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Abstract #6291 Published in IGR 2-2
Chronic glaucoma: definition of the phenotype
Hitchings RAEye 2000; 14: 419-421
In this editorial, the author states that the purpose of his article is to trace the development of the term 'chronic glaucoma' from its early beginnings to the present day. He is particularly interested by what we will mean by the term chronic glaucoma in the future. Originally, glaucoma was seen as the coexistence of a hard eye and visual loss. With the advent of the ophthalmoscope and the tangent screen in the 19th century, and accurate ways to measure IOP, the concept of glaucoma changed into a disease in which raised IOP causes visual loss and glaucomatous cupping. The cause of the raised pressure remained a mystery and trabecular sclerosis was suggested. With the advent of gonioscopy, primary open-angle and closed-angle glaucoma could be differentiated. For a long time, the diagnosis of glaucoma was one that included an intraocular pressure above the normal range. When large population surveys showed that 20-30% of all primary glaucomas had an IOP within the normal range, IOP was degraded to a risk factor. Today, glaucoma is defined as an optic neuropathy involving loss of neurons within the optic nerve, giving a characteristic deformation known as glaucomatous cupping. It will have an associated deficit in visual function and a risk factor will be elevated IOP. A major change in definition will come from recognition that defective visual function may be hard to detect in the early stages of the disease. The author concludes with a system of segmental analysis of the optic disc which was developed at Moorfields Eye Hospital and incorporated into the software of the scanning laser ophthalmoscope (Heidelberg). The system automatically separates normal discs from suspect and abnormal ones. Using this system, many discs will be in the suspect range. The second part of the program deals with evidence of progression. With the same type of sector analysis, progression can be described on the basis of disc analysis. The author feels that future method of diagnosing glaucoma will arise from measurement data. Glaucoma will be seen as an acquired deformity of the optic disc, characteristic in appearance, with either sector measurements that fall outside the normal range or evidence of progressive change in one or more sectors. These changes at the optic disc may be associated with evidence of visual loss, and with an elevated IOP.
Dr. R.A. Hitchings, Glaucoma Research Unit, Moorfields Eye Hospital, City Road, London EC1V 2PD, UK
