Indian Journal of Ophthalmology

ORIGINAL ARTICLE
Year
: 1993  |  Volume : 41  |  Issue : 2  |  Page : 71--73

Anterior chamber depth and lens thickness in primary angle-closure glaucoma : A case-control study


Sandeep Saxena, PK Agrawal, VB Pratap, Rajiv Nath 
 Department of Ophthalmology, King George's Medical College, Lucknow, India

Correspondence Address:
Sandeep Saxena
G-19, River Bank Colony, Lucknow 226 018, U.P.
India

Abstract

Anterior chamber depth and lens thickness have been considered as important biometric determinants in primary angle-closure glaucoma (PACG). In a tertiary care centre-based case-control study, 70 patients and equal number of controls were investigated to analyse the strength of association and predictability of anterior chamber depth (ACD) and lens thickness (LT) in the disease. Mean (+/- S.D.) ACD and LT in the cases and the controls were found to be 2.28 +/- 0.19, 2.87 +/- 0.10; 4.57 +/- 0.34 and 4.13 +/- 0.19 mm respectively. Two sample t test demonstrated statistically significant difference in the ACD and LT between the cases and the controls (Difference being -0.59, 0.44; 95% confidence interval of the difference: -0.64, -0.53 and 0.34, 0.53 respectively, P < 0.01). Logistic regression analysis demonstrated statistically significant protective effect of ACD over PACG (P < 0.01). The odds ratio corresponding to an increase of 0.01 mm in ACD and LT were computed as 0.83 and 1.11 respectively



How to cite this article:
Saxena S, Agrawal P K, Pratap V B, Nath R. Anterior chamber depth and lens thickness in primary angle-closure glaucoma : A case-control study.Indian J Ophthalmol 1993;41:71-73


How to cite this URL:
Saxena S, Agrawal P K, Pratap V B, Nath R. Anterior chamber depth and lens thickness in primary angle-closure glaucoma : A case-control study. Indian J Ophthalmol [serial online] 1993 [cited 2024 Mar 28 ];41:71-73
Available from: https://journals.lww.com/ijo/pages/default.aspx/text.asp?1993/41/2/71/25620


Full Text

Primary angle-closure glaucoma (PACG) occurs in eyes with a recognizable anatomical predisposition. Von Graefe [1] reported the association of glaucoma with a shallow anterior chamber. Rosengren [2] found that pa�tients with glaucoma had a smaller anterior chamber depth (ACD) than normal persons. He also suggested that the shallow anterior chamber in acute glaucoma existed prior to the acute rise in pressure. [3] Tornquist [4] found anterior chamber to be genetically determined. He also reported that the anterior chamber of the fellow eye of persons with uniocular acute glaucoma is shallower compared to normals.[5] The characteristic shallow anterior chamber of PACG is caused by abnormal correlation between structure of the lens and eye ball. [6] The crystalline lens continues to grow throughout life [7],[8] partly at the expense of the anterior chamber, the depth and volume of which gradually diminish. [2],[9],[10],[11] The growth of the lens leads to shallowing of approximately 0.35 to 0.50 mm of ACD in 50 years. [6] The diminution of the dimensions of the anterior chamber caused by the growth of the lens may play an important role in the pathogenesis of angle-closure glaucoma. [12]

This study was undertaken to analyse, statistically, the strength of association and predictability of anterior chamber depth and lens thickness. for occurrence of the disease in Indian subjects based at a tertiary care centre.

 SUBJECTS AND METHODS



This case-control study was done from December 1990 to December 1991. The definition of the disease was given as "Patients presenting with a history of pain with or without redness, associated with diminution of vision, coloured haloes, raised intra�ocular pressure and gonioscopically narrow angle of the anterior chamber without any evidence of secon�dary cause of raised intraocular pressure". Seventy consecutive patients of primary angle-closure glaucoma evaluated at the hospital were included. Equal number of controls were taken (aged more than 40 years) from those listed for refraction who were subjected to the same investigations. All subjects underwent a detailed examination including refraction and gonioscopy. Anterior chamber depth, lens thickness and axial length of the eye were measured by a BioPhysic Medical Paxial Biometer-Pachymeter, (France; Propagation speed: Cornea: 1550 m/s, Lens : 1640 m/s, A.C. and Vitre�ous: 1532 m/s) by an observer blinded to case control status of the subjects. All subjects of the sampling frame were included in the final data analysis. The results were analysed using biostatistical computer software. Logistic regression analysis was done with the help of software Mult LR 87. A probability of was accepted as being statistically significant.

 RESULTS



The mean age of the cases was 51.17 years. Male: Female ratio was 1:1.91. Summary of the biometric variables namely anterior chamber depth, lens thick�ness and axial length of the eye are shown in [Table 1].

A two sample t test, comparing the ACD and LT of the cases and the controls respectively, was done. Mean standard deviation (STDEV) and standard error of the mean (SEMEAN) along with 95% confidence interval of difference between two means and t-score as well as P-value of the significance test were com�puted. Mean ACD (� STDEV) in the cases was 2.28 (� 0.19) mm, whereas it was 2.87 (� 0.10) mm in the controls. The difference between the two means was computed as -0.59 (P95% confidence - interval of the difference being -0.64, -0.53 [Table 2] . Mean LT (� STDEV) in the cases was 4.57 (� 0.34) mm, whereas it was 4.13 (+ 0.19) mm in the controls. The difference between the two means was computed as 0.44 (P0.05). Anterior chamber depth demonstrated a highly statistically significant protective effect over PACG (odds ratio [13] Tomlinson and Leighton, [12] Lowe and Clark [15] and Lee, Brubaker and Ilstrup. [16] A similar association of LT with PACG was demonstrated by Lowe. [6] The odds ratio corresponding to change of 0.01 mm in ACD was 0.83, meaning that the odds of getting the disease get reduced to 83% upon an increase in ACD by 0.01 mm. The odds ratio corresponding to a change of 0.01 mm in LT was 1.11, meaning that the odds of getting the disease get increased by 11% upon an increase of LT by 0.01 mm. The association between PACG and LT was however, not found statistically significant (P>0.05), after adjusting for other variables including refractive error and anterior chamber depth in the logit model [Table 4][Table 5]. However, a two sample t test, done to compare mean lens thickness of the cases and the controls, demonstrated a statistically significant asso�ciation (P<0.01) [Table 3]. The results of the logistic regression analysis and the two sample t test appear different as far as the statistical significance of the association of lens thickness and primary angle�closure glaucoma is concerned. This can be explained by the phenomenon of confounding. The contribu�tion of lens thickness in shallowing of anterior chamber depth having been adjusted in the logit model, its association does not remain significant. This shows that, an increase in lens thickness acts through anterior chamber depth only, whereas shallowing of anterior chamber depth is due to increase in lens thickness as well as changes in other biometric determinants.

Acknowledgements: We are thankful to Professor R.C. Saxena, M.S., for reviewing our manuscript.

References

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