Glaucoma’s are a group of diseases having in common gradual loss of retinal nerve fibers leading to characteristic excavated appearance (called glaucomatous cupping) of the starting point of the optic nerve . This is associated with specific pattern of loss of visual field.
Neglected, this fetal disease gradually devours your field of vision from the periphery and ultimately leads to complete blindness. That is why it is called the ‘silent killer of sight’ and is, at present, the second leading cause of blindness world-wide. High intra-ocular pressure, as opposed to our previous belief, is no longer considered an essential pre-requisite for occurrence of glaucomatous damage, though lowering eye pressure still remains the mainstay of its treatment.
The cause of glaucoma is unknown. In most of the cases it is due to rise in intra ocular pressure which can cause irrecoverable damage to the optic nerve and can result in permanent loss of vision. But, glaucoma can also result from structural weakness or poor blood supply of the optic nerve head in presence of a statistically “normal” IOP (10-21mmhg). Hence the vulnerability of the optic disc is another factor that needs to be considered. Accordingly, the diagnosis of glaucoma requires more than just the mere measurement of intraocular pressure. On the other hand persons with high IOP may not have glaucoma at all (ocular hypertension). Congenital glaucoma may be caused due to genetic defect or intrauterine infection like rubella.
The Humphrey Field Analyzer(HFA) is the recognized standard of care for early diagnosis and management of ocular diseases resulting in visual field loss.It is used to confirm that glaucoma has affected the visual function, to evaluate the severity and to monitor progression of the disease.
The Analyser can be used for screening, monitoring and assisting in the diagnosis of certain conditions. There are numerous testing protocols to select, based on the purpose. The first number denotes the extent of the field measured on the temporal side, from the centre of fixation, in degrees. The '-2' represents the pattern of the points tested. They include:
10-2: Measures 10 degrees temporally and nasally and tests 68 points. Used for macula,retinal and neuro-ophthalmic conditions and advanced glaucoma
24-2: Measures 24 degrees temporally and 30 degrees nasally and tests 54 points. Used for neuro-ophthalmic conditions and general screening as well as early detection of glaucoma
30-2: Measures 30 degrees temporally and nasally and tests 76 points. Used for general screening, early glaucoma and neurological conditions.
The above tests can be performed in either SITA-Standard or SITA-Fast. SITA-Fast is a quicker method of testing. It produces similar results compared to SITA-Standard, however repeatability is questionable and it is slightly less sensitive.
The Analyser projects a series of white light stimuli of varying intensities (brightness), throughout a uniformly illuminated bowl. The patient uses a handheld button that they press to indicate when they see a light. This assesses the retina’s ability to detect a stimulus at specific points within the visual field. This is called retinal sensitivity and is recorded in 'decibels' (dB).
The Analyser currently utilises the Swedish Interactive Thresholding Algorithm (SITA); a formula which allows the fastest and most accurate visual field assessment to date. Results are then compared against an age-matched database which highlights unusual and suspicious vision loss, potentially caused by pathology.
Yag Peripheral Iridotomy
Yag PI is a laser management for patients who may develop glaucoma.
when a person has not developed glaucoma but falls in the category of glaucoma suspect because of Anterior chamber Angle closure patient goes for YAG-PI
in Yag-PI, a hole is made so that the aqueous drainage is increased and the IOP is brought down. Thus, reducing the chances of developing glaucoma.
Yag Cap is the cleaning of the posterior capsule of the pseudophakic patient.
this is done in patients where after cataract surgery, the posterior capsule of the lens opacities in nearly 20% of operated patients.
A central aperture in the posterior capsule is made by Laser shots to clear the visual axis.