Pseudoexfoliation was first described by Lindberg in 1917, is an age-related systemic disorder with primary ocular manifestation having strong genetic component. Genetically linked to lysyl –oxidase-like-one (LOXL-1) gene.[1] Pseudoexfoliation (PEX) is an age-related idiopathic condition characterized by progressive production and accumulation of extracellular matrix fibrillary material in the intraocular and extraocular tissues.[2] The prevalence of PEX over the age of 60 years is roughly 10-20%, increasing to 40%over the age of 80 years, and is highly dependent on race and ethnicity.[3,4]

Ocular involvement in PEX primarily manifests with anterior segment findings. PEX material accumulation has also been found on the lens capsule, pupillary border, the iris, non-pigmented ciliary epithelium, lens zonules, trabecular meshwork, and corneal endothelial cells in the posterior ciliary artery, vortex vein and central retinal artery walls. The material has also been demonstrated along vascular endothelium, corneal epithelial basement membrane and stroma. Moreover, various clinical studies have reported that PEX material affects ocular blood flow and vascular resistance. In fact, PEX  is also considered as a systemic vascular disease, referred to as PEX vasculopathy.[5] Several studies have shown the influence of PEX on the cornea, specifically the corneal endothelial cell density [ECD], with multiple studies showing decreased ECDs of patients with PEX and PEXG compare to control patients. [6-8]

Structural damage of optic nerve head and RNFL in glaucoma may precede functional loss. About 30–50% of retinal ganglion cells may be lost before any visual fields changes are detected. Retinal nerve fibre layer thickness analysis using optical coherence tomography (RNFL-OCT) is a documented investigative tool to detect preperimetric glaucoma and helps to detect glaucoma early. SD-OCT is a computerized imaging technology that produces high resolution, quantitative and reproducible measurements of RNFL and retinal ganglion cell complex and helps in differentiating normal eyes from patients with early glaucoma.[9-11]

With this thing in mind, we aimed to estimate the retinal nerve fibre layer (RNFL) thickness in patients of pseudoexfoliation with (PEXG) and without glaucoma (PEX) by optical coherence tomography (OCT) and determine the corneal endothelial morphometric changes by Non-contact Specular Microscope in patients of pseudoexfoliation with (PEXG) and without glaucoma (PEX). 

This cross-sectional analytical study was conducted in the Department of Ophthalmology, Indira Gandhi Medical College, and Shimla among the selected patients of pseudoexfoliation with and without glaucoma from July 2018 to June 2019 i.e. one year. Assuming a difference of average RNFL thickness of 11.69(mm) (85.52 ± 19.7mm in pseudoexfoliation with glaucoma (PEXG) patients[12], Confidence level 95% and power of study 80%, a sample size of 46  each in 2 study groups and 1 control group  was calculated. All consecutive patients presenting to ophthalmology OPD and diagnosed with pseudo exfoliation with and without glaucoma during the study period were  included in the study till the completion of sample size. 

We included normal healthy controls without any glaucomatous optic disc damages and an IOP <21 mmHg in group 1, patients clinically diagnosed as pseudoexfoliation without glaucoma (PEX) in group 2, and Patients already diagnosed as pseudoexfoliative  glaucoma(PEXG) in group 3. Optical Coherence Tomography (TOPCON 3D OCT-1MAESTRO) was done for studying RNFL thickness in control, patients of pseudoexfoliation (PEX) and pseudoexfoliation with glaucoma (PEXG). Non-Contact Specular Microscope (Topcon SP-1P Version 1.41) was used to determine the corneal morphometric changes by estimating CCT (central corneal thickness), ECD (Endothelial cell density), HEX (Hexagonal cell ratio) and CV (Coefficient of variation) in cell size.

The collected data was entered into the Microsoft Excel spreadsheet 2007 for further processing and analysis. Statistical analysis was done by using Epi Info Version 7 software. Descriptive statistics, frequency and percentages were determined for categorical variables with 95% confidence interval. Mean & standard deviation was determined for quantitative variables. To compare outcome in study groups appropriate statistical test of significance was used (Chi square test for categorical variables, ANOVA for quantitative variables).  A p value of <0.05 was considered statistically significant.

There were a total of 138 participants in our study, 46 in each group. The mean age of healthy controls (Group 1), patients of Pseudoexfoliation without Glaucoma (Group 2) and Pseudoexfoliation with Glaucoma (Group 3) was 64.28±10.49 years, 68.43±9.88 years and 66.52±8.38 years respectively. According to gender distribution in healthy controls  (Group 1), there were 19 males and 27 females, in patients of  Pseudoexfoliation without Glaucoma (Group 2)   there were 24 males and 22 females and  Pseudoexfoliation with Glaucoma (Group 3)   there were 32 males and 14 females. Among visual acuity in left eye,in Group1 it was in the  range from 6/6 to 6/36, In Group 2 it was in the range from 6/6 to FC 2/60 and in group 3 it was in the  range from 6/6 to PL-VE. Among visual acuity in Right eye, in Group1 it  was in the range from 6/6 to6/36 , in Group 2 it was in the range from 6/6 to FC and in group 3 it was in the range from 6/6 to PL-VE. In the present study intra ocular pressure < 10 mm of Hg in left eyes was found in 0, 11 & 3 patients in group 1, 2 & 3 respectively. Intra ocular pressure between 10-20 mm of Hg was found in 44, 35 & 21 patients in group 1, 2 & 3 respectively .  Similarly intra ocular pressure between 21-25 mm of Hg was found in 2, 0 & 22 patients  in group 1, 2 & 3  respectively. In the present study intra ocular pressure < 10 mm of Hg in right eyes was found in 2, 13 & 34 patients in group 1, 2 & 3 respectively.  Intra ocular pressure between 10-20 mm of Hg was found in 44, 31 & 27 patients in group 1, 2 & 3 respectively. Similarly intra ocular pressure between 21-25 mm of Hg was found in 0, 2 & 15 patients in group 1, 2 & 3  respectively. Vertical cup disc between 0.3 -0.4 was found   in all  46 healthy controls  (Group 1) and 39 patients of  Pseudoexfoliation without Glaucoma (Group 2) and none of the patients of pseudoexfoliation with glaucoma . It was 0.5-0.6   in all 7  patients of Pseudoexfoliation without Glaucoma (Group 2), 0.6-0.7 in 1 patient of Pseudo-exfoliation with Glaucoma (Group 3)  , 0.7-0.8 in 3 patients of Pseudo-exfoliation with Glaucoma (Group 3)and 0.8-0.9 in 42 patients of Pseudo-exfoliation with Glaucoma (Group 3). (Table 1). 

Table 1: Intraocular Findings of the Study Participants (N=138)

Mean RNFL Thickness(µm) in group 1 , group 2 and group 3 was 104.38±9.84, 89.47±13.52 and 72.73±13.54. There was significant difference between the mean RNFL thickness between all the three groups. (Table 2).

Table 2: Mean RNFL Thickness among Study Participants

Mean Central Corneal Thickness (CCT) (µm) in group 1 , group 2 and group 3 was 512.09±28.227, 496.74±30.873 and 577.89±59.82. The difference between the  mean CCT between all the three groups was found to be non-significant. Mean Coefficient of variation (CV) (%)    in group 1 , group 2 and group 3 was 35.98 ±3.448, 37.37±4.255 and 37.85±8.962. 

The difference between the mean Coefficients of variation (CV) between all the three groups was found to be statistically non- significant. Mean Endothelial cell density (ECD)(cells/mm²) group 1 , group 2 and group 3 was 3017.26±323.239, 2586.33±505.156 and 2248.50±479.909. The difference between the mean ECD between all the three groups was found to be statistically significant. Mean Hexagonal Ratio (HR) (%) in group 1 , group 2 and group 3 was 31.85±29.74, 29.74±9.15 and 32.41±16.44. The difference between the  mean Hexagonal Ratio (HR)  between all the three groups was found to be non-significant (Table 3).

Table 3: Non contact specular microscopic findings of the study participants (N=138)

This cross-sectional analytical study was conducted in Indira Gandhi Medical College, Shimla, in the Department of Ophthalmology. Glaucoma is a disease characterized by progressive, irreversible optic neuropathy and degeneration of the retinal ganglion cells and their axons, causing a corresponding loss of the visual field (VF) and is one of the major causes of blindness worldwide.  So, in glaucoma, early detection of VF progression is essential, because the damage is irreversible.

Mean RNFL thickness was seen decreased in all PEX patients in all quadrants; however, statistically significant differences were detected in all quadrants except left nasal quadrant. Similar to our findings, [13] also found that RNFL in patients with PEX was significantly thinner than controls in all quadrants except the nasal quadrant.

In contrary to our study results, [10] found that average RNFL thickness in PEX patients was thinner than healthy subjects but found no significant difference between PEX and healthy subjects in RNFL thicknesses according to quadrants.

In our study mean total RNFL thickness(µm) in group 1 , group 2 and group 3 was 104.38±9.84, 89.47±13.52 and 72.73±13.54. There was significant difference between the mean RNFL thickness between all the three groups on post hoc analysis. Similar findings  were reported in study done [11] in which  RNFL thickness was higher in the PEX and control groups compared to the PEXG group (p<0.001).

[15] reported that thinner RNFL measurements may be related with the increasing risk of development of glaucoma in PEX patients. [16] in their study found that the RNFL thickness and the cross-sectional area of the RNFL were decreased in eyes with pseudoexfoliation, but in their study mean IOP of eyes with PEX was higher than controls. Therefore the difference in RNFL thickness might be the result of either the structural alterations or higher IOP.

Mean Central Corneal Thickness (CCT) (µm) in group 1, group 2 and group 3 was 512.09±28.227, 496.74±30.873 and 577.89±59.82. In our study, the difference between the mean CCT between all the three groups was found to be non-significant on post hoc analysis.

 Similar findings were reported in the study done [10]

In our study Mean CCTs were thinner in the PEX group than in the PEXG and control groups. Similar finding was observed in the study done [13]. Similar to our study , Inoue and coworkers[12] reported thinner corneas in individuals with PEX  compared to controls. [17] stated that mean CCT in eyes with PEX was significantly lower than in normal eyes.

[18] found that CCT was less in eyes with PEX than in those without, although there was no difference in CCT between eyes with PEXG and normal eyes.

[12] also found that mean CCT in eyes with PEX was lower than in normal ones, but there were no significant differences in these factors between the PEX eyes in patients with and without glaucoma. In a recent study, [18]reported that CCT was significantly thinner in the eyes with PEX but similar in PEX glaucoma patients and controls.

Contrary to our study, [19] showed that CCT was not affected by the presence of PEX and their results were in agreement with previous studies. [20]  reported that CCT in eyes with PEX  was thicker than CCT found in the other eye of the same patient that did not have PEX. Moreover, [21,22] did not find any significant differences between the mean CCT values of the eyes with PEX and normal ones.

Lower CCT values in the eyes with PEX material may be a result of decrease in corneal stromal cell density. Moreover, higher CCT values may be because of decreased endothelial cells in PEX glaucoma patients. 

Concerning CCT in subjects with PEX, references in the literature are controversial. Nevertheless CCT must be assessed in patients with PEX  in order to avoid the underestimation of the IOP. Maintenance of corneal thickness depends on an intact barrier function and a healthy endothelium, but reports regarding CCT in eyes with PEX and PEXG are controversial. We found that mean CCTs were significantly thinner in PEX, but not in PEXG eyes. Such a reduction in CCT may be explained by the decreased densities of corneal cells. Despite significant decrease  in the density of corneal cells in PEX and PEXG, advanced alterations in the corneal endothelium can affect stromal hydration, thereby resulting in increased CCT. Furthermore, a concomitantly elevated IOP may also contribute to greater CCTs in PEXG. Hence, it would be useful to use confocal microscopy to assess the relationship between severity of endotheliopathy and corneal thickness changes in PEX and PEXG eyes. 

In a recent study, [23] showed that  the decreased stromal cell densities can explain the thinner CCT in the eyes with PEX. Decreased endothelial cell density and morphologic changes in corneal endothelium had also been reported in different studies. Results of this study are  also compatible with Zheng’s morphological study. There is not a consensus about the effects of PEX  on CCT. Previous studies resulted in lower or higher CCT results than normal eyes. 

Mean Endothelial cell density(ECD)(cells/mm²)  in group 1 , group 2 and group 3 was 3017.26±323.239, 2586.33±505.156 and 2248.50±479.909. In our study the difference between the mean ECD between all the three groups was found to be statistically significant on post hoc analysis.

In our study Mean endothelial cell densities were significantly lower in the PEX and PEXG groups compared with the control group (p<0.05). The PEXG group had significantly lower mean endothelial cell densities compared with the PEX group (p<0.05). Similar findings were reported in study done [12]

Mean Coefficient of variation (CV)(%) in group 1 , group 2 and group 3 was 35.98 ±3.448, 37.37±4.255 and 37.85±8.962. There were higher percentages of mean Coefficient of variation (CV)    in the PEX and PEXG groups compared with those of the control group (p<0.05). Our study findings were similar to study done [13] In our study the difference between the mean Coefficient of variation (CV)    between all the three groups was found to be statistically non- significant on post hoc analysis.

Mean Hexagonal Ratio (HEX)(%) in group 1 , group 2 and group 3 was 31.85±29.74, 29.74±9.15 and 32.41±16.44. In our study the difference between the  mean Hexagonal Ratio (HR)  between all the three groups was found to be non-significant on post hoc analysis.

 There were higher percentages of mean Hexagonal Ratio (HR) in the normal healthy subjects and PEXG groups compared with those of the PEX group   (p<0.05). This finding was contrary to study done [13]

SD-OCT is a very reliable investigative tool to measure RNFL thickness, which helps in detecting preperimetric glaucoma. RNFL thickness was decreased in PEX and PEXG patients and this may be a predictive factor for occurring more progressive and dangerous glaucoma in these patients.

In addition, our study showed that the endothelial cell density was decreased, pleomorphism and polymegathism of cells were increased, and pseudo exfoliative materials were precipitated in endothelial cells of PEX & PEXG eyes.

Furthermore, our study indicated that there were more morphological abnormalities of corneal endothelial cells and decrease in RNFL thickness in PEXG eyes compared to PEX. Alterations in corneal endothelium in PEX, along with the fact that these alterations are manifested more profoundly in PEXG, suggest a correlation between the specific alteration and the stage of disease progression.

The RNFL thickness and Endothelial Cell Density were statistically more decreased in PEXG patients as compared to PEX and normal healthy subjects and it may be depictive of progressive corneal damage.

The authors declare that they have no conflict of interest

No funding sources

The study was approved by the IGMC Shimla, Himachal Pradesh, India

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