TNOA Journal of Ophthalmic Science and Research

ORIGINAL ARTICLE
Year
: 2018  |  Volume : 56  |  Issue : 3  |  Page : 146--149

Patterns of pseudoexfoliation deposits and its relation to intraocular pressure and retinal nerve fiber layer defects


Gargi Sathish, Ebitha Kalarikkal Elias 
 Department of Ophthalmology, Government Medical College, Kottayam, Kerala, India

Correspondence Address:
Dr. Ebitha Kalarikkal Elias
Kurikkattayil, Muttambalam Post, Kottayam - 686 004, Kerala
India

Abstract

Aims: The aims were to study various patterns of pseudoexfoliation (PXF) deposits over anterior lens capsule and its relation with intraocular pressure (IOP) and peripapillary retinal nerve fiber layer (RNFL) defects. Settings and Design: A cross-sectional study was conducted in the outpatient department of a tertiary care center. Subjects and Methods: Newly detected cases of PXF not on any antiglaucoma medications were selected. Central corneal thickness-corrected IOP was recorded with applanation tonometry. The four patterns that were made out are– three ring pattern (3R), two ring with no central disc (2R), radial pigmentary (RP) with multiple radial lines and combined (CR) pattern. RNFL thickness with optical coherence tomography was recorded. Statistical Analysis Used: Frequency calculation and analysis were done using t-test and Chi-square test as applicable using SPSS software. Sensitivity, specificity, and diagnostic accuracy of ring pattern in detecting high IOP and RNFL defects were calculated. Results: Out of 40 eyes with PXF, 17 and 15 eyes had 3R and 2R patterns, respectively. When out of 32 eyes with ring pattern, 8 recorded IOP >20 mmHg and 18 had RNFL defect. Sensitivity, specificity, and diagnostic accuracy of ring pattern in detecting RNFL thinning were 56.25%, 100%, and 65%, respectively. Conclusions: PXF is a severe form of glaucoma, with about 45% having severe disc damage even at presentation. Detection of ring pattern mandates early treatment and follow-up even with borderline IOP. RP pattern also requires regular follow-up as progression to severe damage may occur with age.



How to cite this article:
Sathish G, Elias EK. Patterns of pseudoexfoliation deposits and its relation to intraocular pressure and retinal nerve fiber layer defects.TNOA J Ophthalmic Sci Res 2018;56:146-149


How to cite this URL:
Sathish G, Elias EK. Patterns of pseudoexfoliation deposits and its relation to intraocular pressure and retinal nerve fiber layer defects. TNOA J Ophthalmic Sci Res [serial online] 2018 [cited 2019 Jan 17 ];56:146-149
Available from: http://www.tnoajosr.com/text.asp?2018/56/3/146/243767


Full Text



 Introduction



Pseudoexfoliation (PXF) is an age-related systemic microfibrillopathy characterized by accumulation of gray-white fibrogranular extracellular material produced by abnormal basement membranes of aging epithelial cells.[1] Ritch and Schlötzer-Schrehardt observed that the deposits on the lens capsule are classically seen as three ring (3R). The central disk may be absent in 20%–60% of cases. A homogeneous ground-glass appearance of lens surface in one eye compared to other may represent an early (precapsular) stage. In a slightly later (pregranular) stage, a ring of about 80 faint, radial, nongranular striae may be seen on the mid-third of the anterior capsule behind the iris. Ultrastructurally, the precapsular layer consists of microfibrils.[2] Amritha et al. described four patterns of PXF deposits on anterior lens capsules such as classic 3R, two ring (2R), radial pigmentary (RP), and combined (CR).[3] PXF is the most common identifiable cause of secondary open-angle glaucoma. It is associated with high intraocular pressure (IOP), greater diurnal fluctuation, pressure spikes, severe optic nerve head (ONH) damage, rapid field loss, poor medical response, and more chance of surgical intervention. Pressure can rise dramatically even within a matter of months. This is dangerous because patients may not be seen for a year, and during which their IOP might have risen and significant damage might have happened before they come for the next visit. Hence, early detection, severity assessment, close monitoring, and treatment are mandatory. It would be useful if there are characteristics that can predict the severity of disease before significant optic nerve damage occurs.

This study aims to find out the various patterns of deposits of PXF and to find whether any relation exists between the patterns of deposits and severity glaucoma as measured by IOP and peripapillary retinal nerve fiber layer (RNFL) defects.

 Subjects and Methods



This is a cross-sectional study conducted in the outpatient (OP) department of a tertiary care center from March 2016 to March 2017. The study was approved by the review board of the institution. All patients with PXF detected by slit-lamp examination in one or both eyes who are not on any antiglaucoma medications were included in the study. Pseudophakic and aphakic eyes were excluded as surgery may alter the distribution of deposits. Those with a history of uveitis, trauma, or other secondary glaucoma were also excluded from the study. In eyes with cataract precluding fundus view and optical coherence tomography (OCT), pattern of deposits was studied prior and OCT done within 2 weeks of cataract surgery.

Age, sex, and laterality of the disease were noted after getting informed written consent. Three IOP recordings were taken in the morning OP hours using applanation tonometer. Central corneal thickness was measured using SP 3000P Topcon specular microscope with pachymeter and corrected IOP was recorded. The highest recording was selected for each patient and grouped as <10 mmHg, 11–14 mmHg, 15–19 mmHg, and more than 20 mmHg. More than 20 mmHg was taken as significant high IOP. Pupil was dilated using a combination of 0.8% tropicamide and 5% phenylephrine eye drops.

The pattern of PXF on anterior lens capsule was studied. The four patterns are as follows:

Classic 3R with central disc of PXF followed by a clear zone surrounded by a peripheral ringClassic 2R with no central discRP with multiple radial lines extending from periphery to middle third of the anterior lens capsuleCR with both classic and radial pattern in the same eye.

Fundus examination was done by slit-lamp biomicroscopy with 90 D lens to look for any glaucomatous change. OCT RNFL with 3D Topcon OCT was done and the presence or absence of peripapillary RNFL thinning in each quadrant was noted. RNFL thinning is defined as RNFL thickness <5 percentile in RNFL thickness map of fast RNFL scan. RNFL thickness was grouped as no thinning, thinning in one-quadrant, and thinning in two or more quadrants.

Data were entered in Microsoft Excel and frequency of different variables was calculated and analysis done using Chi-square test for qualitative variables and t-test for quantitative variables using SPSS version 24 (IBM, US). P < 0.05 was considered significant. Sensitivity, specificity, and diagnostic accuracy of ring pattern (including both 3R and 2R) in diagnosing high IOP (>20 mmHg) and RNFL thinning (in at least one-quadrant) were calculated.

 Results



Forty eyes of 22 patients were selected. Of these, 18 eyes had PXF bilaterally.

The age of the patients ranged between 52 and 81 years [Table 1].{Table 1}

Of the 22 patients, 15 (68.1%) were females and 7 (31.8%) were males.

Hence, though IOP more than 20 mmHg was recorded only in 22.5% eyes, RNFL thinning was seen in 45% [Table 2] and [Table 3].{Table 2}{Table 3}

Majority of eyes had 3R pattern, but none had CR pattern [Table 4].{Table 4}

IOP in 3R pattern ranged between 9 and 24 mmHg. When 8 of 32 eyes (25%) with ring pattern had IOP >20 mmHg, only one of 8 RP (12.5%) had high IOP (P = 0.7) [Table 5].{Table 5}

Nine of 17 (52.9%) eyes with 3R and 9 of 15 eyes (60%) had RNFL thinning in at least one-quadrant, but none of RP eyes had thinning in OCT (P = 0.001). Greater RNFL damage is seen in 3R than 2R pattern [Table 6].{Table 6}

The sensitivity, specificity, and diagnostic accuracy of ring pattern in detecting high IOP were 25%, 87.5%, and 37.59%, respectively. However, a higher sensitivity, specificity, and diagnostic accuracy of 56.25%, 100%, and 65% were found for ring pattern in detecting RNFL thinning.

 Discussion



PXF syndrome is a complex ocular degenerative disorder characterized by production and progressive accumulation of flaky dandruff-like material all over anterior segment of eye and may also involve visceral organs. It is usually bilateral. Initially, one eye may be affected, but over time it may be bilateral. In this study, out of 22 patients, 18 had bilateral disease, two had unilateral and in two, the other eye was pseudophakic. Prevalence of PXF increases with age and the mean age may vary according to the geographic location.[4] In this study, 53% belonged to 71–80 years' age group. Sex predominance also varies among studies [Table 1]. Nilgun et al. study that PXF was found to be generally more prevalent in men than in women, but this gender association is not always reproducible.[5] In this study, out of 22 patients, 15 (68.1%) were females, with a male-to-female ratio of 1:2.

PXF is the most common identifiable cause of secondary open-angle glaucoma. IOP escalates faster than primary open-angle glaucoma and hence early detection and follow-up is ideal or else the rapid progression will culminate in vision loss as patients are usually asymptomatic. PXF glaucoma (PXG) is difficult to control and has worse prognosis and associated with frequent vascular ischemic episodes.[6] PXG develops in approximately 50% of patients with PEX syndrome over time.[7] The frequency of glaucoma varies in different studies. In Kozart and Yanoff study, 15% had ocular hypertension (IOP >22 mmHg but no cupping or field loss) and 7% had glaucoma.[8] Andhra Pradesh eye study showed that four (5.5%) of those with PXF had glaucoma. Ocular hypertension was also more frequent in eyes with PXF (9.3%). In our study, only 22.5% had an IOP >20 mmHg, but over 45% had glaucomatous ONH damage on fundus examination and had significant RNFL thinning in OCT. This disparity could be due to the fact that IOP recordings were taken only in the morning hours, and since PXG is associated with significant diurnal fluctuation, one-time IOP recording is never sufficient. Other possible explanations could be that PEX may have a different clinical profile based on racial or geographic origin and that IOP alone might not be the contributing factor for optic nerve damage. Marked and site-specific elastosis is noted in the lamina cribrosa of eyes with PXG, suggesting an abnormal regulation of elastin synthesis and/or degradation in the optic nerve.[9]

PXF may have different patterns of deposits over anterior lens.[3] The classical being the 3R pattern with a translucent central disc with occasional curled edges, clear zone corresponding to the contact with the moving iris and a peripheral granular zone which may have radial striations.[8] The central zone may be absent in few or the peripheral zone may not be seen (due to the poor pupillary dilatation) producing the 2R pattern. RP pattern has radially arranged pigmented or flaky deposits with clear zones in between extending from the periphery to the middle third. The RP pattern is difficult to identify and can be easily missed. In bilateral cases, different patterns may be seen in both eyes. In CR pattern, both ring and radial patterns are seen in the same eye. In Rao and Padhy study, out of 84 eyes, 39 had ring pattern, 39 RP pattern, and six had combined pattern.[3] However, in our study, out of 40 eyes, 32 (80%) had ring pattern and only 8 (20%) had RP pattern and none had combined pattern. Of the eight RP eyes, four had bilateral RP, one had unilateral RP with other eye normal, and three had RP in one and ring pattern in the other eye. It was observed that all eyes with RP pattern had good pupillary dilation, and dilation was affected only in eyes with ring pattern. Of the 32 ring patterns, 17 (53.1%) had 3R pattern. Curling of deposits was seen in just one eye with ring pattern. Rao and Padhy study showed that the baseline IOP in the RP group (18 ± 2.3 mmHg) was significantly lower than the other two forms (CR 20 ± 3.2 mmHg and classical 28 ± 2.3 mmHg). Proteins blocking trabecular meshwork was described as the major mechanism of PXG as IOP rise was found in the severe 3R rather than RP pattern. However, there are studies that prove that molecular changes leading to TM damage also leads to raised IOP irrespective of extent, stage, or pattern of exfoliation deposits. In this study, IOP was >20 mmHg in four eyes (23.5%) with 3R, four eyes (26%) with 2R, and one eye (12.5%) with RP. Hence, pattern alone cannot significantly predetermine IOP rise, although ring pattern is more likely to have a high IOP.

The most prominent neuroretinal rim (NRR) defects in patients with primary open-angle glaucoma are at the inferotemporal and superotemporal sectors, followed by the temporal and nasal sectors. However, the NRR defects in exfoliation glaucoma group are diffuse without a sectorial preference.[10] Rao study showed that eyes with bilateral PXF had larger cup-to-disc ratios and thinner RNFL at presentation than their unilateral counterparts despite comparable baseline IOP. This may show that bilateral PXF cases have already had glaucomatous damage at presentation, mandating early antiglaucoma treatment in eyes even with borderline IOP.[11] In this study, glaucomatous disc changes were seen in 18 (45%) eyes with PXF, and these eyes showed RNFL thinning in OCT. Of these, 14 (35%) eyes had RNFL thinning in just one quadrant and the rest four (10%) had thinning in two or more quadrants. Thinning in inferior quadrant was seen in nine eyes and superior quadrant in seven eyes.

Furthermore, RNFL thinning was seen in 9 of 17 3R eyes (52.9%) and 9 of 15 (60%) 2R eyes but none of RP eyes (P = 0.001). Out of the nine 3R eyes with RNFL thinning, five had RNFL thinning in one quadrant and four had thinning in two or more quadrants, whereas all the nine 2R eyes had RNFL thinning in one quadrant only. This shows that severe optic nerve head damage is seen in 3R pattern, which may suggest that 3R is a more aggressive stage of disease and RP is an initial stage.

According to our study, ring pattern is highly specific (100%) in detecting ONH damage with a diagnostic accuracy of 65%. However, ring pattern has a specificity of 87.5% though a low diagnostic accuracy of 37.5% in detecting high IOP. Hence, detecting ring pattern in slit lamp can predict a severe glaucomatous damage so that intensive treatment and follow-up can be initiated without delay.

Performing phasing of IOP over a day instead of three recordings in morning hours would have yielded more accurate results and help monitor diurnal fluctuation of IOP. RP pattern being a subtle finding seen only in dilated pupil can be easily missed and hence prevalence of it may be higher.

 Conclusions



PXF is a severe form of glaucoma, with about 45% having severe disc damage even at presentation. Detection of ring pattern mandates early treatment and follow-up even with borderline IOP as severe glaucomatous damage is seen in these eyes. Even though it is an early form of disease, RP pattern, requires regular follow-up, as progression to severe damage, may occur with age.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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