258 259 In some cases, it is not possible to be certain whether an individual optic disc is glaucomatous. The clinical findings and results of investigation should be considered together to guide management. 260 261 Glaucomatous damage results in characteristic signs involving (a) the optic nerve head, (b) the peripapillary area and (c) the retinal nerve fibre layer. 262 263 Optic nerve head. Pathological cupping is caused by an irreversible decrease in the number of nerve fibres, glial cells and blood vessels. A documented increase in cup size is always significant (Fig. 11.8). If an eye with a small optic disc and correspondingly small cup develops glaucoma, the cup will increase in size, but even in the presence of substantial damage may still be smaller than that of a large physiological cup. 264 265 Subtypes of glaucomatous damage. Four morphological glaucomatous disc appearances have been described and although the majority of discs are unclassifiable the descriptions encompass a useful overview of patterns of glaucomatous damage and may provide clues to underlying pathological processes. 266 267 Focal ischaemic discs (Fig. 11.9A) are characterized by localized superior and/or inferior notching and are associated with localized field defects with early threat to fixation. 268 269 Myopic disc with glaucoma (Fig. 11.9B) refers to a tilted (obliquely inserted), shallow disc with a temporal crescent of parapapillary atrophy, together with features of glaucomatous damage. Dense superior or inferior scotomas threatening fixation are common. This morphology is most common in younger male patients. 270 271 Sclerotic discs (Fig. 11.9C) are characterized by a shallow, saucerized cup and a gently sloping NRR, variable peripap-illary atrophy and peripheral visual field loss. The peripap-illary choroid is thinner than in other disc types. Patients are older, of either gender and there is an association with systemic vascular disease. 272 273 Concentrically enlarging discs (verified by serial monitoring) are characterized by fairly uniform NRR thinning (Fig. 11.9D) and are frequently associated with diffuse visual field loss. IOP is usually significantly elevated at presentation. 274 275 Non-specific signs of glaucomatous damage. Other disc signs of glaucomatous damage include: 276 277 Disc haemorrhages (Fig. 11.10A and B) often extend from the NRR onto the retina, most commonly inferotemporally. Their presence is a risk factor for the development and progression of glaucoma. They are more common in NTG but can also occur in healthy individuals as well as patients with systemic vascular disease. When screening for glaucoma, approximately three out of four people with a disc haemorrhage will not have glaucoma. 278 279 *Table 11.3 Correction Factors for Estimating Optic Disc Diameter* 280 281 282

Lens	Correction factor
Volk 60D	×0.88–1.0
Nikon 60D	Around 1.0
Volk 90D	×1.3
Volk 78D	×1.1
Goldmann 3-mirror	×1.27

283 284 285 286 287 ![Four images display close-up views of the eye's optic disc, each showing a distinct pattern of blood vessels and a central pale area.](https://cdn.orris.care/cdss_images/6dce4d45ea4b3c882924512114630e3a4ae7beac5021d41e500e94d576858246.png) 288 289 *Fig. 11.7 Optic disc asymmetry. (A) and (B) Physiological cupping in a normal individual showing a larger optic disc in the right eye than in the left eye. The white bar shows the difference in [... Output truncated due to length. 4780 tokens/17493 characters removed ...]