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Is combined mechanism glaucoma a distinct entity?

  • Glaucoma
  • Published:
Graefe's Archive for Clinical and Experimental Ophthalmology Aims and scope Submit manuscript

Abstract

Purpose

Primary adult glaucomas that have an occludable angle with peripheral anterior synechiae which are too few to account for the chronically raised IOP, or the glaucomatous optic neuropathy, do not fit the definition of either POAG or PACG and can be considered as combined mechanism glaucoma (CMG). We aimed to compare the clinical features and anatomical parameters of combined mechanism glaucoma with age, sex, and refraction-matched POAG and chronic PACG eyes.

Methods

Consecutive adult patients with definitive optic nerve head and perimetric changes of glaucoma were screened at a tertiary care center. All glaucomatous eyes having an IOP > 22 mmHg on at least three separate occasions and glaucomatous optic neuropathy consistent with moderate visual field loss in the eye were divided as POAG, PACG, and CMG. Eyes with occludable angles having < 90° of goniosynechiae were diagnosed as CMG. A detailed clinical examination, ocular biometry, and ASOCT were performed in the better eye of all individuals.

Results

A total of 93 patients with similar visual field index or pattern standard deviation on perimetry were evaluated: 32 POAG, 31 CMG, and 30 PACG. The mean anterior chamber depth was 3.47 ± 0.37 mm in POAG, 2.81 ± 0.32 mm in PACG, and 3.06 ± 0.26 mm in CMG (p < 0.0001). Mean lens thickness was 4.22 ± 0.27 mm in POAG, 4.53 ± 0.35 mm in PACG, and 4.44 ± 0.29 mm in CMG (p = 0.0004). Iridotrabecular contact on ASOCT was nil in POAG, a mean of 87.60 ± 12.802% in PACG eyes, and 15.23 ± 14.19% in CMG eyes, p < 0.0001. CMG was similar to PACG in terms of corneal diameters and lens thickness and had an axial length in between PACG and POAG. On ASOCT, all parameters had highest values in POAG eyes and the least in PACG eyes, with CMG eyes having values in between the other two groups, p value of < 0.0001 between each group for all parameters.

Conclusion

This study has demonstrated significantly different anatomical parameters in eyes with CMG, in addition to the differences on gonioscopy and iridotrabecular contact, indicating that CMG is discernibly dissimilar to PACG and POAG.

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Authors and Affiliations

  1. Glaucoma Services, Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute Of Medical Sciences, Room no 494, 4th floor, New Delhi, 110029, India

    Ramanjit Sihota, Sailesh Kumar, Talvir Sidhu, Neha Midha, Ajay Sharma, Suresh Yadav, Viney Gupta & Tanuj Dada

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  1. Ramanjit Sihota
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  2. Sailesh Kumar
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  3. Talvir Sidhu
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  4. Neha Midha
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  6. Suresh Yadav
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Correspondence to Ramanjit Sihota.

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The authors declare that they have no conflict of interest.

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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

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Informed consent was obtained from all individual participants included in the study.

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Sihota, R., Kumar, S., Sidhu, T. et al. Is combined mechanism glaucoma a distinct entity?. Graefes Arch Clin Exp Ophthalmol 256, 1961–1969 (2018). https://doi.org/10.1007/s00417-018-4050-5

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  • DOI: https://doi.org/10.1007/s00417-018-4050-5

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