanation of the finding is 'a selection artifact' by referring ophthalmologists. Glaucoma patients with thinner corneas have lower pressure readings on Goldmann tonometry, and we and many others have observed how patients with very clear manifest normal tension glaucoma are missed in ophthalmic practice - probably just because they fail to raise a suspicion of glaucoma in the examining ophthalmologist unless the discs are very abnormal. The normal tension glaucoma patient has a good chance of (or a high risk of) being classified as normal after a comprehensive eye examination - even if the reason for the visit is a positive family history of glaucoma.
M & T Commentary:
As we consistently stress in our lectures, be obsessively compulsive in your examination of optic nerve heads. If there is any reasonable suspicion of even early glaucomatous optic neuropathy, obtain a CCT measurement and recheck the IOP at a different time of the day. Also, a baseline scan (GDx-VCC, OCT, or HRT) could be helpful as well.
Comment by the IGR Editor
The role of peripapillary atrophy (PPA) in the management of glaucoma remains intriguing. The advantage of peripapillar atrophy over disc hemorrhages is that peripapillar atrophy is always present. Jonas presents a review on peripapillar atrophy in which he states that it is "among several morphologic variables to detect glaucomatous abnormalities. It is a variable of the second order." It is also useful for the differentiation of various types of glaucoma or differentiation from AION.
M & T Commentary:
While ONH hemorrhages can be a marker for progressive optic nerve disease, we have never found PPA to be particularly helpful in our glaucoma evaluations or monitoring.
RE: Medical Treatment
Comment by Donald Minckler
A retrospective clinic-based case series by Osborne et al. analyzes presumed allergies due to topical or systemic medications among consecutive patients with primary open-angle glaucoma who reported discontinuing a drug because of allergic symptoms during the recruitment period May 1999 through September 2001.
The authors interpret the data as indicating that brimonidine (0.2%) among all currently utilized agents, is most likely to cause allergic symptoms (itching follicular conjunctivitis, chemosis, periocular dermatitis) and most importantly that this drug predisposes and accelerates subsequent allergic reactions to other topical agents including some timolol preparations and dorzolamide.
Nevertheless, the conclusions highlight an important issue in suggesting that a widely utilized glaucoma drug, long-recognized as relatively allergenic, may accentuate or predispose to allergy among subsequently employed agents, which by themselves are less likely to induce allergic symptoms. The conclusions imply that brimonidine is an immune stimulant and the clinical implication would be to place this agent last in the trial spectrum.
Evaluation of retinal nerve fiber, optic nerve head, and macular thickness measurements for glaucoma detection using optical coherence tomography: Medeiros FA; Zangwill LM; Bowd C; Vessani RM; Susanna R Jr.; Weinreb RN.
American Journal of Ophthalmology 2005; 139: 44-55
Conclusions: RNFL and ONH measurements had the best discriminating performance among the several Stratus OCT parameters. A combination of ONH and RNFL parameters improved the diagnostic accuracy for glaucoma detection using this instrument.
Optical coherence tomography longitudinal evaluation of retinal nerve fiber layer in glaucoma: Wollstein G; Schuman JS; Price LL; Aydin A; Stark PC; Hertzmark E; Lai E; Ishikawa H; Mattox C; Fujimoto JG, et al.
Archives of Ophthalmology 2005: 123: 464-470
Conclusions: A greater likelihood of glaucomatous progression was identified by OCT vs automated perimetry. This might reflect OCT hypersensitivity or the true damage identified by OCT before detection by conventional methods.
M & T Commentary:
Once again, it is demonstrated that structural changes commonly precede functional compromise. While scanning instrumentation is not an absolute essential in glaucoma care, the information obtained with these devices can help refine and quantify diagnostic and therapeutic care. Plan to purchase one of these as soon as practical.
Optic nerve damage in highly myopic eyes with chronic open-angle glaucoma: Jonas JB; Budde WM.
European Journal of Ophthalmology 2005; 15: 41-47
Conclusions: At a given intraocular pressure in chronic open-angle glaucoma, optic nerve damage may be more pronounced in highly myopic eyes with large optic discs than in non-highly myopic eyes. This may suggest a higher susceptibility for glaucomatous optic nerve fiber loss in highly myopic eyes than in non-highly myopic eyes.
Enhance postoperative filtering bleb-induced vision difficulties with well-fitted GP contact (oxygen-permeable) lenses: Pederson K.
Optometry 2005; 76: 115-122
Conclusion: GP contact lenses can be successfully worn in eyes with filtering blebs. However, to reduce the risk of complication and infection, proper fitting guidelines should be followed and patients should return for evaluations at intervals of 6 months or less.
Subacute Angle Closure Glaucoma
Headaches as the main presenting symptom of subacute angle closure glaucoma: Nesher R; Epstein E; Stern Y; Assia E; Nesher G:
Headache 2005; 45: 172-176
The diagnosis of subacute angle closure glaucoma is suspected in patients with narrow angles of the anterior chamber of the eye, presenting with periodic ocular, or periocular pain. However, some patients may present with headaches in the absence of significant ocular discomfort, which often leads to misdiagnosis and delay in specific therapy. Subacute angle closure glaucoma should always be considered in the differential diagnosis of adult-onset headaches.
M & T Commentary:
While excellent advice, always be sure to order a "sed rate" in older patients with new onset HA once you have ruled out angle closure events via tonometry and gonioscopy.
The investigation of retinal nerve fiber layer thickness in eyes with optic nerve head drusen: Ocakoglu O.
Neuro Ophthalmology 2004; 28: 205-214
Purpose: To investigate the effect of optic nerve head drusen (ONHD) on the retinal nerve fiber layer (RNFL) thickness. Conclusion: We found a significant decrease in the RNFL thickness of ONHD patients compared to that of the control subjects. The measurement of VF indices did not show a significant difference between various degrees of ONHD. In contrast, RNFL thickness was significantly correlated with the amount of ONHD. This suggests that OCT may allow the detection of early changes in RNFL thickness in ONHD patients before observable changes in the visual field are seen.
M & T Commentary:
Since the majority of patients with visible ONHD have visual field defects, it is always wise to do a 30-2 visual field on all such patients.
Nonarteritic ischemic neuropathy developing soon after use of sildenafil (Viagra): a report of seven new cases: Pomeranz HD; Bhavar AR.
J Neuroophthalmology 2005; 25: 9-13
Seven patients, aged between 50 and 69 years, had typical features of nonarteritic anterior ischemic optic neuropathy (NAION) within 36 hours after ingestion of sildenafil citrate (Viagra) for erectile dysfunction. Six patients had vision loss within 24 hours after use of the agent. Final visual acuity in the affected eye ranged from 20/20 to light perception. Both eyes were affected in one individual. All affected individuals had pre-existing hypertension, diabetes, elevated cholesterol, or hyperlipidemia. Seven similar cases have been previous reported. Sildenafil may provoke NAION in individuals with an arteriosclerotic risk profile.
M & T Commentary:
The preponderance of contemporary literature has not shown a direct cause-and-effect relationship. The key here is that patients with significant systemic cardiovascular disease who have a small optic nerve head and/or a small C/D ratio are certainly at risk for NAION, with or without the use of any ED drug.
Compliance and persistency in glaucoma follow-up treatment: Schwartz, GF
Current Opinions in Ophthalmology 2005; 16: 114-121
Purpose of Review: To summarize research published between 1980 and October 2004 regarding compliance (the extent to which patients' behaviors correspond with providers' recommendations) and persistency (total time on therapy) in patients diagnosed with open-angle glaucoma or ocular hypertension; to suggest approaches ophthalmologists [M & T: and optometrists] might consider to improve compliance and persistency; and to identify areas warranting future research. Recent Findings: Medication compliance, the focus of most compliance-related research, has been measured using a variety of methods including self-reports, the medication possession ratio, and electronic monitoring. Noncompliance rates of at least 25% commonly have been reported. The primary obstacles to medication compliance appear to be situational/environmental (e.g., being away from home or a change in routine) or related to the medication regimen (e.g., side effects or complexity). Persistency with ocular hypotensive therapies has been found to be poor. Retrospective cohort studies using survival analyses have reported that fewer than 25% of patients are persistent over 12 months. Summary: Accurately assessing patient compliance and persistency is important to optimizing patient care. Physicians may mistake either medication noncompliance or lack of persistency with poor efficacy. Such errors would likely increase health care costs if they result in unnecessary changes to a patient's therapeutic regimen or in surgery.
M & T Commentary:
The main reason we see established glaucoma patients every three to four months is to urge them to comply and persist with their therapy. (We also check their IOP and examine their ONH.) Unrelenting encouragement plays a powerful role in glaucoma patient care. Also, frequent "no-show" patients, in our experience, are commonly "non-compliant." Be sure to have a system in place in your offices to monitor glaucoma patient "no-shows." This enhances care and defends against malpractice.