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   Table of Contents      
CASE REPORT
Year : 1996  |  Volume : 44  |  Issue : 3  |  Page : 167-168

Glaucoma like defect on automated perimetry caused by cataract


Schell Eye Hospital and Department of Ophthalmology, Christian Medical College, Vellore, India

Correspondence Address:
Ravi Thomas
Schell Eye Hospital, Arni Road, Vellore 632 001, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


PMID: 9018996

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How to cite this article:
Thomas R, Kuriakose T, George T. Glaucoma like defect on automated perimetry caused by cataract. Indian J Ophthalmol 1996;44:167-8

How to cite this URL:
Thomas R, Kuriakose T, George T. Glaucoma like defect on automated perimetry caused by cataract. Indian J Ophthalmol [serial online] 1996 [cited 2019 Dec 12];44:167-8. Available from: http://www.ijo.in/text.asp?1996/44/3/167/24579

The association of senile cataract with primary open angle glaucoma is a common occurrence. Modern automated perimeters allow the clinician to determine localized loss (presumably due to glaucoma) after adjusting for depression caused by media opacities such as cataract.[1],[2]

We describe a case where a localized scotoma resembling a glaucomatous field defect was caused by cataract.


  Case report Top


An 81 year old female was referred to the glaucoma clinic with borderline intraocular pressures (21 mmHg) and field defects on automated perimetry in both eyes. The cataracts in both eyes were similar: nuclear sclerosis with posterior subcapsular opacities that involved mainly the inferior half of the lens but also extended just above the visual axis [Figure:1]. The best corrected visual acuity in both eyes was 6/24, J4. The cup disc ratio was 0.2:1 in the right eye, and 0.3:1 in the left eye with healthy neuro-retinal rims. There was no fundus pathology to explain the field defect. The field defect including the localized defect that persisted in the pattern deviation seemed commensurate with the morphology of the cataract and was reproducible on repeat testing [Figure:2]. The localized nature of the defect was also reflected in the global indices (pattern and corrected pattern standard deviations); the glaucoma hemifield test was outside normal limits. The patient underwent phacoemulsification with implantation of an intraocular lens in the right eye. The field one week after surgery (with the same pupillary diameter as preoperatively) is shown in [Figure:3]. The best corrected vision was 6/9, J1. Most of the defects, including that in the pattern deviation plot had disappeared.


  Discussion Top


Despite automation and sophisticated statistical analysis perimetry has several pitfalls. Experts have cautioned that fields should not be interpreted in isolation, but in the light of clinical findings.[3]

The diffuse depression caused by cataract was discussed in a recent review.[4] Cataracts are considered to cause a diffuse field loss which can be determined by the total deviation plot. The localized defect remaining in the pattern deviation plot then represents localized loss and is usually attributed to glaucoma.[1],[2] The assumptions underlying these mathematical analysis have however been questioned.[5]

In our case the localized nature of the cataract inferiorly accounted for the localized superior field defect. Optically the posterior subcapsular area is behind the nodal point of the eye and an inferior opacity will translate as a superior field defect. Using manual perimetry localized field defects have been attributed to cataract.6 To our knowledge, such changes on automated perimetry have not previously been correlated with cataract morphology. We have subsequently examined three other patients referred as glaucoma suspects, where the morphology of the cataracts seemed to explain the field defects.

In a glaucoma suspect such localized defects would be attributed to glaucomatous damage. Similar field defects occurring in patients under follow up for glaucoma could be mistaken for progression.

Our case documents another pitfall in automated perimetry. Localized cataractous changes can cause glaucoma like field defects and must be specifically looked for before attributing these to glaucoma[6].

 
  References Top

1.
Lieberman MF, Drake MV. Statistically assisted interpretation. Computerized Perimetry - a simplified guide. 2nd ed. Thorofare, NJ: Slack Inc, 1992:101.  Back to cited text no. 1
    
2.
Anderson DR. Single field printout statpac analysis. Automated static perimetry. St Louis: Mosby Year Book Inc, 1992:80.  Back to cited text no. 2
    
3.
Anderson DR. Interpretation of a single field. Automated static perimetry. St Louis: Mosby Year Book Inc, 1992:158.  Back to cited text no. 3
    
4.
Heijl A, Asman P. Pitfalls of automated perimetry in glaucoma diagnosis. Curr Opin Ophthalmol 6:246-251, 1995.  Back to cited text no. 4
    
5.
Jay JL. Computerised perimetry - the emperor's new clothes? Br J Ophthalmol 78:513-514, 1994.  Back to cited text no. 5
    
6.
Bigger JF, Becker B. Cataracts and open-angle glaucoma: the effect of cataract extraction on visual fields. Am J Ophthalmol 106:480-484, 1988.  Back to cited text no. 6
    




 

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