Servicios Profesionales de Óptica

05/12/2025

23/11/2025

13/11/2025

11/11/2025

The ISNT rule is an ophthalmic mnemonic used to describe the typical configuration of the neuroretinal rim (NRR) width in a healthy optic nerve.
The acronym ISNT stands for the four quadrants of the optic disc:
_Inferior
_Superior
_Nasal
_Temporal
The rule states that, in a normal, non-glaucomatous eye, the width of the neuroretinal rim (the tissue surrounding the optic cup) is thickest to thinnest in the following order: Inferior > Superior > Nasal > Temporal.

SIGNIFICANCE IN OCULAR PRACTICE
The primary significance of the ISNT rule lies in its use as an aid for the clinical diagnosis and screening of glaucoma.
_Glaucoma Detection: Glaucoma is a progressive optic neuropathy that typically causes damage and thinning to the neuroretinal rim, with a characteristic preference for the superior and inferior poles of the optic disc.
_Violation of the Rule: When the neuroretinal rim begins to thin due to glaucoma, the ISNT pattern is often violated. For example, the superior or inferior rim might become thinner than the nasal rim, or even the temporal rim, thus violating the established order. Violation of the ISNT rule (e.g., if Superior is thinner than Nasal) can significantly raise the clinician's suspicion for glaucomatous damage.
_Clinical Screening: Clinicians, when examining the optic nerve head with instruments like an ophthalmoscope or slit-lamp, use the ISNT rule as a quick, subjective way to assess the health of the optic disc.

LIMITATIONS
While helpful, the ISNT rule is not a definitive diagnostic tool and has limitations:
_Variability: Studies have shown that a significant percentage of normal eyes may naturally deviate from the strict ISNT order, particularly regarding the nasal quadrant.
_Other Conditions: Certain non-glaucomatous conditions, like some forms of optic disc cupping (especially in children) or highly myopic/tilted discs, can also violate the ISNT rule.
_Modern Imaging: Its utility is sometimes debated with the rise of objective, quantitative imaging technologies like Optical Coherence Tomography (OCT), which provide precise measurements of the Retinal Nerve Fiber Layer (RNFL) thickness and neuroretinal rim width.
In summary, the ISNT rule is an important historical and clinical guideline that, when assessed alongside other factors (such as the cup-to-disc ratio and visual field tests), helps clinicians screen for and manage glaucoma.

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10/11/2025

HYPOPYON ULCER ✅✅

29/10/2025

Could Allergies Foster Glaucoma Development?

Using blood samples to measure immunoglobulin-E levels, researchers found a potential association between allergen sensitization rates and the risk of developing glaucoma. Key findings include:

▪ Among 1,175 patients in the analysis, pollen allergens and dust mites all presented with a degree of sensitivity, while animal dander didn’t have any impact on the glaucoma group.
▪ Sensitization rates for dust mites were the highest in both groups among all tested allergens (12% for glaucoma patients and 11.7% for others).
▪ Birch pollen had the second highest rates for both groups (4% for glaucoma patients and 4.1% for others).
▪ Oak pollen sensitization rates showed opposite results, with 2% for glaucoma patients and 4% for others.

Read more in the latest Review News: https://www.reviewofophthalmology.com/article/could-allergies-foster-glaucoma-development

02/10/2025

11/04/2025

Schematic of The Visual Pathway displaying VF Loss at Different Stages:
◾Relative afferent pupillary defect (rAPD) will be evident in the most anterior part of the visual pathway in more severe retinal or optic nerve diseases with both ipsilateral and contralateral rAPD possible.
◾The VFs tend to be more congruous further back along the pathway, especially at the visual cortex.
◾The monocular crescent is reflected by the most temporal VF in each eye extending from around 60º to 90º.
◾The most anterior part of the primary visual cortex (Locations A&B) is the most likely anatomical location of the monocular crescent.
◾The macular representation of almost one half of the visual cortex is outlined by E&F with locations C&D reflecting the remainder of the VF.
➖Lesions in severe retinal conditions and ON have asymmetric visual dysfunction, thus a rAPD is often present and associated VF defects (Locations 1&2).
➖Chiasmal lesions typically produce bitemporal VF defects with a hallmark feature of respecting the vertical midline with various levels of rAPD depending upon the congruity of pupillary fiber involvement (Location 3).
➖Optic tract lesions (Locations 4&5) will have a subtle contralateral rAPD because there are more crossed than uncrossed pupillary fibers, and they may have a complete homonymous hemianopia in more severe cases.
➖VF defects caused by lesions at the LGN are rare: they display a characteristic bilateral “pie-shaped” VF defect without rAPD.
➖There is no rAPD found in lesions at or beyond the LGN.
➖Temporal lobe lesions are characterized by an incongruous superior “pie in the sky” VF defect, and parietal lobe lesions by an incongruous inferior “pie on the floor” VF defect (Locations 7&8).
➖Larger lesions in the temporal or parietal lobe regions may result in complete homonymous hemianopias. Such findings beyond the LGN may be discriminated by evaluating the associated clinical signs and symptoms associated with lesions in specific visual areas.
➖VF defects at the visual cortex are characterized by their congruous nature, and lesions at this location is where macular sparing of the VF can occur (Locations 9 to 12).
➖The visual cortex above the calcarine sulcus projects to the contralateral inferior VF, and vice-versa for the area below the calcarine sulcus.
➖The most anterior part of the visual cortex represents the monocular temporal crescent, and thus with this exception, all other cortical lesions cause bilateral VF loss beyond the optic chiasm.
Credit: www.reviewofoptometry.com

11/12/2024

Macular telangiectasia:
▪️Macular telangiectasia is a retinal pathology that leads to the formation of abnormal neovascular complexes and loss of central vision.
▪️In macular telangiectasia type 2, there are three distinct features that can be observed on OCT.
▪️There is:
1) disruption of the EZ,
2) the presence of large inner and/or outer retinal cavitations, and
3) the presence of internal limiting membrane drape.
▪️The internal limiting membrane drape can be seen as a thin membrane that crosses a cavity at the base of the fovea.
Credit: www.journals.lww.com